Articles in press have been peer-reviewed and accepted, which are not yet assigned to volumes /issues, but are citable by Digital Object Identifier (DOI).
Research on improving magnetic field adaptability of high-precision IFOG
XU Bao-xiang, XIONG Zhi, HUANG Ji-xun, YU Hai-cheng
Accepted Manuscript  doi: 10.3788/IRLA20200239
[Abstract](187) [FullText HTML](84)
The magnetic non-reciprocity error is one of the main factors that restrict the application of high-precision IFOG, and the error is related to the strength of magnetic field and the twist rate of fiber. The magnetic field sensitivity of fiber coil is more than 10° / h / GS due to the twisting of the fiber, even if permalloy is used to shield the magnetic field, the shielding effectiveness can only reach about 30 dB, which cannot meet the requirements of high-precision IFOG. The influence of the connection gap between shielding materials on shielding effectiveness is analysed by an equivalent circuit model and finite element simulation, the influence of the twist rate on the magnetic field sensitivity is deduced by formula. Through these analyses, the improvements that changed the connection of shielding materials from screw connection to laser welding and made the fiber de-twist are proposed. Through the measure of fiber de-twist, the magnetic field sensitivity of the fiber coil is reduced by 89.3%; through the improvement of laser welding, the shielding effectiveness is improved from 31 dB to at least 64 dB, the magnetic field sensitivity is reduced from 0.0265°/h/Gs to less than 0.0004°/h/Gs, and the bias stability of the IFOG in different temperature is improved by more than 7.5%. These improvements can improve the precision of the fiber coil in the magnetic field and temperature environment.
Random laser radiation behavior of liquid crystal in photonic crystal fiber carrier
Wu Rina, Song Yunhe, Lu Jiaqi, Gao Rui, Li Yeqiu, Dai Qin
Accepted Manuscript  doi: 10.3788/IRLA20200171
[Abstract](550) [FullText HTML](113)
A hollow-core photonic-crystal fiber filled with a mixture of nematic liquid crystal TEB30A, chiral agent S-811 and laser dye PM597 is pumped by a frequency-doubled Nd: YAG laser with a wavelength of 532 nm. The laser emission spectra is measured and the random laser radiation behavior in the photonic-crystal fiber carrier is investigated. When side-pumping is applied to the fiber, the emitted random laser with a wider radiation direction from the side face has a wavelength range of 590−605 nm and an FWMH of 0.3 nm. When end-pumping is employed to the fiber, the emitted random laser from the end face has a wavelength range of 580−605 nm and an FWMH of 0.3 nm. After the sample is heated to the isotropic temperature, the laser emission with both pumping methods is shut down. The experimental results demonstrate that the dye doped liquid crystal mixture in the micropore induce the random laser emission in the photonic-crystal. The change in the mean free path of photon transport and the fluctuation of the dielectric tensor of chiral nematic liquid crystals with temperature are the main factors affecting the laser intensity.
Development of beam brightness enhancement based on diamond Raman conversion
BAI Zhen-xu, CHEN Hui, LI Yu-qi, YANG Xue-zong, QI Yao-yao, DING Jie, WANG Yu-lei, LÜ Zhi-wei
Accepted Manuscript  doi: 10.3788/IRLA20200098
[Abstract](901) [FullText HTML](667)
High brightness laser sources with different wavelengths play an important role in the fields such as military, industrial, and life sciences etc. However, due to the intrinsic spectral and thermophysical properties of current available laser gain materials, it is difficult to take into account the wavelength and output power of the traditional inversion lasers, which even leads to the decrease of beam brightness. To overcome this problem, beam cleanup by using nonlinear optical technology have been carried out in recent years, which is directly transferring the low-quality beam generated from inversion lasers into high-beam quality through the effects such as stimulated Raman or Brillouin scattering. Among them, with excellent properties such as high Raman gain coefficient, high thermal conductivity and wide spectral transmission range, diamond exhibits excellent beam brightness enhancement characteristics while realizing high efficiency Raman conversion, which provides a new technical path to generate high power and high brightness laser beam. Here, the development of brightness enhancement based on first-order and cascaded Raman conversion of diamond is reviewed, and its future applications are discussed.
Research on ultra-low power consumption methane detection system based on NDIR technology
Zhao Qingchuan
Accepted Manuscript  doi: 10.3788/IRLA20200140
[Abstract](148) [FullText HTML](93)
In order to meet the needs of low power consumption methane detection technology, an ultra-low power consumption infrared methane sensor and system based on non-dispersed infrared spectroscopy is developed, which is based on the characteristics of methane gas molecules having main absorption peak in the infrared band of 3.2 μm~3.4 μm. The selection of LED and PD devices and the design of optical path are studied based on the analysis of the principle of infrared differential detection. The power consumption of infrared methane sensor is reduced to 10 mW by using LED packets of pulses current drive technology. The influence of temperature change on the measurement of methane concentration is studied by experimental method, the temperature compensation algorithm formula is obtained by data analysis and linear fitting of normalization method. The performance experiment is carried out on the detection system platform, and the basic performance parameters are given. The system has the advantages of low power consumption, anti-interference of water vapor and good detection stability, and has important application value.
Influence of Gaussian mirror parameters on LD-pumped Nd:YAG laser
MENG Pei-bei, SHI Wen-zong, JIANG Shuo, QI Ming, DENG Yong-tao, LI Xu
Accepted Manuscript  doi: 10.3788/IRLA20200127
[Abstract](93) [FullText HTML](42)
The influence of eccentricity and laser performance of LD-pumped Nd:YAG laser was investigated experimentally at different parameter Gaussian mirrors. Largest energy, narrowest width and smallest divergence can be obtained simultaneously only when the optical axis, laser crystal axis and Q-switch axis were in agreement, furthermore the optical axis went through the reflectivity center of Gaussian mirror. When eccentricity appeared, the energy, pulse width and divergence degraded more with smaller reflectivity radius or larger center reflectivity of Gaussian mirror. For 2.5 mm reflectivity radius and 30% central reflectivity Gaussian mirror, energy decreased 7%, pulse width increased 33%, and divergence increased 20% under 0.5 mm eccentricity. For laser performance, the smaller the reflectivity radius or center reflectivity of Gaussian mirror, the better the beam quality and the smaller the optical-to-optical efficiency. Considering the eccentricity influence and laser performance, 2.75 mm reflectivity radius and 20% center reflectivity Gaussian mirror was optimum. When the pump energy was 984 mJ, output energy of 128 mJ, pulse width of 7.3 ns, and beam quality M2 factor of 4.6 at 1064 nm were achieved, corresponding to the optical-to-optical efficiency of 13%. The experimental results in this paper can be a reference of the laser design and alignment.
1 123 nm Q-switched Nd: YAG laser based on gold nanocages and MoS2 saturable absorbers
Zhang Bin, Li Ying, Liu Binghai
Accepted Manuscript  doi: 10.3788/IRLA20200084
[Abstract](407) [FullText HTML](290)
Based on gold nanocages (GNCs) and MoS2 as saturable absorber (SA), respectively, passively Q-switched Nd: YAG lasers at 1 123 nm were demonstrated. When Q-switched laser with GNCs as SA, Q-switched pulse with the shortest pulse duration of 253 ns and maximum pulse repetition rate of 326 kHz was achieved under the pump power of 6.04 W with the maximum average output power of 221 mW. Compared with the experimental results of MoS2 Q-switched laser, the gold nanocage Q-switched laser has higher output power and efficiency, narrower pulse width and higher repetition rate. These results indicated a great potential of the GNCs film as SA in the near-infrared region.
Powerful iodine stabilized He-Ne laser as wavelength reference
WANG Jian-bo, YIN Cong, SHI Chunying, WANG Hanping, CAI Shan,    
Accepted Manuscript  doi: 10.3788/IRLA20200111
[Abstract](1034) [FullText HTML](481)
In order to meet the requirement of high output power of the laser monochromatic light source in the precision measurement, a high-power iodine stabilized He-Ne laser system with a fully enclosed, integrated structure was developed. The principle of saturation spectral detection, the method of absorption peak recognition and locking and the frequency stability of iodine stabilized laser were studied. Firstly, the basic principle of detecting saturation absorption spectrum of iodine molecular using the three harmonic method was introduced, and its mechanism of eliminating the power background was analyzed. Then, the stability of the integrated resonant cavity in the iodine stabilized laser was demonstrated, and the effects of axial expansion and lateral asymmetric deformation on the output power were discussed in detail. After that, the correspondence between the profile of laser output power and the iodine molecular saturation absorption peaks was presented, the feasibility of using the secondary harmonic signal to achieve absorption peak recognition was introduced, and the long-term locking ability of high-stability resonant cavity was demonstrated. Finally, the wavelength stability and reproducibility of high-power iodine stabilized He-Ne laser were analyzed. The experimental results shown that the standard deviation for the frequency jitter of high-power iodine stabilized He-Ne laser was 33 kHz, the stability at 1000 s and the reproducibility in three months were 4.1×10−13 and 3.3 kHz (7.0×10−12), respectively. Its absolute frequency was 3.0 kHz lower than the recommended value by the International Committee for Weights and Measures (CIPM).
Development on High Precision CO2 Isotope Measurement System Based on Infrared TDLAS Technology
Hou Yue, Pengquan Zhang, Guanyi Yu, Huang Kejin
Accepted Manuscript  doi: 10.3788/IRLA20200083
[Abstract](1059) [FullText HTML](471)
For natural gas distribution monitoring, it is very important to measure the CO2 isotope with high precision. In this paper, the tunable diode laser absorption spectrum (TDLAS) technology is adopted to realize the high precision CO2 isotope measurement through the absorption spectrum line of 13CO2/12CO2 at 4.3 μm. The measurement system consists of a mid-infrared interband cascade laser (ICL) operating in a continuous wave mode, a long-path multipass cell (MPGC) and a mid-infrared mercury-cadmium telluride (MCT) detector. Aiming at the problem that the intensity of 13CO2 and 12CO2 absorption spectra is affected by the temperature, an MPGC high precision temperature control system is developed. In the experiment, five CO2 gases of different concentrations are configured to calibrate the measurement system, and the response linearity is up to 0.9996. The results show that when the integral time is 92 s, the isotope measurement precision is as low as 0.0139‰, which has practical application value.
Accepted Manuscript
[Abstract](2930) [FullText HTML](910)
Depolarization Mechanism and Compensation Scheme of Radially Polarized Beams
YANG Ce, PENG Hong-pan, CHEN Meng, MA Ning, XUE Yao-yao, DU Xin-biao, ZHANG Xie
Accepted Manuscript  doi: 10.3788/IRLA202049.20200038
[Abstract](855) [FullText HTML](1836)
Depolarization mechanism and compensation scheme of radially polarized beams under non-uniform pumping are investigated. Theoretical analysis shows that, for the non-uniform pumping status, the thermal induced shear birefringence caused by the thermally induced shear stress within the cross-section of the isotropic crystal is the main reason for the depolarization of the radially polarized beams. Related experiments were designed to evaluate the depolarization of the radially polarized beams which under non-uniform pumping conditions by using two methods of thin-film polarizer (TFP) measurement and purity measurement, in which the TFP measurement method is used to detect the overall depolarization of radially polarized beams and the purity measurement method is used to detect local depolarization of radially polarized beams. With a peak pump power of 1.1 kW, the depolarization measured by the two evaluation methods is 2.34% and 2.53%, respectively. Based on the theoretical analysis and evaluation results, a combination of phase modulation and spatial mode matching was considered in the design of the depolarization compensation scheme, which improved the depolarization of the radially polarized beams by 59%. Meanwhile, a picosecond radially polarized beam with a pulse energy of 19.36 mJ, a purity of 90.13%, and a beam quality M2 factor of 3.8 was achieved.
Numerical study on backward light amplification and damage in high-power fiber laser
Sheng Quan, Si Hanying, Zhang Haiwei, Zhang Junxiang, Ding Yu, Shi Wei, Yao Jianquan
Accepted Manuscript
[Abstract](4079) [FullText HTML](2144)
The amplification of both continuous-wave (CW) and pulsed backward signal in high-power master-oscillator-power-amplifier based fiber laser are investigated using rate equation model. The results show that the CW backward light would be amplified significantly by the high-power amplifier and thus decrease the laser output seriously. For the pulsed backward signal, the pulse energy would not be amplified obviously since the energy storage is absent in CW fiber laser. Considering the damage threshold of the fiber and devices including end-cap and fiber Bragg grating (FBG), the amplification of CW backward light may damage the FBG of the laser oscillator, and the backward laser pulse with millijoule level pulse energy may damage the fiber, while there also exists the risk of end-cap damage when pulsed backward laser incidents.
Effects of gain distribution on self-similar amplification of picosecond pulses
Zhang Yun, Liu Bowen, Song Huanyu, Li Yuan, Chai Lu, Hu Minglie
Accepted Manuscript
[Abstract](5151) [FullText HTML](2254)
The effects of gain distribution on self-similar amplification of picosecond pulses in a Yb-doped fiber laser system are studied by numerical simulation. Ultrashort laser pulses amplified in self-similar amplification theoretical model is established to analyze the impact of pump configuration, fiber length and total gain coefficient on the self-similar amplification evolution and laser output performance. Detailed numerical simulation reveals that the best self-similar amplification result can be found for different cases, where high-quality self-similar pulses with ~100 fs transform-limited pulse duration are obtained. It is demonstrated that the self-similar evolution speed in a forward-pumping scheme is faster than that in a backward-pumping scheme for a fixed seed pulse. Furthermore, the results indicate that for the self-similar amplifier with different fiber lengths and gain coefficients, the forward-pumping scheme shows better evolution results in lower seed energy and longer wavelength range, while the backward-pumping scheme is more suitable for the higher seed energy and shorter wavelength range.
Thermal damage of monocrystalline silicon irradiated by long pulse laser
Guo Ming, Zhang Yongxiang, Zhang Wenying, Li Hong
Accepted Manuscript
[Abstract](107) [FullText HTML](92)
In view of the thermal damage law and mechanism of monocrystalline silicon for millisecond pulsed laser, the temperature of monocrystalline silicon irradiated by millisecond pulsed laser is measured by high precision point temperature meter and spectral inversion system. Then the temperature evolution process is analyzed. Also, the temperature state during the whole process of thermal damage of monocrystalline silicon irradiated by millisecond pulsed laser and the corresponding damage structure are studied. The results of this study show that the peak temperature of laser-induced monocrystalline silicon increases with the increase of energy density when the pulse width is fixed, When the pulse width is between 1.5 ms-3.0 ms, The temperature decreases with the increase of pulse width. Temperature rise curve shows inflection point when it is close to the melting point (1687 K), the reflection coefficient is from 0.33 to 0.72. During the gasification and solidification stages, it also shows the gasification and the solidification plateau periods. Thermal cleavage damage of monocrystalline silicon precedes thermal erosion damage. Stress damage dominates under low energy density laser irradiation, while thermal damage dominates under high energy density laser irradiation. The damage depth is proportional to the energy density and increases rapidly with the increase of the number of pulses.
Laser-Matter Interaction
Laser assisted 3D metal microprinting (Invited)
Lin Zijie, Xu Jian, Cheng Ya
2020, 49(12): 20201079.   doi: 10.3788/IRLA20201079
[Abstract](32) [FullText HTML](6) [PDF 2274KB](0)
In recent years, the demand for fabrication of 3D metal micro/nanostructures has been rapidly increased in the fields of science and engineering due to their unique physical/chemical properties and flexible configurations. Therefore, various innovative techniques for 3D metal printing at the microscale have been developed, which have attracted intensive attentions. Among those techniques, laser-based assisted 3D metal microprinting exhibits superior performance in terms of its advantages of non-contact processing, flexible patterning capability, and so on. Some of current representative techniques for laser assisted 3D metal microprinting were firstly reviewed from basic principles, technical characteristics, to typical applications. To meet the challenges on fabrication of 3D metal microstructures with high smooth surfaces, high melting points and high conductivities, a glass-microchannel molding technique for assisting 3D metal microprinting was demonstrated. Finally, possible directions and potential applications of laser-assisted 3D metal printing were discussed.
Femtosecond laser induced microstructures in diamond and applications (Invited)
Wang Huafeng, Sun Ke, Sun Shengzhi, Qiu Jianrong
2020, 49(12): 20201057.   doi: 10.3788/IRLA20201057
[Abstract](12) [FullText HTML](4) [PDF 1908KB](0)
For many years, silicon and germanium have been considered the suited semiconductor materials for detectors and integrated optoelectronic devices fabrication. However, compared with diamond-based devices, such tetravalent semiconductors are less resistant to radiation damage, and the devices are less stable under harsh conditions or under high-energy light radiation. In recent years, due to the excellent optical and mechanical properties, diamond has become a promising material in the application of integrated photonics, sensors, and quantum optics etc. The laser-induced microstructures of diamond represents a powerful tool used for the development optical 3D-contacts devices all-carbon detectors graphite resistors on diamond, as well as the realization of single photon source. The physical mechanisms of femtosecond laser induced color center, graphitization and refractive index change in diamond were demonstrated. Based on this, the applications of the femtosecond laser induced micro-nano structures in diamond for single photon source, sensor and optical waveguide were introduced. Then, the future developing tendency in this field was prospected.
Research progress of third-order nonlinear optical effects excited by vectorial light fields (Invited
Gu Bing, Hu Yueqiu, Wen Bo
2020, 49(12): 20201050.   doi: 10.3788/IRLA20201050
[Abstract](6) [FullText HTML](4) [PDF 1923KB](0)
Polarization-structured intense laser interacting with nonlinear optical material results in many novel third-order nonlinear optical effects, reflects the nonlinear optical property of the material, and modulates the propagation behavior of the beam itself. Herein, the research progress of third-order nonlinear optical effects excited by vectorial light fields was reviewed. Firstly, the basic theory of third-order nonlinear optical effects excited by arbitrary polarized lights was briefly introduced, such as nonlinear Schrödinger equation, beam propagation equation, and isotropic and anisotropic third-order nonlinear optical coefficients. The Z-scan techniquefor characterizing third-order nonlinear optical coefficients was also introducd. Under the weak focusing condition, the expressions for the focal field of three types of vectorial light fields were provided, i.e., radially polarized beams, hybridly polarized beams, and lemon-type Poincaré beams. Secondly, the isotropic and/or anisotropic third-order nonlinear optical effects excited by a variety of vectorial light fields was revisited, includinganisotropic nonlinear optical effects induced by radially polarized beams, isotropic and anisotropic Kerr nonlinearities excited by hybridly polarized beams, isotropic and anisotropic nonlinear optical effects induced by lemon-type Poincaré beams. Lastly, the prospects of their applications of vectorial light fields in nonlinear polarizationrotation, beam shaping, controllable field collapsing filaments, and optical limiting were briefly discussed.
Recent progress in nonlinear optics of 2D organic-inorganic hybrid perovskites (Invited
Zheng Yunhao, Han Xiao, Xu Jialiang
2020, 49(12): 20201063.   doi: 10.3788/IRLA20201063
[Abstract](20) [FullText HTML](9) [PDF 2331KB](4)
Since the advent of perovskite materials, the numerous organic-inorganic hybrid perovskites have thrived vigorously over the decades. Two-dimensional (2D) organic-inorganic hybrid perovskites containing prototypical inorganic octahedron frames and diverse organic cations feature characteristics of intrinsic quantum-well structures and intriguing optoelectronic properties, and have therefore attracted research attention intensively for their optical applications in light emitting, sensing, modulation, photovoltaic cells and telecommunication devices. The low-cost and solution-processed fabrications as well as the alternative organic spacer cations endue 2D hybrid perovskites with flexible layer distances, number of layers, and variable lattice distortion, leading to effectuate the adjustable frameworks as well as higher tunability in optical and photonic applications. In particular, they also demonstrate distinguished and appealing nonlinear optical (NLO) characters whether in the second-order, third-order NLOs or the higher-order NLOs such as second-harmonic generation (SHG), terahertz generation, two-photon absorption (2PA), and saturable absorption (SA), three-photon absorption (3PA), etc., under the excitation of laser pulses. Here, we discuss on the construction of the various 2D hybrid perovskites with different structural features. Furthermore, some representative properties and applications of these 2D hybrid perovskites are discussed in both linear and nonlinear optical regimes. Lastly, the status quo and challenge of 2D hybrid perovskites are elevated, and the future developments of 2D hybrid perovskites is prospected.
Application of continuous wave and pulsed lasers in triplet−triplet annihilation upconversion (Invited)
Cao Huaiman, Hou Yuqi, Zhao Jianzhang
2020, 49(12): 20201068.   doi: 10.3788/IRLA20201068
[Abstract](8) [FullText HTML](3) [PDF 1443KB](0)
The triplet−triplet annihilation upconversion is a new technology for photonic upconversion, which has the advantages such as continuous wave excitation, tunable upconversion wavelength and high upconversion quantum yields. In this upconversion process, as the energy donor, photosensitizer absorbs the light excitation, and intersystem crossing occurs, then sensitizes the energy acceptor through the triplet−triplet energy transfer process. Finally, the triplet−triplet annihilation of the energy acceptor in the triplet state generates a single excited state which can produce high−efficiency fluorescence (i.e. upconversion luminescence), thus the low−energy light is converted into higher−energy upconversion luminescence, which provides a feasible method for improving the photoelectric conversion efficiency of solar cells or the efficiency of photocatalysis, etc. It is desired to select appropriate lasers to excite the photosensitizer/energy donor system to study the steady upconversion luminescence and the upconversion kinetics. For instance, continuous wave diode pumped solid state laser (DPSSL) was selected as the light source to excite photosensitizer/acceptor system, upconversion luminescence was observed, and the effect of laser power density on upconversion luminescence can be studied conveniently. Additionally, in order to analyze the kinetic process of upconversion luminescence, with optical parametric oscillator (OPO) tunable pulsed laser as the light source, the lifetime of the triplet state, the kinetic characteristics of intermolecular energy transfer and triplet annihilation of photosensitizers can be studied. The application of continuous wave and pulse lasers in triplet–triplet annihilation upconversion experiments was introduced.
Control of the wettability of graphene oxide surface with femtosecond laser irradiation (Invited)
Wang Feiyue, Zou Tingting, Xin Wei, Yang Jianjun
2020, 49(12): 20201064.   doi: 10.3788/IRLA20201064
[Abstract](6) [FullText HTML](4) [PDF 1459KB](0)
Modification of material surface morphology and properties based on femtosecond laser irradiation is a novel processing technology developed in recent years, which has shown unique advantages in high-speed, large-area and periodic subwavelength structure fabrications. Here this method was employed to rapidly fabricate uniform subwavelength grating structures on the surface of GO film, and then the processing mechanisms, the change of morphology and liquid wettability were investigated comprehensively. Through using different experimental parameters such as the laser power and the scanning speed, the rGO grating structures with variable depth-width ratios and surface "roughness" were obtained, leading to the controllable wettability with the liquid contact angles in a range of 15° to 75°, and their contact angles were found to increase by an average of 20° after 20 days in the air. Our work lays a solid foundation for femtosecond laser micro/nano-processing of two-dimensional materials. It is expected to have the future applications in the field of droplet collection, microfluidic control, and so on.
Single mode-no core-single mode fiber based surface plasmon resonance sensor (Invited)
Chen Yuzhi, Li Xuejin
2020, 49(12): 20201055.   doi: 10.3788/IRLA20201055
[Abstract](8) [FullText HTML](7) [PDF 1158KB](0)
Optical fiber surface plasmon resonance (SPR) sensor combines the advantages of optical fiber sensor like miniaturization, online transmission, easy operation and SPR biodetection technology, which is highly sensitive, highly selective and label-free. It is currently a research hotspot of immunological biosensors. However, the signal of traditional multi-mode fiber based SPR sensor is easy to be lost and distorted in long-distance transmission. In this paper, a single mode-no core-single mode fiber based SPR sensor was proposed, which could effectively reduce the loss and distortion in signal transmission, and was suitable for connecting with the current optical fiber network. In order to eliminate the interference signal in the sensor, the core diameter of the no core fiber was changed, the methods of removing background interference and Gaussian fitting were adopted, and finally the sensor with the sensing region of 61.5 μm no core fiber was selected, the effective SPR spectrum signal was extracted from it. The sensitivity of proposed sensor is 1153.40 nm/RIU and the resolution is 1.70×10−4 RIU. The successful development of this kind of optical fiber biosensor provides a new idea for intelligent medical treatment and telemedicine.
Nonlinear absorption and optical limiting of platinum(Ⅱ) terpyridine complexes (Invited)
Sun Wenfang
2020, 49(12): 20201078.   doi: 10.3788/IRLA20201078
[Abstract](4) [FullText HTML](2) [PDF 1918KB](0)
The reported work in 2003-2019 on the reverse saturable absorption (RSA) or two-photon absorption (TPA) and/or optical limiting (OPL) of platinum(II) terpyridine complexes was summarized in this minireview. Photophysical properties, including the ground-state absorption (GSA), excited-state absorption (ESA), excited-state lifetimes, and the quantum yields of triplet excited-state formation, RSA/OPL at 532 nm for ns laser pulses, TPA characteristics in the near-IR spectral regions, and the structure-property correlations were reviewed. This paper is composed of four sections. First, the current status of OPL materials and devices, the general requirements for reverse saturable absorbers and two-photon absorbing materials, and the different types and characteristics of square-planar platinum(II) complexes were briefly introduced. Then the photophysics and RSA/OPL of six series of Pt(Ⅱ) terpyridine-analogous complexes and the structure-property correlations were discussed. Following it the TPA of five series of Pt(Ⅱ) terpyridine complexes and the impacts of structural variations on the TPA cross sections (σ2) were reviewed. Finally, brief conclusions were drawn based on the reported studies. A general trend discovered was that the charge transfer absorption band(s) and the ESA can be readily tuned by substituents on the acetylide or the terpyridine ligand. Introducing electron-donating substituent to the acetylide or terpyridine ligand or improving the coplanarity between the aromatic substituent and the terpyridine ligand red-shifted the ground-state charge-transfer absorption band(s) at the price of decreasing/quenching the triplet ESA, which consequently reduced the RSA/OPL at 532 nm. Extending the π-conjugation of the terpyridine ligand dramatically improved the σ2 values of the Pt(Ⅱ) terpyridine complexes. Incorporation of electron-withdrawing π-conjugated aromatic substituent restrained the GSA to < 500 nm while keeping a long-lived triplet excited state with broadband ESA in the visible spectral regions and moderately strong TPA in the NIR regions. This approach could provide a solution for developing broadband OPL materials.
Coupling efficiency of non-uniformly correlated beams into a single-mode fiber in turbulence (Invited)
Lin Shuqin, Zhang Jiqian, Zhu Xinlei, Wang Fei, Cai Yangjian, Yu Jiayi
2020, 49(12): 20201049.   doi: 10.3788/IRLA20201049
[Abstract](5) [FullText HTML](2) [PDF 1270KB](0)
The coupling efficiency of non-uniformly correlated beams through atmospheric turbulence was studied. The results show that the fiber coupling efficiency of such beams is higher than that of the traditional Gaussian Schell-model beam; and the regulation of the coherence length of such beams can improve the fiber coupling efficiency; for different transmission distances, the optimization of the coupling efficiency can be achieved by adjusting the coherence length of such beams. Moreover, the effect of the light source parameters: beam waist and wavelength; coupling lens parameters: received aperture and focal length; turbulence intensity on the coupling efficiency of optical fiber was also discussed. The results show that the application of optical field correlation structure manipulation technology in improving the coupling efficiency of optical fiber has important value in the field of free space optical communication.
Terahertz flexible stretchable metasurface based on double resonance response (Invited
Wang Jing, Tian Hao
2020, 49(12): 20201059.   doi: 10.3788/IRLA20201059
[Abstract](7) [FullText HTML](3) [PDF 1268KB](0)
Active control of terahertz wave characteristics in stretchable devices is essential for advanced terahertz applications involving large mechanical deformation or stretching. Here, a dual band terahertz active control device based on different mechanisms was designed and fabricated by combining metal metasurface with elastic film polydimethylsiloxane. Based on the deformation mismatch between metal and elastic film under tension, the double band modulation effect was realized by using the periodically sensitive cross structure metasurface. Under 36% deformation, the dipole mode and the lattice resonance mode were exploited to experimentally achieve dual-band modulation with a modulation depth of 90% and a modulation depth of 78% at 1.26 THz and 2.41 THz, respectively. The operating frequency through the lattice mode had a large dynamic range, which could be tuned from 2.41 THz to 1.85 THz. Since the mechanisms of the electric dipole resonance mode and the periodic lattice resonance mode were independent from each other, the two resonance frequencies were designed independently, which allowed the frequency interval of the dual-band modulation to be geometrically adjustable. The stretchable metasurface presented in this paper is simple to prepare, and has the advantages of large intensity modulation depth and wide frequency tuning range. It can be used not only in active control of terahertz wave, but also in passive displacement sensing.
Preparation and optical nonlinearity of PMMA living radical polymerization materials functionalized with indium chloride porphyrin (Invited)
Xu Chaoyue, Ma Pengfei, Liu Dajun
2020, 49(12): 20200398.   doi: 10.3788/IRLA20200398
[Abstract](0) [FullText HTML](1) [PDF 1621KB](0)
5,10,15-triphenyl-20-(4-hydroxyphenyl) chloroporphyrin indium was synthesized. Using 2-chloropropionyl chloride end-capped mono-hydroxy metalloporphyin as initiator, methyl methacrylate as monomer and CuCl/PMDETA as the catalyst system, a new linear polymethylmethacrylate (PMMA) with asymmetric indium porphyrin end functionalized was synthesized by atom transfer radical polymerization (ATRP) method. The structure of porphyrin compounds was characterized by Fourier transform infrared spectroscopy (FT-IR), ultraviolet-visible spectroscopy (UV-vis) and nuclear magnetic resonance hydrogen spectrum (1H NMR) techniques.Molecular weight and molecular weight distribution of the linear polymers were obtained by gel permeation chromatography (GPC). It indicated that the molecular weight distribution was narrow and the molecular weight distribution range was between 1.11 and 1.21. Meanwhile, the polymerization reaction had a good controllability.By Z-scan method, the third-order nonlinear optical properties of porphyrin compounds were tested using a frequency-doubled mode locked Nd: YAG picosecond laser system at wavelength of 532 nm with 21 ps pulse, the results showed that the third-order nonlinear polarizability (χ(3)) of polymer with polymerization degree of 16 and molecular weight of 2414 is 1.144 × 10−12 esu.
Laser Material & Optoelectronic Devices
Advanced Laser Technology
Research progress of high-power diamond laser technology (Invited)
Bai Zhenxu, Yang Xuezong, Chen Hui, Jin Duo, Ding Jie, Qi Yaoyao, Li Sensen, Yan Xiusheng, Wang Yulei, Lv Zhiwei
2020, 49(12): 20201076.   doi: 10.3788/IRLA20201076
[Abstract](16) [FullText HTML](9) [PDF 2102KB](4)
With the highest thermal conductivity, low thermal expansion coefficient, high chemical inertness, and excellent optical properties among known materials, diamond can meet the application requirements of many extreme conditions in the fields of mechanics, optics, and materials, etc. In recent years, with the improvement of the chemical vapor deposition preparation technology, the optical quality of synthetic diamond has been rapidly improved, which leads to the optical grade diamond crystals excellent power improvement, coherence enhancement, and frequency conversion ability due to their excellent Raman and Brillouin characteristics. Meanwhile, diamond lasers overcome the thermal effect in the particle number inversion laser based on the traditional gain media, and the difficulty to consider both the wavelength and power. The research progress of high-power diamond laser technology was summarized, and the development trend and application of diamond lasers were prospected.
Advances in the technology of 850 nm high-speed vertical cavity surface emitting lasers (Invited)
Tong Haixia, Tong Cunzhu, Wang Ziye, Lu Huanyu, Wang Lijie, Tian Sicong, Wang Lijun
2020, 49(12): 20201077.   doi: 10.3788/IRLA20201077
[Abstract](8) [FullText HTML](3) [PDF 1327KB](2)
Vertical-cavity surface-emitting lasers (VCSELs) have important applications in the short-distance optical interconnection attributed to their advantages, such as low cost, low threshold current, high modulation bandwidth and low power consumption. With the development of big-data and supercomputer technology, the performance demand of short-distance optical interconnection is increasing quickly, which also proposes a challenge for high-speed 850 nm VCSEL. In this paper, the latest development of high-speed 850 nm VCSEL technology was reviewed from the aspects of bandwidth-limited factors and new modulation methods, and the growing trend of this technology is prospected and summarized.
Review of random laser research (Invited)
Du Wenyu, Hu Zhijia, Cao Zhigang, Zhang Guosheng, Wang Yan, Luo Weidong, Yu Benli
2020, 49(12): 20201052.   doi: 10.3788/IRLA20201052
[Abstract](8) [FullText HTML](6) [PDF 2010KB](2)
Due to its unique structure and low coherence, random lasers are widely used in fields such as speckle-free imaging, sensing, and light therapy. The feedback mechanism of random lasers is light scattering introduced by disordered media. High threshold and non-directionality are its main disadvantages. In order to solve these problems, researchers used the one-dimensional confinement of optical fibers to obtain random fiber lasers with a low threshold and a certain directionality. In the past ten years, the development of random lasers has experienced a process from incoherent feedback to coherent feedback, from complete disorder to controllable output parameters. A large number of studies have tried to explain the physical nature of random lasers using quantum theory, chaotic laser theory, and numerical analysis. The origin and development history of random lasers and random fiber lasers were reviewed, the classification and related principles of random lasers were introduced, the methods of controlling random laser output parameters were summarized, the recent typical applications of random lasers were demonstrated, fiber random lasers feedback types and gain mechanisms were analyzed, and finally the future of random lasers development was prospected.
LD-pumped high-repetition-rate all-solid-state femtosecond lasers (Invited)
Zheng Li, Wang Huibo, Tian Wenlong, Zhang Dacheng, Han Hainian, Zhu Jiangfeng, Wei Zhiyi
2020, 49(12): 20201069.   doi: 10.3788/IRLA20201069
[Abstract](16) [FullText HTML](4) [PDF 1611KB](2)
Compared with traditional ~100 MHz femtosecond lasers, the mode spacing is larger of GHz femtosecond lasers so that each comb can simply be resolved. Furthermore, the less dense of longitudinal modes results in higher average power. Therefore, it has more important application value in many research fields, such as comb-resolvabled spectroscopy, direct optical frequency comb spectroscopy, optical arbitrary waveform generation and astronomical spectrograph calibration. In this review, the generation schemes of GHz femtosecond pulses and the corresponding technical challenges of GHz-repetition-rate all-solid-state femtosecond lasers pumped by laser diode were introduced in detail firsly. Secondly, the international research progresses of all-solid-state GHz femtosecond lasers based on SESAM passively mode-locking and Kerr-lens mode-locking were summarized. Finally, the application value and research object of our group in all-solid-state GHz-repetition-rate femtosecond lasers were forcasted based on our preliminary research results.
Progress in photonic integrated chaotic semiconductor laser (Invited)
Chai Mengmeng, Qiao Lijun, Zhang Mingjiang, Wei Xiaojing, Yang Qiang, Xu Hongchun
2020, 49(12): 20201066.   doi: 10.3788/IRLA20201066
[Abstract](8) [FullText HTML](3) [PDF 1915KB](0)
Chaotic laser has been widely applied in the fields of secure optical communication, random number generation, chaotic lidar, chaotic optical time domain reflector and distributed optical fiber sensing due to its characteristics of wide-spectrum, noise-like, low-coherence and so on. Photonic integrated chaotic semiconductor laser is a kind of chaotic laser which is small in size, stable and low-cost. The progress of photonic integrated chaotic semiconductor laser and its main applications in recent ten years were reviewed. Firstly, the photonic integrated methods of chaotic semiconductor laser were introduced. Then, the classification of photonic integrated chaotic semiconductor lasers was demonstrated. According to the perturbation mode, the external cavity structures including straight cavity, multiple-cavity, ring cavity, two-dimensional cavity and mutual injection were discussed. The advantages and characteristics of these devices were compared. Furthermore, the applications of photonic integrated chaotic semiconductor lasers in optical time domain reflectometer, secure optical communication and random number generation were introduced. Finally, the key integration techniques, time delay signature and intermittent chaos in photonic integrated chaotic laser were discussed.
Research of beam smoothing technology in high power laser driver (Invited)
Gao Yanqi, Li Fujian, Ji Lailin, Zhao Xiaohui, Xia Lan, Feng Wei, Liu Dong, Shi Haitao, Liu Jiani, Rao Daxing, Cui Yong, Ma Weixin, Sui Zhan
2020, 49(12): 20201074.   doi: 10.3788/IRLA20201074
[Abstract](6) [FullText HTML](2) [PDF 1645KB](1)
In the process of laser driven inertial confinement fusion, the inhomogeneity of light field with different spatial frequencies will cause the hydrodynamic instability, imprinting and laser plasma instability in implosion. These instabilities will eventually affect the compression ratio of implosion, thus affecting the ignition. In order to control the focal spot nonuniformity and suppress instabilities, beam smoothing technology was proposed to control the beam target coupling process through light field control. Beam smoothing can be divided into spatial smoothing and temporal smoothing. Spatial smoothing can reduce the low-frequency inhomogeneity by controlling the wavefront shape. Temporal smoothing reduces the speckle in the focal spot by controlling the coherence of the laser beam, and then reduces the medium and high frequency inhomogeneity. With the increasing demand for laser-plasmas instability suppression at higher laser power density, some new beam smoothing methods have emerged. The application of beam smoothing technology in large laser facilities was introduced, and the currently proposed beam smoothing technologies were summarized and analyzed.
Ultra-low timing jitter femtosecond laser technology (Invited)
Pi Yihan, Wang Chunze, Song Youjian, Hu Minglie
2020, 49(12): 20201058.   doi: 10.3788/IRLA20201058
[Abstract](8) [FullText HTML](5) [PDF 1415KB](0)
The time jitter of a femtosecond laser is the short-term deviation of the optical pulse position relative to its ideal equally spaced pulse position. Femtosecond lasers emit uniformly spaced ultrashort pulse train. The quantum-noise-limited timing jitter can be as low as few tens of attoseconds in millisecond time scale. This unique property and its advanced applications constitute a new branch of ultrafast research, "Attosecond precision ultrafast photonics". In this paper, the recent advances in femtosecond laser timing jitter research, high-precision timing jitter characterization methods, and the ultralow timing jitter that can be achieved by different kinds of femtosecond laser sources were reviewed. Finally, the application of low-jitter femtosecond lasers in the fields of synchronization of large-scale scientific instruments, high-speed analog-to-digital conversion, absolute ranging technology and coherent beam combination are introduced.
Recent development of low noise laser for precision measurement (Invited)
Wang Yajun, Gao Li, Zhang Xiaoli, Zheng Yaohui
2020, 49(12): 20201073.   doi: 10.3788/IRLA20201073
[Abstract](11) [FullText HTML](4) [PDF 1676KB](4)
The measurement accuracy of laser precision measurement is mainly limited by optical field noise and various technical noises. After the de-coupling technical noises, quantum noise becomes the main factor limiting the measurement accuracy. Based on the intensity noise characteristics of solid-state single-frequency lasers, the main sources of intensity noise and their influence on the power noise spectrum were described, and three kinds of intensity noise suppression techniques, including traditional DC feedback control, optical AC coupled feedback control and quantum squeezer, were reviewed in this paper. By reviewing the development history of relevant technologies, the current development level and future development trend of intensity noise suppression technology were summarized-the noise suppression scheme combining three technologies is an important approach to solve high sensitivity detection.
Chirped-pulse optical parametric oscillators and the generation of broadband midinfrared laser sources (Invited)
Liu Pei, Heng Jiaxing, Zhang Zhaowei
2020, 49(12): 20201051.   doi: 10.3788/IRLA20201051
[Abstract](10) [FullText HTML](5) [PDF 1895KB](1)
Mid-infrared laser sources with broad instantaneous-bandwidth are critical for many applications, including infrared micro-spectroscopy, environmental monitoring, medical diagnosis, and ultra-short pulse generation. In this article, the output spectrum bandwidth from synchronously pumped optical parametric oscillator (SPOPO) was focused on and a scheme, chirped-pulse optical parametric oscillator (CPOPO) was proposed to achieve broadband output beyond the limitation of pump pulse width. The CPOPO with self-phase modulation (SPM) or chirped quasi-phase matching (CQPM) were studied and achieved through period-poled lithium niobate (PPLN) based SPOPO. The outputs covered 2.9-3.9 μm (~27 THz) with power up to 92 mW and 2.9-5.0 μm (~44 THz) with 64 mw, respectively.
Research progress of 2 µm Ho single-doped solid laser and application of ZnGeP2 on middle-long-wave infrared (Invited)
Liu Gaoyou, Wei Disheng, Chen Yi, Yang Ke, Mi Shuyi, Li Junhui, Yang Chao, Wang Ruixue, Duan Xiaoming, Dai Tongyu, Yao Baoquan, Ju Youlun, Wang Yuezhu
2020, 49(12): 20201056.   doi: 10.3788/IRLA20201056
[Abstract](8) [FullText HTML](5) [PDF 1274KB](3)
2 µm, 3-5 µm and 8-12 µm infrared lasers are located in the atmospheric transmission window, which have broad applications in laser medicine, laser imaging, environmental monitoring, lidar, chemical remote sensing and infrared countermeasure. Based on the optical nonlinear frequency conversion technology and nonlinear optical crystals, it has obvious advantages in achieving middle-long-wave infrared solid lasers, such as compact and simple structure, wide tunable wavelength range and high output power. Using ZnGeP2 crystal with 2 µm Ho single-doped solid laser as pump especially has an outstanding performance in middle-long-wave infrared field. In the aspect of average output power, it has reached the level of 102 W@3-5 µm, 12.6 W@8.2 µm and 3.5 W@9.8 µm. Moreover, they all have a beam quality factor M2 less than 3 and the corresponding optical-to-optical conversion efficiency of 3-5 µm is about 60%. This paper reviewed the research progress of 2 µm Ho single-doped solid laser and application of ZnGeP2 on middle-long-wave infrared in detail.
Research progress on direct generation of ultrashort pulse OAM vortex beams (Invited)
Wang Sha, Zhang Zhicheng, Deng Guoliang, Zhou Shouhuan
2020, 49(12): 20201061.   doi: 10.3788/IRLA20201061
[Abstract](8) [FullText HTML](3) [PDF 1621KB](0)
Orbital angular momentum (OAM) vortex beam has a phase singularity with a twisted wave-front, whose complex amplitude comprises the helical term exp (ilθ). OAM vortex beam has been widely used in optical manipulation, imaging, optical communication, sensing and so on. Ultra-short pulse OAM vortex beams have the advantages of both vortex beams and ultra-short pulses, and can be applied to chiral material processing, long distance transmission, strong field physics and nonlinear frequency conversion. Direct generation of ultra-short OAM vortex beams has the advantages of compact and simple system and good beam quality. The research progress on direct generation of ultra-short OAM vortex beams was summarized. At present, the pulse width of the ultra-short OAM vortex beam generated by the active method is still limited to a few hundred femtoseconds. How to obtain the pulsed vortex beam output within 100 femtoseconds or even with a few cycles through the direct output method will be an important future development direction.
Research progress on the high power flowing-gas circulation diode-pumped alkali vapor laser (Invited)
Ji Yanhui, He Yang, Wan Haohua, Sun Junjie, Chen Fei
2020, 49(12): 20201080.   doi: 10.3788/IRLA20201080
[Abstract](7) [FullText HTML](4) [PDF 1564KB](3)
Diode pumped alkali metal vapor laser (DPAL) combines the technical characteristics of both diode laser and gas laser, with the advantages of high quantum efficiency, large excited emission cross section, small refractive index perturbation, convenient thermal management and rich output wavelength, which can achieve high efficiency, high power and high beam quality near infrared laser output, and has important applications in industrial manufacturing, military, medical and scientific research fields. For closed static DPAL, under the condition of high power pump, the working gas temperature in the steam pool increases, and the thermal effect is serious, resulting in the decline of DPAL performance. The circulating flow DPAL uses gas flow to take away waste heat, which can significantly alleviate the thermal effect of working gas, so as to achieve high-power laser output. At present, it has become the mainstream technical route to achieve high power laser output. In this paper, the principles and current development of the flowing-gas circulation DPAL are outlined, the obstacles and solutions of high power scaling of DPAL are analysed, and prospects for the future development of high-power alkali metal lasers.
Research progress of 2-4 μm mid-infrared antimonide semiconductor lasers (Invited)
Yang Chengao, Zhang Yi, Shang Jinming, Chen Yihang, Wang Tianfang, Tong Haibao, Ren Zhengwei, Zhang Yu, Xu Yingqiang, Niu Zhichuan
2020, 49(12): 20201075.   doi: 10.3788/IRLA20201075
[Abstract](7) [FullText HTML](2) [PDF 2368KB](0)
The 2-4 μm band is a very important infrared atmospheric window. Lasers operating in this band have a wide range of applications in gas detection, medical application and industrial processing. The low-dimensional structure of antiminide semiconductor materials has the unique advantage of narrow forbidden band, direct transition luminescence, and is an ideal material system for realizing mid-infrared semiconductor lasers. In recent years, research on antimonide semiconductor lasers at home and abroad has made important progress, achieving wavelength expansion of quantum well luminescence, room temperature continuous lasing of high-power single chip and laser bars, and continuous room temperature continuous operation of multi-band single-mode lasers. Due to the complex composition of the low-dimensional materials of the antimonide and the special interface passivation properties, the epitaxial materials and process preparation techniques are difficult. Based on the basic principle of antimonide semiconductor lasers, this paper reviewed the research status at home and abroad, introduced the design scheme of the low-dimensional structure lasers antimonide materials, and the main progress of key preparation techniques, and analyzed the performance optimization, focused on research and development direction of such lasers in the future.
Research progress and prospect of spectral beam combining (Invited)
Jiang Man, Ma Pengfei, Su Rongtao, Li Can, Wu Jian, Ma Yanxing, Zhou Pu
2020, 49(12): 20201053.   doi: 10.3788/IRLA20201053
[Abstract](10) [FullText HTML](5) [PDF 2163KB](4)
Spectral beam combining (SBC) uses dispersive elements or dichroic elements to make multi-channel lasers of different wavelengths overlap in the near-field and far-field at the same time, so as to combine the laser beam with single aperture output. It is one of the technical approaches to achieve high power and high beam quality laser output, which has attracted great attention of researchers. Especially in the past decade, with the continuous improvement of the performance of grating and other combining components, the spectral beam combining laser output with high power and high beam quality has played an important role in industry, national defense and other fields, and has a wide application prospect. The research progress of SBC was reviewed for the two typical laser working medias of semiconductor laser and fiber laser. The current mainstream scheme and research status of high power SBC at home and abroad were summarized. In addition, combined with our research works on SBC, the development trend of SBC in recent years were shown, and the future development prospect of SBC technology was forecasted.
2.86 μm lasing in Ho3+/Pr3+ codoped fluoroaluminate glass fiber (Invited)
Zhang Jiquan, Liu Mo, Xu Niannian, Jia Shijie, Wang Shunbin, Wang Pengfei
2020, 49(12): 20201062.   doi: 10.3788/IRLA20201062
[Abstract](6) [FullText HTML](3) [PDF 1356KB](0)
Fluoroaluminate, fluoroindate and fluorozirconate glass samples were prepared by using melt-quenching method, their abilities of resistance to deliquescence were studied by water treatment experiment, proving that the fluoroaluminate glass had better stability than the others. Thus Ho3+/Pr3+ codoped fluoroaluminate glasses with different concentrations were fabricated, the properties of spectral transmittance were measured, showing a high transmittance and wide transmission window. Under the pump of an 1150 nm Raman laser, the emission spectra were obtained for analyzing the emitting mechanism. 2 Ho3+/0.2 Pr3+ codoped fluoroaluminate glass preform were fabricated by suction method and fiber by rod-in-tube method. Using the cutback method, the loss of the fiber at 793 nm was 1.8 dB/m. By using the 1150 nm Raman laser as pump source, a 2.865 μm lasing with output power as high as 207 mW were detected in an 8.6 cm-long fluoroaluminate glass fiber, its slope efficiency was 11.4%. The above research results show that fluoroaluminate glass fiber is a gain medium material that can be used to develop stable mid-infrared fiber lasers.
Repetition frequency variation of a 2 μm GaSb-based passively mode-locked laser (Invited
Li Xiang, Wang Hong, Qiao Zhongliang, Zhang Yu, Niu Zhichuan, Tong Cunzhu, Liu Chongyang
2020, 49(12): 20201054.   doi: 10.3788/IRLA20201054
[Abstract](6) [FullText HTML](3) [PDF 1470KB](0)
Multi-gigahertz optical pulse trains generated from mode-locked semiconductor lasers are promising for a number of applications in many areas. For most of these applications, a fixed and stable pulse repetition frequency is necessary. Since the repetition frequency of such lasers is primarily determined by the effective refractive index of the laser waveguide and the laser cavity length, uncertainties during device fabrication as well as cleaving process may bring deviations to the repetition frequency. To gain better knowledge of how working conditions of such lasers effect their repetition frequency and thus compensate the above-mentioned deviations, a novel 2 µm InGaSb/AlGaAsSb single quantum well (SQW) mode-locked laser (MLL) was presented in this work. It has a two-section configuration (gain section and saturable absorber section separated by an electrical isolation region) and stable mode locking was achieved in this laser under a variety of bias conditions up to 60 ℃. Repetition frequency variations of this mode-locked laser with bias condition (gain section current Ig, absorber section voltage Va) and working temperature (T) were systematically recorded, and the mechanisms behind these variations were analyzed. It is believed that this work enables us to have a better understanding of passively mode-locked semiconductor lasers and is of interest to better meet the application-required frequencies.
320 nm ultraviolet laser in blue laser diode double end pumped Pr:YLF crystal (Invited)
Li Xinqi, Qu Dapeng, Chen Qing, Liu Tianhong, Zheng Quan
2020, 49(12): 20201070.   doi: 10.3788/IRLA20201070
[Abstract](11) [FullText HTML](4) [PDF 1094KB](2)
A 320 nm ultraviolet laser with Pr:YLF crystal was pumped by different wavelength blue laser diode was designed and double end pumping mode was adopted. The structure of the laser is V-folded cavity. A 444 nm blue laser diode with pump power of 3 W and a 469 nm blue laser diode with pump power of 1.4 W was used as pump source. The Pr:YLF crystal has a length of 12 mm and a doping concentration of 0.3%. The phase-matched LBO crystal was used as frequency doubling crystal. By optimizing the resonator parameters, when the incident pump power is 5700 mW, the maximum output power of 320 nm ultraviolet continuous laser with 1005 mW is output, and the optical conversion efficiency is about 17.6%.
Laser Material & Optoelectronic Devices
Rare earth ions doped optical functional glass and application (Invited)
He Dongbing, Hu Lili, Chen Shubin, Tang Jingping, Wang Biao, Zhang Liyan, Wang Xin
2020, 49(12): 20201081.   doi: 10.3788/IRLA20201081
[Abstract](11) [FullText HTML](3) [PDF 1080KB](0)
The luminescence and laser properties of rare earth are produced by the transition of 4f electrons between different energy levels. Due to its special properties, rare earth ions doped optical-functional glass have played important roles in high power laser system, whether as active or passive components. Nd3+, Er3+ doped phosphate laser glass, which have high rare earth ion doping concentration, preparation characteristics with large size and high uniformity, can be used in high energy laser as an important gain medium material; Volume Bragg grating based on Ce3+-doped Photo-Thermo-Refractive glass, is a multifunctional optical components in high power laser system, owing to its excellent wavelength and angular selectivity, high diffraction efficiency, high thermal stability and high damage threshold. In this paper the latest progress of Nd3+, Er3+ doped phosphate laser glass and Volume Bragg grating base on Ce3+-doped Photo-Thermo-Refractive glass were reported.
Surface enhanced nonlinear absorption of chalcogenide Ge28Sb12Se60 film (Invited)
Liu Yichao, Zhou Yao, Zhao Jianxing, Zhou Jianhong, Song Yinglin
2020, 49(12): 20201071.   doi: 10.3788/IRLA20201071
[Abstract](10) [FullText HTML](3) [PDF 1197KB](0)
A nano-structure that supported the localized surface plasmon (LSP) was fabricated by using thermal evaporation and annealing processes to enhance the nonlinear absorption of chalcogenide Ge28Sb12Se60 (GSS). The Z-scan experiment was carried out to measure the nonlinear refractive and nonlinear absorption of the fabricated samples. By analyzing the characteristics of the transmission spectra of the samples, the mechanism of the nonlinear absorption enhancement was revealed. Finally, the influence of the GSS thickness on the enhancement nonlinear absorption was studied. The proposed LSP nano-structure is easy in fabrication due to the lithography-free process, which provides significant reference for designing nonlinearty enhancement devices.
Growth, structure, and spectroscopic properties of Yb,Ho,Pr:GYTO single crystal (Invited
He Yi, Dou Renqin, Zhang Haotian, Liu Wenpeng, Zhang Qingli, Chen Yingying, Gao Yuxi, Luo Jianqiao
2020, 49(12): 20201067.   doi: 10.3788/IRLA20201067
[Abstract](5) [FullText HTML](2) [PDF 1318KB](0)
A new mid infrared laser material Yb,Ho,Pr:GYTO crystal was grown successfully using Czochralski method for the first time. The structural parameters were obtained by the X-ray Rietveld refinement method. The X-ray rocking curves of the (100), (010), and (001) diffraction face of Yb,Ho,Pr:GYTO crystal were measured. The full widths at half maximum of those diffraction peaks are 0.036°, 0.013°, and 0.077°, respectively, which indicates a high crystalline quality of the as-grown crystal. Laser Ablation Inductively-Coupled Plasma Mass Spectrometry was used to measure the concentrations of Yb3+, Ho3+, Pr3+, and Y3+ ions in the Yb,Ho,Pr:GdYTaO4 crystal. The effective segregation coefficients of Yb3+, Ho3+, Pr3+, and Y3+ in Yb,Ho,Pr:GYTO crystal are 0.624, 1.220, 1.350, and 0.977, respectively. The room-temperature polarhosized absorption spectra of Yb,Ho,Pr:GdYTaO4 was measured and the corresponding absorption transitions were assigned. The 2.9 μm fluorescence spectrum excited by 940 nm LD presents that the strongest emission is located at 2908 nm. In addition, the Yb-Ho-Pr energy transfer mechanism in GYTO was also demonstrated. Compared with Ho:GYTO crystal, the lifetime of 5I7 level of Yb,Ho,Pr:GYTO crystal is reduced by 87.13%, which is close to that of the upper level 5I6, indicating that Yb,Ho,Pr:GYTO crystal is easier to realize population inversion and laser output.
Review of magneto-optic materials for high power laser isolators (Invited
Chen Jie, Zhou Shengming
2020, 49(12): 20201072.   doi: 10.3788/IRLA20201072
[Abstract](5) [FullText HTML](3) [PDF 1742KB](0)
As the key component of optical isolators, magneto-optic(MO) materials play an important role especially in high power laser system to ensure one-way light propagation, protect the laser sources and stabilize the laser output. The recent research progress of the MO materials used in near-infrared high power optical isolators was introduced. The key thermal-optic characteristics of MO materials under high power laser conditions and their effects on device performance were illustrated in detail. The studies and high power performance of several newly developed MO material candidates like TSAG crystal, TAG ceramic, and TGG ceramic were reviewed and compared with the commonly used TGG single crystal and Tb-doped glasses on aspects of Verdet constant, thermal conductivity, magneto-optic figure of merit and so on. Among them, TAG ceramics were discussed emphatically including the effects of ions doping and synthesis technology on its magneto-optic and thermal-optic properties. At last, the newest progress on the study of TAG ceramics was introduced, as well as the application prospect and research trend of MO materials used in the 3-5 μm mid-infrared region.
Spectrum cleaning and stability improvement of femtosecond optical parametric oscillator (Invited)
Tong Hui, Qin Zhipeng, Xie Guoqiang, Qian Liejia
2020, 49(12): 20201060.   doi: 10.3788/IRLA20201060
[Abstract](11) [FullText HTML](5) [PDF 1100KB](2)
A method for spectrum cleaning and stability improvement of femtosecond optical parametric oscillator (OPO) based on intracavity dispersion management was proposed and demonstrated for the first time. For high-power femtosecond OPO, the output pulses generally have irregular broadband spectrum varying with time, and the output power show a remarkable fluctuation. Through employing lithium niobate (LiNbO3) crystal to introduce additional negative dispersion in the cavity, transform-limited femtosecond pulses with cleaning and smooth spectrum by temporal filtering effect of pump pulses were realized, and the spectrum stability and power stability of femtosecond OPO were greatly improved. This method is a simple and flexible way to realize the spectrum cleaning and stability improvement of femtosecond OPO, and is of significant value for the development of high power ultrashort-pulse OPO.
Study on end treatment process and laser performance of Yb doped PCF (Invited)
Feng Suya, Yu Chunlei, Wang Meng, Wang Shikai, Hu Lili
2020, 49(12): 20201065.   doi: 10.3788/IRLA20201065
[Abstract](7) [FullText HTML](3) [PDF 1283KB](0)
An efficient and fast processing technology of photonic crystal fiber (PCF) end face based on the homemade Ytterbium (Yb) doped large mode area (LMA) PCF was demonstrated. By using carbon dioxide laser splicer, the PCF was rotated and laser heated at the same time. The optimal heating power and time were determined by comparing the collapse effect of the fiber under different laser heating power and heating time. For examining the optical fiber treated, the fiber laser system was built. The experiment results indicate that the collapse of the end face does not have a great influence on the laser properties of the fiber when it is compared with laser experiments without end processing results. High quality PCF collapse face can be achieved by the experimental method described, the air holes collapsed boundary are neat and uniform, meanwhile the influence of the collapse treated on the laser properties of the optical fiber is not obvious. The experimental process is short and the success rate is high, which proves that it is an effective method to deal with the end face of PCF by laser heating collapse, greatly expands the use range of the PCF, and has very strong practical value.