Special issue—Single-frequency laser technology
2022, 51(6): 20220237.
doi: 10.3788/IRLA20220237
Single-frequency fiber laser has the merits of excellent monochromaticity and high spectral power density, and it has widespread application needs in, for example, coherent communication and sensing, lidar, gravitational wave detection and nonlinear frequency conversion. At present, single-frequency fiber laser technologies are moving towards the direction of higher output power, broader spectral range, and higher overall performance, and have become the research frontier and hotspot in the field of laser technology. This manuscript systematically combed through the important progress of single-frequency fiber lasers in recent years. Specifically, the landmark works with respect to the implementation mode of single-frequency lasing, power scaling, wavelength expanding and performance improvement were reviewed. In addition, the current challenges as well as future trends of single-frequency fiber laser technology were also discussed.
2022, 51(6): 20220400.
doi: 10.3788/IRLA20220400
An acoustic optical modulator (AOM) laser power feedback loop was used to suppress the intensity noise of the pump laser, and the intensity noise reduction of more than 5 dB (@f=1 Hz-50 kHz) was obtained. The relative intensity noise of the 2 μm single-frequency fiber laser obtained 3-15 dB suppression (@f=1 Hz-50 kHz), and the intensity noise level was close to the detector limit (@f=40-400 Hz). Meanwhile, its frequency noise is also suppressed by 3-8.4 dB. After the two-stage Thulium-doped polarization-preserving fiber amplifier, the output power of the 2 μm single-frequency laser was increased to about 5.2 W with almost no significant increase in frequency noise, and the frequency noise levels were all at 100 Hz/\begin{document}$\sqrt {{\rm{Hz}}} $\end{document} ![]()
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2022, 51(6): 20210970.
doi: 10.3788/IRLA20210970
Stimulated Raman scattering is a mature technology that provides laser outputs with flexible wavelengths. Stable single-longitudinal-mode (SLM) Stokes is able to be achieved in a simply designed oscillator due to the nature of spatial hole burning free of Raman gain. Therefore, the Raman laser is considered as an attractive and potential method to generate SLM output with a particular wavelength. As the single-crystal diamond synthetic technology matures, high-power continuous-wave SLM diamond Raman lasers have been widely investigated for the past few years. In this review, the mechanism of Raman SLM operation in Raman oscillator and the state art of the SLM diamond Raman lasers are summarized. At last, the future investigations of continuous-wave SLM diamond Raman lasers are proposed.
2022, 51(6): 20220133.
doi: 10.3788/IRLA20220133
Re:YAG-SiO2 multicomponent glass fiber is fabricated by a molten core method, in which a Re:YAG is used as the core material and a quartz tube is used as the cladding material. It has the advantages of high doping concentration, high mechanical strength, and is easy to fuse with quartz fiber. Recently, the single-frequency fiber laser has been studied extensively based on the Re:YAG-SiO2 fiber. In this paper, the development of the Re:YAG-SiO2 fiber fabrication and the single-frequency laser technology based on Re:YAG-SiO2 fiber in 1.0 μm, 1.5 μm and 2.0 μm were reviewed. The difficulties and challenges of Re:YAG-SiO2 fiber fabrication and single-frequency laser based on this type of fiber were also given.
2022, 51(6): 20220119.
doi: 10.3788/IRLA20220119
Tunable single-frequency fiber lasers (TSFFLs) possess the characteristics of wide tuning range, high optical signal-to-noise ratio (OSNR), narrow linewidth, low noise, and excellent compatibility. They also have attracted extensive attention from researchers at home and abroad because of their important application value in the spectroscopy, optical detection, optical sensing, fiber communication and so on. In this paper, the tuning and longitudinal-mode selection key techniques of TSFFLs were introduced briefly. The TSFFLs with different wavelengths of 1.0 μm, 1.5 μm, 2.0 μm, and mid-infrared were summarized and their research status at home and abroad was reviewed. The results obtained in tuning range, laser linewidth, OSNR, power scaling, flatness of output power, and other output performances were also shown. In addition, combined with our new progress, the recent development of TSFFLs based on compound cavity structure was introduced. Furthermore, the future development trend of TSFFLs was also forecasted.
2022, 51(6): 20220127.
doi: 10.3788/IRLA20220127
In recent years, high-power single-frequency (SF) erbium-doped fiber lasers with narrow linewidth and low noise have been intensively studied, driven by application requirements in the fields of coherent detection, lidar, laser cooling and gravitational wave detection. The research progresses of high-power SF erbium-doped fiber lasers were reviewed in this paper, including SF erbium-doped fiber lasers and high-power SF erbium-doped fiber amplifiers. The development trend and challenges of the high-power SF erbium-doped fiber lasers were analyzed, and the next development direction was prospected.
2022, 51(6): 20220300.
doi: 10.3788/IRLA20220300
The space-based gravitational wave detection frequency band is located in the range of 0.1 mHz-1 Hz, because the gravitational wave source information with larger characteristic quality and scale is contained in the aforementioned frequency band. At present, large-scale laser interferometer space-based gravitational wave detection projects based on different sizes and space orbits have been gradually implemented. It should be emphasized that the laser intensity noise and frequency noise should be suppressed in the laser source system of the interferometer. Moreover, as the first level device of laser noise characterization and suppression, the performance of photoelectric detection will directly affect the effect of laser noise suppression. First of all, on the basis of selecting low noise chip and high stable bias system, the whole circuit was designed by self-reducing circuit and transimpedance-amplifying circuit. In addition, in electromagnetic shielding, low temperature drift factor element, low noise power supply and active temperature control and other technical means, realize the development of high gain and low noise balanced homodyne detection system. Finally, the gain and bandwidth of the photodetector were evaluated and tested by combining the fast Fourier transform method and the number line power spectral density algorithm, and the intensity noise of the laser was detected and characterized in the 0.05 mHz-1 Hz band by using the detector. The experimental results show that the electronic noise spectral density of the balanced homodyne detector is less than 3.6×10−5 V/ Hz1/2 in the frequency range of 1 mHz-1 Hz, which is less than the noise requirement of the laser source for space-based gravitational wave detection. When the incident light power is 400 μW, the gain of the balanced homodyne detection system is measured to be more than 40 dB in the frequency range of 0.1 mHz-1 Hz. What’s more, the spectral density of laser intensity noise is 3.6×10−2 V/ Hz1/2 at 1 mHz. Low noise photoelectric detection and laser intensity noise characterization are achieved, which provide key device support for laser intensity noise characterization and suppression in space-based gravitational wave detection.
2022, 51(6): 20220325.
doi: 10.3788/IRLA20220325
Based on fiber ring lasers, we designed a single-wavelength and dual-wavelength switchable single-frequency ytterbium-doped fiber laser. A high-finesse filter was composed of a three-port circulator, an unpumped ytterbium-doped fiber and a fiber Bragg grating, which was used to suppress the number of modes in the resonator. By tuning polarization controller, comb spectra and dynamic gratings were formed within Polarization Maintaining Ytterbium Doped Fiber(PM-YDF) and realized the output of a single-frequency fiber laser with narrow linewidth. The output linewidth of the laser was 346 Hz at 1064.37 nm, and the optical signal-to-noise ratio was greater than 50 dB. The instability of wavelength and power was within 0.01 nm and 0.2 dB in 30 min. By adjusting the polarization controller, the single and dual wavelengths could be switched to each other, and the dual wavelengths were located at 1064.156 nm and 1065.236 nm, respectively. This technology provides a new way for dual wavelength output of ultra-narrow linewidth lasers.
2022, 51(6): 20220401.
doi: 10.3788/IRLA20220401
Our self-built dual-wavelength single-frequency fiber laser was used as a seed, and after being amplified by an acousto-optic modulator and multi-stage fiber, the laser was injected into a 100-meter long high nonlinear fiber with the zero-dispersion point of at 1550 nm. With the help of the four-wave mixing effect of the highly nonlinear fiber, a series of new spectral components were finally obtained under the pumping of the peak power of 13 W, and a total of 46 new spectra were generated in the range of 20 dB. These spectra spanned 1.337 THz and contained only one longitudinal mode in each spectrum. Since the new spectrum was generated based on the four-wave mixing effect, there was no gain competition between different spectra, so the multi-wavelength single- frequency of the laser can exist stably, and the spectral intensity was close to each other. The multi-wavelength single-frequency fiber laser not only has the advantages of a single-frequency fiber laser such as narrow linewidth, high coherence, and low noise, but also can simultaneously output multiple wavelengths of single-frequency lasers in an all-fiber structure, which makes it possible to have very important applications in the fields of multiplexing optical communication, optical frequency conversion, lidar, microwave photonics and so on.
2022, 51(6): 20210879.
doi: 10.3788/IRLA20210879
Narrow linewidth fiber lasers can be used in applications such as remote sensing, nonlinear frequency conversion and beam combination. In this paper, the typical structures and corresponding working principles of narrow linewidth fiber laser oscillator were introduced. The single-frequency mode selecting technologies were summarized from the perspective of obtaining narrower linewidth, and the power scaling technologies were summarized from the perspective of generating higher power. The current status of narrow linewidth fiber laser oscillator was reviewed, and the development of narrow linewidth fiber laser technologies was prospected.
