Invited papers
2019, 48(7): 702001.
doi: 10.3788/IRLA201948.0702001
Optical phase conjugation(OPC) is a technique that generates a light field with reversed wavefront and identical amplitude distribution as the incident light. It has a unique feature of suppressing the aberration of incident beam induced by inhomogeneous or disturbing medium. Although this technique has been extensively studied since the 1970s, it has become more attractive because of unprecedented achievements and prospective potentials in biomedical applications. OPC-based techniques have been successfully utilized to form a focus through/inside highly scattered biological samples. It opens a new avenue by significantly enhancing the light delivery in biological tissue for high-resolution imaging, diagnosis and treatment of medical diseases. In order to provide insight into its further development, recent progress of OPC techniques for focusing light through/inside biological tissue was summarized.
2019, 48(7): 702002.
doi: 10.3788/IRLA201948.0702002
Conformal metasurfaces can break the restrictions between the geometry of an object and its optical functionality and allow the scattering wavefronts to be modulated willingly. Here, it is demonstrated that adaptive conformal metasurfaces is composed of achiral mirror symmetry -shaped gold antenna, which can be integrated on arbitrary substrate to achieve curved holography in the visible range (=450 nm). The underline modulation scheme of conformal metasurface relies on the Pancharatnam-Berry phase, which can be continuously controlled in each subwavelength unit cell by rotating the orientation angle of the antenna. Such conformal metasurfaces decorated on curved topological objects can be employed in various practical application such as curved lens focusing, invisibility cloaking, and security printing technologies.
2019, 48(4): 402001.
doi: 10.3788/IRLA201948.0402001
The terahertz(THz) far-field radiation properties of a butterfly-shaped photoconductive antenna (PCA) were experimentally studied using a home-built THz time-domain spectroscopy(THz-TDS) setup. To distinguish the contribution of in-gap photocurrent and antenna structure to far-field radiation, polarization-dependent THz field was measured and quantified as the illuminating laser beam moved along the bias field within the gap region of electrodes. The result suggests that, although the far-field THz radiation originates from the in-gap photocurrent, the antenna structure of butterfly-shaped PCA dominates the overall THz radiation. In addition, to explore the impact of photoconductive material, radiation properties of butterfly-shaped PCAs fabricated on both low-temperature-grown GaAs(LT-GaAs) and semi-insulating GaAs(Si-GaAs) were characterized and compared. Consistent with previous experiments, it is observed that while Si-GaAs-based PCA can emit higher THz field than LT-GaAs-based PCA at low laser power, it would saturate more severely as laser power increased and eventually be surpassed by LT-GaAs-based PCA. Beyond that, it is found the severe saturation effect of Si-GaAs was due to the longer carrier lifetime and higher carrier mobility, which was confirmed by the numerical simulation.
2019, 48(4): 402002.
doi: 10.3788/IRLA201948.0402002
In view of many technical constraints and techcical bottlenecks in traditional gating imaging system, a novel self-triggering instantaneous gating imaging of waveguide grating microarray that considered self-triggered gating and instantaneous imaging was proposed. This article not only showed a complete self-triggered gating imaging principle and device model, but also explained the advantages of quantum dot films based on perovskite in transient gating imaging. In the end, the spatial modulation effect of waveguide gratings microarray, electron beams, electronically pumped imaging and the instantaneous luminescence effect of quantum dot film based on perovskite, were calibrated and modeled in the vacuum test system. The feasibility of the technical scheme was proved by experiments.
2019, 48(4): 402003.
doi: 10.3788/IRLA201948.0402003
With the increasing demand of infrared imaging technology for time resolution, spatial resolution, spectral resolution and optical stability, the contradiction between the four is becoming more intense. The molecular filter was a filter device with a comb-like discrete transmission spectrum type. The selective transmission was realized by the resolution of the wavelength of the light by the molecular energy level transition. The effect was optical but the mechanism was quantum. Molecular filtering provided a new way for conflict resolution. Based on the theory of molecular spectroscopy, the working mechanism and theoretical model of three types of molecular filter imaging techniques, such as differential absorption, magneto-optical rotation and Doppler modulation, were presented. Combined with the related work of the research team, the applications were introduced separately:differential absorption molecular filtering in remote sensing monitoring of vehicle exhaust, magneto-optical rotation molecular filtering in combustion diagnosis, and Doppler modulated molecular filtering in spaceborne atmospheric wind and temperature remote sensing. Finally, the technical characteristics and applicability of the three mechanism filtering methods were analyzed.
