KEYWORDS: Mercury cadmium telluride, Pulsed laser operation, Laser irradiation, Semiconductors, Signal detection, Temperature metrology, Photovoltaics, High power lasers, Electric field sensors
To study the effects of the semiconductor structure of the HgCdTe detector by high-energy pulsed light irradiation, building 2D models to simulate the changes of the internal temperature and the structure of the PN junction of the HgCdTe chip after being irradiated by a high-energy pulsed light with wavelength of 1064 nm. Simulation results show that after being irradiated by a high-energy pulsed light, the PN junction of the detector chip will disappear briefly, at the same time, a high temperature is generated on the illumination surface of the chip, and a temperature difference is formed inside the chip. After the laser irradiation, the temperature difference inside the chip changes the distribution of the carriers, creating a temperature difference electromotive force, offsets some of the built-in electric field in the PN junctions, deviating the HgCdTe detector from its normal operating state.
A new phenomenon was discovered in the experiment of the HgCdTe detector irradiated by the laser, namely the photoinduced latch-up effect. Based on this phenomenon, a two-dimensional simulation model of laser irradiation on the detector chip was established by using COMSOL Multiphysics simulation software. The carrier concentration distribution, photo-induced current, and temperature in the photosensitive chip were simulated after being irradiated by a single-pulse laser with different power to explore the principle of the latch-up effect triggered by the laser. The research shows that there is a PNPN structure in the photosensitive chip, with parasitic bipolar transistors PNP and NPN. Both parasitic transistors are turned off if the photosensitive chip is working normally. A large number of photo-generated carriers are generated when the photosensitive chip is irradiated by a high-power pulse laser, and the two parasitic transistors are triggered to conduct and form a positive feedback loop, resulting in a large current and triggering the latch-up.
Single-heterogeneous junction GaAs/Ge solar cells induced by 532nm laser with the pulse width of 12ns are investigated. Results indicate that the GaAs/Ge solar cells would mostly be damaged when laser is focused on its grid lines. Its surface damage morphology initially occurs at 0.35J/cm2 by the single laser pulse with nanosecond duration. Theoretically, the nanosecond laser pulse leaded damage mainly comes from both the thermal and the mechanical effects. These experimental conclusions are tested and verified by scanning electron microscope with energy dispersive spectroscopy and X-ray photoelectron spectroscopy.
There is always a challenge on large aperture medium power laser’s resonator design, stable resonator would supports significant higher order transverse modes, folded and telescope stable resonator are too complex and not preferred by engineers, unstable resonator need rather large round trip gain to compensate its high geometric out-coupling, which is difficult for this kind of laser since its gain length is limited due to the power level and large aperture. Partial feedback unstable resonator had been proposed to tackle this difficulty since the early days of laser development, however, the debates of its effect never stopped even with those distinguished optical resonator scientists such as Siegman, Anan’ev, and Weber. Recently integrated partial feedback unstable resonator design had been successfully demonstrated on a medium size chemical oxygen iodine laser. In this paper, we carry this resonator configuration on a small scale discharge driven supersonic nozzle array Hydrogen Fluoride chemical laser, a typical large aperture short gain length device. With magnification equals 4/3, we successfully get ten Watts level ring beam output.
This paper reports on the disappearance of photosensitive area extension effect and the novel
temperature dependence of junction performance for mid-wavelength HgCdTe detectors. The
performances of junction under different temperatures are characterized by laser beam induced current
(LBIC) microscope. The physical mechanism of temperature dependence on junction transformation is
elaborated and demonstrated using numerical simulations. It is found that Hg-interstitial diffusion and
temperature activated defects jointly lead to the p-n junction transformation depended on temperature,
and wider band gap compared with the long-wavelength HgCdTe photodiode may correlate with the
disappearance of photosensitive area extension effect.
To overcome the shortcomings of Shack-Hartmann wavefront sensor, we developed a lightfield wavefront detection system,
which is able to complete the large field of view, multi-perspective wavefront detection in a single photographic exposure.
The lightfield wavefront detection system includes an imaging primary mirror, a lenslet array and a photosensitive device.
The lenslet array is located on the imaging plane of the imaging primary mirror and the photosensitive device is located on
the focal plane of the lenslet array. In this system, each lenslet reimages the aperture and forms a low-resolution image of
the aperture. Compared with the Shack-Hartmann sensor, this lightfield measuring method can obtain imaging arrays in
different perspectives. By comparing the array information with the standard information, we can obtain the slope matrix of
the wavefront in different perspectives and restore the wavefront in a large field of view. Based on Fourier optics, we built
the corresponding theoretical model and simulation system. By busing Meade telescope, turbulent phase screen, lenslet
array and CCD camera, we founded the experimental lightfield wavefront measuring system. Numerical simulation results
and experimental results show that this wavefront measuring method can effectively achieve the wavefront aberration
information. This wavefront measurement method can realize the multi-perspective wavefront measurement, which is
expected to solve the problem of large viewing field wavefront detection, and can be used for adaptive optics in giant
telescopes.
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