As located in the focal plane of the imaging system, the image sensor will be easily influenced by the huge optical gain, which is brought in the image sensor by the external optical system and microlens on the surface of the device. Laser has a great influence on the image sensor, which is a sensitive link of the anti-laser reinforcement of the imaging system. Improving the performance in extreme light conditions in order to study the vulnerability of image has an important significance of reinforcement. As a typical visible light image sensor, which has advantages of sensitivity, high dynamic, small, light and so on, IT-CCD has been widely used in the fields of reconnaissance, detection and military. An 800nm femtosecond pulse laser was used to carry out experimental research on the laser irradiation effect of IT-CCD. The results shown that the local pixel of IT-CCD was in a state between undamaged and the white point damaged after irradiating by the laser, which was named by gray point. It was shown that the influenced pixels of IT CCD were changed by the laser, but no obvious deformation occurred. Through microscopic detection and analysis, the damage mechanism was expounded, further analysis was done. With focus ion beam (FIB) technique, it was found that there was photosensitive potential well, micro-structure of SiNx filling layer under microlens of the IT-CCD. When the gray point damage occurred, neither the photosensitive potential well at the bottom of the device was damaged, nor was the microlens structure on the surface. It turned out that the SiNx filling layer was influenced by the laser. Through elucidating the mechanism of this damage of the gray point, it lays a foundation for damage mechanism research.
In order to study the mechanisms of thermal damage during laser machining in GaInP/GaAs/Ge tandem solar cells (TSCs), the spatial electroluminescence (EL) characterization on sub-cells pre and post laser irradiation was carried out. Results showed that post laser irradiation, the EL of GaAs middle cell increased to saturation in the damage zone, but decreased to zero at the rest part. A theory was put up to explain this phenomenon by using two-unit equivalent circuit model, and then verified through GaInP top cell spatial EL analysis. Conclusion was drawn that current redistribution induced by local shunt resistance decreasing in GaInP top cell was the main cause for the EL enhancement in GaAs middle cell.
To increase the lifetime of components in high power lasers and to study downstream light field the influence of the damaged optical components, numerical model of surface profile of damaged optical components were built with particle swarm optimization algorithm, and the relationship between the damage degree and the parameter of numerical model was analyzed. First laser irradiation experiment was carried out to acquire the damaged optical components. Then surface morphology was measured with Zygo interferometer system. With a typical Gaussian filter. A numerical model of one dimensional lineout of surface profile was established with particle swarm optimization algorithm. Numerical results shows that the model was valid with the particle swarm optimization (PSO) algorithm. The results also shows that there was a relationship between parameter of the model and the damage degree.
In this paper, a series of effects of CCD interaction with laser are taken together in consideration. These effects divide the light intensity axis into three sections named respectively as ‘normal’, ‘dazzle’ and ‘damage’, along the positive direction. For the effects on first two sections, a general model is proposed to describe them, which reflect the performance jump charateristics of CCD under laser irradiation. In fact, the model contains the jump functions of three performance parameters, which are response efficiency, charge transfer inefficiency and leakage current. Thereinto, the first is used to describe the pixel itself, and the remaining two are used to describe the influence between pixels. The leakage current parameters include a variety of situations, such as the leakage current between pixels, the leakage current between channels and even the leakage current between subarrays in a large array. When all three kinds of parameters don’t jump, the CCD works normal. When anyone of them jumps, the CCD is dazzled by light. Of course, the parameter jump in a dazzled CCD can return to normal when light intensity decreases. However, the damage section on light intensity axis is temporarily not described in this paper. After all, the damaged CCD is not a CCD again.
The effect of single junction GaAs solar cells irradiated by 808nm, 1070nm and 10.6um CW lasers is investigated. The results show that, as long as under the same laser coupling intensity, the damage modes of solar cells under different irradiation conditions are similar. With the increase of laser coupling intensity, the maximum temperature of solar cells rises, and the maximum power of solar cells shows a ‘stair-step’ decline. The multiple irradiation experiments of triple junction GaAs solar cells by 1070nm CW laser are carried out. The results show that when the laser intensity is more than 12.8W/cm2 , the performance degradation of solar cells will show a significant accumulation effect. In addition, the thermal sensitive damage factors are explored and verified. The results show that the maximum temperature and the duration of high temperature are sensitive factors for laser irradiation damage of solar cells.
Three types of laser irradiating experiments on single junction GaAs solar cells with the same laser energy coupling intensity were carried out, which were irradiated by in-band (808 nm) and out-of-band (1.07 μm) continuous wave lasers respectively and simultaneously. On the basis of the changes of current-voltage characteristic curves of irradiated solar cells, the damage degrees could be divided into three stages which were gently, seriously and thoroughly damaged stages. The damage mechanism was studied from two aspects: output changes of solar cell equivalent circuit under different configuration settings, thermal analysis model. The results show that damage degrees of gently and thoroughly damaged stages is insensitive to irradiation intensity. However, the damage degree of seriously damaged stage is sensitive to irradiation intensity and this is regarded to be related to thermal decomposition of GaAs. Moreover, the increase of PN junction defects leads to performance degradation of irradiated solar cells. In conclusion, the thermal damage leads to the increase of PN junction defects, thus results in the performance degradation of cells.
Besides the excessive saturation effect, a new mechanism of temporary black screen of CCD camera induced by laser is found. The final output of CCD camera is the difference between the signals in effective pixels and optical black pixels. As the effective pixels of CCD camera are being irradiated by intense laser, many carriers induced by photo overflow from effective pixels into the optical black pixels. As a result, both the effective and optical black pixels will reach saturation, which makes the final output of CCD become zero. This effect has the same black screen phenomenon as the excessive saturation, and is named as pseudo-excessive saturation effect in this article.
In the paper, the performance of Si devices with change of carrier lifetime was reported with finite volume method. In the two-dimensional axisymmetric semiconductor model, based on Si p-n junction structure, direct recombination, auger recombination and the SRH (Shockley-Ready-Hall) recombination were taken into consideration. Both cathode and anode was made via ohmic contact. Two kinds of device models with p+-n or n+-p type were built accordingly. 1064 nm laser was used as signal beam in the model. Numerical simulation had been studied under different bias voltage and carrier lifetime. Compared with the results, it was found that the device performance was affected by the minority carrier lifetime obviously. It also inferred that performance of Si devices was degenerated by laser indirectly.
In this paper, an advanced non-mechanical beam aiming and pointing system is presented. Traditional beam steering is based on the mechanical systems. In the complex and expensive systems, beam jittering and many other problems are major limitations. However, beam steering with optical phased array (OPA) devices can realize agile beam control with random access pointing and high efficiency. Our system is mainly based on phased only spatial light modulators (SLM), which can realize beam steering non-mechanically. Based on the conventional one dimensional beam steering method of SLM, two dimensional beam steering method was presented at first in order to demonstrate the feasibility of the whole system. Then the whole system was tested. Our beam steering system can steer beam to a target which was moving at the speed of 3.8mrad/s within the field of view. The RMS error of the system was 0.0246mrad in one dimension, and 0.139mrad in two dimension respectively. Meanwhile the whole process was recorded by another camera in order to show the results.
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