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.
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 this article, an overview of laser dazzling effect to buried channel CCD camera is given. The CCDs are sorted into staring and scanning types. The former includes the frame transfer and interline transfer types. The latter includes linear and time delay integration types. All CCDs must perform four primary tasks in generating an image, which are called charge generation, charge collection, charge transfer and charge measurement. In camera, the lenses are needed to input the optical signal to the CCD sensors, in which the techniques for erasing stray light are used. And the electron circuits are needed to process the output signal of CCD, in which many electronic techniques are used. The dazzling effects are the conjunct result of light distribution distortion and charge distribution distortion, which respectively derive from the lens and the sensor. Strictly speaking, in lens, the light distribution is not distorted. In general, the lens are so well designed and fabricated that its stray light can be neglected. But the laser is of much enough intensity to make its stray light obvious. In CCD image sensors, laser can induce a so large electrons generation. Charges transfer inefficiency and charges blooming will cause the distortion of the charge distribution. Commonly, the largest signal outputted from CCD sensor is restricted by capability of the collection well of CCD, and can’t go beyond the dynamic range for the subsequent electron circuits maintaining normal work. So the signal is not distorted in the post-processing circuits. But some techniques in the circuit can make some dazzling effects present different phenomenon in final image.
In this paper we build an experimental apparatus to measure the reflectivity and temperature of the foil in different conditions. The experimental results show that the growth of oxide film can be divided into 3 stages which corresponding to logarithmic, linear and parabolic rate law. A mathematical model is introduced to explain the phenomena observed in experiment. Numeral calculations are made for 30CrMnSi steel while cw-laser wavelength is 1.07μm. The numerical solutions are in agreement with the experimental data.
A special waveform of CCD being irradiated by intense laser is explained and simulated. Its specialty is that reference level is altered and becomes equal with saturated data level, which can answer for CCD’s black video induced by laser and named as excessive saturation effect. Alteration of reference level has been explained by signal charges injection into the measuring well during reference time. In CCD, wells barriers are largely lower than channel stop. After that all transfer wells are crammed, many remained signal charges getting rid of clock’s control can be hold in channel, and move along it in thermal diffusion and self-induced drift. They can fill up the measuring well ahead of clock’s permission and alter reference level to saturated data level. Based on the explanation, the waveform is simulated on an equivalent circuit of CCD’s charge measurement structure, which is built on the platform of Multisim2001. The voltage sources and switches are used to manipulate the charge and discharge of a capacitor, which simulates the charge injection and resetting of measuring well. The clocks controlling switches represent the injection and reset clocks in CCD. To simulate clock’s impact on output, other capacitor is used to connect it to capacitor that represents the measuring well. The equivalent circuit is validated by the simulated normal waveform. Then, altering the clock and charging the capacitor ahead, the excessive saturation waveform is simulated, which validates the explanation to excessive saturation effect.
The experimental setup was established for studying damage effects on silicon photoelectric detector materials induced by 800nm and 150fs repetitively-pulsed laser. The detector is irradiated by single shot and multiple shots respectively. The laser damage thresholds of silicon photoelectric detector material were measured. The surface morphologies of the material damaged by laser were analyzed. The surfaces damaged by laser with different energy were compared. The thresholds vary with the number of laser shots. According to the accumulation theory, the damage threshold is the power function of the shot number. Experimental results show that threshold of single shot that damages the silicon photoelectric detector is 0.156J/cm2. The laser damage threshold decreases with the increasing number of laser pulses, but the minimum value exists. The damage is mainly caused by the mechanical effect rather than thermal effect. In fact, the thermal effect during the interaction is so small that it can’t even be observed. Resistivity of the silicon photoelectric detector irradiated by femtosecond laser decreases and finally tends to a constant value.