Key Engineering Materials Vol. 552

Abstract: Laser scribing of hydrogenated amorphous silicon (a-Si) is a crucial step in the fabrication of thin film photovoltaic modules. The required line width of the laser scribing process for a-Si thin film solar cell preparation is 30 m~50 m, the dead zone is less than 300 m in size, and the line depth should be compliant with the process requirements. Thus, the high imaging quality and focal depth of the optical system is required in the laser scribing system. Three crucial laser patterning steps (known as P1, P2 and P3 in the photovoltaic literature) are integrated in the thin film silicon module manufacturing sequence. Therefore, efforts to optimize these laser processes are demanded by the photovoltaic industry. In particular, the state of the remaining material after laser treatment is known to have a critical influence on the electrical properties of the final devices. This paper focuses on the P3 laser scribing process with the peculiarity that it has been done in single solar cells. By evaluating it in single solar cells rather than in finished module, it is possible to isolate its effect on the device characteristics since the P1 and P2 scribings are omitted. To study the effect of the P3 scribing length, several scribings can be done in the same cell. As it will be shown, the high speed motion systems needed for precision laser scribing plays an important role in this experiment. They can be responsible for the electrical losses after the scribing of the solar cells. If this is dealt with properly, it can be seen that the P3 scribings have very little effect on the electrical characteristics of the processed solar cells.

Abstract: A high beam quality and high stability laser amplifier baseing on LDA side-pumping Nd-Glass which applied to amplify a nanosecond laser pulse source has been developed in the paper. In addition, Liquid crystal spatial light modulator is used in the amplifier for spatial beam shaping so as to improve the near-field uniformity. When the flat top pules with the pulse width of 3ns and energy of 500nJ are injected as the seed pulse, the average output energy of the laser amplifier is 100mJ. The modulation degree near field is less than 1.22:1, and the beam angle drifting of the far-field laser is less than 10 μrad.

Abstract: In order to realize the dual-wave length lasing based on stimulated Raman scattering principle, the dual-wavelength single-mode optical fiber Raman laser is established. Firstly, 80m long G652b single-model quartz fiber is pumped by Nd3+:YAG solid pulse laser, and its output spectra when without grating which are measured and studied. Then, a linear external-cavity fiber laser is designed with fiber Bragg grating as mirrors to gain 1062nm and 1066.5nm laser output. To change pump energy (65.2uJ~100.4uJ), the mean-variances of energy percentages are all about 7.58%,and dual-wavelength energy ratio is close to 1:1. Pump pulse widths are close to 32.14ns. Finally, the main parameters of laser are analyzed too. The dual-wavelength single-mode optical fiber Raman laser can be applied to Raman amplifier filed.

Abstract: 920 nm OPS-VECSEL has an important application in laser display. We constructed and optimized a 920 nm optically pumped semiconductor vertical external-cavity surface emitting laser (OPS-VECSEL) with active region of In0.09Ga0.91As quantum well (QW) system pumped by 808 nm laser diode module. By the finite element method, self-consistent solutions of the semiconductor electronic and optical equations are realized to calculate the characteristics parameters of OPS-VECSEL. The performances of device, especially the mode, the threshold and the optical-optical translation efficiency, were analyzed by dealing with different numbers of QWs (1, 2 and 3) in one period, QW depth, barrier width, the component and dimension of the non-absorption layer. We chose the best structure of them. On this basis, we optimized the external cavity mirrors reflectivity and the simulation showed that the performances would be significantly increased.

Abstract: In this paper, we investigated the stochastic resonance (SR) phenomenon in a laser system with correlated pump noise and quantum noise. The signal-to-noise ratio (SNR) is calculated when a square sine pulse signal is added to the system. The effects of the duty cycle of pulse signal and the correlation strength of noises on the SNR are discussed. Some valuable phenomena are investigated to improve the output SNR of laser.

Abstract: According to current situation of testing beam divergence angle of low power laser indicator, this paper is designed to develop a testing system for beam divergence angle of low power laser indicator based on virtual instrument. A sport utility is used in this system - data acquisition card for the displacement data acquisition and motion control and a video card for images acquisition. The use of labview graphical programming language to develop host computer program including Man-machine Interface and functional code, realizes Data acquisition, process, display, storage and motion control; ensures the system accurate and efficient.

Abstract: 2.3 μm InGaAsSb/AlGaAsSb lasers with multiple quantum wells(MQWs) have been demonstrated.The growth temperature of quantum wells is 440°C,and the growth quality of InGaAsSb/AlGaAsSb MQWs is examined by X-ray diffraction and Photoluminescence(PL) at room temperature.The energy band structure of MQWs was calculated by one-dimensional finite-difference method(1D-FDM)

Abstract: Spatial resolution is an important parameter in distributed optical fiber Raman temperature sensor system (DOFRTS). In this paper, a 10 kilometers long DOFRTS with spatial resolution of about 6 meters is constructed. The spatial resolution is limited by electrical bandwidth of the photodetector circuit and the data acquisition part. The abrupt temperature changes along the fiber axis are treated as temporal pulse signals, and a linear amplitude coefficient modification algorithm is used to improve the spatial resolution. The experimental results show that the temperature amplitudes from 3 meters region to 6 meters can be modified accurately. Therefore, a DOFRTS of high spatial resolution but low system cost could be successfully constructed.

Abstract: This paper introduces two types of precise temperature controllers for high power semiconductor laser diodes. We apply a category of self-tuning parameter fuzzy-PID controller，and a kind of neuronal network optimized rules fuzzy-PID controller to realize stable temperature controlling. we simulate these two methods by Matlab. The result proves that the new method has more superiority than traditional means, such as PID controlling, etc. And further improvement on constant temperature control will inevitably promote the reliability of LD.

Abstract: Based on the target reflection section defined by The Bidirectional Reflectance Distribution Function, a method of approximate calculation and analysis of the cone and plate’s reflection section in laser-illuminated condition are derived in the paper. With the method, reflection section of cone is calculated and analyzed. Experimental platform was established with 1.319m Nd:YAG laser, measuring the reflection section of cone in diverse incident angle. Curve of the plate, cylinder and cone relative illumination changing in diverse incident angle were measured. The results of this study are helpful for many applications such as weapon designing, target invisible, and system modeling.