Study On Spectral Beam Combining System Of Semiconductor Laser Array With External-cavity Feedback

The semiconductor laser spectral beam combining technology because it can obtain high power laser output,high power density,high beam quality and semiconductor laser with small volume and light weight,high efficiency,long service life,easy modulation and high reliability has become an international research focus.The whole external-cavity spectral beam combining system will combine all laser beams through the dispersion characteristic of the diffraction grating,so the diffraction grating is the key of the spectral beam combination technique.Based on the principle of the spectral beam combining technique and the diffraction grating,a sub-wavelength fused silica transmission grating was studied for the external-cavity feedback spectral beam combining system of the semiconductor laser array in this paper.The diffraction efficiency of 91.2%(TE mode)was obtained by designing and optimizing a 940 nm sub-wavelength fused silica transmission grating with the help of Rsoft optical design software.According to the simulation results,the commercial transmission grating with similar simulation parameters was used to realize the external-cavity feedback spectral combination beam source of the 940 nm semiconductor laser array.The output power of the laser was 46 W and the width of the spectrum was 14.36 nm.Based on the design parameters of the grating,the fabrication process of fused silica transmission grating was studied.The fused silica transmission grating with period of 530 nm,duty cycle of 0.5 and ridge height of 300 nm was fabricated by holographic exposure and ICP etch technique.