Research On Key Technologies Of Spectral Beam Combining Of Diode Lasers Based On Volume Bragg Gratings

Semiconductor lasers have the advantages of high photoelectric conversion efficiency,compact structure,low cost,stable system,and long life.They have broad application prospects in high-power semiconductor lasers in the industrial field.Aiming at the application of volume Bragg gratings in semiconductor laser external cavity spectral beam combining system,a design scheme based on semiconductor laser array external cavity spectral beam combining system is proposed in the paper.The effects of various parameters of volume Bragg grating on the diffraction efficiency are simulated.Design optimization and,experiments are carried out to verify and analyze the spectral beam combining system based on reflection gratings.The main research contents are as follows:(1)Five semiconductor laser array combining structures based on a fast-axis collimator,a slow-axis collimator,and a reflective volume Bragg grating are designed,and the input and output beams collimated by the fast-and slow-axis are compared through optical simulation..(2)Based on the beam combining principle of volume Bragg gratings and Kogelnik coupled wave theory,the direct relationship between the wavelength selectivity and angular selectivity of transmission and reflection volume Bragg gratings and the grating parameters is derived,and the thickness,period and refractive index modulation of the grating are calculated.Quantitative analysis of the effect on diffraction efficiency provides a basis for structural optimization of volume Bragg gratings.(3)Propose the equivalent model of volume Bragg grating-nano-diameter hole structure,and use the equivalent medium theory and rigorous coupled wave theory to the effective refractive index,diffraction efficiency and the length of the rectangular hole model of the nano-diameter hole model when different polarized light is incident upon,respectively.The method provides a solution,and solves the influence of factors such as visible light band,nearinfrared light band,incident angle,and circular hole shape on the grating,and gives appropriate design opinions.(4)Use FDTD software to carry out targeted comparison and discussions on the volume Bragg gratings based on photo thermal refraction glass and the nano moment hole model with multiple film layers stacked with the same parameter settings,including incident angle,incident wavelength and other spectral selections.The effects of angularity and angular spectral selectivity directly demonstrate that nano pore structures can be used as equivalent models of volume Bragg gratings.(5)Based on the grating external cavity beam combining principle,the relationship between the output wavelength interval and various parameters is derived,and an experimental platform for external beam spectral beam combining based on a reflective semiconductor laser is set up,which achieves five combined elements within a spectral width of about 13 nm.