Research On Spectral Beam Combining Of Diode Laser With Double Gratings

Spectral beam combining refers to the process of emitting incident beams of different wavelengths and different angles at the same angle by the dispersion of the diffraction grating.Spectral beam combining can greatly improve the beam quality of semiconductor laser arrays and realize the output of high-power lasers,which is of great significance to expand the application of semiconductor lasers in military,industrial and people's livelihood.In this paper,a double-grating spectral beam combining system is designed and simulated in ZEMAX software.The system consists of light-emitting units,a collimating module and a combining module.The main contents of our research and this paper are as follows:(1)The illuminating mechanism,transmission characteristics and characterization of the beam quality of the semiconductor laser are introduced.The basic principle and advantages of the double-grating spectral beam combining are explained.Based on this,the design and selection of the illuminating units are completed.The divergence angle,the beam waist radius,and the astigmatic distance of light emitting units,and the center wavelength and the incident angles between the respective light emitting units are calculated;(2)The collimating module with double-grating spectral beam combining is designed,which includes a fast axis collimating lens and a slow axis collimating lens.The fast axis collimating mirror is a cylindrical mirror with a plane and an elliptical shape,and the slow axis collimating mirror is a cylindrical mirror with a flat surface and a round surface.After the optimized design,the collimation module has a good collimating effect on the divergent beam emitted by the semiconductor laser array;(3)The combined module with double-grating spectral beam combining is designed.The module consists of a pair of dispersive gratings with identical parameters and parallel to each other.If the line width of the light source are considered,the beam quality of the combined beam is slightly reduced,however,the double-grating spectral beam combining system designed in this paper has excellent combining performance,and its beam quality is close to that of a single-tube semiconductor laser.At the line width of 0.4 nm,the beam quality M~2 factor of the fast axis and the slow axis are 1.7707 and 1.7706,respectively;(4)The influence of the angle error of the focusing grating on the combining process is studied.The angle error is divided into the incident angle error of the slow axis direction of the focusing grating caused by the rotation of the focusing grating plane,and the grating constant error in both the fast axis and slow axis directions caused by the rotation of the grating scribe line at a certain angle.The influence of the former is less on the spectral combination,while the influence of the latter is greater on the spectral combination and needs to be avoided and overcome in practice.