Research On Technology Of Spectral Beam Combination Of Diode Laser Array Based On Grating External Cavity

High power diode lasers have been used in the fields of pumping source of solid state laser,surface modification,welding,cutting and so on for their high energy conversion efficiency,good reliability,long lifetime and small size.In this thesis,we propose a spectral beam combination system based on diode laser array.And the parts of spectral combination by single grating and the parallel transmission grating and reflector pair configuration are experimentally verified.The main research contents are as follows:(1)First of all,the working principle,the main parameters,the beam characteristics and the beam quality evaluation methods of diode lasers are discussed and analyzed,which can provide the basis for the following simulation works.(2)A diode laser array spectral combination system based on fast-axis collimator(FAC),slow-axis collimator(SAC)and beam transform system(BTS)has been designed and analyzed.The collimation effects of different configurations are compared by using the ZEMAX software.The simulation results show that the configuration of applying BTS could increase the freedom of the parameter design of SAC,which can achieve the high beam quality in slow axis of the diode laser array.(3)A novel collimator based on double focal lens are proposed,which could collimate the diode laser array in both directions simultaneously,to solve the question of bad collimation effect of diode laser array with high fill factor.Because the parameter design of the SAC and FAC are limited by the compact space of diode laser array with high fill factor,the double focal lens is the only way to achieve collimation with reducing the installation and adjustment deviation.(4)A spectral beam combination system based on the parallel transmission grating and reflector pair configuration are designed and analyzed.This configuration is derived and improved from conventional single grating combining system,which could compress the spectrum interval of emitters in the diode laser array by letting the beam pass the grating twice by a reflector paralleled to the grating.The experiment platform is built to compare the output spectrum of the two different configurations to verify the parallel transmission grating and reflector pair configuration can achieve the half spectral interval compared to the traditional single grating.The measured spectral intervals of a 3 emitters array and a 5 emitters array based on single grating structure are 4.36 nm and 4.69 nm,respectively,while the measured spectral intervals of a 3 emitters array and a 5 emitters array based on single grating structure are 2.15 nm and 2.35 nm,respectively,which can double the numbers of the emitters within the same spectral width to achieve high output power.