Research On Spectral Beam Combining Of Multiple Single-emitters On Composite Grating

Semiconductor laser has the advantages of high electro-optical efficiency,small size,light weight and easy integration,so it is widely used in many fields.However,the poor beam quality of semiconductor laser restricts its development.In view of these problems,laser beam combination technology will be a good solution.The single-emitter semiconductor laser has the characteristics of little thermal effect,no "smile effect" and limited output power of single device.Based on the spectral combination technology of single-emitter semiconductor laser,this thesis aims to obtain a laser output module whose beam quality is the same as that of a single luminous unit and output power is the sum of the power of all luminous units.The main work is as follows:1.Based on the spectral combination theory of double grating,the effects of the number of single emitters involved in the combination,the spacing and the focal length of the focusing lens on the spectral width and wavelength spacing,as well as the effect of the incident Angle of the beam on the diffraction efficiency of the grating are studied.The efficiency model of spectral bunching unit was established and the influencing factors of bunching efficiency were analyzed.2.Based on ZEMAX software,a multi-emitter double grating spectral combination model is established.A beam collimation shaping system based on fast axis collimation mirror(FAC),slow axis collimation mirror(SAC)and transmission lens was designed,and an equivalent feedback optical path was established.The effect of focal length of focusing lens on spectral beam combination efficiency was analyzed.Based on the efficiency model of spectral beam combination system,the effects of grating diffraction efficiency and external mirror reflectance on beam combination efficiency are discussed.3.A spectral combination system based on parallel double grating structure is proposed.By placing a secondary grating completely parallel to the primary grating,the combined beam passes through the grating twice for diffraction,and the compression of the combined spectral interval can be realized through optical simulation.4.The experimental platform of single-emitter semiconductor double grating spectral combination was built.The stepped space combination was used to synthesize the single-emitter laser in the fast axis direction.laser output,the beam quality is close to that of a single light emitting unit.It is verified that the parallel double grating beam combination structure can effectively compress the spectral interval and multiply the number of light emitting units within the same gain spectral line range.Then the brightness and power density of the laser module are improved.5.A three-fold beam reduction system was used to reduce the luminescent cell spacing from 3mm to 1mm,thus the overall line width of the output spectrum was compressed from 6.4nm to 2.2nm.In the experiment,28 W laser output was obtained,the beam combination efficiency was 55%,and the overall beam quality was4.50 mm · mrad.The wavelength interval was compressed by tripling the beam reduction system,the overall spectrum width was reduced,and the laser brightness was improved.6.By adjusting the distance between the external cavity feedback mirror and the telescopic system,the crosstalk problem caused by stray light entering the optical system is prevented.