Analysis of physical mechanism of beam crosstalk insemiconductor laser array spectral-beam-combined system br

In spectral beam combining systems based on a grating-external cavity, due to some factors such as the"smile" effect of the semiconductor laser array and the error of the optical components in the external cavity,the beam from one emitter transmits into the external cavity and then can return to other emitters, therebyforming beam crosstalk between the two emitters. In this work, in order to investigate the physical mechanismof beam crosstalk and the influence of beam crosstalk on beam properties such as locked spectra and beamcombining efficiency, based on the optical feedback semiconductor rate equation, the beam modes that canstably oscillate in the coupling cavity are derived, and the coupling cavity oscillating model is built. With theconsideration of the mode competition mechanism in the coupling cavity, the effects of different crosstalkbetween two emitters with different intervals on the locked spectra are analyzed in detail. The results show thatcrosstalk leads to the shift of the peak of locked spectrum and the generation of sub-peak. The crosstalkbetween two closer emitters has a more serious influence on the beam spectrum structure, combined beam spot,and combining efficiency. The combining efficiencies influencing the 1st, 2nd and 3rd crosstalk are 45.5%, 50.2%,and 63.8%, respectively (When there is no crosstalk, the efficiency is 80.1%). Finally, the results of thetheoretical analysis are verified experimentally, and the experimentally observed spectra under the influence ofcrosstalk show phenomena such as peak degradation, peak shift, edge burrs, and side lobes in spectra, which areconsistent with the theoretical predictions. Moreover, according to the simulation results and experimentalobservations, it is found that the crosstalk can be suppressed to a certain extent by increasing the spacingbetween emitters, and the Galileo telescope system is suggested to suppress crosstalk and optimize the spectralstructure and beam combining efficiency. Compared with the Kepler telescope structure, the Galileo telescopedoes not have a real focal point, which can prevent the local power from being too high, thereby damaging theoptical components