The design of the AlGaAs/InGaAs/GaAs laser heterostructure with an ultra-narrow waveguide was developed and studies on the generation of high-power laser pulses with high beam quality were carried out. The heterostructure design included a 100-nm-thick waveguide and an InGaAs quantum well for a lasing at 1060 nm. For the studies the mesa-stripe geometry single-mode lasers with a 5.1-μm-width contact were fabricated. The mesa-stripe geometry parameters were optimized using a 2D-simulation of waveguide properties, taking into account the spatial distribution of temperature and gain. As a result, the divergence was of 18.5 and 5 degrees in the growth direction and parallel to the heterostructure layers, respectively. Studies of the light-current characteristics in the range of pulse durations of 5–1000 ns showed that the peak power of 1.75 W was limited by the catastrophic optical damage. The dynamics is associated with modes of high-quality factor that approach their threshold conditions at high pumping level. A spectral line of these modes is redshifted relative to a fundamental one.
Studies of multimode and single-mode semiconductor lasers with a surface distributed Bragg reflector (S-DBR) were carried out. S-DBR with a period of 2 μm was formed in the upper cladding layer by contact photolithography. The spectrum width for all laser designs did not exceed 0.3 nm both at continuous wave (CW) and pulse of 100 ns pump. Temperature stability of emission wavelength increase from a value of 0.35 nm/°С for a Fabry-Perot laser to a value of 0.075 nm/°С for a S-DBR laser was demonstrated. The relatively low output optical power of high-order S-DBR lasers is associated with the presence of diffraction modes emitting from the surface of the DBR.