High-power semiconductor laser systems based on 1.5 – 1.6 μm single-frequency distributed feedback (DFB) lasers with a sidewall Bragg diffraction grating are developed and their current – voltage, light – current, and spectral characteristics are experimentally studied. The characteristics of conventional lasers with a Fabry – Perot cavity and DFB lasers fabricated from one and the same heterostructure are compared. At a pump current not exceeding 700 mA, a conventional laser with a cavity length of 1.6 mm and a mesa-stripe width of 3 μm emits a power no lower than 200 mW versus 150 mW of the DFB laser; both lasers are mounted in a housing 11 mm in diameter. The DFB laser mounted in a butterfly housing emits a power no lower than 100 mW at the exit of the single-mode cable at a pump current not exceeding 500 mA, which, at a 60 % coupling efficiency, corresponds to a power no lower than 165 mW; the side-mode suppression ratio in this case is no lower than 53 dB. It is shown that the wavelength deviation with changing pump current and temperature is almost an order of magnitude lower for the DFB laser than for the conventional laser.
The current – voltage, light – current, and spectral characteristics of high-power multimode semiconductor lasers emitting at wavelengths of 1.5 – 1.6 μm are studied experimentally. It is shown that the cw output power of a C-mount laser with a cavity length of 2.6 mm and a mesa-stripe contact width of 100 μm exceeds 4 W at a pump power of 15 A. The output power in a pulsed regime amounts to 20 W at a pulse duration of 100 ns, a pulse repetition rate of 5 kHz, and a pump current no higher than 80 A. The dependences of the laser wavelength and spectral width on the pump current are presented. The current – voltage and light – current characteristics, as well as the characteristic temperatures of the lasers, are calculated.
It is shown experimentally and theoretically that increasing the pump current of a laser diode and simultaneously lowering its temperature can ensure an order of magnitude increase in the range of pump currents where the diode emission frequency is tuned to the caesium D2 line. The results are compared to the case where the laser diode and fibre Bragg grating temperatures are maintained constant and only the laser pump current is varied.
High-power 1.5 – 1.6-μm semiconductor lasers with an asymmetric periodic optically coupled waveguide are developed and their current – voltage, light – current, and spectral characteristics are experimentally studied. The characteristics of these lasers are compared with the characteristics of traditional lasers based on double separate-confinement heterostructures. It is shown that the developed lasers have lower divergence and almost the same threshold and power characteristics as conventional lasers with Fabry – Perot resonators. The developed lasers with a cavity length of 1.6 mm and a mesa-stripe contact width of 3 μm mounted in a housing 11 mm in diameter have a power no lower than 200 mW at a pump current not exceeding 700 mA with a divergence of 25 – 35° versus 45° typical for conventional lasers.
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