High Power Diode Laser Research In Mitsubishi Electric

Kenj i Ikeda; Hisao Kumabe; Hirofumi Namizaki; Wataru Susaki

doi:10.1117/12.944354

9 August 1988 High Power Diode Laser Research In Mitsubishi Electric

Kenj i Ikeda, Hisao Kumabe, Hirofumi Namizaki, Wataru Susaki

Proceedings Volume 0893, High Power Laser Diodes and Applications; (1988) https://doi.org/10.1117/12.944354
Event: 1988 Los Angeles Symposium: O-E/LASE '88, 1988, Los Angeles, CA, United States

Abstract

In practical uses, life time is an important parameter for high power diode lasers. In general, one can find out two components in degradation mode of the A1GaAs/GaAs lasers, that is, gradual and sudden increases of operation current to keep the output power constant. The gradual degradation might be due to increase of non-radiative recombination centers in an active region, or to some kinds of facet oxidation which results in slow reduction of reflec-tivity. In order to avoid or eliminate the gradual degradation, it has been required to reduce the mechanical stress and temperature rising and to passivate the facets. The sudden increase of operation current could be understood in terms of facet degradation, which is mainly caused by high optical power density. The most radical case is the so-called COD(catastrophic optical damage). The COD is one of thermal effects coming from local temperature rising attributed to self-absorption of light at the facet region where the population inversion is lost by fast surface recombination velocity. The COD level is increased by passivation of dielectric film such as Si₃N₄ or Al₂0₃ to 1.5-2.0 times higher than the bare facet. As absorption intensity at the facet is determined by not output power but inner power at the facet, the inner power is an essential parameter for high power diode lasers. Output power is varied by changing the facet reflectivity, even though the inner power is controlled to be same level. It is generally known that inner power density at passivated facet corresponds to approximately 2-3MW/cm² . The relationship between output power Po and inner power Pi is expressed as

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Kenj i Ikeda, Hisao Kumabe, Hirofumi Namizaki, and Wataru Susaki "High Power Diode Laser Research In Mitsubishi Electric", Proc. SPIE 0893, High Power Laser Diodes and Applications, (9 August 1988); https://doi.org/10.1117/12.944354

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