The Analysis on 808 nm Semiconductor Laser Facet Temperature Characteristics

Abstract

The facet temperature characteristic of 808 nm semiconductor laser was researched. Catastrophic optical mirror damage (COMD) is one of major factor, which drastically limits optical power and lifetime of semiconductor laser. The heat source of semiconductor laser facet and the facet temperature field distribution were analyzed. The model of facet temperature distribution was established. The facet temperature characteristic of 808 nm semiconductor lasers for the ZnSe passivation coating of facet and uncoated the ZnSe passivation coating was analyzed. It is found that the temperature of device with the coated ZnSe passivation coating is lower than uncoated ZnSe passivation coating by 5.3C. It can effectively reduce the semiconductor laser facet temperature and improve the COMD threshold of 808 nm semiconductor laser with ZnSe passivation coating. Introduction 808 nm high power semiconductor lasers are widely used in pumping solid state laser[1-2], laser medical[3-4], material processing and military applications[5]. With the increase on output power and brightness of solid state laser, we need more performance pumping source[6]. Semiconductor laser devices are subject to optical power, drive current and thermal effect while working. The facet of semiconductor laser devices can be easily oxidized and oxidized facet will dramatically degenerate device, even result in catastrophic optical mirror damage (COMD) [7] and make device failure. In order to improve the COMD threshold of semiconductor laser facet, the most common method is to coat passivation film which can also protect facet and make semiconductor laser work at high power. We selected ZnSe as facet passivation film to reduce the facet temperature. The energy gap width of ZnSe material is 2.75eV, which is much larger than GaAs material. This can effectively prevent electrons and holes diffusing and recombining at the facet, reduce optical absorption and facet heat. The resault is ZnSe passivation film can effectively inhibit the semiconductor laser facet being oxidized, improve COMD threshold and output power. Physical Model There were two parts of heat generated by semiconductor laser, the heat source from active region and the heat source from non-active region[8-9]. (1)The heat source from active region(Qact): Under working condition, the active region generated lots of carriers and photons. The result of the carriers and photons was nonradiative recombination, radiant absorption and absorption of the spontaneous radiation, and then generating a large amount of heat. (2)The heat source from non-active region(QF): the facet heat source was the joule heat. The total temperature distribution of facet: J act Q Q Q + = (1) However, when semiconductor lasers was under high continuous current condition or high International Industrial Informatics and Computer Engineering Conference (IIICEC 2015) © 2015. The authors Published by Atlantis Press 854 intensity pulsed current condition, facet heat will gradually ascend, which leads to light absorption of facet, and generates more heat. The heat made quantum well bandgap become narrow, resulting in more light absorption and generating more heat. As to analyse temperature distribution of facet, facet optical loss heat source(Qopt)[10] is a need parameter when the divices work at high continuous current condition or high intensity pulsed current condition. Qopt is that the heat generated by light absorption of facet under high temperature condition. Therefore, the facet heat source of divice under high continuous current condition or high intensity pulsed current condition: J opt F Q Q Q + = (2) The total temperature distribution of facet: