Characterization of the high power laser diode and beta iron disilicde by microscopic Raman spectroscopy

点击翻译按钮获取中文摘要

In this project we have surveyed the availability of microscopic Raman spectroscopy for the characterization of the high power laser diode facet and have characterized the basic properties of iron disilicide deposited by pulsed laser deposition method.Most generally GaN and related alloys are used on blue or violet laser diodes. We applied the microscopic Raman spectroscopy to the violet laser diode facet in operating condition. Laser light from active laser diode can be blocked by the filter and its level is low enough to obtain Raman signal. Although applicable to the red laser diode, it is considered that this method is not applicable to GaN system because of the strong yellow emission from the diode. This strong yellow emission overlaps with relatively weak Raman signal, even under threshold current. According to the theoretical consideration, it is difficult to remove the thermal energy produced at the facets of the light emitting devices under high power operation condition by thermal conduction of the crystals. Direct solution of this problem is to fill the device package with the thermal conduction fluid. Helium is the most effective material and some liquids are available depending on the condition of devices.β-FeSi_2 polycrystalline microstructure was successfully formed at low temperature in the form of droplet with room temperature pursed laser deposition and post-annealing below 350℃ employed. Evidence of the β-phase formation was obtained through microscopic Raman spectroscopy and TEM analysis. The low temperature nature may originate from formation of intermediate amorphous phase possibly provided by quick heat removal from Fe-Si melts generated by laser ablation. This low temperature scheme offers an alternative method of producing polycrystalline β-FeSi_2 without higher temperature processes, which could be beneficially compatible with the standard Si device fabrication processes.