Long-term wavelength stability of high power laser diode bars on microchannel coolers

摘要

Laser diode reliability depends on both power and spectral stability over time. This report examines cases in which both corrosion and ionic deposition resulted in wavelength shifts from less than 1 nm to greater than 7 nm in 60 - 100W bars on microchannel coolers. Both corrosion and deposition seemed to be exacerbated by frequent and/or lengthy periods of stagnation in the DI water system. Analytical results including SEM images of FIB cross-sections illustrate deposits of up to several microns thickness of dielectric (oxide) material, as well as voiding caused by corrosion of Ni-plating out from under Au-plating through pinhole defects. Thermal modeling confirms the effect of such features on thermal resistance, correlating to observed wavelength shifts. Actions taken to address these issues are discussed.