Facet degradation of high-power diode laser arrays

Abstract

Micro-Raman facet temperatures of high-power diode lasers with different waveguide architectures are compared. For regular operation conditions, the thermal behavior of "unaged" arrays emitting in the 808-nm wavelength region with different architectures is similar, however, with an increased load thermal behaviors differ significantly and exhibit failure events at facet temperatures typically between 150 and 450 deg C. From various experiments, among them facet temperature measurements for ultrahigh-power operation as well as by preparative failure analytics, we provide evidence that in arrays the front facets are significantly affected by device operation and influence the failure behavior of the whole high-power diode laser also in cases when the device failure is accompanied by dislocation creation inside the device

Mechanisms and fast kinetics of the catastrophic optical damage (COD) in GaAs‐based diode lasers

“…Nevertheless, the COD process in present QW devices is still clearly driven by emission power. Statistical analysis of T facet -measurements for different BA device batches under cw high-power operation (1.7 W) has been reported by Tomm et al [110]. This work allowed for a systematic comparison of different waveguide designs with respect to T facet and -in this way -to their tendency to develop COD.…”

“…The intensities of Stokes-and anti-Stokes lines follow Bose-Einstein statistics. Line intensity ratios and spectral line shifts that may be extracted from the same spectra, allow for an independent extraction of facet temperatures and an agreement of both data sets represents a successful crosscheck [110]. In general, the temperature values determined from line shifts show a smaller scattering but might be systematically affected by strain causing an additional line shift.…”

“…Among others, phonons represent the elementary excitations relevant for the inelastic scattering process. Since cleaving of (100)-oriented standard GaAs substrate material results in (110) facet planes, transverse optical phonons are of special relevance according to the Raman selection rules. Typically, several sets of such phonons are detectable which belong to the different binary sublattices of the active region materials such as the GaAs-and AlAs-sublattices for waveguide made of Al x Ga 1 x As.…”

Simulation of facet heating in high-power red lasers

“…Facet temperatures were measured by micro-Raman (uR) spectrometry; see, e.g., ref [28]. The excitation source was the 488 nm line of an Ar-ion laser focussed on the front facet on a spot which diameter, 0i/ e~l um, covers the active region.…”

Thermal properties of high power laser bars investigated by spatially resolved thermoreflectance spectroscopy

“…However, limitations regarding device lifetime and reliability still limit their access to all potential application fields. Reabsorption of the laser radiation 6 and catastrophic optical damage (COD) 7 are among the mechanisms which cause laser bar degradation and consequently limit emitted optical power and device lifetime.…”