Catastrophic facet and bulk degradation in high power multi-mode InGaAs strained quantum well single emitters

Abstract

Extensive investigations by a number of groups have identified catastrophic sudden degradation as the main failure mode in both single-mode and multi-mode InGaAs-AlGaAs strained quantum well (QW) lasers. Significant progress made in performance characteristics of broad-area InGaAs strained QW single emitters in recent years has led to an optical output power of over 20W and a power conversion efficiency of over 70% under CW operation. However, unlike 980nm single-mode lasers that have shown high reliability operation under a high optical power density of ~50MW/cm 2 , broad-area lasers have not achieved the same level of reliability even under a much lower optical power density of ~5MW/cm 2 . This paper investigates possible mechanisms that prevent broad-area lasers from achieving high reliability operation by performing accelerated lifetests of these devices and in-depth failure mode analyses of degraded devices with various destructive and non-destructive techniques including EBIC, FIB, and HR-TEM techniques. The diode lasers that we have investigated are commercial MOCVD-grown broad-area strained InGaAs single QW lasers at ~975nm. Both passivated and unpassivated broad-area lasers were studied that yielded catastrophic failures at the front facet and also in the bulk. To investigate the role that generation and propagation of defects plays in degradation processes via recombination enhanced defect reaction (REDR), EBIC was employed to study dark line defects in degraded lasers, failed under different stress conditions, and the correlation between DLDs and stress levels is reported. FIB was then employed to prepare TEM samples from the DLD areas for cross-sectional HR-TEM analysis.

Catastrophic optical bulk damage (COBD) — A new degradation mode in high power InGaAs-AlGaAs strained QW lasers

“…These hot spots can lead to a significant temperature rise at localized areas and can eventually damage output facets of unpassivated InGaAs-AlGaAs QW lasers (or Type I lasers) [1] and passivated and unpassivated AlGaAs QW lasers (or Type II lasers) [7] as the process including optical absorption and carrier recombination causes local temperatures to reach a threshold for COMD. This process generates a series of blisters at the front facet that are separated by multiples of a filament-to-filament spacing.…”

“…Type III lasers have a significantly longer latency period compared to Type I and Type II lasers before they degrade. During this latency period, recombination enhanced defect reaction (REDR) can increase the density of pre-existing point defects [1,6]. We used DLTS to identify pre-existing point defects such as EL2 traps in pre-and post-aged Type I and Type III lasers and it is well known that EL2 traps behave as highly efficient NRCs [6].…”

“…Introduction Two groups reported catastrophic optical bulk damage (COBD) in multi-mode InGaAs-AlGaAs strained quantum well (QW) lasers in 2009 [1,2]. COBD is different from catastrophic optical mirror damage (COMD) in that dark line defects (DLDs) are initiated from the inside of a laser cavity (thus, it is called "bulk"), whereas DLDs are initiated from the front facet for COMD [3].…”

“…They reported in 2011 that their lasers no longer degrade by COMD, but most of them degrade by COBD [4]. Non-radiative recombination centers (NRCs) [1] and bulk defects [2] were proposed as the root causes of COBD, but in our recent publication, we reported that bulk defects are unlikely the root causes for COBD especially in state-of-the-art lasers [5]. In the present study, we further investigated degradation mechanisms responsible for COBD in multi-mode InGaAsAlGaAs strained QW lasers.…”

Degradation mechanism of SESAMs under intense ultrashort pulses in modelocked VECSELs

“…This mechanism has been known to cause catastrophic optical damage in InGaAs QW lasers through facet oxidation or defect formation under high-power operation [38][39][40][41] . To test this hypothesis, we wanted to examine if the rate of degradation would depend on the proximity of the InGaAs QW to the semiconductor-air interface.…”