Effect of thermal lensing and the micrometric degraded regions on the catastrophic optical damage process of high-power laser diodes

Abstract

Catastrophic Optical damage (COD) is one of the processes limiting the lifetime of high-power laser diodes. The understanding of this degradation phenomenon is critical to improve the laser power and lifetime for practical applications. In this paper we analyze the defect propagation inside the cavity of quantum well (QW) highpower laser diodes presenting COD. For this, we studied the effect of highly localized thermal gradients and degraded regions on the laser field distribution. Finite element method (FEM) simulations are compared to experimental cathodoluminescence (CL) measurements. The presence of micrometric hot spots inside the QW induces the thermal lensing of the laser field. The laser self-focusing inside the cavity eventually generates a new hot spot, and, in a repetitive way, a sequence of hot spots would be created. This would account for the propagation of the dark line defects (DLDs) characteristic of this degradation mode.

Numerical Simulation of the Whole Thermal Lensing Process with Z-Scan-Based Methods Using Gaussian Beams

“…Furthermore, the relation obtained for Z-scan linking the signal to the induced phase shift in the center of the beam at = 0 (with a closed aperture sensing the maximum of the intensity profile) is ∆ = 0.14Δ 0 . The sensitivity is defined as the ratio of Comparing the results given by the fits according to Equation ( 5) on one side and Equation (6) on the other, one can notice that we do not obtain the same value for θ. Indeed, the fit realized in Figure 5 by Equation ( 6) takes into account the average value of the signal along the entire length of the V axis.…”

“…Many applications use the thermal lens (TL) principle as an ultrasensitive spectrophotometric readout [1] to characterize different physical phenomena, for example (recently found in the literature) to investigate molecular/particle dynamics [2], to measure the photothermal parameters of opaque solids [3], to understand thermal lensing effects using Z-scan-based methods at multiple laser repetition rates and multiple average powers [4,5], to study the effect of highly localized thermal gradients on the catastrophic optical damage process of high-power laser diodes [6], to evaluate optically induced temperature changes in colloidal samples for photothermal therapy [7], to quantify very low concentrations in solutions [8], and to image single light-absorbing nanoparticles by photothermal microscopy [9]. Recently, we have demonstrated experimentally the feasibility of extracting an image of the phase shift induced by TL and applying this method to map an inhomogeneous thin film doped with different concentrations of silver nanoparticles transversally [10].…”

Mode competition in broad-ridge-waveguide lasers

“…Both effects play a major role in the context of catastrophically optical mirror damage (COMD). However, COMD is a very complex process being still under research [34][35][36][37].…”