Semiconductor Laser Engineering, Reliability and Diagnostics: A Practical Approach to High Power and Single Mode Devices

Part II

DIODE LASER RELIABILITY

Overview

Responsible for the significant improvement of the high-power performance of diode lasers in the past years has also been a remarkable progress in the optical strength of semiconductor materials and device structures. Optical strength is the capability to resist optical damage during laser operation. Optical damage phenomena can happen in the bulk of the laser cavity and above all at the susceptible laser mirror facets. They belong to the group of sudden laser degradation modes and depend strongly on the optical emission density, laser material system, structure, type, and concentration of defects in the laser cavity, at interfaces, and at mirror surfaces. The power limits at catastrophic optical damage (COD) events could be increased significantly by various technological concepts and approaches, which will be discussed in detail in this part.

To illustrate the progress, record-high, continuous wave (cw) critical power densities to COD at mirror facets of >100 MW/cm2 have been reported for the demanding single-mode, edge-emitting 980 nm GaAs-based pump diode lasers (Lichtenstein et al., 2004). These devices delivered COMD-free output powers >1.7 W within a near-field area of ~ 3 μm×0.6 μm at FWHM 2×10−8 cm2 assuming a uniform optical filling of the near-field spot.

Excellent laser reliability has been usually associated with InP-based materials ...