Abstract
Optical gain and optical losses are separately measured in commercial laser diodes by simple analysis of spectral and electrical characteristics, and with no special specimen preparation or handling. The aim is to bring device analysis, for characterization and reliability purposes, closer to the intimate physical processes that rule over laser diode operation. Investigation includes resonating and non-resonating optical cavities.
Highlights
The origin of the concept of optical gain itself follows from Einstein’s intuition about the stimulated emission within a framework of quantum energy exchanges [1,2]. The extension of his considerations to the non-equilibrium steady state for an infinite uniform domain leads to different forms of rate equations [15,34,67], which are the foundation for laser diode theory
The original method of Cassidy calculates the ratio | F |2+ /| F |2min, and gets the same quantity ρ as for the Hakki–Paoli method. The advantage in this case is that the smoothing of maxima introduced by the experimental equipment is no more a concern, so that extreme resolution is no longer required for gain measurements
The hypothesis of diffusing protons across the two different 3D geometries of the devices allowed us to reconstruct the link between the time varying proton density and the observed variations in the LI curves, up to measurement of a diffusion coefficient corresponding to the known value for interstitial hydrogen diffusing in gallium arsenide and indium phosphide at room temperature
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. It takes advantage of the results, and, referring to one more formulation from the foundation papers on laser diodes, proposes an alternative formula to replace those of Section 2, suitable for gain calculation when spectra do not show any modulation caused by optical resonances. The origin of the concept of optical gain itself follows from Einstein’s intuition about the stimulated emission within a framework of quantum energy exchanges [1,2] The extension of his considerations to the non-equilibrium steady state for an infinite uniform domain leads to different forms of rate equations [15,34,67], which are the foundation for laser diode theory. It is not a trivial point, because of its implications for some gain measurement methods proposed in the literature
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