Characterisation of a 760 nm vertical‐cavity surface‐emitting laser structure by reflectance and photomodulated reflectance

Abstract

AbstractPhotomodulated reflectance (PR) studies are conducted on the wafer of a vertical‐cavity surface‐emitting laser (VCSEL) designed for oxygen sensing up to high temperatures. By varying the angle of incidence, the VCSEL cavity mode (CM) is tuned through the positions of two static PR features, revealing the ground‐state electron to heavy‐hole and light‐hole quantum well (QW) transition energies. The PR is also measured over a large temperature range, revealing that the CM becomes tuned to the heavy‐hole QW transition at a temperature of 115 ± 1 °C, where the energies coincide at ∼1.631 eV (760 nm). It is observed that when tuned, the width of the CM feature in the reflectance spectrum is maximised. Reflectance simulations confirm that this broadening occurs when the CM is tuned with an excitonic transition, where the cavity absorption is maximised. Therefore, monitoring this broadening as the energies of the CM and QW are varied relative to each other could provide an additional, non‐destructive technique for determining the VCSEL ground‐state QW transition energy and the conditions under which it is tuned to the CM. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)