Modelling and experimental characterization of double layer InP/AlGaInP quantum dot laser

Abstract

Spectrum of an InP/AlGaInP self- assembled double-layer quantum dot (QD) laser fabricated by metal–organic vapor-phase epitaxy is theoretically and experimentally investigated. A bimodal QD size distribution (small and large QD groups) was detected which is formed during the fabrication. A model is proposed based on rate equations accounting for the superposition of two inhomogeneous QD groups. The total output power and the power spectral density (PSD) of the fabricated QD laser are experimentally characterized at room temperature. The output spectrum is segmented into the sum of two Gaussians curves (super Gaussian) belonging to the small and large QD groups. The peak PSD and the spectral width of each group are extracted and their dependency on the injected current density is analysed. The peak of the large QDs is found to be dominant at small current while the peak of the small QDs dominated at high current alongside a reduction in its spectral width leading to lasing based on them. This behaviour is attributed to the saturation of the large QDs energy levels due to its relatively long radiative lifetime. The experimental analysis is in a good agreement with the theoretical results.

Effective reflectivity for flat and spherical external cavity semiconductor laser with multi spatial mode beam profile

“…Effective reflectivity is a term adopted by the previous literature theoretical models [6][7][8][9] to describe the external cavity interactions while considering the output beam profile as a plane wave. In spite of the practical measurement of the semiconductor edge emitting laser beam profile indicating the multi spatial beam nature of the output laser field beam profile which is described by a combination of higher order Hermite Gaussian spatial beams [10][11][12][13][14][15][16][17] .…”