InGaAs-GaAs quantum-dot lasers

TLDR

Quantum‑dot lasers provide superior lasing characteristics compared to quantum‑well and wire lasers, featuring a delta‑like density of states that yields broad‑gain spectra (~50 meV FWHM), ultrahigh material gain (~10^5 cm^–1), high differential gain (~10^–13 cm^2), and strong nonlinear gain effects. The InGaAs‑GaAs quantum‑dot lasers achieve record threshold current densities of 40 A cm^–2 at 77 K and 62 A cm^–2 at 300 K, maintain a characteristic temperature of 385 K up to 300 K, reach internal quantum efficiencies of ~80 %, exhibit a linewidth enhancement factor of ~0.5, and allow emission tuning from 0.95 µm to 1.37 µm at 300 K, while their modulation bandwidth is limited by nonlinear gain but can be improved by optimizing the energy separation between QD and barrier states.

Abstract

Quantum-dot (QD) lasers provide superior lasing characteristics compared to quantum-well (QW) and QW wire lasers due to their delta like density of states. Record threshold current densities of 40 A/spl middot/cm/sup -2/ at 77 K and of 62 A/spl middot/cm/sup -2/ at 300 K are obtained while a characteristic temperature of 385 K is maintained up to 300 K. The internal quantum efficiency approaches values of /spl sim/80 %. Currently, operating QD lasers show broad-gain spectra with full-width at half-maximum (FWHM) up to /spl sim/50 meV, ultrahigh material gain of /spl sim/10/sup 5/ cm/sup -1/, differential gain of /spl sim/10/sup -13/ cm/sup 2/ and strong nonlinear gain effects with a gain compression coefficient of /spl sim/10/sup -16/ cm/sup 3/. The modulation bandwidth is limited by nonlinear gain effects but can be increased by careful choice of the energy difference between QD and barrier states. The linewidth enhancement factor is /spl sim/0.5. The InGaAs-GaAs QD emission can be tuned between 0.95 /spl mu/m and 1.37 /spl mu/m at 300 K.