Large-Optical-Cavity (AlGa) As–GaAs Heterojunction Laser Diode: Threshold and Efficiency

Abstract

Detailed operating properties and first-order theory of the large-optical-cavity (LOC) laser diode are described, including threshold current density, efficiency, mirror damage under pulsed operation, and cw operation at room temperature. This new structure differs from the single-heterojunction and conventional double-heterojunction laser in that the optical-cavity thickness can be made very large and is varied independently of the pair recombination region which is always less than a diffusion length thick. Large optical cavities are possible with high differential quantum efficiencies at room temperature because the radiation propagates predominantly in low-loss n-type material, allowing the design of lasers for specific applications. The problem of catastrophic degradation in the wide-cavity devices is reduced because of the lower optical flux density. The threshold current density depends on the width of the mode-guiding region, increasing with increasing thickness of that region. Power conversion efficiency values of 22% have been achieved at room temperature with narrow-cavity lasers.