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.