Algorithm for measuring the internal quantum efficiency of individual injection lasers

Abstract

A new algorithm permits determination of the internal quantum efficiency η_i of individual lasers. Above threshold, the current is partitioned into a ’’coherent’’ component driving the lasing modes and the ’’noncoherent’’ remainder. Below threshold the current is known to grow as exp(qV/n₀KT); the algorithm proposes that extrapolation of this equation into the lasing region measures the noncoherent remainder, enabling deduction of the coherent component and of its current derivative η_i. Measurements on five (AlGa)As double‐heterojunction lasers cut from one wafer demonstrate the power of the new method. Comparison with band calculations of Stern shows that n₀ originates in carrier degeneracy.