Algorithm for measuring the internal quantum efficiency of individual injection lasers

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Abstract
A new algorithm permits determination of the internal quantum efficiency ηi 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 ηi. 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.