Measurement of optical cavity properties in semiconductor lasers byFourier analysis of the emission spectrum

摘要

We present several observations on a novel method for thenevaluation of the internal loss properties in semiconductor lasers. Thenmethod we use involves Fourier analysis of the Fabry-Perot mode spectrumnwhen operating the device below lasing threshold. The observation ofnvarious structural features in the Fourier transform domain allows us tonextract important information on the laser cavity. As one example, thenamount of cavity propagation loss/gain, or net gain, can be derived fromnthe decay rate of harmonics of the Fourier spectrum. A comparisonnbetween experimental and calculated gain versus wavelength data fornlasers fabricated in the AlGaAs, AlGaInP, and AlGaInN material systemsnis given. As a second example, this method also allows thenidentification of the density and strength of intracavity scatteringncenters. This is an important capability for the fabrication of bluendiode lasers in the gallium-nitride material system