Nonlinearities of GaAlAs lasers - Harmonic distortion

Abstract

Narrow stripe lasers ( <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2-6 \mu</tex> m) and transverse junction lasers exhibit excellent linearity. The dependence of relative second-and third-harmonic distortion is investigated as a function of modulation frequency and modulation current. Relative second- and third-harmonic distortion of -50 and -70 dB is observed for an optical signal of 4 mW p-p ( <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">f_{m} = 60</tex> MHz). Intermodulation products are compared with the harmonic distortion and good agreement is obtained between the two quantities when the relations for a simple nonlinearity without memory are used. The measured distortion is in agreement with distortion calculated from rate equations.