Harmonic and Intermodulation Distortion in Direct Intensity Modulated Quantum Cascade Lasers

In this paper, nonlinear distortion in a quantum cascade laser arising from direct intensity modulation is studied. Harmonic and intermodulation distortion expressions for small sinusoidal modulation signals are derived using a perturbation method. The expressions are validated by making a comparison with a large signal simulation of a quantum cascade laser equivalent circuit. The effects of bias current, optical modulation depth, and modulation frequency on harmonic and intermodulation distortion are examined.