Spectral perturbations in a semiconductor laser: I. Anomalous splitting in the mode-beating spectrum

Mode-beating spectra and their current and temperature dependences are studied in a semiconductor laser. In the mode-beating spectrum of InGaAs quantum well lasers, the anomalous splitting of the difference-frequency line into three components f⁰, f⁺ and f^- is observed. The splitting increases with increasing optical power above the threshold. The component f⁰ is less mobile and shifts to the red with increasing temperature. The component f⁺ shifts to the blue, whereas the weak f⁰ component shifts to the red. The difference f⁺-f⁰ amounts to 400 MHz, which is ~5% of the value of f⁰ in a 5-mm long diode cavity. No anomalous splitting was observed in quantum dot lasers.