Abstract

The delayed self-homodyne detection technique gives a convenient method to study the linewidth of laser sources. We have performed linewidth measurements on a 1.55-µm noncommercial multi-quantum-well DFB laser using the modified homodyne technique with delays short and by comparing with the coherence time of the laser [1]. The setup includes a phase modulator to average out the critical dependence on the phase matching of the interfering fields when using a short delay. Furthermore, in the detection stage the signal is shifted up to a carrier frequency by an RF-oscillator and a mixer to allow the use of a standard spectrum analyzer. A fit of a theoretical model to the measurement data gives a value for the linewidth.

© 1998 IEEE