Mode locking of strip buried heterostructure (AlGa)As lasers using an external cavity

Abstract

Active and passive mode locking of strip buried heterostructure lasers is observed using an external cavity consisting of a lens and a mirror. Using the second‐harmonic‐generation method to obtain the second‐order autocorrelation function we obtain Gaussian pulses as short as 35.7 psec (FWHM) at a 1.9‐GHz repetition rate. The optical spectrum of the mode locked laser consists of longitudinal modes of the composite cavity spaced by ∼0.05 Å, whose amplitudes are modulated by the 2.09‐Å‐mode spacing of the laser itself, and contained under a Gaussian envelope of 9.5‐Å FWHM. Additional very sharp structure (∼1.6‐psec FWHM) in the autocorrelation is shown to result from the presence of several laser mode groups.