Abstract

Five external-cavity diode lasers (diode lasers with one facet antireflection coated and feedback provided by the mirror at the other end of the external cavity) have been made to operate coherently by placing a spatial filter at the Fourier plane of the lens system in the cavity.¹ For cw operation, the spectral linewidth of the emission from this coherent ensemble was determined to be less than the 7.5-MHz (1.7 × 10⁻⁵-nm) resolution of the Fabry-Perot spectrum analyzer used in the measurement. Preliminary results for pulsed-mode operation are presented for dc biases both below and above threshold. Spectral behavior of the coherent ensemble is compared with that of external-cavity lasers (no spatial filter) and of similarly constructed diode lasers that were not antireflection coated. Operating behavior of the ensemble with all five elements pulsed simultaneously, and also with one or more elements providing cw feedback while the others are pulsed, are presented.

© 1985 Optical Society of America