Narrow-line-width diode laser with a high-Q microsphere resonator

A new modification of external optical feedback (OFB) was used to narrow th e line of a diode laser (DL). A 'whispering gallery' (WG) mode of a high-e microsphere was excited by means of frustrated total internal reflection wh ile the feedback for optical locking of the laser was provided by the intra cavity Rayleigh backscattering. The similar to 600 MHz beatnote of the two laser diodes optically locked to a pair of orthogonally polarized modes of the same microresonator had the indicated spectral width of 20 kHz, and the stability of 2 x 10(-6) over averaging time of 10 s. The feasibility of mi niature sub-kHz-line width laser is discussed. (C) 1998 Published by Elsevi er Science B.V. All rights reserved.