Abstract

We report the active frequency stabilization of a cw titanium sapphire (Ti:Al₂O₃) laser. Our preliminary efforts employ the simplest possible arrangement consisting of a piezoelectrically translated cavity mirror for servo control of the laser frequency and result in a fast laser linewidth of 20-kHz rms (detection bandwidth > 10 Hz). The Ti:Al₂O₃ laser used in our experiments is a commercial ring laser¹ and is locked to a stable optical cavity (FWHM = 2.4 MHz) with an FM reflection technique. The frequency noise characteristics of the locked system are measured with an independent diagnostic cavity (FWHM = 17 MHz) with broadband subtraction of amplitude noise. Although the piezoelectric mirror assembly in the laser cavity is not optimized for low mass or speed and the maximum servo unity gain bandwidth does not exceed a few kilohertz, we nonetheless observe that broadband components of the FM noise spectrum make negligible contributions to the laser linewidth above ~300 Hz for closed loop operation. At present, the residual linewidth of 20-kHz rms is dominated by a number of sharp features associated with mechanical resonances in the laser cavity and with line related harmonic noise.

© 1989 Optical Society of America