We present a novel technique to frequency lock a laser to an optical cavity
. This technique, tilt locking, utilizes a misalignment of the laser with r
espect to the cavity to produce a nonresonant spatial mode. By observing th
e interference between the carrier and the spatial mode one can obtain a qu
antum-noise-limited frequency discriminator. Tilt locking offers a number o
f potential benefits over existing locking schemes, including low cost, hig
h sensitivity, and simple implementation. (C) 1999 Optical Society of Ameri
ca OCIS codes: 120.2230, 120.3180, 230.0250.