Abstract

A laser gyroscope is a rotation sensing device. As the laser is rotated the two counterpropagating pulses in the cavity develop a frequency shift between them proportional to the rotation rate. For values of the rotation rate below a certain cutoff the pulses can lock to the same frequency, making the gyroscope ineffective. This lock-in phenomenon can be caused by backscattered radiation from one pulse (off the acousto-optic modulator, diode, etc.), which is coupled into the counterpropagating pulse. This coupling falls off exponentially as a function of the distance from the backscattering element. Therefore to minimize this coupling one can design a laser for which the pulse crossings are far from the cavity elements. This can be achieved by modulating the diode at twice the cavity round-trip rate (generating two pulses in the cavity) and by simultaneously modulating the acousto-optic modulator (essentially an optical gate) at three times the cavity rate.

© 1992 Optical Society of America