Bidirectional operation and gyroscopic properties of passively mode-locked Nd:YVO4 ring laser

A simple LD-end-pumped, passively mode-locked Nd:YVO4 ring laser with bidirectional outputs was demonstrated, and the gyroscopic properties of the ring laser was studied. The laser was continuous wave mode-locked by use of a semiconductor saturable absorber mirror (SESAM), and both clockwise and counter-clockwise outputs are stable laser pulse trains with pulse duration of 64 ps. The continuous wave mode-locking was obtained under pump power as low as 540 mW. The average output power is 50 mW for the counter-clockwise laser and 52mW for the clockwise laser under pump power of 1378 mW. The whole slope efficiency of the ring laser is about 9.4%. The two output pulse trains of the ring laser were combined to study its gyroscopic properties. The beat frequency of the pulsed solid-state laser gyro versus the rotation rates follows the Sagnac formula. The laser gyro has a large dead band of 6-8 dec/s, which was believed to be caused by the long pulse duration and the colliding of the opposite pulses on the SESAM.