Dual-frequency multifunction lidar

The design and performance of a continuous wave dual-frequency multifunction lidar system is presented. The system is based on the use of the nonlinear dynamics of an optically injected semiconductor laser. Under proper operating conditions, the laser emits a dual-frequency beam with a broadly tunable microwave separation. The two optical lines are coherently locked to each other using an external microwave synthesizer, resulting in a stable microwave beat frequency. The lidar system is capable of simultaneous velocity and range measurement of remote targets. The velocity is measured from the Doppler shift of the microwave beat frequency. The stability of the microwave beat frequency enables accurate measurement of low velocities. In addition, the stable locking enables long-range measurements because of the long microwave coherence length. Ranging is accomplished by extracting the time-of-flight information carried on the residual microwave phase noise. We demonstrate preliminary measurements of velocities as low as 26 μm/s and range measurements of 7.95 km with 2% accuracy.