Efficient Iterative Algorithm for Improving Frequency Sweep Linearity of External Cavity Lasers

Aiming at the problem of poor sweep linearity of frequency-modulated continuous wave lidar, a high-efficiency linearization pre-modulation correction method for external cavity lasers （external cavity diode lasers, ECDLs） with piezoelectric ceramic external cavities was proposed. Based on the ECDL model of volume grating feedback and the bias characteristics of piezoelectric ceramics, an iterative control algorithm that conforms to the physical properties of PZT is designed, and the high linearity frequency-sweeping laser output of ECDL is realized. The laser system can achieve a linear sweep with an output sweep bandwidth of 1.1 GHz under the repetition frequency of 60 KHz, and the residual nonlinearity can reach 10⁻⁷, and the measurement accuracy at the centimeter level at a distance of 80 m has been verified through experiments. Meter-level measurement accuracy is achieved at a distance of 3 km. The results show that the algorithm can effectively solve the linearization correction problem of the piezoelectric ceramic bias device's ECDL.