Efficient iterative algorithm for improving frequency sweep linearity of external cavity lasers

Aiming at the problem of poor frequency sweep linearity of frequency-modulated continuous wave lidar, a high-efficiency linearization pre-modulation correction method for external cavity diode laser (ECDL) 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 conformed to the physical properties of piezoelectric ceramics (PZT) was designed, and the high linearity frequency sweep laser output of ECDL was realized. The laser system could achieve a linear frequency sweep with an output bandwidth of 1.1 GHz under the repetition frequency of 60 KHz, and the residual nonlinearity could reach 10⁻⁷. The measurement accuracy at the centimeter-level at a distance of 80 m was verified through experiments, and the meter-level measurement accuracy was achieved at a distance of 3 km. The results show that the algorithm can effectively solve the linearization correction problem of ECDL of the PZT.