Rayleigh model-based control of piezoelectric-actuated external cavity diode laser for enhanced wavelength stability

Due to the hysteresis nonlinearity and mechanical resonance in the piezo-actuated nanopositioning stages (PANS) of external cavity diode lasers (ECDL), the output light of ECDL is limited by small mode-hop-free tuning range and low scanning frequency. A rate-dependent Rayleigh model-based feedforward-feedback control method is proposed in this work to handle these limitations. First, the modified second-order Rayleigh model is obtained by voltage dependence and rate dependence tests. Then, an inverse Rayleigh model is constructed based on the energy compensation method. Combined with the input signal trajectory optimization method, the optimized compensation signals for triangular waveforms are constructed. To eliminate steady-state errors introduced by feedforward control, the feedforward and feedback control strategy is applied and the corresponding test platform is established. The experimental results show that the displacement response error at the operating frequency is controlled within 1.02%. Finally, synchronous tuning experiments of ECDL are conducted, and the experimental results show that the feedforward-feedback control method can achieve mode-hop-free tuning range of 109.5 GHz under the scanning frequency of 80 Hz. Compared with existing methods, this forward and feedback control method based on the Rayleigh model has the advantages of high linearity of displacement response, low system tracking error, and good system stability.