Optimized optoelectronic measurement electronics for multi-axis heterodyne interferometry with subnanometer precision

Subnanometer precision in multi-axis heterodyne interferometry is crucial for advanced manufacturing, semiconductor fabrication, and ultraprecision metrology, where even minimal signal noise can impact performance and quality. Extremely weak or strong interference light intensities of each axis pose significant challenges to maintaining subnanometer precision. We propose a processing method that optimizes interference signals’ signal-to-noise ratio (SNR) while achieving a larger dynamic range through dual-adaptive feedback. A newly established joint SNR model of an avalanche photodiode (APD) and a trans-impedance amplifier is used to optimize the SNR of the detected interference signal by adjusting the avalanche gain of the APD according to the light intensity. Subsequently, the amplitude of the sampled interference signal is measured using a quadrature demodulation algorithm and held constant using a proportional–integral–derivative-controlled programmable gain amplifier. Implemented on custom-designed optoelectronic measurement electronics, the proposed method helps the multi-axis heterodyne interferometer achieve a 25 pm measurement precision across a dynamic range of 0.1 to 10 μW (1:100). Compared with existing processing methods, it expands the dynamic range 14-fold and improves measurement precision by 55%. By enhancing measurement reliability and accuracy, the proposed approach contributes to achieving subnanometer precision in advanced manufacturing applications.