Miniaturized laser interferometer using dynamic current-wavelength modulation for high precision displacement measurement

Abstract

This study proposes a compact displacement measurement interferometer facilitated by a novel dynamic current-wavelength modulation method for high-precision displacement measurement. This technique compensates for the modulation depth by precisely predicting the optical path difference (OPD) with frequency-scanning interferometry (FSI) to achieve consistent modulation depth over an extensive measurement range. Additionally, a wavelength-locking method was developed for the 1550 nm band, using the P7 absorption peak of hydrogen cyanide (HCN) gas to lock the central wavelength of the laser. The experimental results showed that the wavelength stability can be kept within 128 femtometers for 8 hours with the proposed method. Furthermore, the deviations are less than 40 nm compared to a calibrated laser interferometer within the 300 mm measurement range. This research offers precise positioning feedback for precision engineering, paving the way for advanced semiconductor manufacturing processes.