Self-calibration of the secondary laser source in two-color Linnik interferometer

Abstract

The imaging Linnik interferometer equipped with two lasers of different colors is under development and metrological study at National Metrology Institute of Brazil (INMETRO). This work reports the self-referenced method for practical calibration of the secondary laser wavelength. The method is based on accurate digitalization and comparison of the waveforms for both reference He-Ne stabilized laser at 633 nm and secondary laser diode at 488 nm. The process makes use of multiple step phase-shifting technique for waveform measurement and multi-parameter fit for wavelength extraction. The advantage of the method is that no extra hardware of realignment of interferometer is required to perform the calibration.