Integration of polarization-multiplexing and phase-shifting in nanometric two dimensional self-mixing measurement

Abstract

Integration of phase manipulation and polarization multiplexing was introduced to self-mixing interferometry (SMI) for high-sensitive measurement. Light polarizations were used to increase measuring path number and predict manifold merits for potential applications. Laser source was studied as a microwave-photonic resonator optically-injected by double reflected lights on a two-feedback-factor analytical model. Independent external paths exploited magnesium-oxide doped lithium niobate crystals at perpendicular polarizations to transfer interferometric phases into amplitudes of harmonics. Theoretical resolutions reached angstrom level. By integrating two techniques, this SMI outperformed the conventional single-path SMIs by simultaneous dual-targets measurement on single laser tube with high sensitivity and low speckle noise. In experimental demonstration, by nonlinear filtering method, a custom-made phase-resolved algorithm real-time figured out instantaneous two-dimensional displacements with nanometer resolution. Experimental comparisons to lock-in technique and a commercial Ploytec-5000 laser Doppler velocity meter validated this two-path SMI in micron range without optical cross-talk. Moreover, accuracy subjected to slewing rates of crystals could be flexibly adjusted.

A Novel Method for Quadrature Signal Construction in a Semiconductor Self-Mixing Interferometry System Using a Liquid Crystal Phase Shifter

“…Methods of quadrature signal construction have also been applied to SMI vibration measurement to improve its accuracy. In one instance, the integration of phase manipulation and polarization multiplexing was introduced to self-mixing interferometry (SMI) for highly sensitive measurement [22]. Phases shifts induced by EOMs were utilized to generate multi-harmonics.…”

Integrated Electro-Optics Modulator

“…The e-channel source is a speaker driven by AC voltage, and the o-channel source is a closed-loop one-dimensional piezoelectric ceramic (PZT). In this polarizationmultiplexing system, the formed optical intensity fluctuations induced by the measured two external targets are modulated at different-frequency phase-shifting, therefore, no overlapping error happens after electro-optic modulation/manipulation[9, 10,20].…”