Suppression of frequency-mixing effect for pm-level heterodyne interferometers based on "zero coupling" optical path...

Area of Science:

• Optics and Photonics
• Metrology
• Precision Engineering

Background:

• Stray light in interferometers causes optical path length (OPL) noise, limiting low-frequency displacement measurements.
• Heterodyne laser interferometry is particularly susceptible to this noise, impacting measurement precision.

Purpose of the Study:

• To develop an analytical model for stray light effects in heterodyne laser interferometers.
• To propose and validate a novel noise suppression scheme for enhanced low-frequency displacement measurements.

Main Methods:

• Analytical modeling of stray light and its nonlinear coupling effects on OPL.
• Developing a noise suppression technique by locking stray light OPL to a zero coupling point.
• Experimental verification of the proposed noise suppression scheme.

Main Results:

• Identified specific OPLs of stray light that minimize frequency-mixing impact.
• Demonstrated a significant enhancement in interference displacement measurement noise suppression.
• Achieved a displacement noise level below 6 pm/Hz^1/2 in the 1 mHz frequency band.

Conclusions:

• The proposed scheme effectively suppresses stray light-induced OPL noise in heterodyne interferometers.
• Locking stray light OPL to the zero coupling point is a viable strategy for improving low-frequency displacement metrology.
• The method significantly enhances the precision of interferometric measurements in critical low-frequency applications.