Phase-Drift-Suppression Method Using Higher Order Harmonics in Heterodyne Detection

Abstract

The theory of phase-drift-suppression method and simulated results using sinusoidal and triangular phase modulation have been described. The computed signal intensity is defined as the square root of the sum of squares of each harmonic intensity in the heterodyne beat signal. The relations between the computed signal intensity, its relative standard deviation, and the modulation indexes are shown through simulations. Modulation indexes that suppress the phase drifts were obtained, including up to the eighth harmonic. The stability of the beat signal in sinusoidal and triangular phase modulation was confirmed to increase 245 times using harmonics from the fundamental to the fourth order and a modulation index of 2.8 rad, and to increase 490 times using harmonics from the fundamental to the second order and 2.9 rad.