Longitudinal piezoelectric resonant photoelastic modulator for efficient intensity modulation at megahertz frequencies

TL;DR

This paper introduces a novel longitudinal piezoelectric resonant photoelastic modulator using lithium niobate for highly efficient, single-frequency intensity modulation at megahertz frequencies, with potential applications in LiDAR and imaging.

Contribution

It presents a new type of intensity modulator based on resonant acoustic modes in lithium niobate, achieving record modulation efficiency at high frequencies.

Findings

Achieves record-breaking modulation efficiency in the megahertz range.

Demonstrates integration with image sensors for time-of-flight imaging.

Operates with a wide acceptance angle for practical applications.

Abstract

Intensity modulators are an essential component in optics for controlling free-space beams. Many applications require the intensity of a free-space beam to be modulated at a single frequency, including wide-field lock-in detection for sensitive measurements, mode-locking in lasers, and phase-shift time-of-flight imaging (LiDAR). Here, we report a new type of single frequency intensity modulator that we refer to as a longitudinal piezoelectric resonant photoelastic modulator. The modulator consists of a thin lithium niobate wafer coated with transparent surface electrodes. One of the fundamental acoustic modes of the modulator is excited through the surface electrodes, confining an acoustic standing wave to the electrode region. The modulator is placed between optical polarizers; light propagating through the modulator and polarizers is intensity modulated with a wide acceptance angle and record breaking modulation efficiency in the megahertz frequency regime. As an illustration of the potential of our approach, we show that the proposed modulator can be integrated with a standard image sensor to effectively convert it into a time-of-flight imaging system.