Y-Z cut lithium niobate longitudinal piezoelectric resonant photoelastic modulator

TL;DR

This paper presents a Y-Z cut lithium niobate acousto-optic modulator with record-high efficiency at 7 MHz, achieved through a simple fabrication process, enabling advanced optical modulation and imaging applications.

Contribution

The work introduces a novel, efficient Y-Z cut lithium niobate modulator with a straightforward fabrication method for high-performance optical modulation.

Findings

Achieved 100% modulation at 7 MHz with 1.5 W/cm² power

Demonstrated integration with a 4-megapixel time-of-flight imaging system

Utilized simple electrode coating and resonant excitation techniques

Abstract

The capability to modulate the intensity of an optical beam has scientific and practical significance. In this work, we demonstrate Y-Z cut lithium niobate acousto-optic modulators with record-high modulation efficiency, requiring only $1.5~\text{W}/\text{cm}^2$ for 100% modulation at 7 MHz. These modulators use a simple fabrication process; coating the top and bottom surfaces of a thin lithium niobate wafer with transparent electrodes. The fundamental shear acoustic mode of the wafer is excited through the transparent electrodes by applying voltage with frequency corresponding to the resonant frequency of this mode, confining an acoustic standing wave to the electrode region. Polarization of light propagating through this region is modulated at the applied frequency. Polarization modulation is converted to intensity modulation by placing the modulator between polarizers. To showcase an important application space for this modulator, we integrate it with a standard image sensor and demonstrate 4 megapixel time-of-flight imaging