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

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. Optical intensity modulators are an important component in optics. Here, the authors demonstrate a type of resonant intensity modulator operating in the megahertz frequency regime with record high efficiency and use it for time-of-flight imaging.

Automated summary

In this study, a new type of single frequency intensity modulator, referred to as a longitudinal piezoelectric resonant photoelastic modulator, was reported. The modulator achieved record breaking modulation efficiency in the megahertz frequency regime. It was also demonstrated to be integrated with a standard image sensor for time-of-flight imaging.