Thin-film lithium tantalate for ultraviolet integrated electro-optic modulator

TL;DR

This paper reports the first integrated UV electro-optic modulator on a thin-film lithium tantalate platform, achieving record low VπL and demonstrating potential for high-speed quantum and communication applications.

Contribution

The work introduces a scalable, wafer-compatible UV electro-optic modulator with record low VπL and high bandwidth potential using a compact TFLT platform.

Findings

Record-low VπL of 85 mV·cm at 375 nm

Extinction ratio of 22.7 dB and insertion loss of 1.3 dB

Potential for operation beyond 67 GHz

Abstract

The realization of integrated, high-speed ultraviolet (UV) modulation is pivotal for the advancement of quantum information processing, portable atomic clocks, and secure solar-blind communications. While mature photonic platforms have facilitated sophisticated system-level integration across visible and infrared spectra, high-speed active modulation in UV remains with traditional bulk crystals. Consequently, a scalable integrated solution that simultaneously combines low insertion loss and extreme compactness with high modulation efficiency has remained challenging. Here, we report the first integrated UV electro-optic modulator on a thin-film lithium tantalate (TFLT) platform. By employing a compact lumped-electrode design, we achieve a record-low V{\pi}L of 85 mV\cdot cm at 375 nm, providing an up to four orders of magnitude improvement in terms of bandwidth/V{\pi} L over bulk technologies. The device demonstrates a robust extinction ratio of 22.7 dB, a low insertion loss of 1.3 dB, and a V{\pi} of 4.2V. Although the measured 3-dB bandwidth of 922 MHz is currently limited by photodetector performance, the small device footprint of 1.16 mm and electrode design of 200 {\mu}m indicate intrinsic potential for high-speed operation beyond 67 GHz which is confirmed by the electrical-to-electrical response. This work establishes TFLT as a disruptive platform for wafer-scale compatible active UV photonics, enabling the next generation of scalable quantum and communication systems.