Efficient and tunable frequency conversion using periodically poled thin-film lithium tantalate nanowaveguides

TL;DR

This paper demonstrates a highly efficient, tunable second harmonic generator on a thin-film lithium tantalate platform, enabling precise frequency conversion for advanced photonic applications.

Contribution

It introduces the first functional second harmonic generator on TFLT with ultralow loss and high efficiency, utilizing high-fidelity poling for quasi-phase matching.

Findings

Normalized efficiency of 229 %/W/$cm^2$

Absolute conversion efficiency of 5.5 % at 700 mW pump power

Temperature tunability of -0.44 nm/°C

Abstract

Thin-film lithium tantalate (TFLT) has recently emerged as a promising photonic platform for chip-scale nonlinear optics due to its weaker photorefraction, higher optical damage threshold, broader transparency window, and lower birefringence compared to that of thin-film lithium niobate. Here we develop an ultralow-loss lithium tantalate integrated photonic platform and report the first functional second harmonic generator based on high-fidelity poling of z-cut TFLT. As a result, quasi-phase matching (QPM) is performed between telecom (1550 nm) and near-visible (775 nm) wavelengths in a straight waveguide and prompts strong second-harmonic generation with a normalized efficiency of 229 %/W/$cm^2$. An absolute conversion efficiency of 5.5 % is achieved with a pump power of 700 mW. Such a second-harmonic generator exhibits stable temperature tunability (-0.44 nm/$^\circ C$) which is important for applications that require precise frequency alignment such as atomic clocks and quantum frequency conversion.