Tantala Kerr-nonlinear integrated photonics

TL;DR

This paper introduces tantala (Ta₂O₅) as a new low-loss, high Kerr-nonlinearity material for integrated photonics, enabling efficient nonlinear devices, ultrabroadband Kerr-soliton combs, and supercontinuum generation.

Contribution

The work demonstrates the fabrication and characterization of tantala films for integrated nonlinear photonics, showing advantages over silicon nitride in stress, loss, and nonlinear performance.

Findings

Tantala films have low residual tensile stress of 38 MPa.

Optical quality factor of tantala resonators reaches up to 3.8 million.

Tantala enables ultrabroadband Kerr-soliton frequency combs and supercontinuum generation.

Abstract

Integrated photonics plays a central role in modern science and technology, enabling experiments from nonlinear science to quantum information, ultraprecise measurements and sensing, and advanced applications like data communication and signal processing. Optical materials with favorable properties are essential for nanofabrication of integrated-photonics devices. Here we describe a material for integrated nonlinear photonics, tantalum pentoxide (Ta$_2$O$_5$, hereafter tantala), which offers low intrinsic material stress, low optical loss, and efficient access to Kerr-nonlinear processes. We utilize >800-nm thick tantala films deposited via ion-beam sputtering on oxidized silicon wafers. The tantala films contain a low residual tensile stress of 38 MPa, and they offer a Kerr index $n_2$=6.2(23)$\times10^{-19}$ m$^2$/W, which is approximately a factor of three higher than silicon nitride. We fabricate integrated nonlinear resonators and waveguides without the cracking challenges that are prevalent in stoichiometric silicon nitride. The tantala resonators feature an optical quality factor up to $3.8\times10^6$, which enables us to generate ultrabroad-bandwidth Kerr-soliton frequency combs with low threshold power. Moreover, tantala waveguides enable supercontinuum generation across the near-infrared from low-energy, ultrafast seed pulses. Our work introduces a versatile material platform for integrated, low-loss nanophotonics that can be broadly applied and enable heterogeneous integration.