Simultaneous $ \chi^{(2)} $- $ \chi^{(2)} $ and $ \chi^{(2)} $-$ \chi^{(3)} $ nonlinear processes generation in thin film lithium tantalate microcavity

TL;DR

This paper demonstrates on-chip nonlinear optical processes in lithium tantalate microcavities, achieving efficient generation of multiple wavelengths through cascaded nonlinear effects, highlighting its potential for integrated photonics applications.

Contribution

The study reports the fabrication of high-Q lithium tantalate microdisks supporting multiple nonlinear processes, including cascaded four-wave mixing, sum-frequency generation, and harmonic generation, in a single device.

Findings

Achieved high-Q factors of 10^6 in telecom band and 10^5 in visible band.

Observed multiple nonlinear processes such as cFWM, cSFG, THG, and SHG.

Demonstrated on-chip generation of near-infrared, visible, and UV light.

Abstract

On-chip efficient nonlinear functions are instrumental in escalating the utilities and performance of photonic integrated circuits (PICs), especially for a wide range of classical and quantum applications, such as tunable coherent radiation, optical frequency conversion, spectroscopy, quantum science, etc. Lithium tantalate (LT) has been widely used in nonlinear wavelength converters, surface acoustic wave resonators, and electro-optic, acoustic-optic devices owing to its excellent optical properties. Here, we fabricated a Z-cut lithium tantalate on insulator (LTOI) microdisk with high quality(Q) factors in both telecom (10$^{6}$) and visible (10$^{5}$) bands by optimizing the fabrication. With the Q factor of the LTOI microdisk increasing, we can obtain higher pump light intensity in the cavity which is beneficial to get more optical nonlinear effect easily. By making use of the mode phase matching of interacting waves and inputting high pump power, we experimentally observed on-chip near-infrared light, visible (red, green), and ultraviolet (UV) from microresonator-based $ \chi^{(2)}-\chi^{(2)}$, $ \chi^{(2)}-\chi^{(3)}$, and $\chi^{(2)}$ nonlinear processes such as cascaded four-wave mixing (cFWM), cascaded sum-frequency generation (cSFG), third harmonic generation (THG), second harmonic generation (SHG). It is believed that the LTOI can support a variety of on-chip optical nonlinear processes, which heralds its new application potential in integrated nonlinear photonics.