# Simplified aluminum nitride processing for low-loss integrated photonics and nonlinear optics

## TL;DR

This paper introduces a simplified method for fabricating aluminum nitride devices, enabling high-quality photonic components and demonstrating various nonlinear optical effects.

## Contribution

A novel fabrication method using a single silicon nitride mask and a conductive polymer layer for AlN devices is introduced.

## Key findings

- A high etching selectivity of 4:1 between AlN and the mask was achieved.
- AlN microresonators with intrinsic quality factors up to 1.0 × 10⁶ were fabricated.
- Nonlinear phenomena such as frequency comb generation and supercontinuum generation were demonstrated.

## Abstract

Aluminum nitride (AlN) is an extremely promising material for integrated photonics because of the combination of strong χ(2) and χ(3) nonlinearities. However, the intrinsic hardness of the material and charging effects during electron beam lithography make AlN nanofabrication a challenging process. Conventional approaches often require multiple hard masks and a metal mask to fabricate nanostructures. In this letter, we report a novel, simple method to fabricate AlN microresonators by using a single layer of silicon nitride mask combined with a thin conductive polymer layer. The conductive layer can be conveniently removed during developing without requiring an additional etching step. We achieve a high etching selectivity of 4:1 between AlN and the mask, enabling mid-infrared photonic device fabrication, as well as high intrinsic quality (Q) factors of up to 1.0 × 10⁶ in AlN microresonators. Furthermore, we demonstrate several nonlinear phenomena within these devices, including frequency comb generation, Raman lasing, third-harmonic generation, and supercontinuum generation.