# Multi-functional integrated photonics in the mid-infrared with suspended AlGaAs on silicon

## TL;DR

This paper introduces suspended AlGaAs waveguides on silicon for mid-infrared photonics, demonstrating low-loss propagation, nonlinear frequency conversion, supercontinuum generation, and versatile passive devices, enabling advanced integrated mid-IR systems.

## Contribution

The work presents a novel suspended AlGaAs platform on silicon with high nonlinearity, low loss, and broad transparency, advancing mid-infrared integrated photonics capabilities.

## Key findings

- Propagation loss of 0.45 dB/cm at 2.4 μm
- Octave-spanning supercontinuum from 1.26 to 4.6 μm
- Efficient passive devices like low-loss bends and splitters

## Abstract

The microscale integration of mid- and longwave-infrared photonics could enable the development of fieldable, robust chemical sensors, as well as highly efficient infrared frequency converters. However, such technology would be defined by the choice of material platform, which immediately determines the strength and types of optical nonlinearities available, the optical transparency window, modal confinement, and physical robustness. In this work, we demonstrate a new platform, suspended AlGaAs waveguides integrated on silicon, providing excellent performance in all of these metrics. We demonstrate low propagation losses within a span of nearly two octaves (1.26 to 4.6 $\mu$m) with exemplary performance of 0.45 dB/cm at $\lambda = 2.4$ $\mu$m. We exploit the high nonlinearity of this platform to demonstrate 1560 nm-pumped second-harmonic generation and octave-spanning supercontinuum reaching out to 2.3 $\mu$m with 3.4 pJ pump pulse energy. With mid-IR pumping, we generate supercontinuum spanning from 2.3 to 6.5 $\mu$m. Finally, we demonstrate the versatility of the platform with mid-infrared passive devices such as low-loss 10 $\mu$m-radius bends, compact power splitters with 96 $\pm$ 1% efficiency and edge couplers with 3.0 $\pm$ 0.1 dB loss. This platform has strong potential for multi-functional integrated photonic systems in the mid-IR.