  In the rapidly evolving area of integrated photonics, there is a growing need
for materials that satisfy the particular requirements of increasingly complex
and specialized devices and applications. Present photonic material platforms
have made significant progress over the past years; however, each platform
still faces specific material and performance challenges. We introduce a novel
material for integrated photonics: Aluminum Gallium Nitride (AlGaN) on Aluminum
Nitride (AlN) as a platform for developing reconfigurable and nonlinear on-chip
optical systems. AlGaN combines compatibility with standard semiconductor
fabrication technologies, high electro-optic modulation capabilities, and large
nonlinear coefficients while providing a broad and low-loss spectral
transmission range, making it a viable material for advanced photonic
applications. In this work, we design and grow AlGaN/AlN heterostructures and
integrate fundamental photonic building blocks into these chips. In particular,
we fabricate edge couplers, low-loss waveguides, directional couplers, and
tunable high-quality factor ring resonators to enable nonlinear light-matter
interaction and quantum functionality. The comprehensive platform we present in
this work paves the way for nonlinear photon-pair generation applications,
on-chip nonlinear quantum frequency conversion, and fast electro-optic
modulation for switching and routing classical and quantum light fields.
