AlGaN/AlN integrated photonics platform for the ultraviolet and visible spectral range

We analyze a photonic integrated circuit (PIC) platform comprised of a crystalline Al_xGa_1-xN optical guiding layer on an AlN substrate for the ultraviolet to visible (UV-vis) wavelength range. An Al composition of x~0.65 provides a refractive index difference of ~0.1 between Al_xGa_1-xN and AlN, and a small lattice mismatch (< 1%) that minimizes crystal dislocations at the Al_xGa_1-xN/AlN interface. This small refractive index difference is beneficial at shorter wavelengths to avoid extra-small waveguide dimensions. The platform enables compact waveguides and bends with high field confinement in the wavelength range from 700 nm down to 300 nm (and potentially lower) with waveguide cross-section dimensions comparable to those used for telecom PICs such as silicon and silicon nitride waveguides, allowing for well-established optical lithography. This platform can potentially enable cost-effective, manufacturable, monolithic UV-vis photonic integrated circuits.