# Amorphous silicon-doped titania films for on-chip photonics

## TL;DR

This paper presents a method for depositing amorphous silicon-doped titania films suitable for on-chip photonics, enabling high-quality passive and active photonic elements with low losses and broad substrate compatibility.

## Contribution

It introduces a novel deposition technique for Si-doped TiO2 films and demonstrates their use in fabricating high-Q photonic structures and functionalization with optically active ions.

## Key findings

- Achieved cavity Q-factors >10^5 at 790 nm
- Demonstrated low propagation losses of 5.1 dB/cm
- Enabled evanescent coupling to embedded ions

## Abstract

High quality optical thin film materials form a basis for on-chip photonic micro- and nano-devices, where several photonic elements form an optical circuit. Their realization generally requires the thin film to have a higher refractive index than the substrate material. Here, we demonstrate a method of depositing amorphous 25% Si doped TiO2 films on various substrates, a way of shaping these films into photonic elements, such as optical waveguides and resonators, and finally, the performance of these elements. The quality of the film is estimated by measuring thin film cavity Q-factors in excess of 10^5 at a wavelength of 790 nm, corresponding to low propagation losses of 5.1 db/cm. The fabricated photonic structures were used to optically address chromium ions embedded in the substrate by evanescent coupling, therefore enabling it through film-substrate interaction. Additional functionalization of the films by doping with optically active rare-earth ions such as erbium is also demonstrated. Thus, Si:TiO2 films allow for creation of high quality photonic elements, both passive and active and also provide access to a broad range of substrates and emitters embedded therein.