  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.
