We report the measurement of the inhomogeneous linewidth, homogeneous
linewidth and spin state lifetime of Pr3+ ions in a novel waveguide
architecture. The TeO2 slab waveguide deposited on a bulk Pr3+:Y2SiO5 crystal
allows the 3H4 - 1D2 transition of Pr3+ ions to be probed by the optical
evanescent field that extends into the substrate. The 2 GHz inhomogeneous
linewidth, the optical coherence time of 70 +- 5 us, and the spin state
lifetime of 9.8 +- 0.3 s indicate that the properties of ions interacting with
the waveguide mode are consistent with those of bulk ions. This result
establishes the foundation for large, integrated and high performance
rare-earth-ion quantum systems based on a waveguide platform.Comment: 5 pages, 5 figure