Optical coherence and energy-level properties of a Tm${}^{3+}$-doped LiNbO${}_3$ waveguide at sub-Kelvin temperatures

Abstract

We characterize the optical coherence and energy-level properties of the 795 nm ${}^3$H${}_6$ to ${}^3$H${}_4$ transition of Tm${}^{3+}$ in a Ti${}^{4+}$:LiNbO${}_3$ waveguide at temperatures as low as 0.65 K. Coherence properties are measured with varied temperature, magnetic field, optical excitation power and wavelength, and measurement time-scale. We also investigate nuclear spin-induced hyperfine structure and population dynamics with varying magnetic field and laser excitation power. Except for accountable differences due to difference Ti${}^{4+}$ and Tm${}^{3+}$-doping concentrations, we find that the properties of Tm${}^{3+}$:Ti${}^{4+}$:LiNbO${}_3$ produced by indiffusion doping are consistent with those of a bulk-doped Tm${}^{3+}$:LiNbO${}_3$ crystal measured under similar conditions. Our results, which complement previous work in a narrower parameter space, support using rare-earth-ions for integrated optical and quantum signal processing.

15 pages, 15 figures