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

TL;DR

This study investigates the optical coherence and energy-level characteristics of Tm$^{3+}$-doped LiNbO$_{3}$ waveguides at sub-Kelvin temperatures, providing insights for quantum signal processing applications.

Contribution

It offers a comprehensive characterization of Tm$^{3+}$:LiNbO$_{3}$ waveguides at ultra-low temperatures, comparing indiffusion doping with bulk doping, and expands understanding for integrated quantum optics.

Findings

Properties are consistent with bulk-doped crystals, aside from doping concentration differences.

Coherence varies with temperature, magnetic field, and excitation power, informing optimal conditions.

Results support use of rare-earth ions in integrated optical quantum devices.

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.