Optical decoherence studies of Tm$^{3+}$:Y$_3$Ga$_5$O$_{12}$

TL;DR

This study investigates the optical coherence properties of Tm:YGG at cryogenic temperatures, revealing its potential for quantum memory applications due to its long coherence lifetime and low spectral diffusion.

Contribution

The paper provides the first detailed analysis of decoherence mechanisms in Tm:YGG, demonstrating its superior coherence lifetime compared to other Tm-doped materials.

Findings

Coherence lifetime exceeds 1 ms below 1 K

Spectral diffusion is less impactful than in other Tm-doped crystals

Full spectral hole burning across 56 GHz bandwidth is achievable

Abstract

Decoherence of the 795 nm $^3$H$_6$ to $^3$H$_4$ transition in 1%Tm$^{3+}$:Y$_3$Ga$_5$O$_{12}$ (Tm:YGG) is studied at temperatures as low as 1.2 K. The temperature, magnetic field, frequency, and time-scale (spectral diffusion) dependence of the optical coherence lifetime is measured. Our results show that the coherence lifetime is impacted less by spectral diffusion than other known thulium-doped materials. Photon echo excitation and spectral hole burning methods reveal uniform decoherence properties and the possibility to produce full transparency for persistent spectral holes across the entire 56 GHz inhomogeneous bandwidth of the optical transition. Temperature-dependent decoherence is well described by elastic Raman scattering of phonons with an additional weaker component that may arise from a low density of glass-like dynamic disorder modes (two-level systems). Analysis of the observed behavior suggests that an optical coherence lifetime approaching one millisecond may be possible in this system at temperatures below 1 K for crystals grown with optimized properties. Overall, we find that Tm:YGG has superior decoherence properties compared to other Tm-doped crystals and is a promising candidate for applications that rely on long coherence lifetimes, such as optical quantum memories and photonic signal processing.