Homogeneous Linewidth Behaviour of Narrow Optical Emitters at Sub-kelvin Temperatures

TL;DR

This study investigates the behavior of ultra-narrow spectral holes in solid-state emitters at sub-kelvin temperatures, focusing on linewidth stability and implications for frequency stabilization.

Contribution

It provides new insights into the linewidth behavior of spectral holes at ultra-low temperatures, challenging expectations of negligible broadening.

Findings

Linewidth remains constant at sub-kelvin temperatures as expected.

Observed linear broadening with increasing temperature.

Highlights need for further investigation into linewidth mechanisms.

Abstract

We explore the properties of ultra-narrow spectral holes in ensembles of solid-state emitters in crystals over a range of sub-kelvin temperatures, with a focus on their potential application in frequency stabilization schemes as an alternative to ultrastable cavities. We investigate how the parameters used to burn the spectral hole impact its shape, and how these factors determine the minimum achievable linewidth. In addition to the stability of the hole's center frequency, the linewidth and contrast play a crucial role in frequency locking. At sub-kelvin temperatures, the temperaturedependent T^7 broadening from two-phonon Raman scattering is expected to be negligible, and the spectral hole's linewidth should therefore remain constant in this interval. We observe however a linear broadening with increasing temperature, highlighting the need for further investigation into the mechanisms governing the linewidth at ultra-low temperatures.