Optical vector network analysis of ultra-narrow transitions in $^{166}$Er$^{3+}$:$^7$LiYF$_4$

TL;DR

This paper demonstrates optical vector network analysis on a $^{166}$Er$^{3+}$:$^7$LiYF$_4$ crystal, using RF modulation to characterize ultra-narrow atomic transitions and reconstruct absorption and refractive index changes.

Contribution

It introduces a simple theoretical model for OVNA spectra in dense atomic ensembles, enabling accurate reconstruction of absorption and refractive index near atomic resonances.

Findings

Successfully applied OVNA to $^{166}$Er$^{3+}$:$^7$LiYF$_4$ crystal

Developed a model that describes phase shifts and spectral features

Reconstructed absorption profile and refractive index changes

Abstract

We present optical vector network analysis (OVNA) of an isotopically purified $^{166}$Er$^{3+}$:$^7$LiYF$_4$ crystal. The OVNA method is based on generation and detection of modulated optical sideband by using a radio-frequency vector network analyzer. This technique is widely used in the field of microwave photonics for the characterization of optical responses of optical devices such as filters and high-Q resonators. However, dense solid-state atomic ensembles induce a large phase shift on one of the optical sidebands which results in the appearance of extra features on the measured transmission response. We present a simple theoretical model which accurately describes the observed spectra and helps to reconstruct the absorption profile of a solid-state atomic ensemble as well as corresponding change of the refractive index in the vicinity of atomic resonances.