# Enhanced spectral profile in the study of Doppler-broadened Rydberg atoms

## TL;DR

This study demonstrates enhanced spectral contrast and improved signal-to-noise ratio in room-temperature Rydberg-EIT spectra by optimizing probe intensity, supported by a theoretical model explaining the underlying mechanism.

## Contribution

It introduces a method to enhance spectral contrast and signal quality in Rydberg-EIT spectra at room temperature, overcoming previous limitations.

## Key findings

- Spectral contrast is maximized at an optimal probe intensity.
- Contrast can be increased by 2-4 times compared to weak intensity.
- Signal-to-noise ratio can be improved by 10 to 100 times.

## Abstract

Combination of the electromagnetically-induced-transparency (EIT) effect and Rydberg-state atoms has attracted great attention recently due to its potential application in the photon-photon interaction or qubit operation. In this work, we studied the Rydberg-EIT spectra with room-temperature $^{87}$Rb atoms. Spectroscopic data under various experimental parameters all showed that the contrast of EIT transparency as a function of the probe intensity is initially enhanced, reaches a maximum value and then decays gradually. The contrast of spectral profile at the optimum probe field intensity is enhanced by $2-4$ times as compared with that at weak intensity. Moreover, the signal-to-noise ratio of the spectrum can potentially be improved by 1 or 2 order of magnitude. We provided a theoretical model to explain this behavior and clarified its underlying mechanism. Our work overcomes the obstacle of weak signal in the Rydberg-EIT spectrum caused by an apparent relaxation rate of the Rydberg polariton and weak coupling transition strength, and provides the useful knowledge for the Rydberg-EIT study.