Rydberg EIT in a Doppler-free star configuration

Rydberg atoms within warm vapor cells commonly rely on excitation schemes with two or more lasers arranged in a counter-propagating colinear configuration. Doppler effects in these configurations reduce the efficiency of excitation to the Rydberg state, and can broaden the spectral features. In this work, we demonstrate a three-laser "star" configuration, where the sum of the laser k-vectors is zero. Using EIT and fluorescence spectroscopy we show a four times reduction in the spectral linewidth along with a three times enhancement in the Rydberg density compared to a colinear configuration, in agreement with theoretical predictions.