Towards single-photon emission from zero-wave vector Rydberg polaritons in thermal caesium

Abstract

This thesis presents the design, modelling and preliminary experimental setup of a deterministic single-photon emitter scheme. It relies on storing a three-beam zero-wave vector Rydberg polariton in a caesium thermal vapour through dressed-state electromagnetically induced transparency (EIT).

EIT was experimentally studied through 6S_1/2 -> 6P_1/2 -> 6D_3/2 in room temperature thermal caesium, and data was compared to an analytic model derived for weak probe velocity-averaged hyperfine absorption. Peak heights and widths were over-estimated because of a uniform intensity beam assumption and the lack of a strictly weak probe in the experiment. Along with fluorescence data from the 7P_1/2 -> 6S_1/2 decay at 459.4 nm, EIT was shown to maximise the upper state population whilst simultaneously reducing the line centre probe absorption.

Dressed state three-level EIT is then derived from the four-level ladder Rydberg excitation scheme with laser parameters calculated for a 2pi x 1 GHz dressed state Autler-Townes splitting. The corresponding probe absorption was simulated for continuous wave and pulsed STIRAP excitation demonstrating expectedly weak Rydberg EIT. Polarisation spectroscopy was investigated for probe beam frequency stabilisation yielding a steep slope dispersive error signal. Finally, a bespoke hexagonal vapour cell was designed that minimises astigmatism aberrations from focusing beams across tilted planar interfaces. Dimensioned photographs of the fabricated cell display its readiness for use in future three-beam Doppler-free experiments.