Fast, low-loss all-optical switching via a two-photon ladder transition in warm rubidium vapour

Student thesis: Doctoral ThesisPhD


In this thesis a fast all-optical switch is demonstrated in warm rubidium vapour using the 5S1/2 → 5P3/2 → 5D5/2 rubidium ladder scheme. First, the equations of motion
for the rubidium vapour, in the presence of a weak signal and strong control field, are derived and solved. The equations of motion are solved in the steady state in order
to obtain an estimate of the relative phase shifts and extinction coefficients at a given control field intensity, atomic number density, and control and signal detunings from resonance. Switching is demonstrated experimentally using both a continuous wave signal laser and a pulsed signal laser with 4 ns pulse duration. I show that my scheme is able to significantly outperform a typical commercial lithium niobate phase modulator,
achieving up to a 0.90 ± 0.06 π phase shift with a transmission of 83 ± 2% (or 0.81 dB loss) for the continuous wave signal. For the pulsed signal a transmission of 81±6% (or 0.92 dB loss) and phase shift of 0.53±0.06 π are measured. A typical commercial lithium niobate phase modulator shows a transmission of 45% (or 3.5 dB loss) for a π phase shift. The experimental parameters corresponding to these results are described
within. The transmission values include the insertion loss through the vapour cell. Progress towards making an all-fibre rubidium vapour cell for easy integration into
fibre networks or fibre quantum computers, with fibre feed-throughs and interconnects to single-mode fibre are discussed.
Date of Award27 Mar 2024
Original languageEnglish
Awarding Institution
  • University of Bath
SupervisorPeter Mosley (Supervisor), Josh Nunn (Supervisor), Cameron McGarry (Supervisor) & Alex Davis (Supervisor)

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