Enhancing Sensitivity of an Atomic Microwave Receiver via a Fabry-Perot Cavity
Bo Wu, Dunwei Liao, Di Sang, Yi Liu, Yunqi Fu
Abstract
Rydberg atom-based microwave (MW) atomic receiver is regarded as a promising atomic receiver to surpass the sensitivity of conventional receivers. This article proposes a tunable Fabry-Perot (FP) cavity that locally enhances the MW electric (E) field to improve measurement sensitivities. This FP cavity includes a 0.9947 reflection coefficient periodic metal slit structure and a reflective plate. In our experiment, 21-dB signal-to-noise ratio (SNR) enhancement is achieved by utilizing the FP cavity. Ultimately, the atomic receiver loaded with a FP cavity provides a sensitivity of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$ \mathbf {5 \mathbf {nv/cm/\sqrt {Hz}}}$ </tex-math></inline-formula>@8.57 GHz that is the most advanced sensitivity known based on <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mathbf {^{133}\textrm {Cs}}$ </tex-math></inline-formula> resonant transition <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mathbf {|44D_{5/2}\rangle \rightarrow |45P_{3/2}\rangle }$ </tex-math></inline-formula>. Since the FP cavity is different from the traditional closed cavity and split-ring resonance mechanism, a large enhancement tunable frequency bandwidth of 4.8–12.2 GHz can be achieved by adjusting the plate spacing. In addition, the FP cavity solves the direct coupling between the electromagnetic wave and the resonator in the X-band, which provides mobility and flexibility. We take all the vapor cell wall’s refractive index and metal reflections into account as the resonance-based system is more sensitive to errors.