Microwave and Terahertz Field Sensing and Imaging using Rydberg Atoms

Lead Research Organisation: University of Strathclyde
Department Name: Physics

Abstract

Microwave and terahertz technologies play a critical role in modern life. Microwaves underpin mobile and satellite communications and are used for radar in navigation and meteorology. At higher frequencies, terahertz technologies are used to perform chemical sensing, non-invasive imaging, condition monitoring and more. These applications, and others, require fast detectors offering high sensitivity and the ability to perform spatially resolved imaging, which is particularly challenging in the terahertz domain where the majority of detectors require cryogenic cooling and offer slow thermal response times with limited absolute accuracy.

In this proposal we seek to address this technology gap by developing a new class of atom-based sensors that exploit the extreme sensitivity of highly-excited Rydberg atoms which act as antennae to provide precision electric field measurement across the microwave and terahertz frequency range. Using lasers to excite Rydberg atoms in a thermal vapour cell, the radio-frequency fields can be measured from the resulting perturbation in the transmission of a weak probe beam.

Atom-based sensors provide a number of advantages over traditional electric field measurement techniques; namely (i) they are intrinsically calibrated by relating the atomic properties to SI units to provide full measurement traceability, (2) act as point-like antenna for an in-situ measurement of the field, and (3) can be optically probed to enable sub-wavelength resolution of the radio-frequency field under study.

The proposed research programme will explore a number of key challenges to implementing Rydberg-atom-based electric field sensors, including optimising the cell materials and geometry to minimise the perturbation or suppression of the applied field and developing measurement techniques to achieve the fundamental limits of sensitivity and accuracy. To address these challenges we will combine UK based expertise, including the pioneers of optical detection of Rydberg atoms, to fabricate and characterise atomic vapour cells compatible with microwave and terahertz measurements and demonstrate precision field measurement and 2D imaging of structured radio-frequency fields. To verify the device accuracy we will compare the performance of our sensors to state-of-the-art calibrated references at the National Physical Laboratory. Finally, we will demonstrate real-world application of the sensors to areas including all-optical microwave communication schemes similar to WiFi and characterisation of the complex near-field emission from a terahertz antenna array. These sensors offer a new approach to radiofrequency sensing, imaging and metrology and provide a route to achieving enhanced sensitivity at microwave frequencies whilst providing an enabling technology for emerging applications in the terahertz domain.

Publications

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Chopinaud A (2021) Optimal State Choice for Rydberg-Atom Microwave Sensors in Physical Review Applied

 
Description Our work has involved a systematic study of the accuracy of atom based microwave field sensors, exposing a number of systematic errors that limit applicability of prior results whilst using a sophisticated model to identify and experimentally verify regimes where atom based sensors offer a truly linear and SI-traceable response.

This sensor has been used to perform the analysis of microwave communications using the Rydberg atoms as an antenna with the advantage of being metal free and providing a receiver of smaller size than would be possible using standard antenna designs.

Another area of focus has been studying density dependent effects on Rydberg EIT which is important in identifying regimes for calibrated sensing and this will be communicated in a paper in preparation.
Exploitation Route The results of this work provide a route to developing calibrated references for microwave metrology which can be used in a wide range of applications including digital communications and security and defence sectors.

This is an active area of research within industry and particularly within aerospace and defence where sensitive detection of RF and microwave signals is important for security and communications applications.
Sectors Aerospace, Defence and Marine,Digital/Communication/Information Technologies (including Software),Electronics,Security and Diplomacy