Regular Article

Tunable nonlinear measurement of microwave electric fields with a dressed-state analysis

¹ College of Electronic and Information Engineering, Shandong University of Science and Technology, Qingdao 266590, P.R. China
² College of Electrical Engineering and Automation, Shandong University of Science and Technology, Qingdao 266590, P.R. China
³ Institute of Quantum Optics, Center for Integrated Quantum Science and Technology (IQ ST), Ulm University, 89081 Ulm, Germany

^a e-mail: pengyd@sdust.edu.cn
^b e-mail: qtzeng@sdust.edu.cn
^c e-mail: yuxiali2004@vip.163.com

Received: 19 March 2019
Received in final form: 3 September 2019
Published online: 29 October 2019

Abstract

A nonlinear absorption spectrum is proposed for measuring microwave electric fields with tunable sensitivity using electromagnetically induced transparency (EIT) in Rydberg atoms. Interacting dark resonances could enhance the nonlinear absorption, which shows a linear relationship with the microwave field (MW) strength. Compared with the linear case, the nonlinear measurement of MW field improves spectrum resolution by about one order of magnitude, the nonlinearity increases the EIT peak values by about two orders of magnitude, moreover the probe sensitivity could be improved by ten times from simulation. It is found that increasing the ratio of two coupling fields can improve probe sensitivity. The maximum probe sensitivity is predicted and explained. The above results can be well understood with the aid of the dressed-state theory.