Figure 1
From: Remote sensing of soil moisture using Rydberg atoms and satellite signals of opportunity
(a) High level concept for remote sensing of soil moisture based on reflected satellite signals of opportunity sensed via Rydberg atoms. (b) The probe and coupler laser light are counter-propagated in a Cesium vapor cell to excite atoms to the Rydberg state. The vapor cell is located inside a transverse electromagnetic (TEM) cell, which is used for uniform microwave (MW) field coupling to the vapor cell. Both the MW signal to be detected and the local oscillator (LO) field is coupled into the TEM cell. A beam displacer is used to develop a reference probe beam for balanced detection to reduce technical noise. (c) The coupler drives the atoms to a principal quantum number of n = 66, and MW signal and LO is off-resonant by about 40–65 MHz from the next nearest state 66D5/2-67P3/2 transition of 2.385 GHz.
