Atom-Based Electromagnetic Radiation Electric-Field Sensor

Abstract

A method is presented for measuring the electric field of electromagnetic radiation using the spectroscopic responses of Rydberg atoms to the electromagnetic radiation field. The method entails implementing quantitative models of the Rydberg atom response to the electromagnetic radiation field to provide predetermined atomic properties or spectra for field amplitudes and or frequencies of interest, spectroscopically measuring the response (spectrum) of Rydberg atoms exposed to an unknown electromagnetic radiation field, and obtaining the electric field amplitude and/or frequency of the unknown electromagnetic radiation by using features extracted from the measured spectrum and comparing them to features in a predetermined spectrum among the set of predetermined spectra.

What is claimed is: 
     
         1 . A method for measuring the electric field of electromagnetic radiation using the spectroscopic responses of Rydberg atoms to the radiation to be measured, comprising:
 providing predetermined atomic spectra for atoms of a known type;   placing the atoms within the unknown electromagnetic radiation field to be measured, where the atoms are in a gaseous state and contained in a vacuum enclosure;   propagating one or more light beams through the atoms, where at least one light beam is coupled to a Rydberg state;   measuring an atomic spectrum using the one or more light beams while the unknown electromagnetic radiation is interacting with or has interacted with the atoms;   analyzing the measured atomic spectrum to extract spectral features;   comparing the spectral features from the measured atomic spectrum to spectral features of the predetermined atomic spectra;   matching the measured atomic spectrum to a given spectrum in the predetermined atomic spectra; and   quantifying at least one of field strength or frequency of the unknown electromagnetic radiation field using the given spectrum and the predetermined atomic spectra.   
     
     
         2 . The method of  claim 1  wherein providing predetermined atomic spectra for atoms further comprises determining a model of atomic response in presence of the electromagnetic radiation. 
     
     
         3 . The method of  claim 1  wherein providing predetermined atomic spectra for atoms further comprises calculating the predetermined atomic spectra at a fixed frequency for a range of electric field values. 
     
     
         4 . The method of  claim 1  wherein providing predetermined atomic spectra for atoms further comprises calculating the predetermined atomic spectra at a fixed electric field for a range of frequencies. 
     
     
         5 . The method of  claim 1  wherein providing predetermined atomic spectra for atoms further comprises calculating the predetermined atomic spectra using Floquet theory. 
     
     
         6 . The method of  claim 1  wherein the atoms contained in the vacuum enclosure are maintained at a fixed temperature and density. 
     
     
         7 . The method of  claim 1  wherein measuring an atomic spectrum using electromagnetically induced transparency. 
     
     
         8 . The method of  claim 5  wherein measuring an atomic spectrum of the atoms further comprises
 propagating a probing light beam through the atoms, where the probing light beam has a frequency resonant with transition of the atoms from a first quantum state to a second quantum state; 
 propagating a coupling light beam through the atoms simultaneously with the probing light beam, where the coupling light beam is overlapped spatially with the probing light beam, frequency of the coupling light beam is scanned across a range in which atoms transition from the second quantum state to a Rydberg state; and 
 detecting the probing light beam passing though the atoms using a light detector. 
 
     
     
         9 . The method of  claim 7  wherein measuring an atomic spectrum of the atoms further comprises
 propagating a probing light beam through the atoms, where frequency of the probing light beam is scanned across a range in which atoms transition from a first quantum state to a second quantum state; and 
 propagating a coupling light beam through the atoms concurrently with the probing light beam, where the coupling light beam is overlapped spatially with the probing light beam, frequency of the coupling light beam is resonant with transition of the atoms from the second quantum state to a Rydberg state; and 
 detecting the probing light beam passing though the atoms using a light detector. 
 
     
     
         10 . The method of  claim 1  wherein the spectral features extracted from the measured atomic spectrum are defined as the frequency difference between two split peak pairs in the measured atomic spectrum. 
     
     
         11 . The method of  claim 10  wherein comparing the spectral features from the measured atomic spectrum further comprises overlaying the predetermined atomic spectra onto the measured atomic spectrum and shifting the predetermined atomic spectra such that the predetermined atomic spectra aligns with the measured atomic spectrum. 
     
     
         12 . The method of  claim 11  wherein quantifying field strength of the unknown electromagnetic radiation field further comprises determining Rabi frequency from a splitting of a Rydberg line in the measured atomic spectrum, calculating dipole moment of the relevant Rydberg transition, and computing magnitude of field strength of the unknown electromagnetic radiation field from the Rabi frequency and the dipole moment. 
     
     
         13 . The method of  claim 1  wherein the spectral features extracted from the measured atomic spectrum are defined as one or more of peak heights, peak widths and relative peak positions in a Floquet map. 
     
     
         14 . The method of  claim 13  wherein comparing the spectral features from the measured atomic spectrum further comprises overlaying the predetermined atomic spectra onto the measured atomic spectrum, shifting the predetermined atomic spectra in relation to the measured atomic spectrum so that the spectral features are in agreement, thereby yielding the field strength or frequency of the unknown electromagnetic field. 
     
     
         15 . The method of  claim 1  further comprises measuring the atomic spectrum without the necessity of metal or conductive material in the vacuum enclosure. 
     
     
         16 . A method for measuring the electric field of electromagnetic radiation using the spectroscopic responses of Rydberg atoms to the radiation to be measured, comprising:
 calculating predetermined atomic spectra for atoms of a known type using Floquet theory;   propagating an unknown electromagnetic radiation field towards the atoms, where the atoms are in a gas state and contained in a vacuum enclosure;   propagating one or more light beams through the atoms, where at least one light beam is coupled to a Rydberg state of the atoms;   measuring an atomic spectrum using the one or more light beams while the unknown electromagnetic radiation is interacting with or has interacted with the atoms;   analyzing the measured atomic spectrum to extract spectral features;   comparing the spectral features from the measured atomic spectrum to spectral features of the predetermined atomic spectra; and   matching the measured atomic spectrum to a given spectrum in the predetermined atomic spectra, thereby quantifying one of field strength or frequency of the unknown electromagnetic radiation field.   
     
     
         17 . The method of  claim 16  further comprises measuring an atomic spectrum using electromagnetically induced transparency. 
     
     
         18 . The method of  claim 16  further comprises measuring an atomic spectrum using electromagnetically induced transparency. 
     
     
         19 . The method of  claim 16  further comprises analyzing the measured atomic spectrum to extract peak positions and comparing the peak positions from the measured atomic spectrum to peak positions of the predetermined atomic spectra by overlaying the predetermined atomic spectra onto the measured atomic spectrum and shifting the predetermined atomic spectra in relation to the measured atomic spectrum until the peak positions in the predetermined atomic spectra fall within full width half maximum of the peak positions in the measured atomic spectrum. 
     
     
         20 . A system for measuring the electric field of electromagnetic radiation using spectroscopic responses of Rydberg atoms, comprising:
 a vapor cell containing atoms of a known type;   a source of electromagnetic radiation arranged to emit electromagnetic radiation towards the vapor cell;   a probing light source configured to propagate a probing light beam through the vapor cell, where frequency of the probing light beam is scanned across a range in which the atoms transition from a first quantum state to a second quantum state;   a coupling light source configured to propagate a coupling light beam through the vapor cell concurrently with the probing light beam, where the coupling light beam is counterpropagating to and overlapped spatially with the probing light beam, and frequency of the coupling light beam is resonant with transition of the atoms from the second quantum state to a Rydberg state;   a light detector configured to receive the probing light beam after passing through the vapor cell;   a data store that stores predetermined atomic spectra for the atoms in the presence of the electromagnetic radiation; and   a data processor in data communication with the light detector and the data store, and operates to measure an atomic spectrum for the atoms from the probing light beam received from the light detector and analyze the measured atomic spectrum to extract spectral features, wherein the data processor compares the spectral features from the measured atomic spectrum to spectral features of the predetermined atomic spectra; and matches the measured atomic spectrum to a given spectrum in the predetermined atomic spectra, thereby quantifying one of field strength or frequency of the unknown electromagnetic radiation field.