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Resonant transmission through a dielectric-loaded slot in a thick conducting diaphragm embedded in a rectangular waveguide is modeled using an analytical approximation based on the slot being small compared to a free-space wavelength. An image theory relates this problem to a metasurface consisting of an array of such slots. We demonstrate the existence of ordinary (Fabry–Perot) transmission resonances associated with the fundamental mode of the slot, as well as extremely narrowband (Fano) resonances involving the higher order modes in the slot. The theoretical predictions are confirmed through full-wave numerical simulation and by experimental measurement. Measurements on dielectrics consisting of multiple pieces reveal an additional set of sharp resonances, not predicted by our theory but verified by finite-element simulation. The results have potential application to sensors and material property measurement.

With the redefinition of the International System of Units (SI) that occurred in November 2018, there has been much attention on the development of atom-based sensors for metrology applications that are directly linked to the SI. In particular, great progress has been made in using Rydberg atom-based techniques for electric field (E-field) metrology. These Rydberg atombased E-field sensors have made it possible to develop atom-based receivers, which potentially have many benefits over conventional technologies in detecting and receiving modulated signals.

In this paper, we derive an analytical model for plane-wave transmission through a periodic array of dielectric-loaded slots in an infinite metallic screen of finite thickness (a metagrating). We show the existence of (Fano) resonances associated with the presence of higher order modes in the slots, in addition to the well-known (Fabry–Perot) resonances associated with the dominant mode in the slots. The Fano resonances arise from a physical mechanism distinct from that which is responsible for so-called extraordinary transmission through a grating, which is strongly dependent on the coupling among the slots. Comparison of the analytical model with the results of full-wave simulations shows excellent agreement when the characteristic dimensions of the grating are small compared with a free-space wavelength.

We demonstrate a Rydberg atom-based sensor embedded in a parallel-plate waveguide (PPWG) for amplitude and phase detection of a radio-frequency (RF) electric field. This embedded atomic sensor is also capable of receiving modulated communications signals. In this configuration, the PPWG antenna serves two functions. First, the PPWG antenna acts as a source for a local oscillator (LO) field. The LO is required to use an atomic vapor cell (a glass cell containing a Rydberg atom vapor) as a Rydberg atom-based mixer, which detects the amplitude and phase of a second RF field incident from some remote location. The second function of the PPWG antenna is to capture the RF field arriving from a remote location and concentrate it at the location of the atomic vapor cell for detection. To demonstrate this, we show several examples of phase and amplitude measurements of an RF field with the embedded Rydberg-atom sensor. We also demonstrate the discrimination of the polarization of an RF field and the ability to receive phase-modulated carrier communications signals with this integrated atomic sensor. Embedding the atomic sensor in an antenna allows for the full characterization of a radio frequency field, in that the magnitude, phase, and polarization of an RF field can be measured with one compact integrated quantum-based sensor. Furthermore, the embedded sensor head allows one to easily vary the LO in order to maximize the ability to measure phase and amplitude of the field or modulated signal.

The frequency and incidence-angle dependence of a metagrating consisting of an array of dielectric-loaded slots in a thick perfectly conducting screen is investigated using an analytical method based on a rectangular waveguide model. This model makes experimental validation much simpler than attempting to approximate an infinitely extended array for measurements. In this paper, we study the effect of air gaps in the dielectric loading on the positions and amplitudes of transmission resonances.

Great progress had been made in the use of Rydberg atoms to detect the amplitude, phase, and polarization of electric fields and modulated signals. This has led to several unforeseen applications, which are discussed here.

Extraordinary transmission through a thick slot in a metallic shield loaded with high-permittivity dielectric is demonstrated using an analytical approximation based on the slot being small compared to a free space wavelength. In addition to previously known resonant transmission based on the fundamental waveguide mode of the slot, we show the existence of extremely narrowband resonances associated with the presence of higher order modes in the slot. Numerical simulations have been used to confirm the existence of these resonant transmission phenomena.

We demonstrate simultaneous amplitude and phase measurements of a radio-frequency (RF) field through the use of a Rydberg atom-based sensor embedded inside a waveguiding structure. This measurement uses the Rydberg atom-based sensor in a mixer configuration, which requires the presence of a local oscillator (LO) RF field. The waveguiding structure supplies the LO field. The combined waveguide and Rydberg atom system is used to measure phase and amplitude in the near-field of a horn antenna to extract the far-field pattern.

We discuss several recent extensions of quantum radio frequency (RF) electric field sensors to antenna/receiver applications. These Rydberg atom-based sensors have been previously studied for SI-traceable RF field measurements. We demonstrate the reception of modulated signals, including analog audio and pseudorandom bit sequences, RF phase detection, weak field detection, and the recording of musical instruments.

Recently we derived generalized sheet transition conditions (GSTCs) for electromagnetic fields at the surface of a metascreen (a metasurface with a ``fishnet'' structure, i.~e., a periodic array of arbitrary spaced apertures in a relatively impenetrable surface). The parameters in these GSTCs are interpreted as effective surface susceptibilities and surface porosities, which themselves are related to the geometry of the apertures that constitute the metascreen. In this paper, we use these GSTCs to derive the plane-wave reflection ($R$) and transmission ($T$) coefficients of a symmetric metascreen, expressed in terms of these surface parameters. From these equations, we develop a retrieval approach for determining the uniquely defined effective surface susceptibilities and surface porosities that characterize the metascreen from measured or simulated data for the $R$ and $T$ coefficients. We present the retrieved surface parameters for metascreens composed of five different types of apertures (circular holes, square holes, crosses, slots, and a square aperture filled with a high-contrast dielectric). The last example exhibits interesting resonances at frequencies where no resonances exist when the aperture is not filled, which opens up the possibility of designing metasurfaces with unique filtering properties. The retrieved surface parameters are validated by comparing them to other approaches., 14 pages, 19 figures, 39 references

Rydberg atoms have been used for measuring radio-frequency (RF) electric (E)-fields due to their strong dipole moments over the frequency range of 500 MHz-1 THz. For this, electromagnetically induced transparency (EIT) within the Autler-Townes (AT) regime is used such that the detected E-field is proportional to AT splitting. However, for weak E-fields AT peak separation becomes unresolvable thus limiting the minimum detectable E-field. Here, we demonstrate using the Rydberg atoms as an RF mixer for weak E-field detection well below the AT regime with frequency discrimination better than 1 Hz resolution. A heterodyne detection scenario with two E-fields incident on a vapor cell filled with cesium atoms is used. One E-field at 19.626000 GHz drives the 34D5/2 → 35P3/2 Rydberg transition and acts as a local oscillator (LO) and a second signal E-field (Sig) of interest is at 19.626090 GHz. In the presence of the LO, the Rydberg atoms naturally down convert the Sig field to a 90 kHz intermediate frequency (IF) signal. This IF signal manifests as an oscillation in the probe laser intensity through the Rydberg vapor and is easily detected with a photodiode and lock-in amplifier. In the configuration used here, E-field strength down to ≈ 46 μV/m ± 2 μV/m were detected with a sensitivity of ≈ 79 μVm−1Hz−1/2. Furthermore, neighboring fields 0.1 Hz away and equal in strength to Sig could be discriminated without any leakage into the lock-in signal. For signals 1 Hz away and as high as +60 dB above Sig, leakage into the lock-in signal could be kept below -3 dB.

Resonant transmission through a dielectric-loaded slot in a thick conducting diaphragm embedded in a rectangular waveguide is modeled using an analytical approximation based on the slot being small compared to a free space wavelength. Image theory relates this problem to a metasurface consisting of an array of such slots. We demonstrate the existence of ordinary (Fabry-Perot) transmission resonances associated with the fundamental mode of the slot, as well as extremely narrow-band (Fano) resonances involving the higher-order modes in the slot. The theoretical predictions are confirmed through full-wave numerical simulation and by experimental measurement.

In the quest for a new SI traceable power measurement, we performed measurements of the radiation pressure of a radio-frequency (RF) electromagnetic field. There are several groups around the world investigating methods to perform more direct SI traceable measurements of RF power (where RF is defined to range from 100s of MHz to THz). A measurement of radiation pressure offers the possibility for a power measurement traceable to the kilogram and to Planck's constant through the redefined SI. Towards this goal, we demonstrate the ability to measure the radiation pressure/force carried in a field at 2.45 GHz and 15 GHz using two different devices.

Extraordinary transmission through an inhomogeneous dielectric loaded slot in a an infinite metallic shield of finite thickness is demonstrated. We show that the higher order (Fano) transmission resonances' locations and magnitudes can be controlled by introducing a region of different dielectric constant within the slot.

In this work we demonstrate an approach for the measurement of radio-frequency (RF) power using electromagnetically induced transparency (EIT) in a Rydberg atomic vapor. This is accomplished by placing alkali atomic vapor in a rectangular waveguide and measuring the electric (E) field strength (utilizing EIT and Autler-Townes splitting) for a wave propagating down the waveguide. The RF power carried by the wave is then related to this measured E-field, which leads to a new direct International System of Units (SI) measurement of RF power. To demonstrate this approach, we first measure the field distribution of the fundamental mode in the waveguide and then measure the power carried by the wave at both 19.629 GHz and 26.526 GHz. We obtain good agreement between the power measurements obtained with this new technique and those obtained with a conventional power meter., Comment: 4 page, 7 figures

Extraordinary transmission through a thick slot in a conducting screen loaded with high-permittivity dielectric is demonstrated. In addition to previously known resonant transmission based on the fundamental waveguide mode of the slot, we show the existence of extremely narrowband resonances associated with the presence of higher-order modes in the slot.

In this paper, we demonstrate a new method to control the enhanced transmission due to Fabry–Perot resonances through an array of dielectric-loaded slots in a thick metallic screen. We obtain approximate analytical formulas for each polarization (TM and TE) using a mode-matching technique based on the assumption that the slots are small compared to a free-space wavelength and that the metallic screen is a perfect electric conductor as is appropriate for microwave frequency applications. We show that the bandwidth and locations of enhanced transmission can be controlled by the angle of incidence or by making the material filling the slots inhomogeneous. Computational results are given that demonstrate the influence of the angle of incidence on the enhanced transmission bandwidth. We show that the separation between enhanced transmission frequencies can be controlled by introducing a gap within the slot with a different dielectric constant. Also, we illustrate how the total transmission bandwidth can be increased by adjusting the angle of incidence and the gap size.In this paper, we demonstrate a new method to control the enhanced transmission due to Fabry–Perot resonances through an array of dielectric-loaded slots in a thick metallic screen. We obtain approximate analytical formulas for each polarization (TM and TE) using a mode-matching technique based on the assumption that the slots are small compared to a free-space wavelength and that the metallic screen is a perfect electric conductor as is appropriate for microwave frequency applications. We show that the bandwidth and locations of enhanced transmission can be controlled by the angle of incidence or by making the material filling the slots inhomogeneous. Computational results are given that demonstrate the influence of the angle of incidence on the enhanced transmission bandwidth. We show that the separation between enhanced transmission frequencies can be controlled by introducing a gap within the slot with a different dielectric constant. Also, we illustrate how the total transmission bandwidth can be inc...

Rydberg atoms have been shown to be very useful in performing absolute measurements of the magnitude of a radio frequency (RF) field using electromagnetically induced transparency. However, there has been less success in using Rydberg atoms for the measurement of the phase of an RF field. Measuring the phase of a RF field is a necessary component for many important applications, including antenna metrology, communications, and radar. We demonstrate a scheme for measuring the phase of an RF field by using Rydberg atoms as a mixer to down-convert an RF field at 20 GHz to an intermediate frequency on the order of kHz. The phase of the intermediate frequency corresponds directly to the phase of the RF field. We use this approach to measure the phase shift on an electromagnetic wave from a horn antenna as the antenna is placed at different distances from the Rydberg atom sensor. The atom-based RF phase measurements allow us to measure the propagation constant of the RF wave to within 0.1% of the theoretical value.

In recent work, we derived generalized sheet transition conditions (GSTCs) for electromagnetic fields at the surface of a metascreen (a metasurface with a “fishnet” structure, i.e., a periodic array of arbitrary spaced apertures in a relatively impenetrable surface). The effective electric and magnetic surface susceptibilities and surface porosities that appear explicitly in the GSTCs are uniquely defined and as such serve as the physical quantities that most appropriately characterize the metascreen. These surface parameters are related to the geometry of the apertures that constitute the metascreen and can exhibit anisotropic properties if this geometry is sufficiently asymmetric. These anisotropic properties can result in mode conversion between transverse electric (TE) and transverse magnetic (TM) polarizations when a plane-wave is incident onto a metascreen. Here, we use these GSTCs to derive the plane-wave reflection ( R) and transmission ( T) coefficients of an anisotropic metascreen, in which the coupling between TE and TM polarizations is illustrated. These expressions for R and T are used to develop a retrieval approach for determining the uniquely defined effective surface susceptibilities and surface porosities that characterize the metascreen from measured or simulated data. We present an example of a metascreen whose apertures are filled with a high-contrast dielectric, which shows interesting resonances at frequencies where no resonances exist when the apertures are not filled.In recent work, we derived generalized sheet transition conditions (GSTCs) for electromagnetic fields at the surface of a metascreen (a metasurface with a “fishnet” structure, i.e., a periodic array of arbitrary spaced apertures in a relatively impenetrable surface). The effective electric and magnetic surface susceptibilities and surface porosities that appear explicitly in the GSTCs are uniquely defined and as such serve as the physical quantities that most appropriately characterize the metascreen. These surface parameters are related to the geometry of the apertures that constitute the metascreen and can exhibit anisotropic properties if this geometry is sufficiently asymmetric. These anisotropic properties can result in mode conversion between transverse electric (TE) and transverse magnetic (TM) polarizations when a plane-wave is incident onto a metascreen. Here, we use these GSTCs to derive the plane-wave reflection ( R) and transmission ( T) coefficients of an anisotropic metascreen, in which th...

We discuss a power-measurement technique traceable to the International System of Units (SI) based on radiation pressure (or radiation force) inherent in an electromagnetic wave. A measurement of radiation pressure offers the possibility for a power measurement traceable to the kilogram and to Planck's constant through the redefined SI. Towards this goal, we performed measurements of the radiation pressure in a radio-frequency (RF) electromagnetic field at three frequencies (26.5 GHz, 32.5 GHz, and 40.0 GHz) and power levels ranging from 2 W to 25 W using a commercially available mass scale. We show comparisons between the RF power obtained with this technique and those obtained with a conventional power meter. The results in this paper represent the first step towards the realization of a more direct link to RF power within the newly redefined SI.