Georg Raithel

Sub-wavelength imaging and field mapping via electromagnetically induced transparency and Autler-Townes splitting in Rydberg atoms

We present a technique for measuring radio-frequency (RF) electric field strengths with sub-wavelength resolution. We use Rydberg states of rubidium atoms to probe the RF field. The RF field causes an energy splitting of the Rydberg states via the Autler-Townes effect, and we detect the splitting via electromagnetically induced transparency (EIT). We use this technique to measure the electric field distribution inside a glass cylinder with applied RF fields at 17.04 GHz and 104.77 GHz. We achieve a spatial resolution of ≈100 μm, limited by the widths of the laser beams utilized for the EIT spectroscopy. We numerically simulate the fields in the glass cylinder and find good agreement with the measured fields. Our results suggest that this technique could be applied to image fields on a small spatial scale over a large range of frequencies, up into the sub-terahertz regime.

Millimeter wave detection via Autler-Townes splitting in rubidium Rydberg atoms

In this paper, we demonstrate the detection of millimeter waves via Autler-Townes splitting in 85Rb Rydberg atoms. This method may provide an independent, atom-based, SI-traceable method for measuring mm-wave electric fields, which addresses a gap in current calibration techniques in the mm-wave regime. The electric-field amplitude within a rubidium vapor cell in the WR-10 wave guide band is measured for frequencies of 93.71 GHz and 104.77 GHz. Relevant aspects of Autler-Townes splitting originating from a four-level electromagnetically induced transparency scheme are discussed. We measured the E-field generated by an open-ended waveguide using this technique. Experimental results are compared to a full-wave finite element simulation.

Broadband Rydberg Atom-Based Electric-Field Probe for SI-Traceable, Self-Calibrated Measurements

We discuss a fundamentally new approach for the measurement of electric (E) fields that will lead to the development of a broadband, direct SI-traceable, compact, se lfcalibrating E-field probe (sensor). This approach is based o n the interaction of radio frequency (RF) fields with alkali atoms excited to Rydberg states. The RF field causes an energy split ting of the Rydberg states via the Autler-Townes effect and we det ct the splitting via electromagnetically induced transparency (EIT). In effect, alkali atoms placed in a vapor cell act like an RFto-optical transducer, converting an RF E-field strength measurement to an optical frequency measurement. We demonstra te the broadband nature of this approach by showing that one small vapor cell can be used to measure E-field strengths over a wide range of frequencies: 1 GHz to 500 GHz. The technique is validated by comparing experimental data to both numerical simulations and far-field calculations for various frequencies. We also discuss various applications, including: a direct traceable measurement, the ability to measure both weak and strong fiel d strengths, compact form factors of the probe, and sub-wavelngth imaging and field mapping.We discuss a fundamentally new approach for the measurement of electric (E) fields that will lead to the development of a broadband, direct SI-traceable, compact, self-calibrating E-field probe (sensor). This approach is based on the interaction of radio frequency (RF) fields with alkali atoms excited to Rydberg states. The RF field causes an energy splitting of the Rydberg states via the Autler-Townes effect and we detect the splitting via electromagnetically induced transparency. In effect, alkali atoms placed in a vapor cell act like an RF-to-optical transducer, converting an RF E-field strength measurement to an optical frequency measurement. We demonstrate the broadband nature of this approach by showing that one small vapor cell can be used to measure E-field strengths over a wide range of frequencies: 1 GHz to 500 GHz. The technique is validated by comparing experimental data to both numerical simulations and far-field calculations for various frequencies. We also discuss various applications, including: a direct traceable measurement, the ability to measure both weak and strong field strengths, compact form factors of the probe, and sub-wavelength imaging and field mapping.

Autler-Townes spectroscopy of the 5 S 1 / 2 − 5 P 3 / 2 − 44 D cascade of cold 85 Rb atoms

We study nonlinear optical effects in the laser excitation of Rydberg states. 5S 1 / 2 and 5 P 3 / 2 levels of 8 5 Rb are coupled by a strong laser field and probed by a weak laser tuned to the 5P 3 / 2 -44D Rydberg resonance. We observe high contrast Autler-Townes spectra which are dependent on the pump polarization, intensity, and detuning. The observed behavior agrees with calculations, which include the effect of optical pumping.

Photoassociation of long-range

We observe long-range homonuclear diatomic nD Rydberg molecules photoassociated out of an ultracold gas of Rb87 atoms for 34≤n≤40. The measured ground-state binding energies of Rb87(nD+5S1/2) molecular states are larger than those of their Rb87(nS+5S1/2) counterparts, which shows the dependence of the molecular bond on the angular momentum of the Rydberg atom. We exhibit the transition of Rb87(nD+5S1/2) molecules from a molecular-binding-dominant regime at low n to a fine-structure-dominant regime at high n [akin to Hunds cases (a) and (c), respectively]. In the analysis, the fine structure of the nD Rydberg atom and the hyperfine structure of the 5S1/2 atom are included.

nD

We present a spectral analysis of Rydberg atoms in strong microwave fields using electromagnetically induced transparency (EIT) as an all-optical readout. The measured spectroscopic response enables optical, atom-based electric field measurements of high-power microwaves. In our experiments, microwaves are irradiated into a room-temperature rubidium vapor cell. The microwaves are tuned near the two-photon 65D-66D Rydberg transition and reach an electric field strength of 230V/m, about 20% of the microwave ionization threshold of these atoms. A Floquet treatment is used to model the Rydberg level energies and their excitation rates. We arrive at an empirical model for the field-strength distribution inside the spectroscopic cell that yields excellent overall agreement between the measured and calculated Rydberg EIT-Floquet spectra. Using spectral features in the Floquet maps we achieve an absolute strong-field measurement precision of 6%.

Rydberg molecules

In this work, we demonstrate an approach for improved sensitivity in weak radio frequency (RF) electric-field strength measurements using Rydberg electromagnetically induced transparency (EIT) in an atomic vapor. This is accomplished by varying the RF frequency around a resonant atomic transition and extrapolating the weak on-resonant field strength from the resulting off-resonant Autler-Townes (AT) splittings. This measurement remains directly traceable to SI compared to previous techniques, precluding any knowledge of experimental parameters such as optical beam powers as is the case when using the curvature of the EIT line shape to measure weak fields. We use this approach to measure weak RF fields at 182 GHz and 208 GHz demonstrating improvement greater than a factor of 2 in the measurement sensitivity compared to on-resonant AT splitting RF electric field measurements.

Optical measurements of strong microwave fields with Rydberg atoms in a vapor cell

Abstract Reported is the production of a continuous beam of circular state rubidium Rydberg atoms of principal quantum numbers n around n =67. The circular states are populated using crossed electric and magnetic fields. They are detected continuously by a novel field ionization scheme. The circular character of the atoms is derived from the field ionization patterns, and from microwave spectra of the transitions to circular states with lower n . The circular Rydberg atoms with very large n shall be used for studies of microwave ionization and for one-atom maser experiments.

Using frequency detuning to improve the sensitivity of electric field measurements via electromagnetically induced transparency and Autler-Townes splitting in Rydberg atoms

We measure strong radio-frequency (RF) electric fields using rubidium Rydberg atoms prepared in a room-temperature vapor cell as field sensors. Electromagnetically induced transparency is employed as an optical readout. We RF-modulate the 60

Circular Rydberg states with very large n

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