This study investigates the enhancement of the microwave (MW) electric (E) field due to the Fabry-Perot (FP) effect in cubic cells of varying sizes, and it is confirmed that the lower limit of MW power can be measured. Theoretical simulations and empirical validations are conducted for three vapor cells of different sizes. At a MW frequency of 23.904 GHz, the FP effect in the 10 mm cell is found to significantly enhance the MW E-field relative to larger cells (20 and 25 mm). The results show that, due to the existence of the FP effect, the lower limit of MW power can be measured in the cubic atomic vapor cells with different sizes. These findings contribute to the advancement of the vapor cell design for quantum accuracy measurements and the development of future atomic MW communication technologies.
The geometry effect of a vapor cell on the metrology of a microwave electric field is investigated. Based on the splitting of the electromagnetically induced transparency spectra of cesium Rydberg atoms in a vapor cell, high-resolution spatial distribution of the microwave electric field strength is achieved for both a cubic cell and a cylinder cell. The spatial distribution of the microwave field strength in two dimensions is measured with sub-wavelength resolution. The experimental results show that the shape of a vapor cell has a significant influence on the abnormal spatial distribution because of the Fabry–Pérot effect inside a vapor cell. A theoretical simulation is obtained for different vapor cell wall thicknesses and shows that a restricted wall thickness results in a measurement fluctuation smaller than 3% at the center of the vapor cell.
Most studies on Rydberg atom-based microwave electric field measurement are achieved by using a single atomic vapor cell. In this work, we design an 1×4 uniform linear array of vapor cells by splitting the probe laser and coupling laser, and achieve simultaneous measurement of the microwave electric fields at the center of four vapor cells using Rydberg electromagnetically induced transparency method. At the frequency of the microwave electric field with about 6.92GHz, the measured AT splitting at four different spatial locations is linearly related to the square root of power of the microwave electric field. The microwave measurement for different spatial location allows the Rydberg atoms to meet the need of communications and radar better.
Rydberg-atom electrometry, as an emerging cutting-edge technology, features high sensitivity, broad bandwidth, calibration-free operation, and beyond. However, until now the key atomic vapor cells used for confining electric field-sensitive Rydberg atoms nearly made with traditional glass-blown techniques, hindering the miniaturization, integration, and batch manufacturing. Here, we present the wafer-level MEMS atomic vapor cells with glass-silicon-glass sandwiched structure that are batch-manufactured for both frequency stability and electric field measurement. We use specially customized ultra-thick silicon wafers with a resistivity exceeding 10,000 Ω cm, three orders of magnitude higher than that of typical silicon, and a thickness of 6 mm, providing a 4-fold improvement in optical interrogation length. With the as-developed MEMS atomic vapor cell, we configured a high-sensitivity Rydberg-atom electrometry with the minimal detectable microwave field to be 2.8 mV/cm. This combination of miniaturization and sensitivity represents a significant advance in the state-of-the-art field of Rydberg-atom electrometry, paving the way for chip-scale Rydberg-atom electrometry and potentially opening up new applications in a wider variety of fields.
Rydberg atom-based sensors represent a cutting-edge technology for highly sensitive radio-frequency (RF) electric field detection. Their performance is strongly influenced by the atomic vapor cell's characteristics, which significantly affect the internal field distribution and consequently the sensor's sensitivity. This research examines how relative permittivity, wall thickness, and cell dimensions impact the electric field distribution. Motivated by the growing demand for broadband communication and high-frequency technologies in next-generation systems, the 1-30 GHz frequency range is selected as the operational bandwidth. Results reveal that the resonance frequency of the dielectric cell—determined by its dimensions, relative permittivity, and wall thickness—plays a crucial role in the internal field distribution, making the conventional cell-dimension-to-wavelength ratio alone insufficient for predicting field behavior. Beyond the resonance frequency, field distortion and non-uniformity decrease even as the cell-dimension- to-wavelength ratio increases. Contrary to expectations, reducing cell size does not uniformly diminish field distortion and can significantly enhance the internal field within specific frequency bands. While variations in relative permittivity and wall thickness have a limited effect on the internal field at lower frequencies, these parameters exert a substantial influence near resonance and can even lead to field enhancement, particularly at the cell center. These findings demonstrate that through optimized cell design, the internal field can be engineered to achieve either uniform distributions for high-accuracy metrology or enhanced fields for weak-signal detection. This study provides practical guidelines for developing next-generation quantum RF sensors, communication systems, and radar technologies.
Research of hot atomic vapor systems has a long history. Recently, much-improved technologies, such as lasers, microwaves and digital/analog control systems, have led to exciting progress in this reviving field. Due to its cryogenic-free and vacuum-free deployment potential, room-temperature and quantum-enabled sensing devices using gaseous atoms have become a popular research topic, and engineering such devices has received considerable attention. Proof-of-principle experiments have been performed demonstrating new ideas such as quantum-enhanced motion sensors, next-generation magnetometers, Rydberg enabled microwave sensors, etc. This thesis focuses on my work related to electromagnetic-field sensing using Rydberg atoms in vapor cells, where Rydberg atoms are excited and detected by electromagnetically induced transparency (EIT) spectroscopy. I first investigate the detection of strong magnetic fields (
sim 1~T) in the Paschen-Back regime. The diamagnetic (quadratic) response of the Rydberg levels makes the atoms sensitive to small fluctuations in field strength on a large background. By implementing an isotope-mixed cell, we demonstrate that accurate measurement, within a relative uncertainty of
pm0.12%. Many Rydberg-enabled radio frequency and microwave sensing applications require a capability of zeroing or intentional tuning of small DC electric fields inside the vapor cell. For this purpose, I explore an in-situ DC electric-field sensing and tuning method without using any bulk or thin film electrodes. I find that the photoelectric effect on the vapor cell walls (with invisible, atomic Rb aggregate layers covering the surfaces) can generate tuning fields up to 0.8~V/cm, with an inhomogeneity of about 2%. The spatial distribution of these fields can be directly monitored by quadratic Stark shifts of the Rydberg atoms. This work may inspire new approaches for DC-field control in miniaturized, metal-free atomic vapor-cell devices. Like many other quantum measurements on hot gaseous samples, short interaction time and other technical decoherence processes are the major factors which limit the precision and, in certain cases, the accuracy of the metrological results. In order to study these effects in the context of EIT, I performed an EIT experiment using a
Lambda-type quantum system consisting of the hyperfine ground states and the first excited electronic state of the Rb atoms contained in a buffer-gas-free thermal vapor cell without anti-relaxation coating. Technical line-broadening effects due to inhomogeneity of stray magnetic fields, laser frequency jitter, transverse beam intensity distribution, interaction time distribution, and atom-wall/impurity gas collisions are studied. Experimental results and numerical simulations are compared. These results provide crucial information and quantitative insights for vapor cell sensor design. The development of compact and multi-functional spectroscopy vapor cells is widely considered to be a critical engineering step towards manufacturing field-deployable sensors for real life applications. My R&D efforts towards fabrication of glass spectroscopy cells with integrated, highly-conductive silicon components are presented in the last part of my thesis. I explored various technical challenges and successfully developed a proof-of-principle prototype from scratch. The device allows the application of electric fields inside the cell for particle trapping and for tuning Rydberg transitions. Further, the highly-conductive silicon components enable microwave polarization filtering for microwave sensing applications, plasma-physics studies, etc. Preliminary experimental/technical data and simulations are presented. In summary, in my thesis I report on a comprehensive study of several spectroscopic and field sensing applications of Rydberg and ground-state atoms in vapor cells, as well as forays into novel methods to engineer vapor cells with embedded electrodes.