Hans Liebe Lecture
The U.S. National Committee (USNC) for the International Union of Radio Scientists (URSI), with the generous support of the Liebe family, has established the Hans Liebe Lectureship in microwave and optical spectroscopy as applied to radio science, remote sensing, and telecommunications. This lectureship provides travel support and an honorarium for a distinguished member of the radio science community to deliver a lecture on the professional topic of their interest at each of the annual USNC-URSI Radio Science meetings.
We are pleased to announce that the 12th Hans Liebe Fellow is Dr. Christopher L. Holloway, the RF Fields Group Leader of the U.S. Department of Commerce, National Institute of Standards and Technology (NIST), in Boulder, CO. Dr. Holoway will deliver the 12th Hans Liebe Lecture during the lunch hour of the 2025 NRSM on Friday, Jan. 10, 2025.
Dr. Christopher L. Holloway
Bio:
Dr. Christopher Holloway is a NIST Fellow and an IEEE Fellow and has been at NIST for over 25 years. He is also on the Graduate Faculty at the University of Colorado at Boulder. He is an expert in electromagnetic theory and metrology, quantum-optics, Rydberg-atom systems, and atom-based sensors. He has been involved with URSI for over 30 years in various capacities. He has a publication h-index of 64 with over 350 technical publications and has over 16,200 citations of his papers. He has 10 patents in various fields in engineering and physics. He is the Project Leader for the Rydberg-Atom-Sensor Project and is the Group Leader for the Electromagnetic Fields Group, both at NIST.
Abstract:
Rydberg Atom-Based Sensors: Transforming Measurements and Detection of Radio-Frequency Fields and Time-Varying Signals
Dr. Christopher L. Holloway
National Institute of Standards and
Technology
Boulder, CO 80305, USA
christopher.holloway@nist.gov
The unique properties of Rydberg atoms allow for radio-frequency (RF) spectroscopy, which has resulted in intriguing applications. For example, Rydberg atom receivers allow for the detection and receiving of time-varying fields and communication signals without an antenna and front-end electronics. The idea in these Rydberg atom-based sensors is to replace conventional antennas (which rely on conduction electrons bound by the antenna geometry) with atom-sensors (glass cells filled with atomic vapor: atomic-bound electrons).
One of the keys to developing new science and technologies is to have sound metrology tools and techniques. Atom-based measurements allow for unprecedented accuracy in measurement systems, and as a result, measurement standards have evolved towards atom-based measurements over the last few decades; most notably length (m), frequency (Hz), and time (s) standards. Recently, there has been a great interest in extending this to magnetic (H), electric (E), and other physical quantities. These Atom-based measurements allow for direct International System of Units (SI) traceable measurements. The development of Rydberg atom-based sensors has allowed for SI-traceable measurements for E-fields and RF power. With the great progress in the development of Rydberg atom-based sensors, interesting and unforeseen applications are emerging. These applications include, (1) SI-traceable measurements for electric field and power, (2) amplitude and phase detection of time-varying signals, (3) angle-of-arrival, (4) waveforms and spectrum analyzers, (5) plasma sensors, (6) near-field and sub-wavelength imaging, (7) blackbody detection and thermometry, (8) DC/AC voltage measurements, and even streaming video over the air. As well as many other applications.
One of the more intriguing applications for Rydberg atom-based sensors is in the detection of time-varying signals. These atom-based receivers allow for the detection of amplitude-, frequency-, and phase-modulated signals. In fact, in receiver applications, these Rydberg-atom sensors act like an antenna (to detect the signal) and they perform the demodulation and down conversion automatically. That is, these Rydberg receivers can eliminate a lot of the front-end devices and electronics when compared to conventional receivers. The atom-based sensors have sizes on the order of 10 mm as compared to conventional antennas with sizes on the order of a wavelength of the field being detected. Atom-based sensors are in effect, truly electrically small antennas. The Rydberg atom sensors are broadband, detecting fields from a few kHz to THz (and even down to DC), with large dynamic range (a few micro V/m to kV/m fields). Furthermore, these new Rydberg atom-based sensors will be beneficial for 6G and beyond in that they will allow for the calibrations of both field strength and power for frequencies above 100 GHz.
In this talk, I will present a historical journey of the development of this technology, and in the process, I will summarize this work and discuss various applications.