Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


NIST technique could make sub-wavelength images at radio frequencies


Imaging and mapping of electric fields at radio frequencies (RF)* currently requires the use of metallic structures such as dipoles, probes and reference antennas. To make such measurements efficiently, the size of these structures needs to be on the order of the wavelength of the RF fields to be mapped. This poses practical limitations on the smallest features that can be measured.

New theoretical and experimental work by researchers at the National Institute of Standards and Technology (NIST) and the University of Michigan suggests an innovative method to overcome this limit by using laser light at optical wavelengths to measure and image RF fields.

This is a laboratory apparatus for mapping and imaging of radio frequency (RF) electric fields at resolutions below the usual RF wavelength limit. Rubidium atoms are placed in the glass cylinder (on the right), which is illuminated at opposite ends by red and blue laser beams. The cylinder (2.5 by 7.5 centimeters in size) moves left on a track to enable the narrow laser beams to scan its entire width. The antenna (on the left) generates an RF field, which, depending on its frequency, has a certain effect on the spectrum of light absorbed by the atoms. By measuring this effect researchers can calculate and map the RF field strength as a function of position in the cylinder.

Credit: Holloway/NIST

The new technique uses a pair of highly stable lasers and rubidium atoms as tunable resonators to map and potentially image electric fields at resolutions far below their RF wavelengths (though not below the much shorter wavelengths of the lasers).

This advance could be useful in measuring and explaining the behavior of metamaterials and metasurfaces-structures engineered to have electromagnetic properties not found in nature, such as the illusion of invisibility. Imaging with sub-RF wavelength resolution also could help measure and optimize properties of densely packaged electronics and lead to new microscopy systems and imaging sensors.

Typically, RF field measurements are averaged over antenna dimensions of tens of millimeters (thousandths of a meter) or more. NIST's prototype technique has resolution limited by the beam widths of the two lasers used-in the range of 50 to 100 micrometers (millionths of a meter.) The technique was used to map RF fields with much longer wavelengths of 2863 and 17,605 micrometers (frequencies of 104.77 gigahertz and 17.04 gigahertz), respectively.**

The NIST and Michigan researchers mapped field strength as a function of position at resolutions as low as one-hundredth of an RF wavelength, far below normal antenna limits. Such data might be used to make colorized 2D images. In theory, the technique should work for wavelengths ranging from 600 to 300,000 micrometers.

The rubidium atoms are in a hollow glass cylinder (see photo), which is traversed down its length by two overlapping laser beams that act as stimulants and filters. First, a red laser excites the atoms, which initially absorb all the light. Then, a tunable blue laser excites the atoms to one of many possible higher energy ("Rydberg") states, which have novel properties such as extreme sensitivity and reactivity to electromagnetic fields.

Next an RF field-at the frequency to be mapped or imaged-is applied. This field alters the frequency at which the atoms vibrate, or resonate, altering the frequencies at which the atoms absorb the red light. This change in the absorption is easily measured and is directly related to the electric field strength at that part of the cylinder. By moving the cylinder sideways on a track across the narrow laser beams, researchers can map the changing field strength across its diameter. The blue laser can be tuned to excite the atoms to different states to measure the strength of different RF frequencies.

In the demonstration, researchers measured the strength of standing waves at specific locations inside the glass cylinder. For the two frequencies studied, measurements of the field agreed with results from numerical simulations.

The imaging technique is a spinoff of an ongoing NIST effort to develop a method that will, for the first time, directly link electric field measurements to the International System of Units (SI).

NIST developed the new measurement and imaging technique. University of Michigan co-authors provided the tunable blue laser and assisted in the measurements. The project is funded in part by the Defense Advanced Research Projects Agency.


* The term RF is used here to span the conventional radio, microwave, millimeter wave and terahertz frequency bands.
** C.L. Holloway, J.A. Gordon, A. Schwarzkopf, D. Anderson, S. Miller, N. Thaicharoen and G. Raithel. Sub-wavelength imaging and field mapping via EIT and Autler-Townes splitting in Rydberg atoms. Applied Physics Letters. 104, 244102; Posted online June 16, 2014. doi:10.1063/1.4883635

Laura Ost | Eurek Alert!

Further reports about: NIST cylinder frequencies lasers measurements micrometers properties wavelength wavelengths

More articles from Physics and Astronomy:

nachricht Laser-wielding physicists seize control of atoms' behavior
06.10.2015 | University of Chicago

nachricht Observing the Unobservable: Researchers Measure Electron Orbitals of Molecules in 3D
05.10.2015 | Karl-Franzens-Universität Graz

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Physicists shrink particle accelerator

Prototype demonstrates feasibility of building terahertz accelerators

An interdisciplinary team of researchers has built the first prototype of a miniature particle accelerator that uses terahertz radiation instead of radio...

Im Focus: Simple detection of magnetic skyrmions

New physical effect: researchers discover a change of electrical resistance in magnetic whirls

At present, tiny magnetic whirls – so called skyrmions – are discussed as promising candidates for bits in future robust and compact data storage devices. At...

Im Focus: High-speed march through a layer of graphene

In cooperation with the Center for Nano-Optics of Georgia State University in Atlanta (USA), scientists of the Laboratory for Attosecond Physics of the Max Planck Institute of Quantum Optics and the Ludwig-Maximilians-Universität have made simulations of the processes that happen when a layer of carbon atoms is irradiated with strong laser light.

Electrons hit by strong laser pulses change their location on ultrashort timescales, i.e. within a couple of attoseconds (1 as = 10 to the minus 18 sec). In...

Im Focus: Battery Production: Laser Light instead of Oven-Drying and Vacuum Technology

At the exhibition BATTERY + STORAGE as part of WORLD OF ENERGY SOLUTIONS 2015 in Stuttgart, the Fraunhofer Institutes for Laser Technology ILT and for Ceramic Technologies and Systems IKTS will be showing how laser technology can be used to manufacture batteries both cost- and energy-efficiently.

In the truest sense, it’s all about watts at the Dresden-based Fraunhofer Institute for Ceramic Technologies and Systems IKTS and the Aachen-based Fraunhofer...

Im Focus: New Sinumerik features improve productivity and precision

EMO 2015, Hall 3, Booth E06/F03

  • Drive optimization called automatically by the part program boosts productivity
  • Automatically switching the dynamic values to rapid traverse and interpolation...
All Focus news of the innovation-report >>>



Event News

EHFG 2015: Securing healthcare and sustainably strengthening healthcare systems

01.10.2015 | Event News

Conference in Brussels: Tracking and Tracing the Smallest Marine Life Forms

30.09.2015 | Event News

World Alzheimer`s Day – Professor Willnow: Clearer Insights into the Development of the Disease

17.09.2015 | Event News

Latest News

Graphene teams up with two-dimensional crystals for faster data communications

06.10.2015 | Information Technology

Laser-wielding physicists seize control of atoms' behavior

06.10.2015 | Physics and Astronomy

Flipping molecular attachments amps up activity of CO2 catalyst

06.10.2015 | Life Sciences

More VideoLinks >>>