instrumentation (2)

Comb on a Chip...


Experimental setup to generate a set of stable frequencies in a cryogenically cooled laser microresonator frequency comb. The ring-shaped microresonator, small enough to fit on a microchip, operates at very low laser power and is made from the semiconductor aluminum gallium arsenide.


Topics: Applied Physics, Instrumentation, NIST, Nanotechnology, Semiconductor Technology


Just as a meter stick with hundreds of tick marks can be used to measure distances with great precision, a device known as a laser frequency comb, with its hundreds of evenly spaced, sharply defined frequencies, can be used to measure the colors of light waves with great precision.

Small enough to fit on a chip, miniature versions of these combs — so named because their set of uniformly spaced frequencies resembles the teeth of a comb — are making possible a new generation of atomic clocks, a great increase in the number of signals traveling through optical fibers, and the ability to discern tiny frequency shifts in starlight that hint at the presence of unseen planets. The newest version of these chip-based “microcombs,” created by researchers at the National Institute of Standards and Technology (NIST) and the University of California at Santa Barbara (UCSB), is poised to further advance time and frequency measurements by improving and extending the capabilities of these tiny devices.

Comb on a Chip: New Design for ‘Optical Ruler’ Could Revolutionize Clocks, Telescopes, Telecommunications, NIST

Paper: G. Moille, L. Chang, W. Xie, A. Rao, X. Lu, M. Davanco, J.E. Bowers and K. Srinivasan. Dissipative Kerr Solitons in a III-V Microresonator. Laser and Photonics Reviews. June 2020. DOI: 10.1002/lpor.202000022

Read more…


Image source: Futurism/Dan Robitzski


Topics: Astrophysics, Instrumentation, Space, Space Junk

A massive cloud of space junk—containing more than 23,000 pieces larger than 10 centimeters across—is currently zooming around Earth with an average speed of about 36,000 kilometers per hour. And as companies such as SpaceX and OneWeb plan to launch tens of thousands of new satellites over the next few years, this hazardous clutter will likely pose an increasing threat to space missions and astronauts. One possible solution may be an electrodynamic tether, a device that could help prevent future satellites from becoming abandoned wrecks. The U.S. Naval Research Laboratory plans to test this technology in the next few weeks.

In early November the Tether Electrodynamic Propulsion CubeSat Experiment (TEPCE), already in orbit, is set to make its move under the watchful gaze of telescopes on the Hawaiian island of Maui. The Earth-bound control team is waiting for an ideal 10-minute period at dawn or dusk, when the dim sunlight will offer the best possible view of the shoe box-size spacecraft involved. Once the crew triggers the process, TEPCE should separate into two identical minisatellites joined by a kilometer-long tether as thick as several strands of dental floss. If deployment goes smoothly, the mission can observe how the tether interacts with Earth’s magnetic field in the ionosphere (where much of the space junk orbits) to change the satellites’ velocity and orbit; the results could possibly enable future spacecraft to move around while orbiting Earth—without having to carry unwieldy chemical propellant.

“In other words, it is the sailing ship of space,” says Enrico Lorenzini, a professor of energy management engineering at the University of Padova in Italy, who is not involved in the TEPCE mission. But instead of wind, the electrodynamic tether technology moves thanks to the physical laws that govern electric and magnetic fields. A tether in Earth’s ionosphere—an upper atmospheric layer filled with charged particles such as free electrons and positive ions—can collect electrons at one end and emit them at the other, generating an electric current through itself. The electrified tether’s interactions with Earth’s magnetic field produce an impetus known as the Lorentz force, which pushes on the tether in a perpendicular direction.


Kilometer-Long Space Tether Tests Fuel-Free Propulsion
Jeremy Hsu, Scientific American

Read more…