Frequency comb locked to resonator produces ultraprecise microwave signal

June 28, 2011
National Institute of Standards and Technology (NIST) researchers have created an ultraprecise microwave generator based on a yellow laser beam frequency-stabilized by a high-quality-factor (high Q) optical resonator.

Boulder, CO--National Institute of Standards and Technology (NIST) researchers have created an ultraprecise microwave generator based on a yellow laser beam frequency-stabilized by a high-quality-factor (high Q) optical resonator. A frequency comb is produced that allows microwaves to be produced with a fractional frequency instability of less than 8 × 10−6 at 1 s at room temperature (conventional ultraprecise microwave oscillators require cryogenic temperatures). The apparatus could improve signal stability and resolution in radar, communications and navigation systems, long-baseline interferometry, and certain types of atomic clocks.

"This is the quietest, most-stable microwave generator that's ever been made at room temperature," said project leader Scott Diddams.

Phase fluctuations reduced by a factor of a thousand

The new low-noise system is so good that NIST scientists actually had to make two copies of the apparatus just to have a separate tool precise enough to measure the system's performance. Each system is based on a continuous-wave laser with its frequency locked to an optical resonator. This laser, which emitted yellow light in the demonstration but could be another color, is connected to a frequency comb that transfers the high level of stability to the microwave region. The transfer process greatly reduces--to one-thousandth of the previous level--random fluctuations in the phase of the electromagnetic waves over time scales of a second or less.

The base microwave signal is 1 GHz, which is the repetition rate of the ultrafast laser pulses that generate the frequency comb (the signal could also be a harmonic of that frequency). The laser illuminates a photodiode that produces a signal at 1 GHz or any multiple up to about 15 GHz. For example, many common radar systems use signals near 10 GHz.

REFERENCE:

1. T. M. Fortier et al., Nature Photonics (2011), doi:10.1038/nphoton.2011.121; Published online 26 June 2011.

Follow us on Twitter

Subscribe now to Laser Focus World magazine; it's free!

About the Author

John Wallace | Senior Technical Editor (1998-2022)

John Wallace was with Laser Focus World for nearly 25 years, retiring in late June 2022. He obtained a bachelor's degree in mechanical engineering and physics at Rutgers University and a master's in optical engineering at the University of Rochester. Before becoming an editor, John worked as an engineer at RCA, Exxon, Eastman Kodak, and GCA Corporation.

Sponsored Recommendations

Request a quote: Micro 3D Printed Part or microArch micro-precision 3D printers

April 11, 2024
See the results for yourself! We'll print a benchmark part so that you can assess our quality. Just send us your file and we'll get to work.

Request a free Micro 3D Printed sample part

April 11, 2024
The best way to understand the part quality we can achieve is by seeing it first-hand. Request a free 3D printed high-precision sample part.

How to Tune Servo Systems: The Basics

April 10, 2024
Learn how to tune a servo system using frequency-based tools to meet system specifications by watching our webinar!

Precision Motion Control for Sample Manipulation in Ultra-High Resolution Tomography

April 10, 2024
Learn the critical items that designers and engineers must consider when attempting to achieve reliable ultra-high resolution tomography results here!

Voice your opinion!

To join the conversation, and become an exclusive member of Laser Focus World, create an account today!