FOR
IMMEDIATE RELEASE: April 27, 2000 |
Media
Contact: Collier Smith NIST Boulder Laboratories (303) 497-3198 Donna Cunningham |
Technical
Contact: Steven Cundiff JILA/NIST (303) 492-7858 TN -6227 |
|
Researchers from the Commerce Departments National
Institute of Standards and Technology and Bell
Laboratories of Lucent Technologies have teamed to produce a more precise method for
measuring the frequency of visible and infrared light. The new technology may help
facilitate the development of future generations of atomic clocks, improve the ability to
identify molecules and elements by spectroscopy, and provide more reliable frequency
standards for use by the telecommunications and related industries. This technology also
provides a new level of control over ultrashort light pulses. Reported in tomorrows Science, the technique uses a single laser to measure optical frequency instead of a cumbersome and expensive multiple laser system. The measurements made by the NIST/Lucent system have a higher level of precision than conventionally derived ones because they are compared to the well-defined primary frequency standard of a cesium-133 atomic clock. Eventually, the researchers believe that the level of precision for their technology will be limited only by the performance of the primary standard itself. The experiments were conducted at JILA, a joint research endeavor of NIST and the University of Colorado at Boulder. The researchers "locked" a radio-frequency-clock-stabilized titanium-sapphire laser in a manner that generated a repetitive train of ultrashort optical pulses (referred to as a "repetition frequency"). Each pulse is so short that it contains only about three cycles of light. The output spectrum of such a laser is a series of sharply defined spectral lines, separated by the repetition frequency. The scientists call this spectrum a "comb" because it has the appearance of a common pocket comb. Ordinarily, there would be no fixed relationship between the envelopes of the pulses and the wavelength of the laser light, but in this work, the envelope and the wavelength are locked together with a controlled phase relationship. In addition, the repetition rate of the pulses is locked to the standard cesium microwave frequency (9.2 gigahertz). This makes it possible to determine the absolute frequency of each of the "teeth" of the comb, and provides a means of measuring optical frequencies with a single laser. A visible continuum of lightwave frequencies is generated within a novel air-silica microstructure fiber. Light is very tightly confined to the glass fibers solid core by a ring of air holes surrounding the core. This unusual fiber creates an extremely small effective area, possesses special characteristics for light dispersion and keeps light loss to a minimum. This allows for generation of a frequency continuum with only one thousandth of the power previously needed. As a non-regulatory agency of the U.S. Department of Commerces Technology Administration, NIST strengthens
the U.S. economy and improves the quality of life by working with
industry to develop and apply technology, measurements and standards
through four partnerships: the Measurement and Standards
Laboratories, the Manufacturing
Extension Partnership, the Advanced Technology Program, and the Baldrige National Quality Program. Lucent Technologies, headquartered in Murray Hill, N.J., designs and delivers the systems, software, silicon and services for next-generation communications networks for service providers and enterprises. Backed by the research and development of Bell Labs, Lucent focuses on high-growth areas such as optical and wireless networks; Internet infrastructure; communications software; communications semiconductors and optoelectronics; web-based enterprise solutions that link private and public networks; and professional network design and consulting services. For more information on Lucent Technologies and Bell Labs, visit the companys web site at www.lucent.com or the Bell Labs web site at www.bell-labs.com. |