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Caltech grad students tunable solidstate laser could cut telecommunications and remote sensing costs
Interview by Rick DeMeis -- Design News, February 17, 2003
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NAME: Shervin Taghavi Larigani
PRESENT POSITION: Ph.D. student in electrical engineering at Caltech, Pasadena, CA
DEGREES: Dpl. Ing. University of Paris Orsay, M.S. in electrical engineering, Caltech
AREA OF RESEARCH: Tunable semiconductor lasers and laser optics, under Jakob Van Zyl, deputy director of Physics and Astrophysics at the Jet Propulsion Laboratory (NASA), and Amnon Yariv professor in Electrical Engineering and Applied Physics at Caltech; in the field two years with 13 laser device patents pending.
LATEST ADVANCE: Semi-Ring Fabry-Perot resonator, which is a tunable, single- or multimode semiconductor laser with an interferometer inside a resonator. The laser employs only a single light-coupling region and does not require optical gratings or any moving parts. It demonstrates relatively wide tunability, high optical power, and a large mode suppression ratio (MSR) for low noise, even in the case of a 3 dB coupler between the laser gain medium chip and the tunable filter/mirror. The MSR of more than 60 dB is higher than that obtained with standard tunable lasers (approx. 40 dB) using multiple interferometer techniques.
IMPACT ON DESIGN ENGINEERS? Today's lasers use fine grating structures for tuning, but only at a single wavelength, and the gratings are difficult to fabricate. Without a grating structure, and by just using interferometry, we can easily produce a cheaper laser tunable over a wide range of wavelengths. These lasers could lower the cost of space communications and remote sensing devices needing to function across multiple wavelengths. The laser can be used as either a single-mode laser at 1.5µ, the wavelength of lowest losses for silicon fiber optics communications, or it can work in multimodes, being continuously tunable across a range of wavelengths.
GREATEST CHALLENGE: Taking a simple idea and making it work.
WHY LASER OPTICS? I was frustrated with just a background in electrical engineering. Optics requires more of an understanding of theoretical physics.
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