Distinguished Seminar Speaker: "Fun with Fast (but not Furious) Tunable Lasers in the Infrared" by C. Kumar N. Patel
Friday, October 27, 2017 3:00 PM to 4:00 PM
CREOL Room 102/103
CREOL Room 102/103
C. Kumar N. Patel
Pranalytica, Inc.
Pranalytica, Inc.
Abstract:
The invention and development of all-electronically tuned quantum cascade lasers has made it possible to obtain spectral information, covering over 1 µm in the long wave infrared region, regarding absorbers in less than fraction of a millisecond. The electronic tuning is achieved through the use of a acousto-optically generated phase grating in a crystal. As described previously, the acousto-optic modulator (AOM) tuned QCL is capable of switching lasing wavelengths in time of the order of 0.5 µs, regardless of the size of the wavelength step. The wavelength tuning is achieved via change in the acoustic wave RF frequency. Thus, a complete spectrum covering > 1 µm tuning (for example from ~8.5 µm to ~ 9.5 µm) can be obtained in less than 20 µs, when the RF frequency is changed in response to an analog drive. For experimental reproducibility of spectra, we have implemented a digital scanning system that permits selection of step size and step speed. Using the AOM tuned QCL, we have carried out a number of studies to explore the usefulness of rapid scanning QCL systems. One study involves spectroscopy of liquids. Since almost all liquids absorb very strongly in the long wave infrared region, we have used attenuated total reflection (ATR) to study liquids such as isopropyl alcohol (IPA), ethanol, water, various alcoholic beverage such as vodka, gin and scotch, 2,2,2-trifluroethanol and Epsom salt dissolved in water. In each case a complete spectrum from ~8.5 µm to ~ 9.5 µm is recorded in a single shot 500 µs scan. From these studies, we can verify the claimed “proof” of the alcoholic beverages. In another study, we have explored mixing of gases (R134A HFC bolus injected into a fast flowing stream of air) in a flow tube where time dependent spectra of mixing gases are obtained in >600 consecutive shots during a 300 ms time span. I will describe both studies in detail, including a video showing the flow mixing evolution on millisecond time scale. The fast spectroscopic study of liquids now opens up the potentially exciting area of real time process monitoring in chemical, biological and food and wine industry. The transient flow spectroscopy study clearly indicates that the AOM tuned QCL system will be of immediate use in supersonic flow studies and in the study of combustion and explosion dynamics.
Biography:
Dr. C. Kumar N. Patel is the Founder, President and the CEO of Pranalytica, a company located in Santa Monica, CA, specializing in high power quantum cascade lasers and applications. Pranalytica is the leader in QCL technology through its invention of a radically QCL new structure design, called the non-resonant extraction, which has allowed Pranalytica to offer commercial QCLs that produce highest powers anywhere in the world. He is the inventor of the carbon dioxide, carbon monoxide, and the Spin-Flip Raman lasers. He pioneered the use of these and other lasers to measure trace gases in difficult environments. He was at AT&T (now Lucent Technologies) Bell Laboratories for thirty-two years and was Executive Director of the Physics Division and of the Materials Research Division. Under his leadership, Bell Labs produced some of the most critical technologies for optical communications. The quantum cascade laser was also invented in Physics Division during his leadership. From 1993 to 1999 he was the Vice Chancellor for Research at UCLA. Dr. Patel was elected to the National Academy of Science in 1974 and the National Academy of Engineering in 1978. Dr. Patel has received every major scientific honor in the United States. He received the National Medal of Science given by the President of the United States in 1996. In 2012, he was inducted into the National Inventors’ Hall of fame. In recognition of the CO2 laser’s importance to the medical field, he has been elected as an Honorary Member of the Gynecologic Laser Surgery Society in 1980 and in 1985 he was elected an Honorary Member of the American Society for Laser Medicine and Surgery.
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Bahaa Saleh
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