Professor Amin Dharamsi
Old Dominion University
Norfolk, Virginia
| Organizer: IEEE LEOS |
| Title: Advanced Optical Sensing using Laser
Modulation Spectroscopy |
| Speaker: Professor Amin Dharamsi Old Dominion University Norfolk, Virginia |
| Abstract: The talk will discuss a novel extension to the technique of modulation spectroscopy, in which one uses single mode diode lasers, which are modulated at relatively low frequencies. Phase sensitive detection is used to increase the signal-to-noise ratio. The novelty of the method lies in the fact that one can obtain simultaneous measurements of signals using demodulation at several harmonics of the modulation frequency. The work performed has shown that these higher harmonic signals can be used for identification, sensing, and measuring the concentration of gases. This is a versatile technique that can be used in environmental monitoring as well as in many industrial processes, including those in semiconductor fabrication and in the very wide variety of combustion-driven manufacturing processes. The technique is capable of simultaneous measurements of concentrations and temperatures of multiple species, by using a single diode laser and a single photodetector, without multiplexing. The apparatus is compact, rugged and fiberoptic compatible and can be used in environments that are inaccessible because of hostile conditions or remote location. The innovation of higher harmonic detection also provides a means to resolve overlapping lines. In addition, it allows one to extract basic information about the interaction potential of gaseous molecules, by probing the absorption features at several detection harmonic orders. For instance, it is known that the widely used impact approximation in the Voigt profile for absorption lines fails in the wings. Subtle, but important, features such as quasi-coherent effects that manifest themselves as Dicke-narrowed lines, are not covered by the standard Voigt profile. Since technological advances ultimately rest on an understanding of the underlying science, the technique developed by the nominee allows basic science to be pursued, while simultaneously having a strong impact on a large number of applied endeavors. The cost-effective nature of the apparatus does not come at the expense of the ability to do some very basic scientific measurements in Electrical Engineering and Applied Physics. This particular feature makes the technique a very valuable tool in research, academia and in applications for industry and environmental monitoring. |
| Biography: Professor Dharamsi has made several contributions to the area of non- intrusive measurements with lasers in the past two decades. The work that he is being cited for is in an area where he has been making significant contributions for the past seven years. In particular, Amin Dharamsi has developed a novel extension to the technique of modulation spectroscopy, in which he uses single mode diode lasers, which are modulated at relatively low frequencies. Phase sensitive detection is used to increase the signal- to-noise ratio. The novelty of the method lies in the fact that one can obtain simultaneous measurements of signals using demodulation at several harmonics of the modulation frequency. The work performed has shown that these higher harmonic signals can be used for identification, sensing, and measuring the concentration of gases. Dr. Dharamsi has worked in the broad area of light interaction with matter for approximately twenty-five years and has published his work in the most reputable journals of the profession. In addition to his significant contributions to the area of modulation spectroscopy, which has been cited above, he has published papers on several other topics including: photostrictively generated non-thermal shocks in layered semiconductors; ultrashort optoacoustic pulse generation; thermoluminescence in solids; optically induced reflectivity changes in multilayered mirrors; excited state absorption spectroscopy; non-intrusive measurements of local electric fields; laser line-center stabilization for LIDAR remote sensing of the atmosphere; and, molecular collision complex potential curve calculations for excimer lasers. Aside from the breadth of this work, Dr. Dharamsi's research in these other fields has had an impact on several areas. His work on the interaction of subpicosecond laser pulses with photostrictive materials has resulted in a kinetic model for such interactions with utility in applications ranging from dynamic laser induced gratings to non-thermal material processing; his work on the measurement of electric field induced emission has applications in plasma discharges and has been integrated into work of some European researchers in the Netherlands and Russia. Of particular note is also the fact that he has been very successful in engaging graduate and undergraduate students in his research. The work on modulation spectroscopy is a particularly good example of this mentorship role. In the past five years Amin Dharamsi has actively engaged suitably qualified undergraduates who are placed in a senior thesis program, which leads into graduate studies. Five have obtained the MS degree; another two students have obtained their doctorates. Both of the latter have gone out to responsible positions in the academia and in private industry. One of them, Audra Bullock, won the best student paper award at a LEOS Annual Meeting, and took up a tenure-track Assistant Professor position at the University of Hawaii this past fall. The quality of his mentorship role is also evident by the numerous prestigious fellowships that his graduate students have been awarded. His graduate students are co-authors with him on nine refereed-journal and sixteen conference-proceedings publications. In addition, the PI regularly mentors high school students in the laboratory, and gives talks at, and demonstrations for, local schools. Dr. Dharamsi is a Senior Member of the IEEE and established the LEOS chapter in Hampton Roads, VA, of which he has been serving as Chair. In addition, he is also a Life Member of the American Physical Society. |
| Time and Location: Monday March 10, 2003 at 11:00 a.m. University of Toronto, Wallberg building, Room 116 The Wallberg building is located at 184-200 College Street All are welcome. Refreshments will be served. CONTACT: Emanuel Istrate, e.istrate@ieee.org |
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