Research in our laser laboratory is directed toward the application of novel nonlinear multiphoton laser spectroscopic methods in the development and understanding of new methods in laser analytical spectroscopy. Emphasis is placed on the understanding of fundamental principles of new spectroscopic phenomena. Integration of innovative nonlinear laser techniques and computer interfacing of high-precision instrumentation provides many advantages with new experimental possibilities over conventional laser spectroscopic methods in analytical problem solving.
Novel laser methods, such as nonlinear wave-mixing spectroscopy, offer parts-per-quadrillion-level detection sensitivity at excellent Doppler-free spectral resolution for elemental analysis, and sub-attomole (e-18 mole) detection sensitivity for molecular analytes. By using low-pressure cells such as discharge plasmas, Lorentzian (pressure) broadening is also minimized and, hence, spectral resolution is further enhanced. Optical phase conjugation by degenerate four-wave mixing offers excellent detection sensitivity because optical signal detection is very efficient since the signal is a coherent time-reversed replica of the original probe laser beam. Application of these novel laser methods in chemical analysis has provided significant improvements in sensitivity, selectivity, reliability, and spectral and spatial resolution to levels previously thought impractical in many different atomizers or sample holders including discharge plasmas, graphite furnace atomizers, inductively coupled plasma atomizers, and analytical flames. Wave mixing can be also conveniently interfaced to liquid chromatography, capillary electrophoresis, microchips, lab-on-a-chip, microarrays and other microfluidic systems for biomedical applications.
Continuous-wave lasers, such as ring lasers, argon-ion lasers, solid-state diode lasers, tunable external cavity diode lasers, and pulsed lasers, such as excimer and Nd:YAG pumped dye lasers can be used. These nonlinear spectroscopic methods provide spectral resolution high enough for the study of atomic hyperfine structures and analysis of isotopes in many research areas including biomedical and environmental sciences. We are also interested in fast laser-powered pyrolysis with laser-induced diagnostic monitoring of reaction rates and mechanisms of semiconductor materials. Real-time monitoring of intermediate species could provide better understanding of fundamental physical and chemical processes.
These patented novel nonlinear laser methods yield ultratrace detection sensitivity while maintaining isotope-level chemical selectivity, and hence, they offer new ways of diagnosing mineral poison/deficiency without using radioactive isotopes as biotracers. Trace amounts of isotopes can be fingerprinted at higher resolution. Potential applications include earlier detection of diseases, better design of cleaner drugs, and more sensitive detection of pollutants and chemicals both inside the human body and in the environment.