Stephen E. BialkowskiStephen E. Bialkowski

Professor
Analytical Chemistry
B.S., 1975, Eastern Michigan University
Ph.D., 1978, University of Utah
Postdoctoral, 1978-80, NBS (NIST)
435.797.1907 Stephen.Bialkowski@usu.edu
web page

Research performed in this laboratory applies novel infrared and visible wavelength laser-based spectroscopic and optical processing techniques to molecular chemical analysis. Laser light sources are advantageous in spectrochemical analysis due to their high spectral radiance and their high temporal and spatial coherence.

The inherent sensitivity limitation of conventional infrared absorption spectroscopy is being overcome using infrared laser light sources. Pulsed infrared lasers are used to excite gas-phase analyte species such as the new class of compounds called the alternative fluorocarbons. Sample absorbance is not monitored with infrared detectors. Instead, the perturbation to the sample matrix resulting from the absorbed energy is monitored by observing a change in the beam propagation of a visible probe laser. This technique, called pulsed laser photothermal spectroscopy, surpasses the conventional infrared absorption by reducing the low signal to background luminescence ratio and the use of a infrared detector.

A variety of pulsed laser excited photothermal spectroscopy detection schemes are tested in this research. The ultimate goal is to obtain large signal magnitudes while reducing the shot noise limited background signal. The latter limits absorption spectroscopy and background reduction accounts for the inherent sensitivity of emission spectroscopy. Reduction of the probe laser background for pulsed laser infrared photothermal spectroscopy requires the development of high contrast probe laser radiance detection. Present and future research will be towards this goal. In particular, we are working on the development of an adaptable spatial filter for probe laser beam limiting. Using the limiter, infrared transitions of less than .0001 absorbance units can be observed with visible probe
laser contrasts greater than 300.

Optimum signal recovery is necessary to realize the advantages of pulsed laser spectrochemical techniques. The research also involves design and application of digital signal processing schemes for optimal pulsed signal recovery. Signals obtained in pulsed laser spectroscopy require specialized processing for efficient recovery and facile analytical interpretation. These signals are of high bandwidth, cyclic, and are typically dominated by non-white shot noise. We have found that adaptive matched filter signal processing techniques can be optimal for rapid linear pulsed signal analysis. Work in this area has recently been extended to include the case of non-linear signals observed in many pulsed laser excited spectroscopic experiments and to account for the limiting shot noise statistics of optical detection.

In related research, optical signal processing techniques are being applied for time and wavelength dependent spectroscopic signal analysis. The intrinsic speed and parallel structure of incoherent optical processing schemes are ideally suited to problems involving the analysis of complex mixtures. Optical processing of spectroscopic signals eliminates energy conversion into electric signals, as well as the noise associated with electronic signal processing. In addition to the speed and noise characteristics, the optical processors are also more compact and immune to electrical inference problems.

Selected Publications

A. Chartier, and S.E. Bialkowski, "Obtaining Accurate Measurements of Organic Dye Solutions using Pulsed Laser Photothermal Deflection Spectroscopy," Analytical Chemistry, 67, 2672, 1995.

S.F. Mahmoud, and S.E. Bialkowski, "Laser Excited Fluorescence of Dityrosine," Applied Spectroscopy, 49, 1669, 1995.

S.E. Bialkowski, "Photothermal Spectroscopy Methods for Chemical Analysis," Volume 134 in Chemical Analysis, Wiley, New York, 1996.

S.E. Bialkowski, "Sub-Shot-Noise Light Sources: A Quiet Revolution in Light Control," Critical Reviews in Analytical Chemistry, 26, 101-147, 1996.

A. Chartier, and S.E. Bialkowski, "Photothermal Lens Spectrometry of Homogeneous Fluids with Incoherent White-Light Excitation Using a Cylindrical Sample Cell," Optical Engineering, 36, 303-311, 1997.

S.R. Sousa, and S.E. Bialkowski, "Temperature-Dependent Electron Capture Detector Response to Common Alternative Fluorocarbons," Analytical Chemistry, 69, 3871-3878, 1997.

S.E. Bialkowski, "Overcoming the Multiplex-Disadvantage using Maximum-Likelihood Inversion," Applied Spectroscopy, 52, 591-598, 1998.