George Ritchie, Jr.
My current research interests include the design and development of cross-dispersive spectrograph instrumentation for LIBS (Laser Induced Breakdown Spectroscopy), on which I am collaborating with personnel at Los Alamos National Laboratory and my associates in Tucson, AZ. LIBS is a technique for remotely obtaining atomic emission spectra from the surface of a sample, usually done by hitting the sample with a few nanosecond pulse of infrared laser light having a total energy of about 0.01-0.1 Joule. The laser energy creates a high-temperature plasma near the surface of the sample, consisting of the atomic components of the sample. The atoms in the plasma emit wavelengths in the ultraviolet to visible range (typically 200 - 700 nm). The short lifetime (typically a few microseconds) and complexity of a typical LIBS spectrum requires simultaneous, high-resolution detection of the emitted wavelengths. We have designed a LIBS detection system incorporates a gated, intensified CCD image detector at the focal plane of a cross-dispersed echellette spectrograph. The cross-dispersed spectrograph images multiple diffraction orders onto the CCD detector in separate image locations through the use of a prism element. An integral part of the instrument design is the development of software algorithms for converting the image data from the CCD into spectra that are correctly linearized with respect to wavelength and adjusted for variations in instrumental response. We are also investigating efficient algorithms for element identification from LIBS spectra. Our LIBS spectrograph instrumentation was employed at the recent winter Olympics in Utah, where it was used on-site by Los Alamos personnel for checking the alloy composition of the metal blades on bobsleds.
I have also recently been working on the development of fiber-optic strain sensors, in collaboration with a colleague at the Naval Research Laboratory in Washington DC. These sensors consist of a one-dimensional optical grating structure that is imprinted into the core of an optical fiber using a laser-holographic technique. When a mixture of infrared wavelengths is sent into such a fiber grating, it will backwards reflect the specific wavelength associated with its periodicity. The wavelength reflected by the fiber grating will change if the fiber is subjected to a mechanical tensile stress, since such a stress will change the periodicity of the grating. By monitoring the wavelength that is back-reflected by a fiber grating, one can continuously monitor the stress at the location of the grating. Fiber stress sensors are being developed for possible use in large structures such as bridges and aircraft bodies, where the small size and passive-optical features of the sensors are particularly well suited for permanent imbedding in materials.
- J. Yavelow, L. T. Schepis, J. Nickels, Jr., and G.Ritchie “Cell Membrane Enzymes Containing Chymotrypsin-Like Activity,” in Protease Inhibitors as Anticarinogenic Agents, A. Kennedy and W. Troll, eds. (Plenum, 1993).
- G Ritchie and M. Seaver, “Multichannel Optical Spectroscopy with Video Cameras,” in MacSciTech SEAM '92 Conference Proceedings (1993).
- M. Seaver, J. R. Peele, T. J. Manuccia, G. O. Rubel and G. Ritchie, “Evaporation Kinetics of Ventilated Water Droplets Coated with Octadecanol Monolayers,” J. Phys. Chem., 6389 (1992).
- G. Ritchie and A. Mikovsky “Detection of Infrared Surface-em Waves in a Tapered Air-Gap Prism Configuration,” Bull. Amer. Phys. Soc., 487 (1986).
- G. Ritchie, R. B. Stephens, and E. Burstein “Optical Phenomena at a Siver Surface with Microscopic Bumps,” J. Opt. Soc. Am., B 2, 544 (1985).