Applications of Light for Biomaterials and Safety

Abstract

The interaction of light with biological media represents an increasingly important area of research. Recent expansion of ultrafast laser sources in the midinfrared (MIR) regime is driving research in previously unexplored areas. In particular, the applications of these systems to biological materials is significant due to biological materials response to MIR wavelengths. The first two works presented here are motivated by gaps in the American National Standard for Safe Use of Lasers (ANSI) Z136.1 for eye safety. While we are ultimately interested in the nonlinear effects of MIR laser sources and the potential for retinal damage, we began by studying nonlinear behavior in Zinc Selenide (ZnSe) and air. The nonlinear processes examined were that of harmonic and continuum generation. The filament that was generated by the laser pulse in atmospheric air produced enough visible light at several wavelengths that were determined to be hazardous to the retina. Further work is required by the study in ZnSe to determine if maximum permissible exposure limits for retinal tissue was exceeded, despite significant visible light generation having been observed in spectral analysis. Laser light is not only a threat to safety, but a tool for use in diagnosing and understanding complicated biological structures. Raman spectroscopy allows for precise chemical and molecular analysis. The information Raman spectroscopy provides can identify the composition of unknown materials along with quantification of molecular concentration. Analysis of a commercial Raman spectrometer provided information about the most effective operation parameters for signal-to-noise enhancement. Thereafter, the spectrometer was used in determining the effectiveness of a microfluidic device as a cultivation tool for microalgae produced lipids. The results showed that Raman spectroscopy worked as effectively at measuring lipid production for time-course analysis as conventional methods without causing the damage to the algae cell typical of those conventional methods. Finally, a random Raman laser was investigated as a tool for imaging phenomena with lifetimes on the order of nanoseconds. The work determined the random Raman laser to be a more effective imaging tool when compared to two other conventional strobe methods.