UC Merced

The integration of lasers has advanced imaging and quantitative analysis in the study of biological problems. In this document we describe a class of light sources known as fiber optical parametric oscillators (FOPO). The wavelength tunability of the FOPO system is a fundamental feature for the cellular imaging techniques in perspective. The FOPO converts the wave frequency provided by the pump into two other wave frequencies as its output. The difference between two waves frequencies produced by the FOPO, if corresponding to molecular vibrational transitions, is used to excite specific organic bonds. The current system allows one to probe vibrational transitions between 1050 cm-1 and 2220 cm-1. This spectral range allows one to excite C-D bonds, carbon-deuterium bond (2100 cm-1), C-H bonds (1445 cm -1), C=O bonds ( 1742 cm-1) and others bonds occurring in living cells. As methods we characterize and compare two FOPO systems based on two different photonic crystal fibers (PCF) and two laser pumps in order to assess their suitability for cellular imaging techniques. We optimize power, stability, and tunability of the output wavelength. Our characterization includes measurements of spectral tunability and pulse quality. The results expressed upon comparing of the two systems described in this thesis, showed that the picosecond/long fiber system is superior in terms of usability, average power efficiency, and stability but fails to encompass the full range of wavelengths necessary for the variety of intended applications. In comparison, the femtosecond/short fiber system, delivers superior wavelength tunability and pulse quality at the expense of usability and average power. We conclude that femtosecond/short fiber OPO system is the most suitable system between the two FOPOs systems explored in this study to be applied to nonlinear microscopy techniques. Coherent anti-Stokes Raman spectroscopy (CARS), which is used for imaging of non-stained biological samples, used as an example of nonlinear microscopy applied as a proof-of-concept experiment. The production and characterization of a laser source such as a FOPO that is able to produce desired wavelengths within the scope of cellular imaging, sets the stage for the use of these systems as an unique, efficient, and compact laser source for research of different cellular imaging techniques.