The Brillouin scattering spectra of biological systems have shown to be inherently related to the intrinsic elasticity and molecular constants of tissues involved. Our approach of combining confocal microscopy and high-resolution Brillouin spectroscopy via a virtual imaging phase array enabled 10-microsecond single-pixel acquisition time without dedicated spatial filtering. Such an approach is adapted via a single-frequency fiber-coupled 780-nm wavelength laser, frequency stabilized by Rb-D2 absorption line, polarization extinction scheme, ASE filtering, heated Rb-vapor Rayleigh-scattering absorbent, and spectroscopic EMCCD camera, unified as CMS-VIPA: confocal virtual-imaging phase array microscopespectrometer. Steady strengthening of corneal bulk modulus was observed via spectral shifts of Brillouin scattering from 5.0-5.2 GHz in untreated porcine eyes to 5.7-5.9 GHz in ones cross-linked in riboflavin plus UV-A light at 0.7-0.9 GHz level of enhancement. The cross-linking depths reaching 300400 microns were measured, as predicted by modeling. A noncontact Brillouin spectroscopic microscopy system for in-vivo corneal elasticity measurement is under development.
Results of highly sensitive phase retardance and optical extinction symmetry measurements using a precision ellipsometry apparatus are described. Quartz wave plate retardance measurement accuracy was enhanced through the use of three laser wavelengths at 1064, 632.8, and 532 nm. Optical extinction symmetry phenomena in crystal quartz, KNbO3, Nd:YVO4 and TiO2 was also investigated in order to correlate variations in retardance measurements to crystal quality and orientation accuracy.
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