ABSTRACT
Surface relief gratings are holographically fabricated in thin polybutadiene rubber films produced by both spin coating and dip coating on glass and metal substrates. These thin-film gratings are characterized for their application as efficient transducers for detecting dynamic strain in solids. The performance of these rubber-grating transducers is compared to surface-mounted fiber Bragg gratings for a range of frequencies between 50 Hz and 30 kHz. Dynamic-strain sensitivity around 1 nepsilon/radicalHz is recorded for thin rubber-film grating transducers.
ABSTRACT
Holographic gratings are recorded in azo-dye nitrobenzoxazole-labeled phospholipid thin films by use of 244-nm UV light. The gratings continue to grow for more than 1 h, even after the recording light is removed. The diffraction efficiency of these gratings shows extreme sensitivity to humidity and can increase reversibly by 2 orders of magnitude in air that is saturated with water vapor. This effect is related to the unique characteristics of phospholipid molecules that undergo hydration-dependent structural reorganization and self-assembly.
ABSTRACT
Stimulated Raman scattering with 532-nm pulsed laser light is investigated in a 7.9-microm-core step-index multimode fiber. While low-intensity pump or single-mode LP(01) excitation produces the usual stimulated Raman scattering light, mixed-mode (LP(01) + LP(02)) excitation with pump intensities of ~5 kW uniformly shifts the multiorder Stokes Raman spectrum by an amount determined by fiber parameters, thus making stimulated Raman scattering tunable. This is due to the mediating influence of the four-photon mixing in the fiber.
