Raman spectra of polymethyl methacrylate optical fibres excited by a 532 nm diode pumped solid state laser

Polymethyl methacrylate (PMMA) optical fibres are fabricated by a preform drawing process. The Raman spectra of PMMA fibres are recorded using a diode pumped solid state laser emitting at 532 nm and a CCD-spectrograph in the 400–3800 cm−1 range. The variation of the Raman intensity with the length of the optical fibre is studied. Investigations are carried out on the variation of FWHM of the Raman peak at 2957 cm−1 with the length of the optical fibre and pump power. The differential scattering cross section and gain coefficient of the Raman peak at 2957 cm−1 in PMMA are calculated in relation to that of toluene.

Raman spectra of polymethyl methacrylate optical fibres excited by a 532 nm diode pumped solid state laser

Polymethyl methacrylate (PMMA) optical fibres are fabricated by a preform drawing process. The Raman spectra of PMMA fibres are recorded using a diode pumped solid state laser emitting at 532 nm and a CCD-spectrograph in the 400–3800 cm−1 range. The variation of the Raman intensity with the length of the optical fibre is studied. Investigations are carried out on the variation of FWHM of the Raman peak at 2957 cm−1 with the length of the optical fibre and pump power. The differential scattering cross section and gain coefficient of the Raman peak at 2957 cm−1 in PMMA are calculated in relation to that of toluene

A sensitive fibre optic pH sensor using multiple sol-gel coatings

The fabrication and characterization of a fibre optic pH sensor based on evanescent wave absorption is presented. The unclad portion of a multi-mode optical fibre is coated with a pH sensitive dye, which is immobilized by the sol–gel route. The sensitivity of the device has been found to increase when multiple sol–gel coatings are used as the sensing region. The dynamic range and the temporal response of the sensor are investigated for two different dyes, namely bromocresol purple and bromocresol green. The performance of the device is evaluated in terms of the results obtained during actual measurements.

Light amplification in dye doped polymer films

We report unusual spectral narrowing and laser emission from polymer thin films doped with Coumarin 540 dye. The laser emission from the polymer films is found to be highly dependent upon the excitation length of the medium. Even a short length of 1.75 mm of the dye doped film gave rise to laser emission with FWHM of 0.3 nm for a pump intensity of 825 kW cm−2. The partial reflections from the broad lateral surfaces of the free standing films provided the optical feedback for the laser emission. Occurrence of well-resolved equally spaced resonant modes confirmed the effect of a Fabry–Perot-like optical cavity between the film surfaces.