RESUMEN
The fabrication of an optical cavity at the distal end of an optical fiber has been achieved by Langmuir-Blodgett (LB) deposition of tricosanoic acid. This technique allows nanometer-scale control over the cavity length to a total thickness of ~0.5 microm . The cavity has been shown to act interferometrically and, thus, has potential sensing applications.
RESUMEN
Second-harmonic radiation has been obtained from Langmuir-Blodgett films of E-N -octadecyl-4-[2-(4-dibutylaminophenyl)ethenyl]quinolinium octadecylsulfate, deposited as a waveguide overlay upon optical fiber that is single mode at the pump wavelength (lambda=1064 nm) . A quadratic relationship between the pump power and second-harmonic intensity was observed.
RESUMEN
Fiber-optic chemical sensing has been demonstrated with a side-polished single-mode optical fiber, evanescently coupled to chemically sensitive Langmuir-Blodgett (LB) overlay waveguides. The sensors exhibit a channel-dropping response centered on a wavelength that is dependent on the thickness and the refractive index of the overlay waveguide. It has been shown that pH-sensitive organic dyes proved to be suitable materials for the formation of an overlay waveguide whereas LB deposition provides the required thickness control. A theoretical model of the sensor response, based on the Kramers-Kronig relations and phase matching of the guided modes within the optical fiber and overlay waveguide, shows good agreement with experimental results.
RESUMEN
Evanescent coupling between a side-polished single-mode optical fiber and a single-mode, pH-sensitive Langmuir-Blodgett overlay is used to demonstrate an intrinsic fiber-optic pH sensor. The sensor shows a wavelength sensitivity of 18.8 +/- 0.8 nm/pH and a transmission sensitivity of 9.7 +/- 0.8 dB/pH when operating at 750 nm.