We have developed optical fibers with a thin approximately 40 to 60 nm thick Lithium Niobate Layer
at the glass core and cladding boundary. These Lithium Niobate Cylinder Fibers (LNCF) are now in the
process of being commercialized as strain gauges for bridges, tunnels, pipe lines and aircraft components.
An application as a sonar sensor is also being investigated. LNCF strain sensors use light amplitude
detection rather than phase detection. Amplitude detection is easier to implement and is substantially less
costly. LNCF's when used as light amplitude sensing sonar detectors are over 1000 times more sensitive
than standard Single Mode Fibers. LNCFs use so called "Non Propagating" light modes rather than the
conventional propagating modes.
We are in the process of developing a hollow core fiber that contains a 2 nm to 3 nm thick AlAu alloy film near the core region, see Fig. 1. The fiber has a Photonic Crystal cladding that reflects the light back into the core region.
We have developed optical fibers with a very thin Lithium Niobate Layer at the glass core
glass cladding boundary it is observed that the Lithium Niobate Cylinder Fibers have a
large strain induced light loss of about 2.12784 x 10<sup>-5</sup> per kg per m. These fiber can be
used as strain sensors operating in an amplitude mode rather than in the phase detection
mode as is the case for strain sensors using standard Single Mode Fibers.
Light absorption spectrum measurements and the light intensity dependence of the light absorption spectrum of a fiber with a very thin gold film at the glass core glass cladding boundary are presented. The thickness of the gold film is less than the scattering length of electrons in this metal. The absorption spectrum appears to be strongly light intensity dependent. We also observed the mode structure of light propagating through the gold film. Our fabrication process can produce large area very thin metal films that are very difficult to produce by other methods.
We have measured a net gain of 19.5 dB in a 4 mm long piece of Cd<sub>3</sub>P<sub>2</sub> <b>S</b>emiconductor <b>C</b>ylinder <b>F</b>iber (SCF) at a wavelength of 1550 nm. The fiber was pumped from the side with a 100 mW, 832 nm laser. Side pumping is very inefficient since only a small portion of the pump light is absorbed by the very thin, approximately 6.694 nm thick, semiconductor film. However, this pumping arrangement is very convenient and does not require wavelength sensitive input and output couplers. We also measured the absorption spectrum. The absorption spectrum is in good agreement with a theoretical model. The absorption spectrum exhibits a step due to the two direct energy gap conduction bands of the Cd<sub>3</sub>P<sub>2</sub> semiconductor film.