Brian Culshaw

Surface plasmon polaritons in thin metal films and their role in fiber optic polarizing devices

The polarization-selective evanescent field coupling of an optical wave in a 1.3- mu m, fiber to surface, plasmon polaritons supported by a thin aluminium film was investigated theoretically and experimentally. Good agreement was observed between the theoretically predicted conditions for efficient coupling and the experimentally determined conditions for high TM/TE extinction ratio of the optical field. The use of silver and chrome in place of aluminum was investigated experimentally at 1.3 mu m, and 0.63- mu m devices using aluminium were also studied. The results led to the realization of readily manufacturable, high-extinction-ratio (>50 dB) low-loss ( >

Mode-hop-free single-longitudinal-mode erbium-doped fiber laser frequency scanned with a fiber ring resonator

We describe the experimental construction of a single-longitudinal-mode erbium-doped fiber ring laser equipped with a ring resonator filter. The system is designed to avoid mode hopping and can be frequency scanned for spectroscopic sensor applications. We modified a conventional ring resonator filter to have the capability to reduce transmittance of unwanted modes, which is essential for frequency scanning without mode hopping.

Intra-cavity and ring-down cavity absorption with fibre amplifiers for trace gas detection

We present the design of a fibre optic system for both intra-cavity and ring down absorption measurements in trace gas detection. The system is constructed from standard fibre optic components with a micro-optic gas cell.

A distributed fibre optic sensor for hydrocarbon detection

We present a distributed fibre optic sensor that incorporates hydrocarbon-swellable polymers to produce a microbend loss. Detection of hydrocarbon fuels at multiple locations along a 2km sensor length is readily achievable using standard OTDR techniques.

Mode hop free single mode fibre ring laser with frequency scanning using a fibre ring resonator filter combined with Mach-Zehnder interferometer

In order to obtain stable single longitudinal mode (SLM) operation from a fibre laser, both broad band and narrow band tunable filters are required. A fibre ring resonator filter (FRRF) simply composed of two directional couplers can be used for this purpose together with a cheap, commercially available, tunable band pass filter having a FWHM of a few nm. However, if one tries to make a FRRF by splicing two commercial directional couplers, it is difficult to increase the free spectral range (FSR) to greater than 1 GHz because of the short length of fibre to handle. This small FSR usually gives rise to laser mode jumping to FRRF modes rather than to main cavity modes, which makes the system inappropriate for frequency scanning. In this paper, we introduce a FRRF combined with a Mach-Zehnder interferometric filter (MZIF) as a simple solution to this problem.