S.T. Davey

The absorption and fluorescence spectra of rare earth ions in silica-based monomode fiber

Rare-earth ions have been systematically incorporated into the cores of silica-based optical fibers, and the absorption and fluorescence spectra have been measured. The results provide basic data for a wide range of possible future fiber-based devices. For specific telecommunications applications, ions that could be useful for sources in the 1.3- mu m and 1.5- mu m low-loss windows are identified. It is suggested that Er/sup 3+/, Nd/sup 3+/, and Tm/sup 3+/ are the most promising ions for semiconductor pumping with GaAs-based laser diodes. >

CW room temperature operation of praseodymium-doped fluorozirconate glass fibre lasers in the blue-green, green and red spectral regions

Abstract We report room temperature, continuous-wave oscillation of Pr3+-doped fluorozirconate fibre lasers at around 491 nm, 520 nm, 605 nm, 635 nm and 715 nm. An output power of 250 mW has been obtained 635 nm for 800 mW of pump power from an argon ion laser operating at 476.5 nm. Tunable operation of the red transitions has been investigated, with output powers in excess of 30 mW being obtained. Q-switched pulses of 75 ns (fwhm) and 20 W peak power at 635 nm have also been generated.

The fabrication, assessment and optical properties of high-concentration Nd3+- and Er3+-doped silica-based fibres

Abstract A method has been developed to fabricate and quantify silica-based fibres doped with high concentrations of Nd3+ and Er3+. These fibres are based on an Al2O3-P2O5-SiO2 core glass and are free from cluster centres, indicating their potential as components in short length devices.

All-optical switching in a 200-m twin-core fiber nonlinear Mach-Zehnder interferometer.

All-optical switching is demonstrated in a 200-m-long fiber nonlinear Mach-Zehnder interferometer. The only stabilization mechanism used is passive enclosure of the interferometer. Stable operation is obtained by using a twin-core fiber. The experiment demonstrates the feasibility of use of fiber nonlinear Mach-Zehnder interferometers for ultrafast switching and pipeline logic.

The fabrication and optical properties of Nd3+ in silica-based optical fibres

Abstract We discuss the fabrication and optical properties of Nd3+-doped silica-based optical fibres as a function of core glass composition. The absorption and fluorescence spectra are shown to be very dependent on P2O5 concentration. This has resulted in multi-component host glass type optical behaviour from silica-based fibres.

A review of fluoride fibres for optical amplification

Abstract This paper reviews the current world-wide status of fibres based on the fluoride glass system for optical amplification, with particular emphasis on telecom applications. The key feature of fluorozirconate glasses, with the very long wavelength multiphonon edge, is the accompanying relatively low non-radiative decay rate of excited rare-earth dopant ions. This gives unique opportunities compared with the better known oxide glass systems. Amplifiers with high gains have been demonstrated at important wavelengths such as 0.8, 1.3 and 1.5 μm. Improvements to allow the fabrication of more efficient fibres are also discussed.

Second-harmonic Generation in Glass Fibres

Abstract Experiments on frequency doubling of 1064 nm and 1053 nm radiation with non-phase-matched and (close to) phase-matched germania-doped silica fibres are reported. The greatest conversion efficiencies are obtained with non-phase-matched fibres that are single-mode at the second-harmonic wavelength, in which phase-matching is thought to arise from a self-written grating. Competition between grating self-writing and self-erasure in these fibres in the absence of an external seed is also reported. Phase-matched fibres allow the formation of the nonlinearity to be studied independently of the phase matching. The nonlinearity is optically induced by exposing the fibre to short-wavelength visible radiation. An enhancement of 104 to 105 in conversion efficiency between the fundamental and the phase-matched LP31 second-harmonic mode over the intrinsic background second harmonic has been observed. We also report on the occurrence of phase-matched second-harmonic generation (SHG) and non-phase-matched SHG in...

Ultraviolet absorption studies on photosensitive germanosilicate preforms and fibers

Detailed measurements of the ultraviolet absorption spectra of germanosilicate preforms, multimode and single‐mode fibers are presented. Significant differences between the spectra of preforms and fibers are revealed and these differences are thought to be caused by the stresses induced during fiber pulling. Measurements are also presented of the changes in the absorption spectra in single‐mode fibers into which reflection gratings have been written using an ultraviolet laser. These results suggest that changes in the absorption between 200 and 600 nm are not responsible for the inferred changes in the refractive index.

The optical properties of ZrF4-based glasses with extended Pr3+ :1G4 →3H5 fluorescence lifetimes

Thermally stable ZrF 4 -based glasses with Pr 3+ : 1 G 4 → 3 H 5 fluorescence lifetimes longer than that of conventional ZBLAN glass have been developed. In addition to lifetime measurements the transmission characteristics, absorption spectra, 1.3 μm emission spectra and refractive indices of these novel glasses were determined. Fourier transform infrared reflectance and phonon sideband spectra suggest that the prolonged lifetimes are due to a reduction in the phonon energy in the vicinity of Pr 3+ ions and a decrease in the electron-phonon coupling strength

UV spectroscopy of optical fibers and preforms

Ultraviolet loss spectra of optical fibers and preforms have been measured over the wavelength range from 200 nm to 600 nm. The observed spectra consist of a number of well-known absorption bands, most of which have been associated with germanosilicate related defects. We have found that the size of the absorption peaks in fibers is typically many orders of magnitude smaller than the corresponding absorption peaks in the preforms from which the fibers were drawn. In particular, the 240 nm absorption band, so evident in preform spectra, is very much weaker in the fibers spectrum. Exposure of the fibers to broad-band uv radiation increases the size of the absorption peak at 325 nm, and also produces new bands at 380 nm and 305 nm, not previously ascribed to any defects. Fibers exposed to high power uv-laser radiation to form Bragg reflection gratings in the infrared, show the appearance of a previously unassigned band at 300 nm. Applying the Kramers-Kronig transformation to the measured changes in the absorption spectrum of the fiber between 200 nm and 600 nm, gives a calculated index change which is not sufficient to explain the observed refractive index change of approximately equals 10-4.