Index mapping for fibres with symmetric and asymmetric refractive index profiles.

The application of phase imaging to refractive index profiling of an optical fiber slice is described. It is shown that the refractive index profile of axially symmetric and asymmetric optical fibers can be obtained from quantitative phase image of thin transverse optical fiber slices. Although this method requires careful and time consuming sample preparation, one advantage of this technique is that it can be applied to a wide range of optical fibers. In this paper results for both symmetric and non-symmetric fibers are presented and good agreement with the industry-standard refracted near-field technique demonstrated.

Diamond waveguides fabricated by reactive ion etching.

We demonstrate for the first time the feasibility of all-diamond integrated optic devices over large areas using a combination of photolithography, reactive ion etching (RIE) and focused ion beam (FIB) techniques. We confirm the viability of this scalable process by demonstrating guidance in a two-moded ridge waveguide in type 1b single crystal diamond. This opens the door to the fabrication of a diamond-based optical chip integrating functional elements such as X-crossings, Y-junctions, evanescent couplers, Bragg reflectors/couplers and various interferometers.

Bend loss in structured optical fibres.

Bend loss characterisation tests are carried out in two air-silica structured fibres: a periodic photonic crystal fibre and a non-periodic fibre. An explanation based on resonant coupling between interstitial zones accounts for the improved confinement of non-periodic structured optical fibres.

Refractive index profiles of Ge-doped optical fibers with nanometer spatial resolution using atomic force microscopy.

We show a quantitative connection between Refractive Index Profiles (RIP) and measurements made by an Atomic Force Microscope (AFM). Germanium doped fibers were chemically etched in hydrofluoric acid solution (HF) and the wet etching characteristics of germanium were studied using an AFM. The AFM profiles were compared to both a concentration profile of the preform determined using a Scanning Electron Microscope (SEM) and a RIP of the fiber measured using a commercial profiling instrument, and were found to be in excellent agreement. It is now possible to calculate the RIP of a germanium doped fiber directly from an AFM profile.

Micromachining structured optical fibers using focused ion beam milling.

A focused ion beam is used to mill side holes in air-silica structured fibers. By way of example, side holes are introduced in two types of air-structured fiber, (1) a photonic crystal four-ring fiber and (2) a six-hole single-ring step-index structured fiber.

Simultaneous multidopant investigation of rare-earth-doped optical fibers by an ion microprobe.

The relative distribution of five elements present in the core area of several optical fiber samples has been obtained by utilizing nanoscale-secondary ion mass spectrometry. A strong correlation between the rare-earth (RE) ion and aluminum was observed, consistent with aluminum's improving the solubility of the RE ion. The central dip in distribution was less severe than that observed for germanium, characteristic of the collapse process during fabrication of the fiber preform.

Self-aligning method of fiber-to-waveguide pigtailing.

An innovative self-aligning technique for the pigtailing of optical fibers to buried channel planar waveguides is presented, based on selective etching. This technique utilizes a plug-and-socket mechanism that is intrinsically self-aligning and mechanically stable. The processes involved have been specifically designed to facilitate the bulk manufacture of pigtailed single or multiple fibers and waveguides. An optimized alignment geometry for the physical connection of fibers to waveguides is presented.

Controlled modification and direct characterization of multimode-fiber refractive-index profiles.

A combination of controlled annealing and characterization by scanning probe microscopy (SPM) is used to demonstrate that the refractive-index proffle of a commercially available silica-based optical fiber can be accurately reconfigured for use as an evanescent field sensor. The process relies on the controlled relocation of the silica glass dopants across the fiber cross section through heat treatment and the accurate measurement of the resulting dopant redistribution with SPM and differential etching techniques. The effect of variable annealing along a length of fiber is to produce a mode transformer to couple light from a laser source into the sensing region of the fiber.