Two-dimensional Index Distribution Research Articles

Interferometric characterization and analysis of silver-exchanged glass waveguides buried by electromigration: slab, channel and slab-sided channel configurations

Channel and slab waveguides were fabricated by thermal Ag+/Na+ exchange in glass and buried by field-assisted diffusion. The mask was fabricated in a two-step photolithographic process by means of low-cost optics. A procedure to thinly and accurately slice samples with standard cutting and polishing machines is demonstrated. The two-dimensional index distribution of the sample slice was measured by a commercial polarizing interference microscope using a light-emitting diode as light source. The index profiles are analysed by taking into account the electromigration dynamics. The main finding is that the index peak of a channel waveguide close to a slab waveguide (slab-sided channel waveguide) was found to be deeper than that of a similar isolated channel waveguide. A preliminary application is proposed to improve the coupling efficiency between the channel and slab buried waveguides used in some integrated optical devices made in glass, such as arrayed waveguide gratings.

Two-dimensional index distribution determination from near-field measurements in single-mode fibres

The refractive-index distribution of single-mode optical fibres can be obtained from transmitted near-field intensity measurements. The generalisation of the method from conventional fibres to noncircularly symmetric guides (e.g. polarisation-maintaining fibres) is discussed. Results obtained both on circular and on polarisation-maintaining fibres are presented.

Measurement of axially nonsymmetrical refractive-index distribution of-a single-mode fiber by a multidirectional scattering-pattern method

A high spatial resolution, typically 0.2 \sim 0.3 \mu m, has previously been achieved by the proposed by one of the authors for measuring refractive-index profiles of optical fibers. This method, therefore, is especially suitable for measuring the index profiles of single-mode fibers. Described in this paper is the modification of this technique for measuring nonsymmetrical index distributions in single-mode fibers. In the modified method, a two-dimensional index distribution in an axially nonsymmetrical fiber is computed from a set of its forward scattering patterns for different directions of incident light. The distribution to be measured is somewhat restricted, i.e., it must have point symmetry. However, the point symmetry includes double symmetry which holds in most of polarization-maintaining fibers. The spatial resolution is as high as the scattering-pattern method for the axially symmetrical case; in the present experiment the resolution limit is 0.28 μm. Results of computer simulation and measurement are shown.