Principal Investigator John Love Project r72

Optical Sciences Centre, Machine CM

Research School of Physical Sciences and Engineering

Co-Investigators Simon Hewlett, Rod Vance, Victoria Steblina and Danial Beltrami

Optical Sciences Centre,

Research School of Physical Sciences and Engineering

Optical Mode Multiplexing

The project addresses the design of new planar integrated optical devices. Planar integrated technology is the optical analogue of integrated electronics, and differs from competing optical technologies in two important ways. The first is that the designer can exercise extremely tight control over the dimensions of optical components, whereas dimension control in competing technologies is often very coarse. The second is that all components are constrained to be in one plane, a constraint not suffered by competing technologies.

What are the basic questions addressed?

1. Asymetric, Adiabatic Y-Splitter

We seek to formulate workable designs of the asymmetric Y-splitter, which allows light in a multimoded waveguide to be split into its constituent modes; conversely it can be used to selectively excite any given single mode of a multimoded waveguide.

2. Specialised Planar Couplers

The symmetric 3x3 and 5x5 fibre couplers overcome fundamental signal-fading problems in interferometric systems. However, such devices comprise nonplanar waveguide arrangements and thus we seek planar mimics for them so that they can be implemented in planar integrated optics.

3. Research into the propagation of beating solitons. A multimoded waveguide is induced and the beating between two or more of its modes gives rise to a soliton written grating. Many novel propagation phenomena were discovered and investigated by this means.

What are the results to date and the future of the work?

During the last year, prototypes for the ideas outlined in the 1993 report were designed and some are now being implemented. Simulations undertaken with the Connection Machine analysed the practicalities of prototype implementation such as device wavelength dependence, spliceloss and mode coupling induced by connections between the prototype devices and the outside world.

A photomask to implement a design for an adiabatic Y splitter is currently being fabricated by Telecom Australia and the device will be experimentally tested in the future.

An Australian Defence Force department has sought and obtained approval in principal to commission the Australian National University to further research the specialised 3x3 and 5x5 couplers described in the 1993 report. The aim of this research will be to bring these couplers to an experimental prototype stage and hence further simulations of such coupler structures using the CM-5 are foreseen.

What computational techniques are used and why is a supercomputer required?

The basic propagation analysis technique used was the Fast Fourier Transform based Beam Propagation method, which reduces the analysis of electromagnetic field propagation in linear waveguides to a two-dimensional image processing problem. Enhancements to the basic algorithm are continuously being made to take advantage of hardware and software upgrades made to the CM-5, and to incorporate the results of new research allowing modified BPMs to analyse more strongly guiding waveguides.

Publications

Design procedures for planar passive coupled waveguide devices, R W C Vance and J D Love, IEEE Proceedings-J: Optoelectronics, 141, 231-241 (1994).

Planar ring-resonator realisation of symmetric 3x3 fibre coupler, R W C Vance, Electronics Letters, 29, (1994).

Matrix Lie-group theoretic design of coupled linear optical waveguide devices, R W C Vance, SIAM Journal of Applied Mathematics, in press.

Asymmetric adiabatic multipronged planar splitters, J D Love, R W C Vance and A Joblin, Optical and Quantum Electronics, in press.

Planar linear coupler design procedure using Mach-Zehnder interferometer cascades, R W C Vance, submitted to IEEE Journal of Lightwave Technology.