Refraction and Optical Fibres Dr Murray Thompson University Senior College Murray.thompson@adelaide.edu.au Prof Tanya Monro Centre of Expertise in Photonics tanya.monro@adelaide.edu.au

Refraction and Optical Fibres “This material has been developed as a part of the Australian School Innovation in Science, Technology and Mathematics Project funded by the Australian Government Department of Education, Science and Training as a part of the Boosting Innovation in Science, Technology and Mathematics Teaching (BISTMT) Programme.”

Refraction and Optical Fibres When light travels from one medium to another it changes speed. It also changes direction.

Refraction From a fast medium to a slow medium, the light bends towards the normal. Slow medium eg glass Fast medium eg air normal Angle of Incidence i Refraction R Partially reflected beam

Refraction From a slow medium to a fast medium, the light bends away from the normal. Slow medium eg glass Fast medium eg air normal Angle of Incidence i Refraction R Partially reflected beam

Snell’s Law of Refraction which is the refractive index from medium 1 to medium 2.

Normal Angle of incidence i Angle of refraction R Refraction towards the normal Refraction away from

Total Internal Reflection When the light goes from slow to fast, as the angle of incidence is increased, the angle of refraction increases as well, until it reaches 90. The angle of incidence when this happens is called the “critical angle.”

Total Internal Reflection – Critical Angle Fast medium eg air Slow medium eg glass Fast medium eg air normal Angle of refraction = 90º Critical angle ic Refracted beam Partially reflected beam

Total Internal Reflection Beyond the critical angle, no refraction is possible and the light is said to ‘totally internally reflect.’

Total Internal Reflection No refraction is possible beyond the critical angle. Slow medium eg glass Fast medium eg air normal Angle of Incidence i Greater than ic

Below the critical angle

At the critical angle Note the reflected ray Note the refracted ray at grazing angle – colour dispersion

Beyond the critical angle Total internal reflection.

Total Internal Reflection qc Water (n=1.3) Air (n=1.0) Snell’s law:

Guiding Light Need to guide light to communicate optically between points First observation of light guiding made by John Tyndall Based on total internal reflection

Photonics is Everywhere Photonics is the science of the photon, the fundamental particle of light. Compact tunable lasers for optical telecommunications Optical fibres for structural strain sensing Sea mice use photonic crystal effects to warn off predators

Optical Fibres Beyond Telecommunications Optical fibres can also have applications in: Medicine Biological and genetics research Defence Industrial materials processing Chemical and pollution sensing Next generation lasers Optical data processing Transmitting light beyond the near-IR And so new types of optical fibres are needed…

Microstructured Optical Fibres fibres with micron-scale transverse features

Why Microstructure? Engineering materials on the scale of the wavelength of light can lead to materials with new optical properties Using air as the cladding of an optical fibre means that fibres can be made from a single material Light can be used to probe the properties of materials located within the air holes Here at Adelaide University, we are setting up facilities to develop a whole new class of optical fibres – soft glass microstructured optical fibres

Overview of Fibre Activities at Adelaide University Fibre Design Software Device Concept Development Capabilities Fibre Test & Characterisation Equipment Materials Development Basic glass melting facilities Advanced glass development & processing Preform Manufacture Extrusion OR Casting Make preform with mm-scale structure Draw Tower Preform Fibre

Structured glass preform Extrusion glass billet OD=29mm h=34mm Stainless steel die Structured glass preform

Extrusion – Preform Variety Structured preforms in one step Flexible geometry Geometric reproducibility Successfully applied to: lead silicates, tellurites, chalcogenides, bismuthates, lead germanates

Careers in Photonics Centre of Expertise in Photonics School of Chemistry & Physics University of Adelaide Professor Tanya Monro Director www.chemphys.adelaide.edu.au/physics/research/photonics

Science Degrees at Adelaide University Bachelor of Science (BSc) - Biomedical sciences - Biophysics - Chemistry - Environmental biology and Ecology - Geosciences (Geology and Geophysics) - Molecular biology and Biotechnology - Physics - Psychology and Behavioural Sciences

A Science Degree Provides… Scientific knowledge Technical skills Problem solving skills Analytical skills Critical thinking Communication skills Initiative Teamwork Time management Responsibility Confidence And Leads to a Career in: Government Health Education Private industry Consultants Research laboratories Own business

Pre-requisites BSc Two science subjects, one chosen from Chemistry, Maths Studies, Specialist Maths, Physics & one from Biology, Chemistry, Geology, Physics Specialist Programs with Physics Physics, Maths Studies and Specialist Maths

BSc (Optics and Photonics) Optics and Photonics is a steadily growing sector in industry Australian tertiary institutions are not producing enough trained people (even allowing for the “bust” in the boom/bust cycle ! ) Physics graduates are readily employable in this industry Named degree makes qualification more recognisable Adelaide is rapidly developing strength in defence photonics (potential employers include: DSTO, Tenix, BAE systems Wide range of other opportunities including in medicine (eg ophthalmology), communications, etc Attractive career opportunities with scope for creativity and practical relevance

Job opportunities in photonics There are opportunities for people with photonics training in Academia, Industry, Defence Requires study of physics and mathematics Bachelor of Science (Optics and Photonics)