Refraction and Optical Fibres

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

2. 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.”

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

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

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

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

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

9. 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.”

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

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

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

13. Below the critical angle

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

15. Beyond the critical angle Total internal reflection.

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

17. 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

18. 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

19. 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…

20. Microstructured Optical Fibres fibres with micron-scale transverse features

21. 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

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

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

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

25. Careers in Photonics Centre of Expertise in PhotonicsSchool of Chemistry & PhysicsUniversity of Adelaide Professor Tanya Monro Director www.chemphys.adelaide.edu.au/physics/research/photonics

26. 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

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

28. 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

29. 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

30. 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)