1. Refraction and Optical Fibres
Dr Murray Thompson
University Senior College
Prof Tanya Monro
Centre of Expertise in Photonics

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. 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

5. 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

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

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

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. 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

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

12. 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

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. Total Internal Reflectionqc
Water (n=1.3)
Air (n=1.0)
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. 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

23. Structured glass preform
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 Photonics School of Chemistry & Physics University of Adelaide
Professor Tanya Monro
Director

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…
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

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)