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

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refraction and optical fibres
Refraction and Optical Fibres

Dr Murray Thompson

University Senior College

Prof Tanya Monro

Centre of Expertise in

refraction and optical fibres2
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 fibres3
Refraction and Optical Fibres
  • When light travels from one medium to another it changes speed.
  • It also changes direction.

Angle of

Refraction R

Slow medium

eg glass

Fast medium eg air

Angle of

Incidence i


Partially reflected beam

  • From a fast medium to a slow medium, the light bends towards the normal.

Fast medium eg air

Angle of

Refraction R

Slow medium

eg glass

Angle of

Incidence i


Partially reflected beam

  • From a slow medium to a fast medium, the light bends away from the normal.
snell s law of refraction
Snell’s Law of Refraction

which is the refractive index from medium 1 to medium 2.



Refraction towards the


Angle of incidence i

Angle of refraction R

Angle of incidence i

Refraction away from


Refraction away from


Angle of refraction R


total internal reflection
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

Angle of refraction = 90º

Refracted beam

Slow medium

eg glass


angle ic

Partially reflected beam


Total Internal Reflection – Critical Angle
  • Fast medium eg air
total internal reflection11
Total Internal Reflection
  • Beyond the critical angle, no refraction is possible and the light is said to ‘totally internally reflect.’
total internal reflection12

Fast medium eg air

Slow medium

eg glass

Angle of

Incidence i

Greater than ic


Total Internal Reflection
  • No refraction is possible beyond 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 reflection16

Air (n=1.0)

Water (n=1.3)


Total Internal Reflection

Snell’s law:

guiding light
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 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 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
Microstructured Optical Fibres

fibres with micron-scale transverse features

why microstructure
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


Device Concept



Fibre Test &



Preform Manufacture

Materials Development

Draw Tower

Preform Fibre

Make preform with mm-scale structure


Basic glass

melting facilities



Advanced glass development & processing

Overview of Fibre Activities at Adelaide University


glass billet



Stainless steel die

Structured glass preform

extrusion preform variety
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
Careers in Photonics

Centre of Expertise in PhotonicsSchool of Chemistry & PhysicsUniversity of Adelaide

Professor Tanya Monro


science degrees at adelaide university
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
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
pre requisites


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
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
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)