1. Waves, Light & Quanta Tim Freegarde
Web Gallery of Art; National Gallery, London

2. Rainbows

3. Rainbows i x r r r i r r  r i

4. Rainbows i x r r r i r r  r i

5. Rainbows i x r r r i r r  r i

6. Rainbows 

7. Rainbows 

8. Rainbows

9. Sinusoidal waves  z
simple harmonic motion
circular motion
where

10. Sinusoidal waves at , wavenumber spectroscopists’ wavenumber
wavelength

11. Sinusoidal waves
at ,
angular frequency
frequency
period

12. Suggested textbooks Hecht Optics Pedrotti & Pedrotti
Introduction to Optics
Smith, King & Wilkins
Optics and Photonics
Show books

13. Birefringence
asymmetry in crystal structure causes two different refractive indices
opposite polarizations follow different paths through crystal
birefringence, double refraction

14. Optical polarization light is a transverse wave: perpendicular to
for any wavevector, there are two field components
any wave may be written as a superposition of the two polarizations

15. Linear dichroism
conductivity of wire grid depends upon field polarization
electric fields perpendicular to the wires are transmitted
fields parallel to the wires are absorbed
WIRE GRID POLARIZER

16. Malus’ law amplitude transmission intensity transmission
WIRE GRID POLARIZER

17. Linear dichroism
crystals may similarly show absorption which depends upon linear polarization
absorption also depends upon wavelength
polarization therefore determines crystal colour
pleochroism, dichroism, trichroism
TOURMALINE

18. Polarization in nature
CUTTLEFISH (sepia officinalis)
the European cuttlefish also has polarization-sensitive vision
… and can change its colour and polarization!
MAN’S VIEW
CUTTLEFISH VIEW
(red = horizontal polarization)

19. Characterizing the optical polarization
wavevector insufficient to define electromagnetic wave
we must additionally define the polarization vector
e.g. linear polarization at angle

20. Categories of optical polarization
linear (plane) polarization
non-equal components in phase
circular polarization
equal components 90° out of phase
elliptical polarization
all other cases

21. Polarization notation
circular polarization
RCP
plane of incidence
right- or left-handed rotation when looking towards source
traces out opposite (right- or left-) handed thread
perpendicular
parallel
linear (plane) polarization
parallel or perpendicular to plane of incidence
plane of incidence contains wavevector and normal to surface

22. Circular dichroism
absorption may also depend upon circular polarization
SCARAB BEETLE
LEFT CIRCULAR POLARIZED LIGHT
RIGHT CIRCULAR POLARIZED LIGHT
the scarab beetle has polarization-sensitive vision, which it uses for navigation
the beetle’s own colour depends upon the circular polarization

23. Optical activity (circular birefringence)
optical activity is birefringence for circular polarizations
CH2
CH3 H
CH2
CH3 H
an asymmetry between right and left allows opposing circular polarizations to have differing refractive indices
l-limonene
(orange)
r-limonene
(lemon)
optical activity rotates the polarization plane of linearly polarized light
CHIRAL MOLECULES
may be observed in vapours, liquids and solids

24. Birefringence
asymmetry in crystal structure causes polarization dependent refractive index
ray splits into orthogonally polarized components, which follow different paths through crystal
note that polarization axes are not related to plane of incidence

25. Optical polarization light is a transverse wave: perpendicular to
for any wavevector, there are two field components
any wave may be written as a superposition of the two polarizations

26. Electromagnetic waves
light is a transverse wave: perpendicular to
Faraday
Ampère

27. Dielectrics z atomic electrons move in response to electric field
resulting atomic dipole radiates field which adds to original z
Faraday
Ampère

28. Birefringence
asymmetry in crystal structure causes polarization dependent refractive index
ray splits into orthogonally polarized components, which follow different paths through crystal
note that polarization axes are not related to plane of incidence

29. Linear polarizers (analyzers)
o-ray
birefringence results in different angles of refraction and total internal reflection
38.5º
e-ray
many different designs, offering different geometries and acceptance angles
e-ray
o-ray
s-ray
a similar function results from multiple reflection
p-ray

30. Waveplates (retarders)
at normal incidence, a birefringent material retards one polarization relative to the other
linearly polarized light becomes elliptically polarized
WAVEPLATE

31. Compensators
a variable waveplate uses two wedges to provide a variable thickness of birefringent crystal
adjust
a further crystal, oriented with the fast and slow axes interchanged, allows the retardation to be adjusted around zero
variable
fixed
with a single, fixed first section, this is a ‘single order’ (or ‘zero order’) waveplate for small constant retardation
SOLEIL COMPENSATOR