Week 4 Dichroism, Optical Antisotropy & Polarisation Devices Flashcards
what does Dichroism do
produces polarised light from unpolarised light by selectively absorbing one component
what is Malus’ Law in words
Intensity transmitted by a dichroic when plane-polarised light is incident on it is I(θ) = I0[cosθ]^2
define an anisotropic/birefringent crystal
a crystal in which the refractive index depends on the direction of oscillation of E of a wave
what does Corollary suggest
velocity of a wave, and the relative permittivity ε also depend on the direction. So it is easier to polarise an anisotropic crystal in one direction relative to another
briefly summarise a Uniaxial crystal
two of the components of ε are equal and the other differs so the refractive index differs in one direction from the others
briefly summarise a Biaxial crystal
all three components of ε are different
what is a negative uniaxial crystal
a uniaxial crystal where the unique refractive index is lower than the other two
what are the two possible solutions from the index relations equations
k^2/n0^2 = ω^2/c^2
kx^2/ne^2 + ky^2/ne^2 + kz^2/n0^2 = ω^2/c^2
what is the final refractive index relation equation
1/n^2 = [sinθ]^2/ne^2 + [cosθ]^2/n0^2
what is true of optically anisotropic crystals and what does this lead to
they have a physical anisotropy
leads to different polarisations behaving differently and double wavefronts or double refraction
what is a retardation plate
waveplates are made of birefringent material, which is cut so that the optic axis is parallel to the surface
what can a retardation plate be used for
used to modify the state of the input polarisation
how does a quartz wedge work
thickness varies along the wedge creating a relative delay between the components of E
how does a glan polariser work
unpolarised light enters and hits a plate so that they split into
how does a Wollaston Prism
two birefringent crystal prism that have different optic axes where at their interface in the centre, the opitc axes change so the e-ray becomes the o-ray and refracts toward the normal
