Optical rotation and linear basis set

In summary, a linear rotator can rotate the angle of linear polarized light while a circular rotator can't.
  • #1
galvin452
15
0
If I have a 45 degree linear polarized light which I then circularly polarize using a 1/4 wave plate and put this through an optical rotary crystal and then using the equivalent 1/4 wave plate but in the reverse oriention, will I get back a 45 degree linear polarized light?

Put another way, as circular polarized light can use a linear basis set 90 degrees out of phase, can the angle of the linear basis set with respect to the 1/4 wave plate orientation be rotated by the optical rotary crystal (while the phase remains circular) or is the basis set orientation always fixed?

I would think the basis set orientation is fixed but just want to make sure.
 
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  • #2
There is no reason why the basis set orientation ought to be fixed. By my understanding the optical rotary crystal can rotate the linear basis set. I'd go through the Jones algebra to be sure though.

Claude.
 
  • #3
Claude Bile said:
There is no reason why the basis set orientation ought to be fixed. By my understanding the optical rotary crystal can rotate the linear basis set. I'd go through the Jones algebra to be sure though.
Claude.

For a linear basis set, one can take each individual linear orientation basis as two oppositely rotating basis set so that each orthogonal linear basis is rotated by the difference between the right and left index of refraction. This would rotate the basis set as you indicated. The amount of rotation dependent on the difference between the left and right rotary index of refraction.

However if one uses a circular basis set the light is totally right circularly (or left circularly depending on the 1/4 wave plate fast slow axis orientation) polarized when entering the optical rotary crystal. Let's assume right circularly polarized, so at best it could only interact with the right index of refraction having no left component. So the right circular polarized light's reorientation would only be the result of the right rotary index of refraction.

That is to say we would get two different results depending on the basis set used.

Where is the mistake?
 
  • #4
Claude Bile said:
. I'd go through the Jones algebra to be sure though.
Claude.

I can't find the Jones matix is for an optical rotary crystal? Do you know it?
 
  • #5
For a linear rotator (say, sugar water), the Jones matrices are: [[cos(δ/2)+icos(2θ)sin(δ/2) isin(2θ)sin(δ/2)], [isin(2θ)sin(δ/2) cos(δ/2)-icos(2θ)sin(δ/2)]] for cartesian basis states and [[cos(δ/2) i*exp(i2θ)sin(δ/2)], [i*exp(-i2θ)sin(δ/2) cos(δ/2)]] for circular basis states, where θ is the azimuthal angle of the fast axis and δ the phase retardation.

For a circular rotator (say, the cholesteric liquid crystal phase), the cartesian Jones matrix is [[cos(δ/2) +/-sin(δ/2)], [-/+sin(δ/2) cos(δ/2)]] and for circular basis states [[exp(-/+ iδ/2) 0],[0 exp(-/+iδ/2)]].
 
  • #6
Andy Resnick said:
For a linear rotator (say, sugar water), the Jones matrices are: [[cos(δ/2)+icos(2θ)sin(δ/2) isin(2θ)sin(δ/2)], [isin(2θ)sin(δ/2) cos(δ/2)-icos(2θ)sin(δ/2)]] for cartesian basis states and [[cos(δ/2) i*exp(i2θ)sin(δ/2)], [i*exp(-i2θ)sin(δ/2) cos(δ/2)]] for circular basis states, where θ is the azimuthal angle of the fast axis and δ the phase retardation.

For a circular rotator (say, the cholesteric liquid crystal phase), the cartesian Jones matrix is [[cos(δ/2) +/-sin(δ/2)], [-/+sin(δ/2) cos(δ/2)]] and for circular basis states [[exp(-/+ iδ/2) 0],[0 exp(-/+iδ/2)]].

Hi Andy, not sure whar you mean by a linear rotator vs a circular rotator. I know you can rotate the angle of linear polarized light which I assume is what you mean by a linear rotator. What is a circular rotator?
 

What is optical rotation?

Optical rotation, also known as optical activity, is a phenomenon where the plane of polarized light is rotated when passing through certain substances. This rotation is caused by the interaction of the polarized light with the asymmetric molecules in the substance.

How is optical rotation measured?

Optical rotation is measured using a polarimeter, which consists of a light source, polarizing filters, and a sample cell. The polarized light is passed through the sample cell and the amount of rotation is measured using a scale or a digital display.

What is a linear basis set?

A linear basis set is a set of mathematical functions used to describe the electronic structure of a molecule or atom. It is a fundamental concept in quantum chemistry and is used to calculate various properties such as energy, geometry, and electronic transitions.

How does the choice of basis set affect calculations?

The choice of basis set can significantly affect the accuracy and efficiency of calculations in quantum chemistry. A smaller basis set may provide faster results, but at the cost of accuracy. On the other hand, a larger basis set may give more accurate results, but also require more computational resources.

What are some common basis sets used in optical rotation calculations?

Some commonly used basis sets in optical rotation calculations include Gaussian-type orbitals (GTOs), Slater-type orbitals (STOs), and numerical atomic orbitals (NAOs). These basis sets differ in their mathematical forms and can be used to model different types of molecules and systems.

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