Understanding Electric Field Changes Passing Through a Waveplate

In summary, the electric field amplitude remains the same before and after passing through a waveplate, but picks up a relative phase shift. There is also an overall phase, but it does not affect the amplitude or polarization of the output wave.
  • #1
raisin_raisin
27
0
Hello,
I am trying to figure out how the electric field changes before and after passing through a waveplate but my notes don't make any sense.
I think
Eextin=Ecos[tex]\theta[/tex] and Eordin=Esin[tex]\theta[/tex]
where theta is the angle the electric field makes with the optic axis.

I can't tell how the amplitude changes on Eout though.

I know they pick up a relative phase but I can't tell if this is in addition to a phase anyway.

i.e is it just
Eextin=Ecos[tex]\theta[/tex]
and Eordin=Esin[tex]\theta[/tex] ei[tex]\Delta\varphi[/tex]

or if it should be the same but with a different amplitude i.e E' not E afterwards (in which case how do I calculate this?) or whether it should be

Eextout=Ecos[tex]\theta[/tex]ei[tex]\varphi[/tex]e
and Eordout=Esin[tex]\theta[/tex] ei[tex]\varphi[/tex]oei[tex]\Delta\varphi[/tex]

Or should it be this with E' instead of E?
This is what my notes suggest but I am hoping it is wrong since delta phi is [tex]\pi[/tex] so it would make it easier if it wasn't.

Thanks for any help.
 
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  • #2
Assuming no absorption or reflective losses, Eext and Eord keep the same amplitudes. They do get a relative phase shift, so just tack on a factor exp(iφ) to one of the amplitudes as you had originally.

I know they pick up a relative phase but I can't tell if this is in addition to a phase anyway.
Yes, there is an overall phase as well, but that is not important as it does not affect the amplitude or polarization of the output wave.
 
  • #3


Hello, I understand your confusion and I will try to explain the changes in the electric field before and after passing through a waveplate. A waveplate is an optical device that alters the polarization state of light passing through it. It has a specific optic axis, which is the direction along which the waveplate has no effect on the polarization state of light. When light with an electric field Einc is incident on a waveplate, the electric field is split into two components - one parallel to the optic axis (Eord) and one perpendicular to it (Eext). This is where the equations you mentioned come into play: Eord = Esinθ and Eext = Ecosθ, where θ is the angle between the electric field and the optic axis.

Now, as the light passes through the waveplate, the two components (Eord and Eext) experience different phase shifts due to the birefringent properties of the waveplate. This phase shift is denoted by Δφ and is dependent on the thickness and material of the waveplate. Therefore, the electric field after passing through the waveplate can be written as Eout = EexteiΔφ + EordeiΔφ. This means that both components of the electric field have picked up a relative phase shift of Δφ.

To determine the change in amplitude of the electric field, we can use the law of conservation of energy. The total energy of the electric field before and after passing through the waveplate must be the same. Therefore, the amplitude of the electric field after passing through the waveplate can be calculated using the equation Eout = Einc. This means that Eextout = EincosθeiΔφ and Eordout = EinsinθeiΔφ. So, the amplitude of the electric field after passing through the waveplate is the same as before, but with a phase shift of Δφ.

I hope this explanation helps you understand the changes in the electric field before and after passing through a waveplate. It is important to note that the phase shift will depend on the specific properties of the waveplate and the incident light. If you need further clarification or assistance, please do not hesitate to ask. Good luck with your studies!
 

Q: What is an electric field?

An electric field is a physical field that describes the interactions between electrically charged particles. It is a vector field, which means it has both magnitude and direction.

Q: What is a waveplate?

A waveplate, also known as a retarder or phase shifter, is an optical device that alters the polarization state of light passing through it. It consists of a birefringent material, such as quartz, that causes a phase shift between the two orthogonal polarization components of light.

Q: How does a waveplate change the electric field of light passing through it?

A waveplate changes the electric field of light by introducing a phase shift between the two orthogonal polarization components. This changes the relative amplitudes and phases of the electric fields, resulting in a change in the overall polarization state of the light.

Q: How does the angle of the waveplate affect the electric field changes?

The angle of the waveplate affects the electric field changes by determining the amount of phase shift that is introduced between the two polarization components. This angle is usually measured relative to the fast axis of the waveplate, which is the axis that causes the least amount of phase shift.

Q: What are some practical applications of understanding electric field changes passing through a waveplate?

Understanding electric field changes passing through a waveplate is important in various applications, such as polarimetry, optical communication, and optical data storage. It is also useful in studying the properties of materials, such as their birefringence and anisotropy.

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