Outer layer refractive index - total internal refection on waveguide

In summary, the conversation discusses the use of waveguide technology in AR lenses, which rely on total internal reflection to function. The current design of AR lenses includes an outer layer with a lower refractive index to allow for this process. This helps to suppress higher order modes and improve signal clarity. The conversation also includes a request for clarification on the meaning of "AR lens" and a repeated request for definitions of the acronym "PDA."
  • #1
Rymazon
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TL;DR Summary
Could an extra layer be better than air?
I am interested in experimenting with AR lenses and one of the main technologies is a waveguide. They rely on total internal reflection, which needs light to go from a higher to lower refractive index medium. I am reading that current AR lenses use an outer layer with a lower refractive index to allow this to happen but why would this be better than having no outer layer and using the refractive index of air, which is lower than most transparent materials? Thanks.
 
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  • #2
As you will realise there are a number of modes that can propagate in an optical waveguide. By making the transition in refractive index at the boundary gentle, those modes having a small angle of incidence at the interface will not be reflected and will pass through. The waveguide then tends to suppress higher order modes. This is desirable for some applications because the higher order modes propagate more slowly and will tend to blur a short signalling pulse. Step-index and graded index optical fibre are useful for fast digital transmission.
 
  • #3
Please define "AR lens". Do you mean gradient index lens? Or augmented reality filter? Or antireflective coating on glass lens?

Please define acronyms (PDA) Please define acronyms (PDA) Please define acronyms (PDA) Please define acronyms (PDA) Please define acronyms (PDA) Please define acronyms (PDA) Please define acronyms (PDA) Please define acronyms (PDA) Please define acronyms (PDA)Please define acronyms (PDA) Please define acronyms (PDA) Please define acronyms (PDA).......
 
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1. What is the outer layer refractive index?

The outer layer refractive index refers to the measure of how much light bends when passing through a material. It is a dimensionless quantity that indicates the speed of light in a vacuum compared to the speed of light in the material.

2. How does the outer layer refractive index affect total internal reflection?

The outer layer refractive index plays a crucial role in total internal reflection on a waveguide. If the refractive index of the outer layer is lower than that of the inner layer, light will be reflected back into the waveguide instead of being transmitted through the outer layer. This phenomenon is known as total internal reflection.

3. What is a waveguide?

A waveguide is a physical structure that is used to guide electromagnetic waves, such as light, along a specific path. It is typically made of a material with a high refractive index, surrounded by a material with a lower refractive index. Waveguides are commonly used in telecommunications and optical devices.

4. How is total internal reflection used in waveguides?

Total internal reflection is used in waveguides to confine light within the high refractive index core of the waveguide. This allows for efficient transmission of light signals without significant loss. Total internal reflection is also used in optical fibers, which are a type of waveguide commonly used for long-distance communication.

5. What factors affect total internal reflection on a waveguide?

The two main factors that affect total internal reflection on a waveguide are the refractive indices of the inner and outer layers, and the angle of incidence of the light. A higher refractive index difference between the layers and a smaller angle of incidence will result in a stronger total internal reflection. Other factors such as the material properties and surface roughness of the waveguide can also play a role.

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