# Tagged Questions

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### How to calculate beam spread of a non-point light source via an aspheric lens

I need to determine the angle, or rate of divergence of light from a single aspheric lens when I place a non-point light source (e.g. LED array) at a given distance from the lens which is less than ...
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### EigenMode expansion for beam propagation

I want to understand how to apply EigenMode expansion method (http://www.photond.com/files/docs/PW03_eme_paper.pdf) for beam propagation on a system of lenses. The interface between two mediums of ...
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### Photon Statistics of a Coherent Gaussian Beam [closed]

Assume that a 100 pW He-Ne single-mode last emits light at 633 nm in a TEM00 Gaussian beam. (a)What is the mean number of photons crossing a circle of radius equal to the waist radius of the beam ...
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### Beam splitters- Direction of use

There are two cases I'm asking about. The square in the middle is a cube beam splitter in the same orientation for both cases. We are looking at the beam splitter from the top. In the first case, ...
I know that in free space, the width of a Gaussian beam can be written as $W=W_0\sqrt{1+(\frac{z}{z_0})^{2}}$. However, I was wondering if it was possible to express this width as a function of ...