Intensity Calculation: Is "wa" is a beam radius or beam diameter?

[apoorav-singh]

I am writing in the context of the function:

atom.groundStateRamanTransition()

For the Electric field calculation, when Intensity is calculated there is an factor of 2 multiplied to the equation.

Ia = 2.0 * Pa / (pi * wa**2)

I have a doubt that,

• Case 1: If "wa" aka beam waist is the diameter (or 1/e^2 for gaussian beam) of the beam. Than for area calculation radius is given as '(wa/2)^2' . So one should get factor of 4 not 2 in the numerator.

• Case 2: If the "wa" aka beam waist radius is entered no factor should follow. Therefore,

Ia = Pa / (pi * wa**2)

If in case I missing something please feel free to correct me.

[nikolasibalic]

Hi @jonathanpritchard could you please verify this and reply?

[jonathanpritchard]

This is beam radius - the definition of peak intensity for a Gaussian beam is 2P/(pi*w0**2) see https://en.wikipedia.org/wiki/Gaussian_beam for proof