Truncating a Gaussian Beam: Effects on Intensity and Other Parameters?

[belal]

Hi All,

I am just wondering whether there is any kind soul to help me out with the following problem:

If a gaussian beam is truncated by the circular aperture situated at the beam waist just before the entrance of a microscope objective lens, what should be the intensity distribution of the beam at the focal plane of the microscope objective. Would truncation of the beam affect any other parameter such as beam waist size, depth of focus?

Thanks in Advance,

Belal

 

[Laser Jock]

I believe that the intensity pattern at the focal plane would be the Fourier transform of a Circ function, namely J_1 a Bessel function of the first kind.

Is the beam collimated before it hits the aperture?

 

[Laser Jock]

Correction:

I thought about it a little more and the intensity pattern would be the convolution of a gaussian and a Bessel function of the first kind (or the Fourier transform of the intensity pattern at the aperture).