Determine the fwhm diameter of the beam 50 mm from the

Question

Problem - Gaussian Beam Propagation to a Detector

Consider a large diameter Gaussian beam with a planar wavefront and waist of 40 mm at a distance of 1 m from a lens of focal length 100 mm.

A second lens is placed after the first lens with a focal length of -50 mm at a distance 50 mm from the first lens.

(a) Determine the FWHM diameter of the beam 50 mm from the second lens (ie. 100 mm from the first lens.) A third lens is placed at the point with a focal length off.

(b) Determine the focal length necessary for the lens so that the light is focused to a FW 1/e²D on the detector with an active area of 1 mm² placed at the focal plane.

(c) Make the same calculations for a laser source with an M² of 1.3.

(d) How does it compare to the Gaussian beam system?