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Unformatted text preview: divergence halfangle; Gaussian beam with mirrors and with a lens. A particular HeNe laser has a farfield divergence angle of 1 mrad at the wavelength 632.8 nm. (a) What is beamwaist, w o ? (b) What is the Rayleigh range? What is the beam size at the Rayleigh range? (d) What is the beam size and radius of curvature at 10 meters? (e) At what distance is the spot size 3 cm? (f) Now insert a lens with focal length +25 cm at a distance of 2 meters. What is the radius of curvature just after passing through the lens? (g) What is the smallest spot size after the lens? (Assume the clear aperture of the lens is large compared to the beam spot size) (h) This lens can sustain laser powers of up to 10 mW/cm 2 without damage to the surface. What is the maximum power at which the laser should be operated in order to avoid damage to the lens? 1...
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This document was uploaded on 09/05/2010.
 Spring '09

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