Parameters of a Gaussian Laser Beam. A 1-mW He-Ne laser produces a Gaussian beam

ID: 2245077 • Letter: P

Question

Parameters of a Gaussian Laser Beam.

A 1-mW He-Ne laser produces a Gaussian

beam of wavelength A = 633 nm and a spot size 2Wo = 0.1 mm.

a) Determine the angular divergence of the beam, its depth of focus, and its diameter at

z = 3.5 x 10^5 km ( approximately the distance to the moon).

(b) What is th e radius of curvature of the wavefront at z = 0, z = Zo, and z = 2Zo,?

axial point z = Zo? Compare this with the intensity at z = Zo of a 100-W spherical

wave produced by a small isotropically emitting light source located at z = 0.

the power is P = 1 mW = 1 x 10^-3 W

the wavelength is A = 633 nm = 633 x 10^-9 m

we know that

A = (h/mv)

where h is planck's constant,m is mass of electron and v is speed of electron

or v = (h/m x A)

where h = 6.63 x 10^-34 J-s and m = 9.1 x 10^-31 kg

the kinetic energy of electron is

K = (1/2)mv^2

Also,

P = (K/t)

where t is time

or t = (K/P)

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