A circular aperture of radius is illuminated on-axis by a Nd:YAG laser,

PHYSICS · Multi-part · Fermi University Physics · Optics & Photonics · Interference and diffraction · Interference and diffraction

What an Instrument Can See, Ch Scalar diffraction theory, derived

Problem

A circular aperture of radius

a = 0.80\,\mathrm{mm}

is illuminated on-axis by a Nd:YAG laser,

\lambda = 1.06\,\mu\mathrm{m}

. A detector sits on-axis a distance

z = 1.2\,\mathrm{m}

beyond the aperture, where the unobstructed irradiance would be

I_0

. ((a)) Compute the Fresnel number

N_F

of the aperture at this distance. ((b)) Compute the on-axis irradiance at the detector, in terms of

I_0