A tabletop scene to be recorded as a hologram has a front-to-back depth of m

PHYSICS · Multi-part · Fermi University Physics · Optics & Photonics · Fourier optics and image formation · Coherence and statistical optics

What an Instrument Can See, Ch Keeping the phase: holography, wavefront modulation and adaptive optics

Problem

A tabletop scene to be recorded as a hologram has a front-to-back depth of d=0.20d = 0.20 m, and is lit and viewed near normal incidence so the extra path length to the back of the scene and back to the plate is 2d2d. The source is a distributed-feedback diode laser with a specified Lorentzian linewidth Δν=15\Delta\nu = 15 MHz, for which the coherence length is ℓc=c/(πΔν)\ell_c = c/(\pi\Delta\nu). ((a)) Estimate the coherence length the source must supply for the whole scene to record with appreciable fringe visibility. ((b)) Compute the diode laser's coherence length and state whether it meets the requirement, quoting the margin as a ratio.

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