An air-spaced ( ) etalon has fixed mirror spacing mm and is used at nm

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

Optics and Photonics, Ch Multiple-beam interference: thin films, multilayers and the Fabry-Perot etalon

Problem

An air-spaced (n=1.00n=1.00) etalon has fixed mirror spacing d=2.00d = 2.00 mm and is used at λ=500\lambda = 500 nm, normal incidence. Its mirrors are first replaced with ones of reflectance R=0.70\mathcal{R} = 0.70, then later with better mirrors of reflectance R=0.95\mathcal{R} = 0.95, the spacing left untouched. ((a)) Find the free spectral range, coefficient of finesse FF, finesse F\mathcal{F} and linewidth Δν1/2\Delta\nu_{1/2} for R=0.70\mathcal{R}=0.70. ((b)) Repeat for R=0.95\mathcal{R}=0.95. ((c)) State which of these four quantities changes when the mirrors are upgraded and which does not, and why.

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