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Unformatted text preview: Ray Optics vs Wave Optics Why the need for Wave Optics? Examples of instances where Ray Optics is not a good enough approximation: Naively this is how a lens work A simple lens requires wave optics to describe its detail operation! Maxwells equations Assumption 1 : Source free (charge does not generate THz) E = B t H = D t + j D = B = Maxwells equations are then: Electrical and Magnetic Permeability B = H D = E Assumption 2 : , are linear (independent of field strength) . In Vacuum In nonvacuum the assum ption is valid at low intensities. In m ost crystals the m aterial becom es nonlinear when Intensity~ 10 20 W / m 2 Assum ing I can focus down the light, what is the power of the laser I need? When is it valid? Assumption 3: Isotropic B = H D = E , m u and eps are tensors Electrical and Magnetic Permeability Note: we are NOT assum ing the m aterial is not hom ogenous Is the assumption realistic? lets look at common materials GaAs Glass (SiO 2 ) = 8.85 10 12 F/m (Faradays/m) = 4 10 7 Henry/m Maxwells equations for...
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 '04
 LIPSON

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