Feb1_Maxwell's equation_With_Notes_From_Michal

# Feb1_Maxwell's equation_With_Notes_From_Michal - Ray Optics...

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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! Maxwell’s equations Assumption 1 : Source free (charge does not generate THz) ∇× E =-∂ B ∂ t ∇ × H =-∂ D ∂ t + j ∇ ⋅ D = ρ ∇ ⋅ B = Maxwell’s equations are then: Electrical and Magnetic Permeability B = μ H D = ε E Assumption 2 : μ , ε are linear (independent of field strength) . In Vacuum In non-vacuum the assum ption is valid at low intensities. In m ost crystals the m aterial becom es non-linear 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 = μ H D = ε 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? let’s look at common materials GaAs Glass (SiO 2 ) ε = 8.85 × 10- 12 F/m (Faradays/m) μ = 4 π × 10- 7 Henry/m Maxwell’s equations for...
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Feb1_Maxwell's equation_With_Notes_From_Michal - Ray Optics...

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