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Unformatted text preview: Page 1 Page 1 Module 4 Lecture 1 Thin film coatings: Reflection properties Page 2 On the program today An EM wave incident at normal incidence on two boundaries in a row. What for? Antireflection coatings for media with different dielectric constants: optical glasses, cameras, computer and cell displays, radar cloaking Lossless weather shields for radars Passband filters with designed filtering shapes Using wave interference effects to trick Maxwells equations Page 3 Generic case: time harmonic xpolarized TEM wave Z=0 Z=L Medium 0 Medium 1 Medium 2 Take m r =1 in all media. Linearly polarized TEM wave allows us to use scalar equations for E Question: for a given wave incident from the left onto boundary 01, what is the reflected wave in 0 and transmitted wave in 2 Page 4 Write down the Efield phasors in the three regions of space Z=0 Z=L Medium 0 Medium 1 Medium 2 z j i e E z j r e E z j t e E 2 z j i e E 1 1 z j r e E 1 1 Page 5 Write down the Efield phasors in the three regions of space Z=0 Z=L Medium 0 Medium 1 Medium 2 z j i e E z j r e E z j t e E 2 z j i e E 1 1 z j r e E 1 1 + + We have ten unknowns (5 Efields and 5 Hfields) minus 1 arbitrary (the amplitude of the incident Efield). But we also have 4 boundary conditions (2 for tangential E and 2 for tangential H), and 5 equations for the E/H ratios in all media (the local wave impedance). SO THERE IS A UNIQUE SOLUTION! Page 6 Solution: start to match from the region where...
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 Spring '11
 victor

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