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Photonic Crystals – it’s all about the mirrors

Photonic Crystals – it’s all about the mirrors. Maksim Skorobogatiy Canada Research Chair in Photonic Band Gap materials and devices. I would like to thank Prof. Yoel Fink fiber research group at MIT, and Prof. Steven Johnson at MIT for their contributions. Periodic electromagnetic media.

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Photonic Crystals – it’s all about the mirrors

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  1. Photonic Crystals – it’s all about the mirrors Maksim Skorobogatiy Canada Research Chair in Photonic Band Gap materials and devices I would like to thank Prof. Yoel Fink fiber research group at MIT, and Prof. Steven Johnson at MIT for their contributions.

  2. Periodic electromagnetic media Low index of refraction High index of refraction 3D photonic crystal

  3. Plane-waves in a uniform dielectric l/n n

  4. Scattering regimes a a>>l incoherent scattering a a~l coherent scattering a<<l averaging a Photonic crystals

  5. Photonic Crystals 1 - D p e r i o d i c i n o n e d i r e c t i o n Periodic electromagnetic media 1887 1987 2 - D 3 - D 1977 p e r i o d i c i n p e r i o d i c i n t w o d i r e c t i o n s t h r e e d i r e c t i o n s quazi-2D microstructured fibers quazi-1D Bragg fibers

  6. Photonic Crystals Components can trap light in cavities and waveguides (“wires”) periodic electromagnetic media with defects

  7. 1D Photonic Crystal 1 - D

  8. Uniform dielectric (transverse wavevector) kt n b (preferred direction) (propagation constant) Our first band diagram w light propagation light cone light line: w = cb / n no light propagation, kt is IMAGINARY b

  9. Two uniform dielectrics (intuitive picture) k1t n1 < b n2 q2 k2t w light cone light propagation in dielectric 1,2 light propagation in dielectric 2 only light line 1: w = cb / n1 light line 2: w = cb / n2 no light propagation in dielectrics 1,2 b

  10. A quest for a perfect mirror Reflectance 1 As index contrast increase TE TM As index contrast increase q1 tan-1(n2/n1) 0 90o Dielectric mirror, low loss, but strong angular and polarization dependence Metallic mirror, low angular and polarization dependence,but very high loss for optical frequencies Reflectance is getting more uniformfor all polarizations and wider region of anglesas index contrast increases

  11. Projected Bands of a 1d Crystal(a.k.a. a Bragg mirror) b conserved Light in the multilayer w Quaterwave stack condition d1n1=d2n2=l/4 n1 d1 n2 d2 TM 1d band gap TE modes in crystal b propagation perpendicular to the layers

  12. Omnidirectional Reflection Air b conserved all incident light (any angle, polarization) is reflected from flat surface [ J. N. Winn et al, Opt. Lett.23, 1573 (1998) ] w light line of air w = cb TM in these w ranges, there is no overlap between modes of air & crystal TE modes in crystal b needs: sufficient index contrast & nhi > nlo > 1

  13. Omnidirectional Mirrors in Practice [ Y. Fink et al, Science282, 1679 (1998) ] Te / polystyrene contours of omnidirectional gap size 3 50% 2.8 40% 2.6 2.4 30% 2.2 20% Reflectance (%) 2 10% 1.8 0% 1.6 Dl/lmid 1.4 1.2 1 1 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2 Smaller index, n 1

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