Photonic Bandgap Structures By Akshay V. Hegde Graduate Student Dept. of Electrical Engineering Course: Optical Communications Instructor: Dr. Pao-Lo Liu

Agenda  Photonic Band Gaps  Photonic Band Gaps & Bragg’s Law  Natural PBS  Artificial PBS  Fabrication of PBS  Self-Assembly Process  Photonic Crystal Fiber  Future Applications  Photonic Giants

Photonic Band Gaps  Photons with a certain range of wavelengths do not have an energy state to occupy in a structure  These photons are forbidden in the structure and cannot propagate  Analogous to forbidden energy gaps in semiconductors E = (hc)/λ

Photonic Band Gaps & Bragg’s Law  Periodic objects reflect incident waves when the dimensions, wavelength and interplanar spacing, satisfy Bragg's Law  Bragg’s Law is valid for any EM wave in any periodic object

Natural PBS The Gemstone Opal

Natural PBS The Mitoura Grynea

Artificial PBS  A lattice fabricated from layers of silicon "matchsticks"  Spherical air holes in a material with a high refractive index

Fabrication of PBS  Two popular methods  Lithography  Defects can be precisely controlled  Ideal for small scale production  Expensive and complex  Self-Assembly  Defects cannot be controlled precisely  Works well for bulk production  Inexpensive and simple An Opal Template

Self-Assembly Process

Photonic Crystal Fiber  A long thread of silica glass with a periodic air holes running down its length

 Type 1- The central hole is absent, high- index defect acts as core  Type 2 - The core has an extra hole, which is a low-index defect (Photonic band gap fiber)  Light is guided along the low refractive index air core by photonic band gap confinement effect  Presently, fabrication of 3D photonic crystals on the scale of a micron is difficult

High-Index Defect FiberLow-Index Defect Fiber High-Index Defect FiberLow-Index Defect Fiber

Future Applications  Highly efficient photonic crystal lasers  High resolution spectral filters  Photonic crystal diodes and transistors  High efficiency light bulbs  Optical computers  Telecommunication & computer networks  Photonic clothes and candy bars?

Photonic Giants  NEC Research Institute & Electrical Engineering Dept. at Princeton University  Dept. of Electrical Engineering at UCLA  Massachusetts Institute of Technology  Sandia National Laboratories, California  Rockwell International, California  Bell Labs  Corning

References  Articles on “Photonic Band Gap Links” (  Physics Web (  Optoelectronics Group, University of Bath ( tml) tmlhttp:// tml  Wired Magazine (

Thank You!