Transcript Photonic Bandgaps - University at Buffalo

Photonic Bandgap
Structures
By
Akshay V. Hegde
Graduate Student
Dept. of Electrical Engineering
Course: Optical Communications
Instructor: Dr. Pao-Lo Liu
Agenda
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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
E = (hc)/λ
 These photons are forbidden in the
structure and cannot propagate
 Analogous to forbidden energy gaps in
semiconductors
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, highindex 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 Fiber
Low-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
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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”
(http://pbglink.com)
 Physics Web
(http://physicsweb.org/article/world/13/8/9)
 Optoelectronics Group, University of Bath
(http://www.bath.ac.uk/physics/groups/opto/pcf.h
tml)
 Wired Magazine
(http://www.wired.com/wired/archive/8.09/optical
.html)
Thank You!