Photonic crystals are periodic dielectric structures that have a band gap that forbids propagation of a certain frequency range of light. This property enables one to control light with amazing facility and produce effects that are impossible with conventional optics.Photonic crystals can be fabricated for one, two, or three dimensions. One-dimensional photonic crystals can be made of layers deposited or stuck together. Two-dimensional ones can be made by photolithography, or by drilling holes in a suitable substrate. Fabrication methods for three-dimensional ones include drilling under different angles, stacking multiple 2-D layers on top of each other, direct laser writing, or, for example, instigating self-assembly of spheres in a matrix and dissolving the spheres

1. PHOTONIC
CRYSTALS
9/15/2017SHAREEF 1

2. CONTENTS
O CRYSTAL
O SEMICONDUCTOR
O PHOTONIC CRYSTAL
O PHOTONIC BAND GAP
O TYPES
O APPLICATIONS
9/15/2017SHAREEF 2

3. What is a crystal?
O A homogeneous solid formed by repeating,
Three dimensional pattern of atoms, ions, or
molecules.
O These have fixed distances between
constituent parts. (from Greek krustallos).
PHOTON:
The quantum of electromagnetic
energy, having zero mass, no electric charge,
and long lifetime.
9/15/2017SHAREEF 3

4. What is a semiconductor?
O It is a type of crystal whose
conductivity is in between a conductor
and insulator.
Examples: Silicon Germanium
9/15/2017SHAREEF 4

5. What is a photonic crystal?
O A photonic crystal is a periodic
structure in an optical medium, which
structure creates unusual optical
dispersion properties
OR
O Crystals having photonic band gap are
called photonic crystals or photonic
band gap crystals.
9/15/2017SHAREEF 5

6. Examples
O Examples in nature which reflect
electromagnetic radiation as
propagation through them is
prohibited.
9/15/2017SHAREEF 6

7. Natural opals
9/15/2017SHAREEF 7

8. Artificial Opal
Artificial opal sample (SEM Image)
Several cleaved planes of fcc structure are shown9/15/2017SHAREEF 8

9. What is Photonic Band Gap?
O Photonic band gap a range of forbidden
frequencies within which a specific
wavelength is blocked, and light is reflected
rather than transmitted.
9/15/2017SHAREEF 9

10. Basics of photonic band gaps
O The behavior of light in a photonic
crystal is similar to the movement
of electrons and holes in a
semiconductor.
O If the periodicity of the lattice is
broken by a missing Si atom or
by various impurity an electron
can have enough energy to be
in the band gap.
O The same for photons in a
photonic lattice, photons move
in a transparent dielectric
material that contains tiny air
holes arranged in a lattice
pattern.
9/15/2017SHAREEF 10

11. Bragg Reflection
2 ( )B Bnd Sin  
9/15/2017SHAREEF 11

12. Differences b/w
semiconductors &PBGC
Semiconductors
O Periodic crystal potential
O Atomic length scales
O Crystal structure given by nature
O Control electron flow
O 1950’s electronic revolution
PBG Crystals
O Periodic variation of dielectric
constant
O Length scale ~ 
O Man-made structures
O Control e.m. wave propagation
O 1990’s optical fibers, lasers,
PBGs --> photonics era
9/15/2017SHAREEF 12

13. What are different types of
PBGS?
O Periodic structure in an optical medium,
can be periodic in
O Single dimension
O Two dimensions
O Three dimensions.
9/15/2017SHAREEF 13

14. One Dimensional PBGC
O The material is periodic in the z-
direction, and homogeneous in the x y-
plane.
O Light propagate only in the z-direction
through 3 different 1d lattice samples.
9/15/2017SHAREEF 14

15. Two Dimensional PBGC
O The material has periodicity in 2
dimensions (that's where the photonic
gaps appear) and is homogeneous in
the third dimension.
O It periodic in the x y-plane and not in
the z-direction as for the 1d lattice.
9/15/2017SHAREEF 15

16. Three Dimensional PBGC
O A three-dimensional photonic crystal was
created using layer-by-layer periodic
structure method.
O The orientations of the axes are rotated by
90o between adjacent layers.
9/15/2017SHAREEF 16

17. Applications
O Suppression of spontaneous emission
9/15/2017SHAREEF 17

18. Applications(contd.)
O Low-threshold lasers, single-mode
LEDs, mirrors, optical filters
O Lasers and optical devices - improved
performance in efficiency and
reduction of background noise
O Fast electronics – inter chip
communication
O Medical and biological application
e.g., microwave resonance therapy (40-
80 GHz), imaging
9/15/2017SHAREEF 18

19. In fiber optic communication
9/15/2017SHAREEF 19

20. Conclusion
O Photonic crystals are going to be the
future semiconductors
O It has many applications irrespective of
fields
9/15/2017SHAREEF 20

21. 9/15/2017SHAREEF 21