Photonic Crystals

By Ravi Raj Singh

(Course Number 300352)

Dr. Dietmar Knipp

Overview:

• Introduction

• Physics of Photonic Crystals

• Fabrication

• Types of Photonic Crystals• Types of Photonic Crystals

• Tuning of Photonic Crystals

• Applications

• References

Introduction

• Definition :

Photonic Crystals are wavelength scale periodic, dielectric microstructures. Their periodic patterns create photonic band gaps periodic patterns create photonic band gaps which forbid the propagation of certain wavelengths of light through the structure.

They affect the motion of an electron in the same manner as that of a semi-conductor.

Physics of Photonic Crystals

• The formation of the photonic band gap is due to Bragg diffraction.

– Light Scattering from periodic planes constructively interfere to form a photonic band gapgap

– EM waves – constructive or destructive interference.

– This implies a range of frequency of light that cannot be transmitted

Physics of Photonic Crystals

Band Gap

Physics of Photonic Crystals

• Different dielectric mediums with no charge

and current

• Insertion of holes in crystal

• Described by Maxwell's Equations• Described by Maxwell's Equations

• The cavities and Dielectric regions can be

symmetric in 1,2 or 3 dimensions.

Fabrication

• Naturally Occurring in the form of Opal.

• The fabrication process

– As dimensions increase fabrication becomes more

difficult -> High Precision neededdifficult -> High Precision needed

• 2 D and 3 D crystals

– fiber techniques for communication fibers

– Use of photolithography and etching

– are also grown from colloidal crystals

Types of Photonic Crystals

Types of Photonic Crystals:

1-Dimensional

The structure has one-directional symmetry.

Examples of Operation:

Acceptance -No attenuationAcceptance -No attenuation

-time period coherent with dielectric spacing

Types of Photonic Crystals:

1-Dimensional

Blocking:

-High attenuation

-Dielectric spacing is incoherent with time period

Types of Photonic Crystals:

2-Dimensional

• Reflected waves cancel out incoming waves

• Same principle

• Drilling of holes• Drilling of holes

Types of Photonic Crystals:

3-Dimensional

• All 3 directions

• Tetrahedral structure - stable

• Example Yablonovite (FCC)• Example Yablonovite (FCC)

– Holes 35° apart

Tuning of Photonic Crystals

• Tuning can be done by insertion of exceptions

in the structure

– Dielectric Defects

– Air Defects– Air Defects

Applications

• 1-D crystals are prevalent in the form of thin

film optics->reflective coatings

• 2-D crystals

• Optical Fibers• Optical Fibers

• Integrated Circuits (thin films)

• Nanoscopic Lasers

• 3-D crystals

– photonic quasi-crystals

– Integrated circuits

Refrences

• “Photonic Crystals: Semiconductors of Light”,

E.Yablonovitch; Scientific American, 2001

• http://ab-initio.mit.edu/photons/

• http://www.st-andrews.ac.uk/~photocryst/• http://www.st-andrews.ac.uk/~photocryst/