Introduction to Photonic Crystals

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Introduction to Photonic Crystals Their
Importance

• Priyanka Milinda Rupasinghe

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What is a photonic crystal?

• Photonic crystal is an artificial
  multidimensional periodic structure (regular
  arrays of materials with different refractive
  indices) with the period of the order of optical
  wavelength.
• The spatial periodic distance of the crystal is
  called the lattice constant a.

http//ab-initio.mit.edu/photons/tutorial/
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Schematics of photonic crystal slabs
Photonic crystals , K Inoue K. Ohtaka, (
Springer, NewYork,2003).
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Historical Background

• The most important discovery about photonic
  crystals is that one can control light freely by
  using 2D and 3D photonic crystals which was first
  illustrated theoretically by E Yablonovitch and
  S. John in 1987.

E. Yablonovitch, Physical Review Letters, vol.
58, pp. 2059, 1987
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Historical Background

• In 1991, Yablonovitch and his coworkers verified
  the existence for a 3-D sample fabricated with
  a in the micrometer region
• In late 1990s Inoue and coworkers were succeeded
  in fabrication of two dimensional photonic band
  structures with near infrared band gap
• In 1995, Cheng and coworkers made an attempt to
  develop a 3-D crystal with full band gap but
  their experimental work failed because the sample
  was not good enough to obtain the full band gap
• However in 1999, Noda and his coworkers succeeded
  in fabricating a 3-D sample with full band gap
  which was the main target at that time

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Why are Scientists and Engineers Interested in
Photonic Crystals?

• Existence of Photonic Band Gap
• The most important discovery of this type of
  photonic crystal structures is the existence of
  photonic band gap. This is a forbidden gap for
  photons. Light cannot enter this region as well
  as electrons can not emit photons. In other words
  photonic band gap is an insulator of light.

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• Photonic bands of 2-D and 3-D photonic crystals

Photonic crystals , K Inoue K. Ohtaka, (
Springer, NewYork,2003).
8

• Photonic band gaps of 2-D photonic crystals for
  TE and TM modes

http//ab-initio.mit.edu/photons/tutorial/L1-bloch
.pdf
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What is the importance ?

• Ability to obtain photonic crystals with ultra
  high refractive indices
• Ability to control spontaneous emission in
  photonic crystal
• Modify the state density and group velocity
• Locate light by structure defects (impurity)
• Because of photonic band gap and artificially
  introduced defects ( impurity), photonic crystals
  are having various scientific and engineering
  applications in modern technology.

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E.g. Light Localization
Localized modes at various defects in a 2D
photonic crystal ( Magnetic field profile)
Photonic crystals , K Inoue K. Ohtaka, (
Springer, NewYork,2003).
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Applications
Photonic crystals , K Inoue K. Ohtaka, (
Springer, NewYork,2003).
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Photonic Crystal Devices

• Light Emitters

• Ultra threshold micro laser which has a point
  defect active region.
• (b) High power distributed feed back (DFB) laser
• (c) High power and stable single mode vertical
  cavity surface emitting laser (VCSEL) with an
  air-hole array.
• (d) Light emitting diode (LED) with high
  efficiency.

Photonic crystals , K Inoue K. Ohtaka, (
Springer, NewYork,2003).
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Photonic Crystal Devices

• Optical Waveguides

• Photonic crystal slab type
• (b) Photonic crystal pillar type
• (c) 3D wood-pile type
• (d) Auto-cloning type

Photonic crystals , K Inoue K. Ohtaka, (
Springer, NewYork,2003).
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Photonic Crystal Devices

• Optical Fibers

• holey fiber
• photonic band-gap fiber
• Bragg fiber.

Photonic crystals , K Inoue K. Ohtaka, (
Springer, NewYork,2003).
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Photonic Crystal Devices

• Light Control Devices

Numerical demonstration of light deflection
(Super prism phenomenon in a 2D PC )

• normalized frequency of 0.55
• (b) normalized frequency of 0.61
• (c) normalized frequency of 0.70

Photonic crystals , K Inoue K. Ohtaka, (
Springer, NewYork,2003).
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Photonic Crystal Devices

• Wavelength Filters

• resonant filters with parallel waveguides
• resonant filters with series waveguides
• resonant filter coupled with free space
• directional coupler
• (e) diffraction filter based on super prism
  effect

Photonic crystals , K Inoue K. Ohtaka, (
Springer, NewYork,2003).
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Typical optical communication technology roadmap
condensed from the original version which was
established by Optoelectronic Industry and
Technology Development Organization (OITDA) in
1999.
Photonic crystals , K Inoue K. Ohtaka, (
Springer, NewYork,2003).
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Thank you