Photonic crystals are periodic optical nanostructures that affect the propagation of light. They contain regions of high and low dielectric constants arranged in a repeating pattern, allowing certain wavelengths of light to pass through while others are forbidden from propagating, known as a photonic band gap. Photonic crystals have applications in lasers, optical fibers, biosensing and more. They can be fabricated through methods like layer deposition, photolithography or drilling holes to achieve one, two or three-dimensional periodicity.

1. PHOTONIC CRYSTALS
Presented By
Mr. Sohail Farman 17170810-007
Mr. Muhammad Ali 17170810-004
Ms. Rafeha Farooq 17170810-062
M.SC Physics
University of Gujrat
Gujrat. Pakistan
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2. HISTORY
• Photonic crystals have been studied in one form or another
since 1887, but no one used the term photonic crystal until
over 100 years later after Eli Yablonovitch and Sajeev John
published two milestone papers on photonic crystals in
1987.
• The early history is well documented in the form of a story
when it was identified as one of the landmark developments
in physics by the American Physical Society.
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3. CONT…
• Before 1987, one-dimensional photonic crystals in the form of
periodic multi-layer dielectric stacks (such as the Bragg mirror) were
studied extensively.
• Lord Rayleigh started their study in 1887, by showing that such
systems have a one-dimensional photonic band-gap, a spectral range
of large reflectivity, known as a stop-band.
• Today, such structures are used in a diverse range of applications—
from reflective coatings to enhancing LED efficiency to highly
reflective mirrors in certain laser cavities.
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4. INTRODUCTION OF PHOTONIC
CRYSTALS
• A crystal is a homogeneous solid formed by repeating, Three
dimensional pattern of atoms, ions, or molecules.
• Fixed distance between parts
• Photonics from photon, the smallest unit of light
• Photonics is the generation, process and manipulation of photon
to achieve a certain function.
• Crystals with periodic dielectric structure having band gap that
forbids propagation of certain frequency range of light are
photonic crystals
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5. CONT…
• Photonic crystals contain regularly repeating regions of high and
low dielectric constant.
• Photons (behaving as waves) either propagate through this
structure or not, depending on their wavelength.
• Wavelengths that propagate are called modes, and groups of
allowed modes form bands.
• Disallowed bands of wavelengths are called photonic band gaps.
• Photonic bandgap is the region in which only specific
wavelength are transmitted and all other are reflected back.
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6. CONT…
• PCs also known as photonic band gap materials.
• These materials have a band gap due to periodicity in the materials
dielectric properties.
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7. EXAMPLES
• Example in nature which reflect electromagnetic radiation as
propagation through them is prohibited.
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8. PRINCIPLE
• Regularly repeating regions of high and low dielectric
constant varies refractive index that controls the photons
movement through the crystal depending upon their
wavelength.
• Periodic arrangement of ions on a lattice gives rise to energy
band structure in semiconductors which control motion of
charge carriers through crystal.
Similarly, in photonic crystals, the periodic arrangement
of refractive index variation controls how photons are
able to move through crystal. 9

9. CONT…
• v
“magical oven mitts” for
holding and controlling light
cavities waveguides
with photonic band gaps: “optical insulators”

10. 10
CONT…
ANALOGY WITH SEMICONDUCTORS
• Semiconductors : potential periodicity
• Photonic crystals : dielectric periodicity
1D

11. FABRICATION
Photonic crystal can be fabricated for One, Two or Three dimensions
• 1-D Photonic Crystals.
Photonic crystals can be made of layers deposited together
• 2-D Photonic Crystals
These can be made by photolithography or by drilling holes in a suitable substrate
• 3-D Photonic Crystals
Drilling the material at different angle. Also by stacking multiple 2-D layer on top of
each other.
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12. FABRICATION CHALLENGES
• Making of the crystals with such precision that least of
the scattering losses occur that may effect the properties
of the crystal.
• To set a design of crystal that fulfill the all requirements
that needed and which gives major product acceptable
widely
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13. WORKING
• Photonic crystals are nanoscale structures. Depending on the frequency
of their dielectric constants either allow or block individual
wavelengths of light.
• Each wavelength of light has a unique physical size, which is what
causes them to appear as different colors.
• In order for a wavelength to be allowed through a photonic crystal’s
structure, it must be compatible with the crystal’s dielectric fields.
• Wavelengths that can pass through these structures are called modes
and groups of modes are called bands.
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14. CONT…
• Wavelengths that cannot pass through these structures are known as
photonic band gaps. While wavelengths produce pure colors in
photonic crystals, they tend to blend together at the photonic band
gaps.
• This causes extreme colors to appear on the photonic crystal’s
surface, thereby producing strange optical phenomena
• The band gap in photonic crystals present the forbidden energy range
where wave behaving photons cannot be transmitted through the
material.
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15. APPLICATIONS
• Photonic Crystals are used for controlling and manipulating
the light flow through the materials by controlling the flow
of photons.
• Use of photonic crystals in drugs and medicine delivery as
lowering the side effects and the high accuracy with multi-
load of dosage.
• photonic crystals use as biosensors, safe and well approach
to target. Conversion of specific targeted place into
informative electromagnetic signals.
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16. CONT…
• 1-D in coating the lenses or color changing paint, 2-D in new class of
optical fiber as traditional differences in refractive indices verses
structural properties to have much control over light
• Lasers and optical devices - improved performance in efficiency and
different approaches over laser light modification such as to make fractals
and beam shape
• Fast electronics – inter chip communication. Applications of this work are
in telecommunications, e.g. for devices that manage high-speed, high
volume data (e.g. internet) traffic.
• Research thoughts, use of 3-D PCs as components in optical computers
would make them 10 times faster than ordinary electronic based
components computers.
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17. CONT…
• Perfect Mirror :There are materials that reflect the frequency range
of interest, with essentially no loss at all.
• Photonic transistor
A transistor is a switch that is turned on and off by signals from other
switches. They perform logic, store information and are the work
horses of digital computing. Photonic transistors use light to perform
the switching functions that are performed by electronic transistors in
conventional computers.
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18. END
Thanks All of You
ANY QUESTION!
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