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Photonic crystals

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.

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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 1
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. 2
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. 3
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 4
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. 5
CONT… • PCs also known as photonic band gap materials. • These materials have a band gap due to periodicity in the materials dielectric properties. 6
EXAMPLES • Example in nature which reflect electromagnetic radiation as propagation through them is prohibited. 7
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
CONT… • v “magical oven mitts” for holding and controlling light cavities waveguides with photonic band gaps: “optical insulators”
10 CONT… ANALOGY WITH SEMICONDUCTORS • Semiconductors : potential periodicity • Photonic crystals : dielectric periodicity 1D
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. 11
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 12
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. 13
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. 14
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. 15
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. 16
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. 17
END Thanks All of You ANY QUESTION! 20