Ideen Taeb Jon Mah

 Combination of photonics and microelectronics  Advantages: Capacity to generate, transport and manipulate data at very high rate  Photonics/Optoelectronics refer to coexistence of electron and photons in the same system  First transmission trunk using glass fibers in 1983  Photon law is tripling the bandwidth every year.

 Compared to copper wire, optical fibers cost less, weigh less, have less attenuation and dispersion and provide more bandwith.  Highly used in electronic systems

 Growing every year, 30% growth every year since 1992  Combined market for optoelectronic components and final end-products currently stands at $30 billion

 Electron vs. Photon ◦ Mass ◦ Charge ◦ Spin ◦ Pauli Exclusion Principle ◦ Velocity

 LED- Advantage of ease of use, 160 degrees circular cone light emission, but low in power  LD- Advantage of high power around 30 mW, but emission in elliptical cone rather than circular.  VCSEL- Have both high power as wells as emission into circular cone, furthermore they can be produced in uniform arrays on wafers

 Forward biased junction  Current flows from n side to the p side  Band Gap or Energy Gap (EG): Difference of energy between the conduction band and valance band  Wavelength of emitted light depends on EG  Most widely used material for visible spectrum: GaAs, GaP, and GaAsP

 Forward biased p-n junctions where emmited photons are confined in an optical cavity  Two types ◦ Edge Emitting: Wide, astigmatic emission ◦ Surface Emitting: Narrower Beam Emission

 Different from LDs and LEDs, light emission occurs in a direction perpendicular to the active region  Have a potential to be operated at orders of Gb/s speed

 P-i-n Photodiodes ◦ A p-n junction with a sandwiched intrinsic layer ◦ Operated in the reverse-biased mode ◦ Response times are in order of 10 ps.

 MSM Detectors ◦ Consists of two interdigitated electrodes which form back to back schottky diodes. ◦ Very fast, can be switched completely on or off with an applied bias ◦ Response time in in order of 1ps

 Free-Space Channels ◦ High-speed communication (>1Gbs) ◦ Wide BW, elimination of impedance mismatch problem ◦ Potential for high density interconnects ◦ Decreased interconnection delays and so on  Disadvantages caused by: ◦ Potentially require a significant change in the way system architectures are designed ◦ Laser wavelength stabilities in the order of 1nm can be expected(Dispersion) ◦ Physical size of some proposed architectures are prohibiting ◦ Power inefficiencies can be limiting ◦ Dependent on weather

 Guided Wave Channels ◦ Can be classified according to the interconnection medium employed and the level of interconnection hierarchy they target

 Speed of propagation in a medium Photon Energy Frequency

 Speed of EM waves in a medium depends on interactions with Electric Field and Magnetic Field

 Critical Angle (Φ 1 ) occurs at Φ 2 =90˚ For angles larger than the critical angle, have total internal reflection (TIR) –Principle behind traditional waveguides different from photonic crystal waveguides –Phase changes with the angle

 n 1 > n 2, but just barely  Then NA is small

 Light of different frequencies propagate at different speeds through the medium ◦ Typical units of ps/nm-km  Due to both material (n = n(λ)) and waveguide effects (effective n 1, n 2 )  Birefringence caused by Polarization Effects (fiber cross section not perfectly circular).  Higher order effects (Kerr effect)

 Due to imperfections in fabrication as well as Rayleigh Scattering ◦ Scattering due to particles smaller than λ (why is the sky blue?) ◦ Units of dB/km ◦ For GeO2-doped single-mode silica fiber ~0.2dB/km at λ=1.55μm Also get attenuation due to bending

 Time-Division Multiplexing (TDM) ◦ E.g. Telephone lines  Frequency-Division Multiplexing ◦ E.g. FM radio

 Wavelength- Division Multiplexing ◦ Optical effect ◦ E.g. Prism  Superprisms made from Photonic Crystals (large dispersion in periodic media)

 Fused Silica (SiO 2 ) Fiber  Can be made extremely pure, then doped to attain desired n  Exhibits very low loss and dispersion at λ=1.55μm  Plastic Fiber  Lossy (~10 2 dB/km)  Flexible, inexpensive, lightweight  Other Glass Fiber  Chalcogenide, fluoroaluminate, etc. for longer wavelengths

 Major problems in coupling fiber 1.The fibers must be of compatible types  Dispersion effects, single mode/multi mode 2.The ends of the fiber must be brought together in close proximity  Matching of NA 3.The fibers must be accurately aligned with eachother

Bragg Gratings: constructive interference where d=distance between gratings

 Optoelectronics market is growing every year  Optoelectronics provide a high bandwidth for communications  Utilize TIR for light propagation in waveguides  Dispersion and attenuation are main drivers in optical fiber design  Interconnections and coupling require precise alignment of optical elements  A number of inter- and intra-chip connection schemes exist and are being explored