SILICON PHOTONICS

SILICON PHOTONICS ARAVIND SURESH(Roll no:09)

S7A EC

OVERVIEW Introduction Optoelectronics at present WDM

AWG and WDM Siliconize photonic

Stimulated Raman Amplification The Raman effect Laser Silicon laser Modulator Coding of optical data Photodetector Interface

The silicon challenges Applications Futurescope & Conclusion Reference

COLLEGE OF ENGINEERING CHENGANNUR

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INTRODUCTION• Moore’s Law(1962)• Presently 1.7billion transistors• More transistors more information can process• Copper wires are used to communicate between peripheral

devices • Wires close to each other can induce currents in one

another• Increased resistance=increased heat =decay of data• Microscopic imperfection, Skin effect, Proxmity effect• Data speed > 10Gbps not achieved • Replace copper with optical fiber and electron with photon


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OPTOELECTRONICS AT PRESENT

• A single fiber strand can now carry up to 14Tbps • Send pulses of light instead of pulses of electron current in guided

medium

• Fibre Optics immune to attenuation- repeaters at over 100 Kms

• Pack dozens of channels by separating channel by wave length-WDM “Wave length division multiplexing”• Use lasers to shoot light pulses through glass fibers• Need of coherent light


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WDMThe wavelength division multiplexing

• Multiplexing upto 160 channels• Bandwidth in the range : 1260-1675 nm• Single Mode Fibre core diameter only- 9 micrometer• Channel separation as low as 0.8 nm • Most commonly used is: C-band transmission window : 1530-1565 nm • Uses AWG (de)multiplexer

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AWG and WDM


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• Array of waveguides with constant length increment• Diffraction and Interference play the role• Advantages-low loss,low cost,ease of network

upgrading• Precision Temperature control: +/-2 Degree C

SILICONIZE PHOTONICS• Means all components are integrated on the silicon chip• To siliconize photonic –• A integrated light source• Device that split, route and direct light on silicon chip• Modulator to encode data into optical signal• Photo detector to convert the optical signal back to

electrical bits• Low cost high volume assembly methods• Supporting electronic for intelligence and photonic

control


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MILESTONES

• All-Silicon Laser-• Silicon is an indirect bandgap material• Need an external source for initial light• Problem of misalignment of external laser• Raman effect 10,000 times stronger in silicon.• STIMULATED RAMAN SCATTERING (SRS) AMPLIFICATION• Intel disclosed development of first continuous wave all-silicon

laser(2005)

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To be continued…


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SRS Stimulated Raman Scattering

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• Pump Laser-500 mW,980nm• Weak Data beam-1550nm(C-band)• Data beam energy passed to molecular vibration• Pump photon absorption• High energy photon emission and wavelength shift• Scattering reduced in C-band• Advantage

The Raman effect LASER


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Silicon laser

• Need wave guide for light beam

• Two photons absorption

• Silicon to absorb pump beam’s photon and release free electrons

• Electron cloud reduce amplification

• P-I-N diode in silicon laser

• Dielectric mirrors in silicon laser


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Silicon laser

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Modulator Modulation –switching one state to another state(on and off) Two types of modulation Direct modulation

-direct switching of source(on-off)-limit 10Gbps~12kmExternal modulation

-used for 10Gbps~100km+ Each time laser turn on it ’chirps’-un desired shift in

wavelength-data distortion Use external modulator chirp free -use lithium nobate-strong electro optic effect External Phase modulation of light without disturbing source


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Modulation


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Encoding optical data(ASK-digital modulation)

• Split the laser into two• Apply electric field to one beam• Speed changes and out of phase• When recombine- result cancel out• No electric field apply -No speed variation and

same phase• When recombine beam encoded with 1’s and 0’s


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The Mach–Zehnder interferometer


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COLLEGE OF ENGINEERING CHENGANNUR 17

MILESTONEScontinued…

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• Silicon Modulator in GHz range

• Early injection current modulator- diode switching

• Free carrier plasma dispertion effect.

• Difficulty to extract carriers out of the path..

• 20MHz limit for silicon modulator-a limit for silicon photonics

• Intel demonstrated the first GHz silicon modulator(2005)

• Speed upto 10 Gbps demonstrated with transistor like device to inject as well as pull

out carriers

• Speed upto 18Gbps demonstrated with optical ring modulator

• Disclosed the development of 40Gbps silicon modulator


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Photo detector/Demodulation

• Collect the photons and convert into electrical signal• Semiconductor diode detectors-the frontrunners -The PIN diode detector -The Avalanche Photodiode detector• InGaAs-least bandgap• Avalanche detectors with built in amplification due to intense

electric field• Noise, dark current and photocurrent fluctuations• Response time-0.5ns typical

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Demodulation & Detection19


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INTERFACE SILICON PHOTONICS

• The construct-Silicon on insulator

• Connecting an optic fibre

• Silicon chip-optic fibre interconnection

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SILICON CHALLENGES

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Kerr Nonlinearity effect Refractive index varies proportional to square of electric field

intensity

Four wave mixing Three waves scatter at a point to produce fourth wavelength


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APPLICATIONS

• Integrating into a Tera-scale system

• Shrinking electronic/medical equipments

• 3D ICs


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An artistic view

FUTURESCOPE & CONCLUSION

• Intel moving on steps towards 50Gbps optical link

• Optical Revolution in:- ELECTRONICS AND COMMUNICATION ENGINEEERING


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REFERENCES www.ieeexplore.ieee.org- Lipson, M.;

Optical Fiber communication/National Fiber Optic Engineers Conference, 2008.;Publication Year: 2008 , Page(s): 1 - 3

techresearch.intel.com domino.research.ibm.com en.wikipedia.org Ebook on Silicon Photonics – Mario Paniccia (Intel Director, Photonics Lab) Fibre Optic Communication – Harold Kolimbiris,Scenior


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This Seminar Ends hereThank You All

SILICON PHOTONICS

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SILICON PHOTONICS

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