nanophotonics in silicon-on-insulator Wim Bogaerts IMEC, 9 June 2006 Photonics Research Group http://photonics.intec.ugent.be “the art of playing with light in all its forms” nanophotonics in silicon-on-insulator Wim Bogaerts IMEC, 9 June 2006 “a trendy prefix indicating the need for nanometer-scale accuracy” “a wafer of silicon buttered with a slice of oxide (insulator) and a delicious layer of silicon” Photonics Research Group http://photonics.intec.ugent.be Photonics Research Group • research group of Ghent University • within Engineering Faculty • within Dept. of Information Technology (INTEC) • associated with IMEC • permanent staff: Roel Baets, Peter Bienstman, Geert Morthier, Dries Van Thourhout, Steven Verstuyft • 30-35 researchers (7 post-docs) • research domains: microphotonics and nanophotonics • http://photonics.intec.ugent.be © intec 2006 - Photonics Research Group - http://photonics.intec.ugent.be Silicon Photonics and UGent-IMEC UGent – INTEC: Photonics Research Group z 3 decades of photonics research z Cleanroom facilities for III-V processing z Photonics modelling z Characterisation z Associated Lab of IMEC 6 years of collaboration on Silicon Photonics IMEC: z Microelectronics Research z Advanced Silicon Processing z “Nanoelectronics” © intec 2006 - Photonics Research Group - http://photonics.intec.ugent.be Overview of this presentation Background on Photonics z What’s the use? z How does a waveguide work? z Photonic Crystals z SOI Nanophotonics UGent - UGent - IMEC achievements z What can we do now? z Some key results Worldwide State-of-the-art Conclusion © intec 2006 - Photonics Research Group - http://photonics.intec.ugent.be Overview of this presentation Background on Photonics z What’s the use? z How does a waveguide work? Whatz Photonic will Crystalswe use photonics for? z SOI Nanophotonics UGent - IMEC achievements Long-haulz What can we Telecom do now? and FTTH Datacomz Some key (chip, results board, metro) SensorsWorldwide & State-of-the-art spectroscopy Conclusion © intec 2006 - Photonics Research Group - http://photonics.intec.ugent.be Telecommunication transmitter receiver medium radio tower radio set radio waves over air TV set TV studio radio waves over coaxial cable © intec 2006 - Photonics Research Group - http://photonics.intec.ugent.be Telecommunication laser photodetector light packets over an optical fiber (= electromagnetic wave) radio tower radio set radio waves over air TV set TV studio radio waves over coaxial cable © intec 2006 - Photonics Research Group - http://photonics.intec.ugent.be Frequency Division Multiplexing radio tower radio set radio waves over air Transmission of signal on carrier wave z Carrier wave has a frequency/wavelength z All carriers travel independent over medium z Receiver can tune in on one carrier © intec 2006 - Photonics Research Group - http://photonics.intec.ugent.be Wavelength Division Multiplexing laser light packets over an optical fiberphotodetector z Use light of different(= electromagnetic wavelengths wave) (‘colors’) z Modulate each carrie z combine/split carriers at r independently laser the end of fibers laser laser detector ISTANCE laser LONG D detector LARGE BANDWIDTH detector © intec 2006 - Photonics Research Group - http://photonics.intec.ugent.be detector Where to use optical fibres? WorldwideWorldwide telecomtelecom © intec 2006 - Photonics Research Group - http://photonics.intec.ugent.be Telecommunication networks Cabinet on the curbside submarine cable © intec 2006 - Photonics Research Group - http://photonics.intec.ugent.be Telecommunication networks © intec 2006 - Photonics Research Group - http://photonics.intec.ugent.be Telecommunication networks © intec 2006 - Photonics Research Group - http://photonics.intec.ugent.be Telecommunication networks Fiber to the curbside © intec 2006 - Photonics Research Group - http://photonics.intec.ugent.be Telecommunication networks Fibre to the home Required: z optical fibres z components in between the fibres z electro-optic conversion at end points LARGE QUANTITIES AND CHEAP © intec 2006 - Photonics Research Group - http://photonics.intec.ugent.be Telecommunication networks © intec 2006 - Photonics Research Group - http://photonics.intec.ugent.be Example: FTTH Triplexer 3 wavelength channels z digital downstream digital downstream z digital upstream (internet, VoIP, digital TV) z analog downstream (CATV) detector laser fiber triplexer: split/combine digital upstream 3 wavelength channels (internet, ...) signals on different detector carrier wavelengths analog downstream (analog TV channels) © intec 2006 - Photonics Research Group - http://photonics.intec.ugent.be Example: FTTH Triplexer digital downstream (internet, VoIP, digital TV) detector fiber digital upstream laser dichroic mirrors (internet, ...) detector analog downstream (analog TV channels) Align 6 optical elements!!! box = 20x10x10 mm © intec 2006 - Photonics Research Group - http://photonics.intec.ugent.be Integration of circuits lumped elements = bringing various transistor radio functions together 1954 on a ‘chip’ z Electronics: photonic IC transistors intel 4004 metal wires for 1971 electrical connections between components z Photonics: waveguides to transport light pentium 4 between components 2002 wavelength filters sources and detectors nanophotonic IC © intec 2006 - Photonics Research Group - http://photonics.intec.ugent.be Integrated Optical Sensors Strain sensor z measure reflection of fiber grating z requires “long” fiber z complex mounting Ring resonator z resonance peak depends on circumference z peak shifts when strained © intec 2006 - Photonics Research Group - http://photonics.intec.ugent.be Integrated Biosensors Today’s Commercial biosensors: Integrated photonic biosensor: Elisa test for protein binding 3µm 75 µm DNA microarray Æ Complex and slow label-processes Æ No labeling Æ Complex interpretation of results Æ Quantitative and fast results Æ Big amounts of analyte Æ Very small amounts of analyte © intec 2006 - Photonics Research Group - http://photonics.intec.ugent.be On-chip interconnects Replace long-range metallic interconnects z large bandwidth z no ohmic losses and heating in waveguide III-V material microlaser SOI waveguide microdetector Optical Interconnect layer Electrical Interconnect layer Silicon transistor layer © intec 2006 - Photonics Research Group - http://photonics.intec.ugent.be I make a photonic IC, and I need... a photonic chip sources modulators optical I/O functional elements waveguides electrical I/O detectors © intec 2006 - Photonics Research Group - http://photonics.intec.ugent.be Overview of this presentation Background on Photonics z What’s the use? z How does a waveguide work? z Photonic Crystals z SOI Nanophotonics WhatUGent is - I MEClight? achievements Howz What can can we we do guide now? light? Whatz Some is keya goodresults waveguide? Worldwide State-of-the-art Conclusion © intec 2006 - Photonics Research Group - http://photonics.intec.ugent.be Light = Electromagnetic Wave Ray of light ≈ Electromagnetic wave z Propagates at speed of light c z Electrical oscillation E z Magnetic oscillation H z Oscillation frequency f f ×λ= c z with a wavelength λ E H c wavelength λ © intec 2006 - Photonics Research Group - http://photonics.intec.ugent.be Electromagnetic Radiation wavelength frequency (meter) (Hertz) -12 10 cosmic radiation 1020 Visible light: wavelength γ -radiation 380 - 760 nm (nm) -10 röntgen 10 18 (X-rays) 10 violet 400 λ -8 blue 10 ultraviolet 1016 green 500 -6 yellow 10 1014 orange 600 infrared -4 red 10 1012 700 -2 10 Radar 1010 1300 1 TV - radio 108 1550 Light for optical fibre communication © intec 2006 - Photonics Research Group - http://photonics.intec.ugent.be Propagation of light In vacuum: light propagates at the speed of light c wavelength In material: light propagates low refractive index n times slower n = refractive index wavelength wavelength becomes n high refractive index times shorter for the same frequency © intec 2006 - Photonics Research Group - http://photonics.intec.ugent.be Light at an interface Change in refractive index n low refractive index z Light rays change direction z Light is partially reflected Effect is more pronounced with a stronger contrast in refractive index high refractive index © intec 2006 - Photonics Research Group - http://photonics.intec.ugent.be Total internal reflection ‘inside to outside’: low refractive index Very oblique rays are totally reflected = Total internal reflection The critical angle with the surface is larger for a stronger contrast in refractive index (less oblique rays are also reflected) high refractive index © intec 2006 - Photonics Research Group - http://photonics.intec.ugent.be Layered (Slab) Waveguide ‘Sandwich’ of material with a high refractive index between material with a low refractive index Light is guided by total internal reflection in a core of high low refractive index refractive index surrounded by a CLADDING cladding of low refractive index CORE high refractive index CLADDING low refractive index © intec 2006 - Photonics Research Group - http://photonics.intec.ugent.be Bends in waveguides Some rays can escape from the waveguide z Better confinement if the contrast in refractive index is adequately large z Less loss if the bends are made sufficiently wide Sharp bends possible with large refractive index contrast © intec 2006 - Photonics Research Group - http://photonics.intec.ugent.be Mode of a waveguide Thin core: Rays are an inaccurate model Light is located in a smeared-out ‘blob’ in and