Photonic Integrated Circuits. Οπτικά Δίκτυα Επικοινωνιών - PDF

Photonic Integrated Circuits Οπτικά Δίκτυα Επικοινωνιών Photonic Integrated Circuits Planar lightwave circuits Integrated optoelectronic devices Wafer-scale technology on substrates (chips) Technology

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Photonic Integrated Circuits Οπτικά Δίκτυα Επικοινωνιών Photonic Integrated Circuits Planar lightwave circuits Integrated optoelectronic devices Wafer-scale technology on substrates (chips) Technology limitations Photonic Integrated Circuits - Technologies III-V Integration Platforms Silicon Photonics Silica-on-Silicon - Silica glass (fused Silica) Polymer Integration Platforms Lithium niobate (LiNbO 3 ) III-V Semiconductor Technology Ultra-wide spectral coverage III-V material system Milestones in III-V laser development Advantages Solutions for: Lasers Optical amplifiers Modulators Detectors Monolithic integration of passive/active components within fully functional chips Ultra-high speed EO characteristics High reliability Disadvantages Extensive integration approach due to CMOS incompatibility Increased propagation losses ( 0.5 db/cm) Limitations of mass production due to small wafers (InP) Low index contrast (Δn/n) III-V Semiconductor Technology III-V monolithic integration of complex devices for (1) (2) (3) (4) (5) (6) (7) (8) Telecom (1)-(3) Datacom (5),(7) Sensing (4),(6) Bio-Medical (8) Meint Smit et al, A Generic Foundry Model for InP-based Photonic ICs, presented at OFC, paper OM3E, March 4-8, 2012, Los-Angeles, CA, USA Hybrid integration on Si-based platforms ICT-RAMPLAS GaInNAs(Sb) SOAs flip-chip bonded on SOI ICT-GALACTICO ICT-BOOM GaAs -and InP-based hybrid integration on SOI platform: InP SOAs bonded on Si platform Silicon Photonics: Overview Ability to reuse the huge technology base and supply chain from electronics industry Future promise Photonic components (i.e modulators, detectors, sources) fully compatible with CMOS technology Photonic links may replace copper links for very short distances and co-exist with electronics in functional optoelectronic chips Silicon Photonics: Key characteristics Advantages Low cost Take advantage of CMOS platform High index contrast - strong light confinement - small footprint Transparent in um region Devices with sub-wavelength dimensions feasible Disadvantages Indirect bandgap material No or weak electro-optic effect Relatively lossy waveguides Lacks efficient light emission- no electrically pumped Si laser 8/12/2014 Οπτικά Δίκτυα Επικοινωνιών Coherent Optical Systems 7 Silicon Photonics: towards silicon laser Approach hybrid silicon photonic integrated circuit technology bonding of functional III-V active components onto silicon-oninsulator substrates InP VCSELs on SOI: ICT-MIRAGE bonding of III-V epitaxial layers wafer or die bonding of III-V films on Si and processing thereof microdisc laser: ICT-HELIOS hetero-epitaxial growth of III-V on Si selectively grow III-V crystals on Si substrate microdisc laser: UCSB selective growth of Germanium on Si growth of Ge layers on silicon oxide trenches Ge laser: MIT Glass: Overview Main technology implementations silica-on-silicon laser inscription on glass TriPlex How it works Waveguiding in glass (SiO2) Introduce dopants to create index difference (small to medium): similar material & dopants used in optical fibers SiO 2 surrounded and encapsulated by high index Si 3 N 4 cladding/box section Glass: Key characteristics Advantages Low propagation loss ( 0.01 db/cm) Low polarization dependence Broad wavelength coverage (vis. to IR) Low-loss coupling to single-mode fiber (less than 1 db typical, 0.15 db is feasible) Weak thermo-optic effect: low temperature dependence Reliable material, tolerance to environmental Disadvantages Large modal area and bending radius: low density integration Limited active functionalities available, most remain in the lab (e.g. amplification) Weak thermo-optic effect: not so efficient for λ-tuning functions Fabrication may involve more costlier processes than competitive technologies for passive component integration (e.g. polymers) 8/12/2014 Οπτικά Δίκτυα Επικοινωνιών Coherent Optical Systems 10 Glass: applications Passive components (commercial) WDM multiplexers FTTH splitters thermo-optic switches Hybrid integration of complex devices III-Vs LiNbO 3 polymers III-V integration on silica-on-silicon platform: ICT-APACHE Polymers: Overview Main material systems SU-8, PMMA, ZPU-12, etc Blending polymer solutions to achieve precise control of material optical properties Main types of polymer platforms Passive Electro-optic Active Polymers: Key characteristics Strengths Low propagation loss ( 0.5 db/cm) Low birefringence Precise and continuous engineering of material properties Unique properties (large TO, EO, non-linear) Good and easy ability to process Ease of hybrid integration via butt coupling Weaknesses Low index contrast, bulky device Not suitable for high temperature process Some materials raise reliability issues No full suite of active functionalities available out of the lab 8/12/2014 Οπτικά Δίκτυα Επικοινωνιών Coherent Optical Systems 13 Polymers: Applications Hybrid Optical/Electrical datacom PCBs Waveguide PCB integration Cards for optical backplane 40G and 100G communication applications High speed Mach-Zehnder modulators Variable optical attenuator arrays Disruptive Technologies Overview: Plasmonics How it works Surface plasmons: coherent electron oscillations at a metal dielectric interface Surface plasmon polaritons: plasmons excited by visible of infrared electromagnetic waves Potential applications Chip-scale communications: Interconnects Sensing: Biosensors, lab-on-a-chip Localized surface plasmon resonance: collective oscillation of electrons in nanometer-sized structures Disruptive Technologies Overview: Photonic Crystals How it works Photonic Crystals (PhC): material with periodic dielectric constant in some particular dimensions (1D, 2D, 3D) Principle of operation: if periodicity lattice is in the order of wavelength of light, it will reflect the light in the particular wavelength Create range of forbidden wavelengths, called photonic bandgap, that cannot propagate through the PhC medium Introduce defects in lattice to trap light and create a non-tir based waveguide Main technology implementations Waveguide Components Photonic Crystal Fibers Slow light Modulators Evanescent Fiber Coupling Disruptive Technologies Overview: Carbon-based materials How it works Graphene: 2-dimensional, crystalline allotrope of carbon / 1-atom thick layer of graphite Absence of bandgap absorbs light over wide spectral range (ultraviolet to terahertz) Material optical properties can be modified be externally tuning the bandgap of graphene layers and bi-layers Carbon nanotubes (CNT): Allotropes of carbon with cylindrical nanostructure based on honeycomb carbon lattice Depending on lattice orientation, CNT acts as metal or semiconductor Semiconductor CNTs are direct bandgap materials and can be used to generate and detect light Single- or multi-walled nanotube configurations are possible Silicon Photonics Photonic Integrated Circuits Example Silicon Photonics Wafer Fabrication Silicon Photonics: Design Crossection The transverse impression of the integration platform Depends on the integration technology Varies according to the process flow Can be directly imported in the crossection simulation tools (mode solvers) Silicon Photonics: Design Waveguide mode Electric field distribution in spatially inhomogenenous structures (waveguides) Self-consistent during propagation The shape of the complex amplitude profile in the transverse dimensions must remain exactly constant Effective index In homogeneous transparent media, the refractive index n can be used to quantify the increase in the wavenumber (phase change per unit length) caused by the medium The effective refractive index n eff has the analogous meaning for light propagation in a waveguide Depends not only on the wavelength but also (for multimode waveguides) on the mode in which the light propagates
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