Advances in Photonics for Information and Communication

64 Pages·0.241 MB·English

by  Pira International Ltd

Advances in Photonics for Information
and Communication
Published by
Pira International Ltd
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UK
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ISBN 1 85802 552 4
© Copyright
Pira International Ltd 2007
Head of publications and events
Philip Swinden
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Publisher
Rav Lally
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Head of editorial
Adam Page
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Global editor
Nick Waite
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Head of US publishing
Charles E. Spear, Jr.
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Claire Jones
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Typeset in the UK by
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Contents
List of tables v Applications 12
List of figures vi Fibre Bragg gratings 12
Executive summary vii Functionality 12
1 Types 13
Holey fibres 13
Properties 13
Features 13
Introduction 1 Types 14
Objective 1 Applications 14
Scope 1 Infrared emitters 14
Definitions 1 Properties 14
2
Waveguides 14
Optical waveguides 15
Tunable solid-state lasers 17
Types 17
Photonic materials and devices 5 Quantum cascade lasers 17
III–V semiconductors 5 Advantages 18
Properties 5 Disadvantages 18
Technical trends 5 Applications 18
II–VI semiconductors 6 Microstructured optical fibres 18
Properties 6 Technical trends 19
Technical trends 6 Properties 19
Rare earth elements 6 Applications 19
Properties 6 3
Technical trends 7
Photonic crystals 7
Properties 7
Technical trends 7 Photonics manufacturing 21
Applications 8 Plasma processing 21
Silicon-on-insulator 8 Reactive ion etching 21
Thick and thin 8 PECVD 21
Fabrication 8 Photolithography 21
Technical trends 9 Trends in lithography 22
Polymers 9 EB lithography 22
Properties 9 Microdrilling 22
Technical trends 9 Percussion laser drilling 22
Quantum dots 10 Trepanning laser drilling 23
Properties 10 Laser cutting 23
Fabrication 10 Polishing 23
Applications 11 In situ process monitoring 24
SiGe heterostructures 11 Laser deposition 24
Technical trends 12 LAMBD 25
Features 12 LCVD 26
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Advances in Photonics for Information and Communication
Contents
4 Market forecast 34
Blue lasers 34
Multimedia services 34
5
Photonics in information and
communication 27
CCD sensors 27
Materials 27 Future outlook and trends
Parameters 27 in photonics 37
Types 27 Outlook for higher bandwidth 37
Applications 27 Outlook for optical switches 37
Next-generation CCDs 27 Outlook for WDM 37
Fibre-optic communications 28 DWDM 38
ATM 28 CWDM 38
Ethernet 29 Trends in photonic crystals 39
FDDI 29 Trends in quantum dots 39
SONET 30 Trends in QC lasers 40
Optical LANs 30 Trends in semiconductors 40
10Gb ethernet 30 Trends in metamaterials 40
Multimode fibre 32 6
Metropolitan area networks 32
Materials and devices 32
Protocols 32
Optical switching 33 Leading photonics suppliers and
MEMS 33 users 41
Thermo-optical switches 34 Suppliers 41
Hybrid switches 34 Users 49
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List of tables
2.1 Fibre Bragg gratings 13 2.2 Tunable solid-state lasers 17
Page v © Copyright Pira International Ltd 2007
List of figures
2.1 Photonic crystal fibre 16 5.1 Wavelength division multiplexing 38
2.2 Quantum cascade laser 18
3.1 L aser-assisted molecular beam
deposition 25
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Executive summary
Information and communications technology encompasses an impressive range of subjects
and an extraordinary range of applications. Photonics has revolutionised communication
and the information processing industry. It includes optical communications, e.g. fibre
optics, lasers and infrared links, optical imaging, e.g. charge-coupled devices (CCDs),
optical data storage and optical computing and lasers.
Photonics for The growth and development in information and communication systems for a faster
information and and more efficient means of collecting and transferring information has led to the use
communication of photonic technologies to meet the demands of modern high-speed communications.
Photonics, an integral aspect of information technology, covers the whole of optics and
electronics, and presents technology and infrastructure for the global internet and mobile
communications. The objective is high bandwidth over long distances with minimal losses,
and fibre optics is the most promising way to achieve this. A fibre-optic system is similar
to the copper wire system that fibre optics is replacing. It is usually composed of a bundle
of glass or plastic threads that sends information as modulated light. Technologies such
as wavelength division multiplexing (WDM) and optical time division multiplexing (OTDM)
further enhance a fibre’s bandwidth.
Lasers are often used for information storage. A laser is used to record high-density
information ranging from megabytes to gigabytes in CDs and DVDs. Fibre-optic systems
use light-emitting diodes (LEDs) as light sources. LEDs are semiconductors that convert
electrical current into light. They are small, reliable and last a long time. To transmit
information, the light emitted from lasers and LEDs has to be modulated using optical
modulators that vary the amplitude of the incoming signal. They can be used in
computers to encode a high-quality data signal onto an optical beam, by turning the
beam on and off to produce 1s and 0s.
There has been a tremendous increase in the capability and quantity of photonic
components. There is a trend towards smaller gadgets. This sudden revolution has been
made possible by new photonic materials that will be used in future applications such
as colossal data storage and high-rate data transfer. The new generation of III–V and
II–VI semiconductors can be operated over a broad wavelength spectrum. Organic
semiconductors, mostly consisting of carbon, hydrogen and oxygen, have contributed to
huge strides in photonic components. Organic materials such as polymers are used to
produce organic LEDs (OLEDs). Quantum dot LEDs can also be used in high-capacity data
storage and optical memories.
Fibre optics and large-area substrates are helping to realise broadband networks
where there is high-bandwidth interconnection of many different components. Silicon
photonics and other communications advances will drive future networks, servers and
computers. By integrating photonics with silicon, different types of devices can be
fabricated on a single chip, reducing the cost and increasing the number of applications.
The key challenges include manufacturing, assembly and material properties.
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Advances in Photonics for Information and Communication
Executive summary
Photonic materials Photonic materials are III–V, II–VI and rare earth semiconductor compounds, photonic
and devices crystals, silicon oxynitride, silicon-on-insulator, polymers, quantum dots and wells, and
silicon germanium (SiGe) heterostructures.
III–V and II–VI III–V and II–VI semiconductors are made by combining elements from groups III and V
semiconductors of the periodic table and groups II and VI of the periodic table. These materials have
excellent light emission and absorption properties (optoelectronic properties) as well
as high carrier mobility properties. Advances in crystal growth technology for III–V
heterostructures have led to the fabrication of lattice-mismatched structures of gallium
arsenide and indium phosphide. This enables the photonic devices and materials to be
integrated for improved functionality. New techniques such as hydride vapour phase
epitaxy (HVPE) are being developed to grow III–V structures on silicon. This makes it
possible to integrate these structures with the silicon-based waveguide. II–VI compounds
are grown by various techniques such as vapour phase epitaxy, chemical vapour
deposition (CVD) and metallorganic vapour phase epitaxy (MOVPE). II–VI materials
are increasingly being used to make nanocrystals as they have strong magneto-optical
properties.
Rare earth elements Rare earth elements are the 15 elements between lanthanum and hafnium in the periodic
table. They are crucial in many technological applications. All have similar chemical
properties and they emit light in an extremely narrow band. Rare earth doped fibres
have gained popularity due to their advantages such as short device length, high power
compatibility and low non-linearity. These fibres are double-cladding fibres typically
inserted in a cavity and optical pumps to provide energy.
Photonic crystals Photonic crystals are dielectric structures that are periodic in nature. Also known as
metallodielectric nanostructures, they are designed to obstruct the propagation of
electromagnetic waves. Optical micro- and nanocavities can be created by designing
defects such as dislocations and holes into photonic crystals.
Silicon-on-insulator Silicon-on-insulator (SOI) is a semiconductor manufacturing technology in which thin
films of single-crystalline silicon are grown over an electrically insulating substrate. SOI
improves electrical performance by reducing parasitic capacitance, especially in high-
speed and very dense circuits.
Quantum dots A quantum dot is a semiconductor nanostructure that confines the motion of conduction
band electrons and excitons in all three spatial directions. The electrons and excitons are
confined by an electrostatic field created at an interface between different semiconductor
materials. An exciton is a bound electron–hole pair.
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Advances in Photonics for Information and Communication
Executive summary
SiGe heterostructures Silicon germanium (SiGe) now has a small but significant percentage of manufactured
semiconductor devices, and its share is predicted to rise substantially when SiGe begins
to be used in CMOS technology to increase performance. The photonic devices comprise
fibre Bragg gratings, holey fibres, infrared emitters, waveguides, tunable solid-state lasers,
quantum cascade lasers and microstructured optical fibres.
Fibre Bragg gratings A fibre Bragg grating is a periodic or constant perturbation of the effective refractive
and 2D structures index in the core of an optical fibre.
Holey fibres Holey fibres have a solid core and light is guided by a modified form of total internal
reflection as air holes in the cladding lower the effective refractive index of the cladding
relative to that of the solid core. In a photonic band gap fibre, the cladding air holes are
arranged in a perfectly periodic fashion. For certain geometries the cladding can form
a two-dimensional photonic crystal with band gaps at well-defined optical frequencies.
Wavelengths within the band gap cannot propagate in the cladding and are confined to
the core. Moreover, the core can have a lower refractive index than the cladding; it can
even be air.
Infrared emitters Different types of infrared emitters are used for different applications. Information and
communications applications commonly use infrared LEDs. Infrared communication is
useful for indoor use in areas of high population density. It does not penetrate walls, so
it does not interfere with other devices in adjoining rooms. Infrared is the most common
method for remote control.
Waveguides A waveguide is a medium that guides and confines waves such as light and sound.
The waveguides used in photonics are optical waveguides (communication) and planar
waveguides (integrated photonics).
Tunable solid-state Solid-state lasers are lasers whose lasing material is distributed in solid media or material
lasers such as a solid rod or a slab of crystalline insulator. Some examples are Ti:sapphire, Cr:
alexandrite lasers and Cr:LiSAF.
Quantum cascade Quantum cascade lasers are a new generation of miniature lasers covering the whole
lasers mid-infrared spectral region. They are based on inter-subband transitions of electrons
inside a quantum well structure. These quantum wells are generally layers of gallium and
aluminium compounds in which the optical transitions occur between electronic subbands
created by quantum confinement in thin alternating layers of semiconductor materials.
Microstructured Optical fibres are glass or plastic fibres that have the ability to guide light along their axis.
optical fibres The fibre cable consists of three layers: core, cladding and jacket. Microstructured optical
fibres (MOFs) contain air holes that run along their length and alter the waveguiding
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Advances in Photonics for Information and Communication
Executive summary
properties. They are also known as index-guiding holey fibres (HFs) or photonic band gap
fibres (PBGFs). MOFs offer immense flexibility in fibre design, and the large refractive
index contrast between glass and air makes it possible to produce wavelength-scale
features that offer a range of interesting properties.
Photonics Photonic materials and devices are manufactured by laser-based diffusion, microdrilling
manufacturing and microcutting, plasma and electron beam (EB) processes, and reactive ion etching.
Other important processes are polishing, patterning and lithography. Polishing smoothes
and shines the substrate. Most polishing is done chemically. Chemimechanical polishing
(CMP) is widely used in the fabrication of ICs and semiconductor materials. It uses a
slurry of colloidal silica (SiO ) suspended in potassium hydroxide (KOH) or some other
2
solution. Lithography is printing or creating patterns on a substrate; it is the main method
of making microchips, where it is known as photolithography or optical lithography. A
pattern is transferred from a photomask or reticle to the substrate surface.
In situ process monitoring is a way to monitor and control semiconductor fabrication
techniques, such as chemical vapour deposition (CVD). There is a need to monitor the
chemical kinetics of the fabrication processes. For example, there is a need to measure
the concentrations and physical distributions of the chemical species in a CVD chamber,
especially at the interface between the wafer and the vapour. New process monitoring
used in filter fabrication will drive up yields and cut costs considerably. Optical monitoring
gives higher yields of thin films.
Laser chemical vapour deposition (LCVD) uses a laser to heat selected areas of a
substrate for fine control of CVD. Laser-assisted molecular beam deposition (LAMBD)
uses a high-power laser beam to evaporate a target inside an ultrahigh vacuum (UHV)
chamber; the target atoms or molecules are then deposited on a substrate. Microdrilling
removes materials to create through holes. Lasers are commonly used for microdrilling
photonic materials. Focusing beams or mirrors can be used to create the desired hole
shape. Two types of drilling are used: percussion drilling and trepanning. Lasers are
commonly used for microcutting photonic materials, usually a high-power pulsed laser
such as a carbon dioxide (CO ) laser, water-guided laser or high-power fibre laser.
2
Plasma etching and plasma deposition are the most widely used processes in
semiconductor fabrication. Plasma etching shoots a high-speed stream of plasma at
the metal. Plasma-enhanced CVD (PECVD) is commonly used in microfabrication to
deposit layers of insulating materials and amorphous silicon. It is used in very large scale
integration (VLSI) and to make thin film transistors (TFTs). Reactive ion etching (RIE) uses
plasma to etch material deposited on wafers. Deep RIE (DRIE) is a highly anisotropic
process used to fabricate microelectromechanical systems (MEMS) plus 2D and 3D
photonic crystals. Electron beams are generated in a high-vacuum environment from an
electron gun. The photonics industry uses electron beams for lithography, drilling and
cutting. EB lithography is used for pattern transfer.
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