The design and manufacture of components and systems underpin the European and indeed worldwide photonics industry. Optical materials and photonic components serve as the basis for systems building at different levels of complexity. In most cases, they perform a key function and dictate the performance of these systems. New products and processes will generate economic activity for the European photonics industry into the 21^st century. However, progress will rely on Europe's ability to develop new and better materials, components and systems. To achieve success, photonic components and systems must: •be reliable and inexpensive •be generic and adaptable •offer superior functionality •be innovative and protected by Intellectual Property •be aligned to market opportunities The challenge in the short-, medium-, and long-term is to put a coordinating framework in place which will make the European activity in this technology area competitive as compared to those in the US and Asia. In the short term the aim should be to facilitate the vibrant and profitable European photonics industry to further develop its ability to commercialize advances in photonic related technologies. In the medium and longer terms the objective must be to place renewed emphasis on materials research and the design and manufacturing of key components and systems to form the critical link between science endeavour and commercial success. All these general issues are highly relevant for the component intensive broadband communications industry. Also relevant for this development is the convergence of data and telecom, where the low cost of data com meets with the high reliability requirements of telecom. The text below is to a degree taken form the Strategic Research Agenda of the Technology Platform Photonics 21 [1], as this contains a concerted effort to iron out a strategy for EU in the area of photonics components and systems.

980 nm vertical-cavity surface-emitting laser based on sub-monolayer growth of quantum dots show at 25 and 85°C for 20 Gb/s without current adjustment clearly open eyes and error free operation with bit error rates better than 10^-12. For these multimode lasers the small signal modulation bandwidth decreases only from 15 GHz at 25°C to 13 GHz at 85°C. Single mode devices demonstrate at 20°C a small signal modulation bandwidth of 16.6 GHz with 0.8 mW optical output power and a record high modulation current efficiency factor of 19 GHz/mA^1/2.

Electroabsorption modulators (EAM) based on quantum-confined Stark effect (QCSE) in multiplequantum wells (MQW) have been demonstrated to provide high-speed, low drive voltage, and high extinction ratio. They are compact in size and can be monolithically integrated with continuous-wave (CW) lasers. In order to achieve both high speed and low drive-voltage operation, travelling-wave (TW) electrode structures can be used for EAMs. The inherently low impedance of high-speed EAMs may be transformed to values close to the standard 50Ohm impedance using periodic microwave structures with a combination of passive transmission lines with high characteristic impedance and active modulator sections with low impedance. Modulation bandwidths of 100GHz (-3dBe) have been accomplished with electrical reflections lower than -10dB in a 50Ohm system. Transmission at 80Gbit/s with non-return-to-zero (NRZ) code has been demonstrated for InP-based TWEAMs using electronic time-domain multiplexing (ETDM), indicating the possibility of reaching speeds of 100Gbit/s and beyond.

High concentration of optical power in a narrow exit angle is extremely important for numerous applications of laser diodes, for example, for low-cost fiber pumping and coupling, material processing, direct frequency conversion, etc. Lasers based on the longitudinal photonic band crystal (PBC) concept allow a robust and controllable extension of the fundamental mode over a thick multi-layer waveguide region to achieve a very large vertical optical mode spot size and, consequently, a very narrow vertical beam divergence. Many undesirable effects like beam filamentation, lateral multimode operation and catastrophic optical mirror damage (COMD) are strongly reduced. 650 nm GaInP/GaAlInP PBC lasers show narrow far field pattern (FWHM~7°) stable up to the highest output powers. Differential efficiency up to 85% is demonstrated. Total single mode output power as high as 150 mW is achieved in 4 μm-wide stripes in continuous wave operation, being limited by COMD due to not passivated facets. The lateral far field FWHM is 4 degrees. 840 nm GaAs/GaAlAs PBC lasers show a vertical beam divergence of 8° (FWHM) and a high differential efficiency up to 95% (L=500 μm). A total single mode CW power approaches 500 mW for 1 mm-long 4 μm-wide stripes devices at ~500 mA current, being COMD-limited. The lateral far field FWHM is 5 degrees. Another realization of a longitudinal PBC laser allows lasing in a single high-order vertical mode, a so-called tilted mode, which provides wavelength selectivity and substantially extends the possibility to control the thermal shift of the lasing wavelength. In a multilayer laser structure, where the refractive index of each layer increases upon temperature, it is possible to reach both a red shift of the lasing wavelength for some realizations of the structures, and a blue shift for some others. Most important, the absolute thermal stabilization of the lasing wavelength of a semiconductor laser can be realized.

Optical communication systems operating at 10Gbit/s require transceivers of low cost, size and power consumption, driving a "hot" source solution. This paper describes the current status of these "hot" devices for different applications. 10 Gb uncooled FP (Fabry Perot) to be used in conjunction with an EDC (Electronic Dispersion Compensation) receiver for LRM transceivers and 10 Gb 1300nm uncooled EML (Electro-absorption Modulator Laser) for LR transceivers are the devices chosen for LAN (Local Area Network) applications (link up to 10 km. These laser sources can be used for different transceiver form factors: XENPAK, X2 and XFP.

The multiplication of fibre optic networks during the years 1980 to 2000 has led to the development of specific packaging designs for laser modules, e.g. butterfly or TO-can coaxial packages. Since the beginning of years 2000, it has become necessary for packaging designers to deal with new requirements in term of module size, cost, thermal and electrical performances, particularly concerning the HF design. From these new requirements, new quasi-standards have appeared: TO-based TOSAs, XMD, and so on... However, these solutions are still based on traditional technologies : die soldering, 3D active alignment, Kovar packages, laser welding, single-chip devices, discrete micro-optics., unsuitable for mass production at very low cost. Today, the challenge for optoelectronic industry is thus to achieve a mutation of the packaging and assembly concepts, similar to the one the microlelectronic industry has done thirty years ago, by introducing advanced packaging technologies in order to address emerging markets and need, such as FTTx and Very Short Reach optical links, at the targeted costs. This will be also done by pushing ahead the integration of several optical function on the same chip or optical board. Some of these emerging technologies, such as optical MCM (Multi Chip Module), passive alignment, new materials for thermal management, flip-chip hybridisation, are key concepts to manage this next step and are reviewed in this paper. These concepts have already been applied in some industrial products and should spread in the next years.

After many years of debate fiber in access is now a high priority for network transformation. Today broadband services in access networks are a key requirement, initially fuelled by the Internet and more recently pushed even harder by video services. Diffusive video initially and interactive video later are likely to generate even faster bandwidth growth. Networks will need to adapt and change if such new services are to be delivered profitably. Fiber in access offers the potential solution to profitable delivery of high bandwidth services as the medium can offer increase bandwidth and reduced network costs at the same time. This is because of its inherent advantage: a high bandwidth-distance product. However fiber in access does imply both a significant financial investment and a technology challenge. For instance, high bandwidth systems such as DWDM-PON will require a high degree of integration and cost reduction for the basic optical devices. This paper looks at such challenges and sets the scene for the technology roadmap required for this new breed of access networks and devices.

"Berlin Access", a regional R&D project carried out by six companies and Heinrich Hertz Institute, Fraunhofer Society, is geared towards low cost solutions for fibre access network architectures (PON and CWDM-PON), ONU transceivers, and passive fibre components. Close communication with system manufacturers, non-incumbent carriers, and a city services supplier implementing a local FTTH network supports orientation towards market demands. In this paper we report on a new FTTH transceiver based on an all-polymer PLC motherboard. The waveguides exhibit high transmission, strong optical confinement, and large operation temperature range. Low loss passively adjusted fibre/PLC coupling is achieved by employing a waveguide taper. Downstream/upstream wavelength separation is accomplished by a directional coupler, or, alternatively, a thin film filter inserted into the input/output waveguide (the latter approach also allowing for the provisioning of an overlay broadcasting channel). The horizontal-cavity surface-emitting laser diode, the pin-photodiode (equipped with a thin film filter for improved crosstalk suppression), and the monitor diode are all flip-chip surface mounted; the light being coupled via 45° waveguide mirrors. Chip mounting can be done with a commercial fineplacer using semi-active automatic alignment. Micro-strip lines with impedances adapted to both laser and photodiode are fabricated on the basis of the PLC films. The polymer motherboard integration scheme offers compact transceiver optical subassemblies and lends itself favourably to highly automized, low cost manufacturing with high yield. Extended functionalities like loss of light alarm or concepts for colourless CWDM ONUs can be easily realized with this concept.

The ever increasing bandwidth demand will put large pressure on classical broadband communication networks. Optical fiber, with its high bandwidth, offers a solution to this emerging problem. Fiber-to-the-home (FTTH) can provide end-users with virtually unlimited bandwidth, creating the opportunity to receive any service they like. FTTH networks consist of a passive network, active equipment and a top-layer which brings the services to the end-user. Companies and organisations who are deploying FTTH networks are not the traditional telecom and cable operators, but utility companies, housing corporations and local communities. The FTTH network deployed in Nuenen is a good example showing the strength of FTTH. In the future, bandwidth demand will increase even more. Intelligent solutions, such as flexible bandwidth, can have large added value for future FTTH networks.

An electrically induced Bragg ReflectorModulator 2.5 mm long has been designed in InP/InGaAsP rib waveguide. By means of an in house code based on a suitable simulation strategy which takes advantage of state-of-the-art electronic simulator such as Silvaco/ATLAS and a general purpose FEM solver such as Comsol Multiphysics, predictions of DC response the transient analysis had been make. The code allows us to use the same grid to evaluate all the quantity of interest, the effective refractive index included. The simulations results show that such a modulator can theoretically reach ultra 40 GHz switching speed.

We report on a miniature solid state emitter structure, which allows electrical pumping of only one single InAs quantum dot (QD) grown in the Stranski-Krastanow mode. The emitter is based on a single layer of low density (~10⁸ cm^-2) QDs grown by Molecular Beam Epitaxy and a submicron AlOX current aperture defined by selective oxidation of high aluminium content AlGaAs layers. The device demonstrates strongly monochromatic polarized emission of the single QD exciton at subnanoampere current pumping. No other emission is observed across a spectral range of 500 nm, proving that indeed just one single QD is contributing. Correlation measurements of the emitted photons show a clear antibunching behavior.

In the field of datacom, 10 Gbit/s sources with a good coupling in monomode silica fibers, whose dispersion minimum occurs at 1.3 μm, are required. Vertical Cavity Surface Emitting Lasers (VCSELs) emitting at 1.3 μm are key components in this field thanks to their compactness, their ability of being operated at high frequencies, their low threshold current and their low beam divergence. Such devices emitting in this wavelength range have been demonstrated using different materials such as strained GaInAs/GaAs quantum wells [1-3], GaInNAs/GaAs quantum wells [4-7], InAs/GaAs quantum dots [8, 9], and antimonides [10], using either molecular beam epitaxy (MBE) or metalorganic vapor phase epitaxy (MOVPE). In the emerging field of photonics on CMOS, there is a need to bond efficient III-V laser sources on SOI wafers. These components should operate at small voltage and current, have a small footprint, and be efficiently couple to Si waveguides, these latter being transparent above 1.1 μm. Since these requirements resemble VCSEL properties, the development of VCSEL emitting above 1.1 μm could therefore benefit to future new sources for photonics on silicon applications. In this context we developed GaAs-based VCSELs emitting in the 1.1 μm - 1.3 μm range with GaInAs/GaAs or GaInNAs/GaAs quantum wells (QWs) as the active materials.

We demonstrate the integration of short-pass and long-pass optical thin film filters targeting Passive Optical Network (PON) applications in a versatile high-speed InGaAs p-i-n photodiode device concept. The optical filters are deposited by RF sputtering into a protective recess on the photodiode bottom-side. This configuration allows to separate the two main functions of optical filtering and opto-electrical conversion. We obtained photodiodes with high optical isolation of 25 dB in the stop-band as well as high responsivity of 0.82 and 0.93 A/W in the pass-band for a short-pass and a longpass filter. We investigated the temperature induced wavelength shift of the filter transmission spectrum between 20 °C and 120 °C and found a conventional linear relationship with a low temperature dependence of only 20 and 83 pm/°C for the short-pass and the long-pass filter. Simulations of the long-pass filter transmission characteristics regarding light incidence angle show a wavelength shift of less than 7nm for angles below 10°. Above 10° a higher shift and polarization dependence appear. Through different thermal cyclings we also demonstrated the environmental stability of the integrated filters.

A novel electrical and optical confinement scheme for surface emitting optoelectronic devices is presented. The scheme is based on epitaxial regrowth of a pnp current blocking layer structure around a mesa etched in the vertical cavity region of the device. The lateral size and orientation of the mesa is defined lithographically and dry etching is used to create vertical mesa sidewalls. By orienting the mesa sidewalls in certain crystallographic directions, it is possible to selectively grow a current blocking pnp layer structure on the exposed n-type lower cladding layer of the cavity whithout obstructing the electrical injection into the active region. The concept is evaluated in 1.2-μm GaAs-based light emitting diodes with InGaAs quantum wells. This type of structure can easily be used as the amplifying region of a vertical cavity laser, providing a good alternative to selective oxidation confinement.

The transfer function of a photonic filter is significantly influenced by the profile of the waveguides forming the device. In this work we discuss requirements for devices based on two geometries, rib and wire shaped waveguides in Silicon-on-Insulator, from both the modal and polarisation standpoints. General guidelines and recommendations for the design of single-mode and polarisation-independent ring resonator filters with large Free Spectral Range (>30nm) are given, together with supportive experimental results.

Nanotechnology is a driver for novel opto-electronic devices and systems. Nanosemiconductors like quantum dots allow controlled variation of fundamental electronic and optical properties by changing the size and shape of the nanostructures. This applies directly to self-organized quantum dots which find a versatile use in many kinds of photonic devices. Wavelength tunability, decreased laser threshold, scalability of gain by stacking quantum dot layers, low linewidth enhancement factor and temperature stability are consequences of three-dimensional carrier confinement in semiconductor quantum dots. Directly modulated lasers using quantum dots offer further advantages like strongly damped relaxation oscillations yielding low patterning effects in digital data transmission. Quantum dot mode-locked lasers feature a broad gain spectrum leading to ultra-short pulses with sub-ps width and a low alpha factor for low-chirp. Thereby, optical comb generators for the future 100G Ethernet are feasible. Semiconductor optical amplifiers based on quantum dots show advantages as compared to classical ones: broad bandwidth due to the inhomogeneous quantum dot size distribution, ultrafast gain recovery for high-speed amplification and small patterning in optical data transmission. We present our most recent results on temperature stable 10 Gb/s, 23°-70°C direct modulation of lasers, ultrafast 80 GHz and short 710 fs optical pulse combs with mode-locked lasers and semiconductor optical amplifiers showing ultrafast amplification of these optical combs as well as error-free 40 Gb/s data modulation, all based on a quantum dot gain medium.

Quantum dot (QD) materials offer attractive performances for the development of lasers and amplifiers at 1.55μm. The 3-D quantification of the energy levels in QD leads to several advantages, such as high optical gain and efficiency, low sensitivity to temperature variations, low noise and low linewidth enhancement factor. We shall present in this paper the growth and basic properties of QD materials for lasers and amplifiers, and device performances with particular interest for optical communications and microwave transmission.

For high speed remote colorless modulation in FTTH technology, a new 10Gbit/s monolithically integrated amplified reflective electroabsorption modulator (R-EAM-SOA) is demonstrated over 50nm spectral range and over 20°C-60°C, with excellent eye diagrams.

A novel DFB laser structure, referred to as CSDFB, is presented that, different from conventional designs, simultaneously allows to obtain very high yield single mode behaviour even without applying facet coatings, high slope efficiency, and low beam divergence. These advantages result from the incorporation of a curved and tapered laser waveguide designed such that a constant period DFB grating can be utilized. Preliminary feedback measurements have indicated enhanced immunity to optical back-reflection in comparison to a conventional DFB structure. The CSDFB design has large potential of reducing transmitter costs due to both reduced chip and module fabrication costs.

The centralized Point-to-Point fibre access approach with a dedicated single mode optical fibre link connecting each customer to a Central Office (CO) has advantages regarding future-proofness, security, and simple and low-cost optical links and transceivers. The potential bottleneck in handling the large number of optical fibres that need to be terminated in the CO, and combined with optoelectronic components, has been studied within the IST 6th Framework Programme integrated project MUSE. The key parts in the CO are the passive cabinet where customer fibres are accessible through fibre connectors in the Optical Distribution Frame (ODF), and the active cabinet with switching equipment and optical transceivers. For the passive cabinet we conclude, that the most efficient solution is that each connection from the active cabinet to a customer passes only one ODF, and that small form factor connectors are used. For the active cabinet we have demonstrated the feasibility of an SFF-size module containing two bi-directional transceiver units by building and successfully testing a prototype, increasing the customer port density by a factor of two compared to commercial transceivers. The power consumption, which impacts power supply, cooling and cost, has been analyzed, and we propose measures to significantly decrease the power consumption.

Next generation networks capable of carrying converged telephone, television (TV), very high-speed internet, and very high-speed bi-directional data services (like video-on-demand (VOD), Game etc.) strategy for Fiber To The Home (FTTH) is presented. The potential market is analyzed. The barriers and some proper strategy are also discussed. Several technical problems like various powering methods, optical fiber cables, and different network architecture are discussed too.