To investigate the potential for dense integration of photonic components, we analyse passive plasmonic/metallic waveguides and waveguide components at optical frequencies by using mostly microwave engineering approaches. Four figures of performance are formulated that are utilised to compare the characteristics of four different slab waveguides with zero frequency cut-off modes. Three of these are metallic based whereas the fourth one, which also serves as a reference, is dielectric based with high index-contrast. It is found that all figures of performance cannot be optimised independently; in particular there is a trade-off between the waveguide Q-value and the transversal field confinement. Microwave methods are used to design several photonic transmission line components. The small Q-value of the metallic waveguides is the main disadvantage when using materials and telecom frequencies of today. Hence plasmonic waveguides do not offer full functionality for some important integrated components, being severe for frequency-selective applications. To achieve a dense integration, it is concluded that new materials are needed that offer Q-values several orders of magnitude higher than metals.

A 400 km standard single mode fiber (SSMF) link with a single light-intensity modulator was upgraded for simultaneous transmission of STM-16 2.5Gbps baseband data and Digital-Video-Broadcast-Terrestrial DVBT utilizing a 40GHz subcarrier. An optical circulator and narrowband fiber Bragg gratings (FBG) were used to separate the signals in the optical domain and allow for simple direct baseband detection of both.

A simple integrated tunable wavelength converter is presented. 10 Gb/s XGM conversion of signals at wavelength 1530-1560 nm to 1531-1556 nm and transmission at 2.5 Gb/s over 25 km SSMF of the converted signals were achieved.

A silicon optical bench for flip chip mounted widely tunable modulated-grating Y-branch lasers is presented. Its impact on the static and dynamic performance of the laser device is evaluated and compared with a conventional aluminum nitride carrier. The carriers exhibited similar thermal and static performance but the dynamic performance was limited by the electrode layout and the higher microwave losses of the silicon optical bench. With improved microwave design of the electrodes, flip-chip mounting on a silicon optical bench is promising for low cost assembly of high-speed multi-electrode devices

We demonstrate >= 60 GHz Electro-Absorption-Transceiver (EAT) composed of monolithically integrated Distributed-Feedback laser (DFB) with low drive voltage Electro-Absorption-Modulator. Clear eye-openings at 50 Gb/s for modulation and detection are presented. The device can be used as efficient and compact size transmitter or as detector in direct 80 Gb/s links. Transmission over 7.2 km long fibre with dispersion compensation is achieved.

A monolithically integrated distributed feedback (DFB) laser and traveling-wave electro-absorption modulator (TWEAM) with >= 100 GHz -dBe bandwidth suitable for Non-return-to-zero (NRZ) operation with on-off keying (OOK) is presented. The steady-state, small-signal modulation response, microwave reflection, chirp characteristic, and both data operation and transmission were investigated. The DFB-TWEAM was found to be an attractive candidate for future short distance communication in high bitrates systems.

We propose a novel protection scheme compatible with smooth migration from TDM-PON to WDM/TDM-PON. We show that our scheme is very cost-effective while keeping connection availability, recovery time and power budget at the acceptable level.

This paper proposes a novel protection scheme based on the cyclic property of an array waveguide grating (AWG) and neighboring connection pattern between two adjacent optical network units (ONUs) for the hybrid WDM/TDM passive optical networks (PONs). Our scheme uses 50% fewer wavelengths while offering one order of magnitude better connection availability than the existing scheme.

A novel opto-electrical tunable dispersion compensator with a tuning time lower than 150 s is proposed and experimentally demonstrated. Compensation of 0-340 ps/nm for a 40 Gb/s NRZ signal is achieved.

In this paper, we propose and experimentally demonstrate a novel tunable optical dispersion compensator (TODC). Dispersion compensation is achieved by splitting the input signal between two dispersive media and adding the resulting signals thereafter. Tunable compensation is attained by controlling the power splitting ratio of the input signal between both dispersive media. The frequency response of the TODC is theoretically assessed considering signal addition in the optical and electrical domains. The latter case is enabled by using optical single side-band (OSSB) modulation, which allows preserving the phase information of dispersive media output signals after direct detection. This is the only case experimentally tested, since it avoids stability problems related with coherent addition of optical signals. A TODC with a tuning range of -340 to 0 ps/nm was designed and experimentally assessed for a 40 Gb/s nonreturn-to-zero OSSB signal. The tunable power splitter consisted of an automatic polarization controller and a polarization beam splitter, which offered a tuning time lower than 150 mu s. A bit error rate lower than 10(-8) was measured on the entire compensation range with a maximum power penalty of 3.3 dB relatively to an SSB signal in back-to-back.

In this work, we demonstrate a reliable all-optical technique for performing optical double sideband (ODSB) to single sideband (OSSB) format conversion of a 40 Gb/s non-return-to-zero signal. It is based on the optimization of a detuned optical filter, which was implemented on a fiber Bragg grating (FBG) with a complex apodization profile. An OSSB signal with negligible distortion was obtained, as the FBG presented a nearly ideal frequency response. Higher tolerance to chromatic dispersion enabled by the OSSB signal in comparison to the ODSB signal was demonstrated on both simulation and experimental results. (C) 2010 Elsevier B.V. All rights reserved.

Colloidal quantum dots (QDs) have been widely studied for nanophotonics and bioimaging applications for which the lifetime of their fluorescence is of critical importance. We report experimental and theoretical characterizations of dynamic optical properties of multi-shell-coated CdSe/CdS/ZnS QDs. Quantum-mechanical studies of fundamental optical excitations and Monte Carlo simulations of energy relaxation mechanisms indicate that the excitonic states are densely compacted in the QDs and are easily photoexcited by the laser pulse in the presence of nonradiative electron-phonon interactions. For spherical QDs, the decay time of spontaneous radiative emission of individual photoexcited excitonic states with zero angular momenta is found to be only tens of picoseconds. In our multi-shell QDs, high-energy excitonic states of nonzero angular momenta have to go through a number of nonradiative electron-phonon interaction steps in order to relax to zero-angular-momentum excitonic states for radiative emission, resulting in an effective fluorescence peak at about 2 ns in the photoncount-time relationship. This explains the measured long average fluorescence lifetime of 3.6 ns. Such a long lifetime facilitates the applications of colloidal QDs in areas such as QD-based solar cells, bioimaging and metamaterials.

We review major breakthroughs in realizing silicon-based active components by heterogeneous integration with III-V semiconductors, or nonlinear organic materials. In more detail we describe examples of our concepts and technological approach addressing this goal. This includes designs for widely tunable filters and new routes for heteroepitaxy and selective area growth of InP on silicon.

We present two concept examples for adding a wide range tunability to Si/SiO2 devices involving a photonic crystal element. They are based on a directional coupler filter of two different geometries, where one of the arms is a Bragg Reflection Waveguide (BRW) used for the bandwidth improvement. The tuning relies on changing the properties of the BRW core. As an illustration we consider the smectic A* liquid crystal as the core material and show that ca 100 nm tuning range is achievable by the core index variations of 0.006 under applying electric field of 5 V/mu m.

In this letter, we experimentally demonstrate terahertz (THz) photonic wireless transmission of high-speed quadrature-phase-shift-keying (QPSK) and 16 quadrature amplitude modulation (16-QAM) signals in the 350-GHz band, with an effort to extend the wireless reach of ultrafast 100 Gbit/s. In the experiment, a narrowband unitraveling-carrier photodiode (UTC-PD) is used for heterodyne generation of THz communication signals, which is transparent to optical modulation formats. Experimental results show that 30 GBd/s QPSK (60 Gbit/s) and 25 GBd/s 16-QAM signals (100 Gbit/s) are successfully transmitted over a 350-GHz wireless link with an extended distance of 2 m. This enhancement is enabled by combining the techniques of employing cutting-edge narrowband UTC-PD as the photomixing THz emitter, spectrally efficient modulation format and advanced digital signal processing algorithms. The achievement makes 100 Gbit/s THz wireless communication systems promising for future smart wireless services.

This chapter provides an overview of unusual multifunctional, specialty single-mode fibers-macrohole fibers, multicore fibers, fibers with internal electrodes, and fibers for high-temperature resistant fiber Bragg gratings. Macrohole fibers belong to the group of microstructured fibers, which encompass a wide variety of fibers with air holes or other structures extending in the axial direction. Functions performed using macrostructured fibers include supercontinuum generation in tapered hole fibers, dispersion management, fibers with decreased bend loss for compact optical fiber wiring, and fibers for polarimetric sensing, and lasers. The introduction of materials in the holes adds the possibility of manipulating the guiding properties of the fiber. This can be achieved by interaction of the guided mode with actively controllable materials in the holes or by using the inserted materials for other active functions, such as a metal electrode to implement electro-optic control of the fiber. The proposed applications for multicore fibers span over lasers and amplifiers, transport fibers for broadband communications, passive, and active fiber optic components such as filters, multiplexers, and various kinds of sensors. The ultimate multicore fiber is the image fiber used in endoscopes and other such devices.

We experimentally evaluate high-speed intensity modulation/direct detection (IM/DD) transmissions with a 1.55-μ text broadband electro-Absorption modulated laser and pulse amplitude modulations (PAM). We demonstrate 80 Gb/s/ λ PAM-4 and 96 Gb/s/ λ PAM-8 transmissions with low-complexity digital equalizers at the receiver. Performance comparison with different types of equalizers are performed, including linear symbol-spaced feed-forward equalizer (FFE), fractional (half-symbol) spaced FFE and decision feedback equalizer (DFE), with different tap number. It is found that for both cases, a 6-Tap symbol-spaced FFE is sufficient to achieve a stable performance with bit-error-rate below the 7% overhead hard decision forward error correction (7%-OH HD-FEC) threshold over a 4 km standard single mode fiber link. Practical considerations including comparison between adaptive and static equalizer implementation and tolerable fiber chromatic dispersion are discussed.

We demonstrate a low cost, non-butt-joint, wide-gain integrated device comprising 1550nm lasers, wavelength selective couplers and 1310nm sensitive photodiodes for diplexer arrays for FTTH use.

The modulation response of an arbitrarily segmented traveling wave electroabsorption modulator (TW-EAM) with a non-periodic electrode layout is analyzed with an effective approach based on the transmission line theory. An optimization method based on a genetic algorithm is used to optimize the segmented electrode with additional capacitive pads for a TW-EAM. Optimized electrode structures are given for 165 mu m-length devices under standard 50 Omega RF termination condition and 210 mu m-length devices with smaller integrated resistors. Great enhancement of performances in modulation response is achieved as compared to the periodic design reported previously. The simulation with the parameters extracted from measurement results suggests that a 3 dB-bandwidth over 100 GHz could be achieved. The eye diagram from the simulation demonstrates that such devices would be competent for a 100Gb/s optical network.

Photonics is far behind electronics in maturity. The devices are orders of magnitude larger than their electronics counterparts and the functionality is low. But it appears that these issues are not fundamentally impossible to solve. In this paper some of the emerging possibilities to overcome the limitations mentioned above are briefly treated, and we discuss the utilization of these comparatively new phenomena to widen the application envelope of photonics technology to generate functions not normally associated with photonics. These developments could lead to quantum leaps in photonics devices, to complement the forceful engineering improvements. Examples of such potential candidate research fields for quantum leaps are: Coherent light matter interaction, plasmonics, quantum information and communications, photonic crystals, intersubband based devices. The list is by no means exhaustive. This paper will concentrate on coherent light matter interaction, plasmonics and photonic crystals

We discuss from a theoretical viewpoint the required advances in material technology and device structures needed to continue the rapid development of photonic circuit spatial integration density. Metamaterials and various waveguide device structures are discussed.

We discuss from a theoretical viewpoint the required advances in material technology and device structures needed to continue the rapid development of photonic circuit spatial integration density.

An approach is presented to reduce the chromatic dispersion-induced distortions in optical links carrying combined baseband and microwave signals. This new method is based on the interplay of intensity dependent phase modulation in semiconductor optical amplifiers (SOAs) and fiber nonlinearities. Theoretical and experimental results are demonstrated for a 400 km long optical link.

The application of microwave / millimeter-wave optical links for future mobile broadband services is limited by the dispersion of the fibre. We present an approach to reduce the chromatic dispersion-induced distortions in optical links carrying combined baseband and microwave signals. This new method is based on the interplay of intensity dependent phase modulation in semiconductor optical amplifiers (SOAs) and fibre nonlinearities. Theoretical and experimental results are demonstrated for different long optical links. The results show that the frequency notches caused by the dispersion-induced carrier suppression effect may be sharply alleviated and the transmitted digital signal performance can be improved. Investigations on a 400 km long fibre link proved the previous statement.

State of the art and prospects regarding semiconductor compact modulators and transmitters for on-off keying and more advanced modulations formats for output bitrates of 100 Gb/s and above are discussed. The implementation of a monolithically integrated transmitter comprising laser and light-intensity modulator is described and the prospects for a fully integrated transmitter for more advanced modulation formats elucidated, all for 100 Gb/s output bitrate.

Electroabsorption modulators (EAM) based on quantum-confined Stark effect (QCSE) in multiple-quantum 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 source lasers. In order to achieve both high speed and low drive-voltage operation, travelling-wave (TW) electrode structures can be used for EAMs. Modulation bandwidths of 100 GHz (-3 dBe) have been accomplished and transmission at 80 Gbit/s with non-return-to-zero (NRZ) code has been demonstrated for InP-based TWEAMs, indicating the possibility of reaching speeds of IOOGbit/s and beyond. In order to further increase the efficiency and reduce the drive voltage, MQW structures using intersubband (IS) instead of interband (QCSE) absorption are being investigated. Materials systems with large conduction band offset, such as GaN/Al(Ga)N or InGaAs/AlAsSb, are required for IS modulators. Critical for the performance of IS modulators is the linewidth of the absorption peak, hence IS modulators have the potential to outperform interband modulators given that a sufficiently high material quality can be achieved.

Electroabsorption modulators (EAM) based on quantum-confined Stark effect (QCSE) in multiple-quantum 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 500hm 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 500hm 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.

We propose an asynchronous optical packet switching node architecture, where congestion resolution is based on shared optical buffers and tuneable wavelength converters. We evaluated our switch by simulations and show that decreasing packet loss probability obtained by optical buffers can be efficiently boosted by adding a few shared tuneable wavelength converters, which allows for reduction of all-optical buffer size. The smaller switch size the larger impact of wavelength conversion on packet loss probability was observed. Furthermore it can be noticed that for the proposed node architecture the higher number of buffer positions the larger improvement caused by applying tuneable wavelength converters can be achieved.

In this talk we will discuss issues related to technology for dense photonic integration based on silicon platform, and review two alternatives to achieve this goal within the diffraction limit; photonic nanowires and photonic crystal waveguides. We will also present examples of our demonstrators to illustrate the feasibility of photonic wires for device miniaturization and benefits offered by photonic crystal dispersion.

Silicon-on-insulator nanowire waveguides appear to be the technology for next generation of super compact integrated devices. Due to a very high refractive index contrast and strong light confinement in the core, the waveguide bend radius can be reduced to a few micrometers and the size reduction of the functional integrated circuits can reach several orders of magnitude in comparison to standard integrated optics based on silica-on-silicon technology. Amorphous silicon is an interesting material allowing for more flexibility in nanowire structures. An array waveguide grating multi/demultiplexer that usually occupies several square centimetres in silica-on-silicon technology can be reduced to the size of 320 x 270 μm².

We present a novel practical method for group delay compensation of Bragg gratings imprinted in planar waveguides for high speed DWDM systems. Although Bragg grating-based wavelength selective devices in optical fibers have reached their maturity, similar components built on the basis of planar technology are still the research issue. We analyze an integrated Mach-Zehnder interferometer-based Add-Drop multiplexer equipped with two pairs of gratings, one designed as a wavelength selective filter and the other one as a group delay compensator.

To solve the processors performance limitations, new chip-to-chip and on-chip communication needs to be introduced. Optical technology will play here a crucial role. Optical links will move into the chip multiprocessors connecting tens or even hundreds of processing elements and forming a photonic network for communication between them. In this talk we will present our solutions of silicon-based CMOS-compatible optical components for the main building blocks in application to computer interconnects.

Silicon-on-insulator material structure allows for very high light confinement in the silicon core due to its high refractive index. The advantages of this technology include the possibility to miniaturize devices and integrate different functions on a single chip, reduction of optical loss and power consumption and potential perspectives for low cost mass production in CMOS technology line. Together with these advantages some new problems appear in comparison to weakly guided light in silica-on-silicon components, causing additional challenges for researchers to be solved. Besides much higher demands for fabrication accuracy, high refractive index contrast introduces additional optical input/output coupling problems as well as much higher polarization sensitivity of nanophotonic structures. Here we will propose some solutions for these problems and illustrate them with designed and fabricated components

We propose and demonstrate an ultracompact on-chip photothermal power monitor based on a silicon hybrid plasmonic waveguide (HPWG), which consists of a metal strip, a silicon core, and a silicon oxide (SiO2) insulator layer between them. When light injected to an HPWG is absorbed by the metal strip, the temperature increases and the resistance of the metal strip changes accordingly due to the photothermal and thermal resistance effects of the metal. Therefore, the optical power variation can be monitored by measuring the resistance of the metal strip on the HPWG. To obtain the electrical signal for the resistance measurement conveniently, a Wheatstone bridge circuit is monolithically integrated with the HPWG on the same chip. As the HPWG has nanoscale light confinement, the present power monitor is as short as ~3 μm, which is the smallest photothermal power monitor reported until now. The compactness helps to improve the thermal efficiency and the response speed. For the present power monitor fabricated with simple fabrication processes, the measured responsivity is as high as about 17.7 mV/mW at a bias voltage of 2 V and the power dynamic range is as large as 35 dB.

A distributed-feedback (DFB) grating was written in twin-hole fibres with internal electrodes. Due to the intrinsic birefringence, the grating has two ultra-narrow peaks (∼0.41 pm and ∼0.27 pm) corresponding to x- and y-polarization. The separation between them can vary from 40 pm to 104 pm when the temperature increases from room temperature to 96°C. The dominant contributions of the Bragg wavelength shift as the increasing temperature are the change in refracitive index of the fibre and the expansion of the substrate (largest). Under the current pulses excitation, full on-off switching with response time ∼2.5 ns has been achieved for x-polarization of the DFB grating.

A novel all-fiber polarization switch was studied in a four-hole fiber with internal electrodes. Nanosecond full on-off switch with duration of 12.6 ns was obtained under the application of high voltage pulses.

The physics of electrically switched FBGs was studied in fibers with internal electrodes. Wavelength shifts due to mechanical effects (nanoseconds) and heat (milliseconds) depend quadratically on the electrical pulse voltage and linearly on pulse duration.

The physics of electrically switched FBGs was studied in fibers with internal electrodes. Wavelength shifts due to mechanical effects (nanoseconds) and heat (milliseconds) depend quadratically on the electrical pulse voltage and linearly on pulse duration.

A FBG was written in a two-hole fiber with internal alloy electrodes. Nanosecond high current pulses cause metal expansion, increase birefringence and tune the gratings with a response time of 29 ns. This short length, low loss, all-spliced high-speed wavelength switching devices described here has potential use in Q-switching fiber laser.

A fiber Bragg grating was written in a side-hole fiber with internal metal alloy electrodes. The initial geometrical birefringence of this fiber gives rise to two Bragg resonances separated by 43 pm. Nanosecond risetime current pulses of up to 23 A were applied to the metal electrode, which heated and expanded rapidly. This caused mechanical stress in the fiber on a nanosecond scale, resulting in a negative shift of the Bragg wavelength peak for the fast axis mode, and positive but smaller shift for the slow axis mode. The fast change increased the peak separation to similar to 143 pm, corresponding to an increase in birefringence from 4.0 x 10(-5) to 1.3 x 10(-4). Both peaks subsequently experienced a red-shift due to the relaxation of mechanical stress and the increasing core temperature transferred from the metal in many microseconds. Simulations give accurate description of the experimental results.

We present fabrication and measurement results of an ultracompact silicon-on-insulator-based echelle-grating triplexer, which uses different diffraction orders to cover a large spectral range from 1.3 mu m to 1.5 mu m, with a footprint of 150 mu m x 200 mu m.

In this paper we present measurement results of an ultracompact echelle-grating demultiplexer based on silicon-on-insulator nanowire platform, in which we introduced a total internal reflection design of the grating facets to improve the diffraction efficiency. An average increase of the diffraction efficiency with 3.7dB is observed for the 3 channels compared to a normal design.

We present the design, fabrication, and characterization of an ultracompact silicon-on-insulator-based echelle grating triplexer. It is based on the cross-order design, which utilizes different diffraction orders to cover a large spectral range from 1.3 to 1.5 mu m with three channels located at 1310, 1490, and 1550 nm and with a footprint of 150 mu m X 130 mu m.