This PDF file contains the front matter associated with SPIE Proceedings Volume 7943, including the Title Page, Copyright Information, Table of Contents, and the Conference Committee listing.

Nano-Plasmonics possesses unique physical properties that enable localization of optical fields beyond the diffraction limit. These highly confined/nanoscale optical modes will enhance light/matter interactions in systems with free electrons in micro/nanoscale geometric structures. Metal-dielectric fluid interfaces can support surface plasmon polaritons (SPPs), which are electromagnetic modes interacting with free electron oscillations. Research work is described on using optofluidic plasmonic chips for implementation of an optofluidic plasmonic sensor, demonstrating in situ, real time, label-free detection of protein-protein interaction. SPP lineshape is modified from Fano to Lorentz for increase of the figure of merit to increase the limit of detection. Novel metal-dielectric nanoresonator composites is presented to increase the surface sensitivity by exciting localized surface plasmon resonance (LSPR) in combination with SPP readout, enabling higher surface field localization. In order to solve the long time challenging issue of overlapping molecule of interest onto LSPR to realize the maximal interaction cross-section, micro-nanofluidics integrated nanochip was developed. We employed electrokinetic forces to control and manipulate the nanoparticles onto the predefined positions.

We have addressed Molecular Beam Epitaxial (MBE) growth of GaAs/AlGaAs multi quantum well (MQW) structure on germanium (Ge) substrate. The growth mechanism includes deposition of a low-temperature (350°C) migration enhanced epitaxy (MEE) grown GaAs layer which was overgrown by a thin GaAs layer grown at low-temperature (475°C). The overgrown GaAs layer was annealed multiple times at 600°C during the growth. We believe the MEE layer and this special annealing scheme effectively blocked the dislocations at the GaAs/Ge interface from propagating into the top epitaxial layers. The morphological and optical properties of the samples were studied by Atomic Force Microscopy (AFM), Cross-sectional Transmission Electron Microscopy (XTEM) and Photoluminescence (PL) measurements respectively. The AFM shows a smooth surface with a root mean square (rms) roughness ~0.16nm which is of the same order to a control sample consisting of a similar MQW structure grown on GaAs substrate. Though some defects at the GaAs/Ge interface are clearly visible from XTEM, the TEM image of the QWs show that they are free from structural defects. From the PL spectra, distinctly sharp peaks are clearly visible for the QWs of different widths and the observed PL linewidth is comparable to that of the control sample.

Fast and low power consumption optical switches are required for photonic networks. To this end, we proposed the optical gate switch using phase change material (PCM) and silicon waveguides. This switch had low power consumption because it consumed power only when the state was changed. Furthermore, the chip size is very small due to the large refractive index change of PCM. In this paper, we studied the phase-change characteristics of various kinds of thin GST film on SOI (silicon-oninsulator). A laser diode (LD) with a wavelength of 660 nm was used to irradiate the material. We compared the optical responses by laser pulse irradiation on GST films, and concluded GST-147 was the most suitable material for the optical switch because it had the lowest phase change threshold. The phase-change characteristics of GST-225 films with thickness of 25 nm, 50 nm and 75 nm were also examined. Thicker GST films had lower phase change thresholds. However, thermal simulations showed that the phase of the bottom part of thicker films may not be changed. Therefore, we concluded that GST films with thicknesses between 25 nm to 50 nm are the most suitable for optical switches.

A highly-sensitive and low-cost optical sensor that requires only power measurement is proposed and investigated. It consists of two cascaded micro-ring resonators with slightly different optical path lengths, used in conjunction with an LED light source. The transmission spectrum of the sensor has a series of peaks with a sinusoidal-like envelope function. The variation of the refractive index of the analyte sample results in an amplified shift in the transmission envelope function, and consequently a change in the transmitted LED power. It is shown that a refractive index variation in the order of 7.0×10^-7 can be detected without any spectral measurement. Preliminary experimental results using a broadband light source are presented.

In this paper we outline recent results which combine defect mediated Photo-Detectors (PDs) in a Ring Resonator (RR) structure. By exploiting the multiple-pass of the optical signal through the detector, we are able to significantly decrease the size of the detector structure while maintaining good responsivity (typically 0.1 A/W). In such a geometry the detector bandwidth is not capacitance limited, while the leakage current is reduced toward 1 nA. We also show that these PDs may be used in the drop port of a RR to monitor the propagating signal. These devices have applicability in multiplexing and potential for integration with high speed modulation functionality.

We report the design and the fabrication of an integrated optofluidic ring resonator based on liquid core antiresonant reflecting optical waveguide (ARROW) operating around λ=635nm with a water filled core (nc=1.33). This waveguide permits a strong coupling between light and analyte as the same microchannel can be used for delivering sample and for confining light. A rectangular-shaped ring resonator has been realized by using four 90-bent waveguides and an multimode interference coupler is used for coupling light from the input bus waveguide to the resonator. The resulting device is very compact, with a total length of 2.5 mm and a required liquid volume of about 0.11nl. The device has been simulated with a two dimensional finite-difference time-domain method for different refractive index core n_c=1.32 (methanol) and n_c=1.43 (dimethylformamide). Moreover, we carried out optical measurements by measuring the transmitted spectrum from the output bus waveguide in both cases. The experimental results confirm that ring with a good quality factor (Q~800) can be achieved in good agreement with the numerical results.

Photonic crystal waveguide bends are generally designed to follow the crystal symmetry directions. For low angle bends higher propagation losses are typically observed. We present three waveguide bending techniques and the resulting photonic crystal geometries that permit low propagation losses for waveguide directional changes that do not correspond to the symmetry directions.

Wavelength-division multiplexing (WDM) is the transmission of many signals through a single communication channel using different wavelengths, each of which carries a separate, independent signal. We present and discuss a reconfigurable WDM based on slow-light, functioning as a bi-directional optical routing and processing network, consisting of photonic crystals designed as drop/add filters. The photonic crystal based routing elements consist of two waveguides coupled through a resonant cavity. Photonic crystals offer the ability to achieve separation of many channels on a much smaller scale than their predecessors. Photonic crystals have led a challenging frontier of miniaturization and large scale integration of high-density optical interconnects, and with the aid of nanomembranes, optical routing networks can set a new standard for high-density optical interconnects.

The model of transformation of one-dimensional, high-contrast silicon photonic crystal (PC) into a Fabry-Pérot resonator is considered. This transformation is achieved either by decreasing the number of periods up to 1.5 or the introduction of optical defect in the ordinary multi-period PC while retaining a high modulation of the resonance peaks up to ~0.95. The simultaneous use of maps of photonic band gaps (PBG) and transmission bands can predict the appearance or disappearance of PBGs in the optical spectra as well as to determine their position and width depending on the order of the band-gap (or stop-band) and the value of the filling fraction. The variation of the refractive index by 0.2 results in significant shift of the resonance peaks of high order up to 10% of the frequency corresponding to the center of the peak.

This paper reports on investigation and possible applications of the optical elements based on one-dimensional (1D) multi-component photonic crystal (PCs). The gap map approach and the transfer matrix method were used in order to mathematically describe multi-component 1D PC structures. We have found that the introduction of the additional regular layer into PC affects the properties of high-order PBGs, resulting in their vanishing in the certain range of the wavelengths and the formation of wide regions of total transparency instead. Tuning the number, position and width of these regions of total transparency in Si PCs has been demonstrated using the map of transmission bands. By analogy with multilayer dielectric coatings the additional component in multi-component Si PCs can be considered as an antireflection layer. The experimental results for the high-contrast multi-component PCs based on SiO₂-Si-SiO₂-Air structure with wide transmission bands are demonstrated in this study. The suggested approach can also be applied to the design of any micro- and nano- structured semiconductor or dielectric materials for application across wide electromagnetic spectrum.

As a result of the evolution semiconductor fabrication tools and methods over several decades, it now possible to routinely design and make optical devices with features comparable to or smaller than the wavelength of the light that propagates through these structures. This paper will review some silicon optical structures with critical features at these extremely short length scales. For example it becomes possible to create segmented waveguide structures with optical properties that can be tuned continuously between those of the cladding and waveguide core, using lithographic patterning rather than varying etch depth. Using thin high index contrast waveguides and the correct polarization, the optical electric field profiles can be shaped to maximize the coupling to molecular monolayers or cladding layers with specific functionality. Examples are given from our recent work on optical biosensors chips which employ grating couplers made by sub-wavelength digital patterning, and use waveguides optimized for coupling to molecular monolayers.

Rigorous modal solutions of silicon nanowires are presented by using a H-field based finite element formulation. It is shown that beam profiles of a circular nanowire are not circular. It is also shown that most of the optical power in a silicon slot waveguide can be confined in the low-index slot region. It is shown here that dispersion properties can be easily controlled by waveguide design of silicon nanowires, as waveguide dispersion dominates over the material dispersion for such sub-wavelength optical structures. Bending losses of such silicon nanowires are also presented.

In this work, we optimize Bragg gratings covered with SU-8 for TM polarized light at a center wavelength of 1550 nm with respect to high reflectivity and large wavelength range employing 3D FDTD simulations. Three different types of lateral grating modulation were studied: I) complete interruption of the waveguide, II) corrugation within the waveguide width, and III) corrugation exceeding the waveguide width. The wavelength response was analyzed with a discrete Fourier transformation algorithm for a Gaussian pulse source. The investigations resulted in a grating structure providing a reflectivity of >70% over a wavelength range of 50 nm. The transmission and the radiation losses amount both to approximately 10–15% each. Corresponding samples of these three Bragg grating structures with lengths of ~10 μm were fabricated employing e-beam lithography and reactive ion etching. In order to enable the experimental verification of the reflectivity a Y-branch separates the light paths of incoming and reflected light directly on the chip. The measured reflection and transmission spectra match well with the simulations and demonstrate the good performance of the optimized Bragg grating reflector.

The effects of roughness induced backscattering in optical waveguides and circuit realized on a silicon-on-insulator platform are investigated. A systematic experimental investigation on low-loss silicon nanowires, with a sidewall roughness rms around 1-2 nm, is presented, showing that a few hundreds of micrometers long waveguide exhibits a backscattering level that can hinder its exploitation in many applications. The effect is typically stronger for TE polarization and is significantly enhanced inside optical cavities, such as microring resonators, where backscattering is coherently enhanced according to the square of the finesse of the resonator and can modify dramatically the spectral response of the resonators, even at moderate quality factors. We found general relationships relating backscattering to the geometric and optical parameters of the waveguides, to polarization rotation effects, and to coupling with higher-order modes. On the basis of these results, design rules to mitigate backscattering effects are proposed. The main statistical properties of roughness induced backscattering were also experimentally derived, these results enabling an accurate modeling of realistic waveguides and the evaluation of the backscattering impact in integrated devices and circuits.

The utilization of Organic Light Emitting Diodes (OLEDs) and Si Avalanche LEDs emitting at 0.45 - 0.75 micron enable the development of high speed all -Silicon CMOS based optical communication systems without the incorporation of materials such as Ge or III-V components. The development of low loss and high curvature optical waveguides in CMOS technology at these wavelengths, however, offers major challenges. Advanced optical simulation software was hence used in order to develop effective CMOS based waveguides, using CMOS materials characteristics, processing parameters, and the spectral characteristics of CMOS Av LEDs. The analyses show that both silicon nitride and Si oxi-nitride offer good viability for developing such waveguides, utilizing 0.2 to 1.5 micron wide CMOS over-layer as well as trench-based technology. Particularly, trench based technology are very attractive, since the optical sources can then be integrated with silicon avalanche based LEDs with trench-based waveguides on the same plane with standard CMOS processing procedures. Effective single mode wave-guiding with calculated loss characteristics of 0.65 dB.cm^-1 and modal dispersion characteristics of 0.2 ps.cm^-1 and with a bandwidth-length product of higher than 100 GHz-cm are predicted.

The modifications to the optical properties of a slab waveguide coated with a patterned thin high dielectric overlay layer are examined. The asymmetric nature of the entire waveguide configuration makes it possible to keep the waveguide mode highly confined in the slab waveguide while enhancing the evanescent wave-overlay interaction. The sensitivity of the guided light to variations in the refractive index, thickness, period, and length of patterned overlay are examined using Finite Difference Time Domain (FDTD) simulations. For various waveguide geometries, transmission and reflection spectrums are obtained from which active and passive optical device configurations are explored.

In this paper, we investigate the criteria for far-field approximation in a 2D problem, including the phase criterion. Using a silicon-lab as the platform, we will also compare these criteria with those of a 3D scattering problem for both sub-wavelength and large objects. The convergence of the exact solution, based on Hankel functions, and the far-field approximation are presented.

A pluggable compact connector between the single-mode optical fiber and the grating coupler in a Si-photonics chip has been prepared using a cost-effective MT-ferrule. The 8-channel MT-ferrule with a dimension of 6.4 mm x 2.45 mm x 8.1 mm was processed to have a compact dimension of 6.4 mm x 2.45 mm x 1.5 mm. It can reduce the cost down to 1/30 of a commercial fiber-array-block unit (FABU). It has guide holes for passive plugging with another MT-ferrule connected to the external light source. Small dimension and simple connection enabled a connector to be directly bonded to the Si photonics chip. The optical insertion loss of each channel the connector showed constant values of 0.41~0.74 dB for the wavelength range from 1520 nm to 1600 nm. The assembled optical connector was directly bonded to the Si chip on which 6-channel waveguides were formed. Each waveguide has a etch depth of 120 nm, a width of 10 μm, and a length of 7.3 mm on a SOI wafer with a 220 nm-thick Si top layer and a 2 μm-thick SiO₂ buried oxide layer. Grating couplers were formed at both ends of each waveguide. The minimum coupling loss of the connector was 5.4 dB.

The mid-infrared spectral region is interesting for bio-chemical sensing, environmental monitoring, free space communications, or military applications. Silicon is relatively low-loss from 1.2 to 8 μm and from 24 to 100 μm, and therefore silicon photonic circuits can be used in mid- and far- infrared wavelength ranges. In this paper we investigate several silicon based waveguide structures for mid-infrared wavelength region.

Plasmonic waveguiding structures have the ability to confine and propagate light over short distances, typically less than a hundred micrometers. This short propagation length is the price that is paid for confining light to dimensions on the order of a hundred of nanometers. With these scales in mind, several plasmonic devices can be proposed (e.g. wavelength multiplexors) and some of them have been already demonstrated such as Y junctions and directional couplers. Although the dimensions involved in such structures are below the diffraction limit, large-scale optical characterization techniques, such as transmitted power, are still employed. In this contribution, we present a characterization technique for the study of the guided modes in plasmonic gap waveguiding structures that resolves subwavelength-scale features, as it is based on atomic force microscope and on near field scattering optical microscope in guided detection.

Optical devices based on SOI have been fabricated and tested for the last decade by using far field optics. Alternatively, near-field scanning optical microscopes (NSOM) have the ability to reach unique optical resolution by converting the evanescent waves into radiation waves that can be detected by conventional far field optics. Thus, the aim of this paper is to show the most recent capabilities of the NSOM in a guided detection to probe SOI-based structures. By using this simple yet powerful configuration, we can observe the propagation of the light in Si-based devices and thus measure the propagation characteristics of the guided modes.

We have designed, fabricated and investigated one-dimensional (1D) micro-cavities in Silicon-on-Insulator (SOI) waveguides. The single mode waveguides are fabricated in a 220 nm silicon device layer. The 1D micro-cavities in Fabry-Perot structure consist of two Bragg-mirror regions formed by a sinusoidal modulation of the waveguide width. The mirror regions are separated by a sub-micron spacer. The SOI photonic structures are produced in a CMOS environment using 248 nm DUV lithography. The waveguides as well as the width modulated mirror regions are designed using a single mask and are fabricated in a shallow trench process. The transmission spectra of these width modulated micro-cavities with different mirror reflectivities and cavity lengths are investigated. Q-factors up to 855 could be observed at 1550 nm wavelength with low insertion loss of 1.9 dB. The width modulated micro-cavities, including the mirror regions, have lengths of less than 20 microns and widths of maximum 450 nm. These small foot-print cavities act as band pass filters and can be used as resonators for laser or electro-optic modulation of light.

We present our work on fully integrated hybrid silicon optical buffers capable of holding 40 byte packets at 40 Gb/s. These devices consist of low loss silicon waveguides and cascaded amplifiers to overcome passive losses in a 1.1 m long delay line. Since cascading multiple gain elements leads to ASE (noise) accumulation, reshaping elements in the form of saturable absorbers are integrated in the delay. Noise filtering in the buffer is investigated by simulating the eye diagram for a delay line with 1R regenerators and comparing it to that of a 2R regenerator. Finally, preliminary experimental data from the optical buffer is shown.

We present the design, fabrication and characterisation of wavelength selectors integrated on silicon-on-insulator (SOI) chips. The devices are able to select one out of 100 or 110 wavelength channels, that could each be modulated at 10 Gb/s. This represents an aggregate input data rate of 1 Tb/s. Wavelength selection is based on successive arrayed waveguide gratings (AWGs) and semiconductor optical amplifier (SOA) arrays hybrid integrated on SOI. The passed wavelength channel is coupled to a hybrid integrated photodiode. The sub-ns response time of the SOAs enables very fast wavelength selection that can be exploited in various communication applications.

SOI based MMIs prove to be versatile photonic structures for optical power splitting/combining, directional coupling, wavelength multiplexing/demultiplexing, etc. Such a structure benefits from relative ease of fabrication, low sensitivity to fabrication error and low temperature dependence. Whilst the majority of previous designs and optimizations investigated single MMIs, there is significant potential to combine MMIs within a single device for the realization of improved device performance. We have designed and simulated a wavelength filter device consisting of a series of MMIs with different lengths. The bandwidth, free spectral range, and extinction ratio can be controlled by changing the MMI's width and length. We have optimized our design to achieve a -3dB bandwidth of 5nm, a free spectral range of 60nm, an extinction ratio of >30dB, and a side peak suppression ratio of >22dB. Such a device can be used for high performance coarse wavelength filtering. The whole structure can fit into a 70μm×300μm area. Temperature sensitivity of the designed structures was also investigated.

In this paper, we present a highly compact silicon nano-membrane based optical phased array fabricated using conventional CMOS processing on silicon-on-insulator that provides for over 10 degrees of beam steering in a silicon slab at λ=1.55μm using transverse-electrical polarized light. A low loss 1-to-12 multi-mode interference (MMI) optical beam splitter with high uniformity is used to provide inputs to the optical phased array. Using an unequally spaced waveguide array permits us to relax the half-wavelength spacing requirement for large angle beam steering, thereby avoiding the optical coupling between adjacent waveguides and reducing the side-lobe-level of the array radiation pattern. S-bend waveguides convert the equally spaced MMI output to the unequally spaced wave guide array, while passively equalizing the phases of each array element to compensate for the MMI output phase profile. Independently controllable thin film metal heaters are used to achieve phase shifting using the strong thermo-optic response of silicon. Heat-insulating air grooves minimize thermal crosstalk, while also achieving and low power consumption.

Silicon photonics shows tremendous potential for the development of the next generation of ultra fast telecommunication, tera-scale computing, and integrated sensing applications. One of the challenges that must be addressed when integrating a "photonic layer" onto a silicon microelectronic circuit is the development of a wafer scale optical testing technique, similar to that employed today in integrated electronics industrial manufacturing. This represents a critical step for the advancement of silicon photonics to large scale production technology with reduced costs. In this work we propose the fabrication and testing of ion implanted gratings in sub micrometer SOI waveguides, which could be applied to the implementation of optical wafer scale testing strategies. An extinction ratio of over 25dB has been demonstrated for ion implanted Bragg gratings fabricated by low energy implants in submicron SOI rib waveguides with lengths up to 1mm. Furthermore, the possibility of employing the proposed implanted gratings for an optical wafer scale testing scheme is discussed in this work.

A ring resonator using a single 2×2 MMI as the coupler section has the distinct advantages of low sensitivity to fabrication error, temperature, wavelength and polarisation. However, the coupling coefficient of the 2×2 MMI coupler is fixed; hence, the performance of this type of device is limited, e.g. transmission spectrum with high extinction ratio is difficult to achieve. We have designed and simulated ring resonators with coupler sections consisting of two 2×2 MMIs and phase shifters, so that the coupling efficiency can be varied from 0% to 100% with relative ease. For a single ring resonator, the transmission spectrum can be controlled to achieve an extinction ratio of >20dB and a spectral bandwidth of <1nm. For a multiple ring filter, the transmission spectrum can be controlled to achieve an extinction ratio of >30dB and a bandwidth of <1nm; in addition, a flat-top transmission spectrum is also achievable. The whole device has a footprint of approximately 200μm by 100μm.

Miniaturization of quantum optical devices down to μm-dimensions and integration into fibre optical networks is a major prerequisite for future implementations of quantum information communication and processing applications. Also scalability, long-term stability and room-temperature operation are important properties of such devices. Lately there have been major improvements in down-sizing logical structures and functionalizing optical fibers. Here we present an alignment free, μm-scale single photon source consisting of a single quantum emitter on an optical fiber operating at room temperature. It easily integrates into fiber optic networks for quantum cryptography or quantum metrology applications. Near-field coupling of a single nitrogen-vacancy center is achieved in a bottom-up approach by placing a pre-selected nanodiamond directly on the fiber facet. Its high photon collection efficiency is equivalent to a far-field collection via an objective with a numerical aperture of 0.82. Furthermore, simultaneous excitation and recollection through the fiber is possible introducing a fiber-connected single emitter sensor that allows near-field probing with quantum mechanical properties.

The spin polarization of carriers in a direct-gap semiconductor is readily quantified by measuring the circular polarization of the recombination light luminescence. However, in silicon, owing to its indirect band-gap, such a direct connection between spin polarization and luminescence has been conspicuously absent. This missing link is established with a theory that provides intuitive relations for phonon-assisted optical transitions between the conduction and valence band edges. The theory is applied to explain recent experiments on spin injection in silicon and further elucidate its desirable spin-dependent properties.

We report the experimental observation and measurement of the polarized electroluminescence from an edge-emission Si based- organic light emitting device (OLED) with a Sm/Au or Sm/Ag cathode. Light collected from the OLED edge comes from the scattering of the surface plasmon polaritons (SPPs) at the device boundary. This experiment shows that such Si-OLED can be an electrically excited SPP source on a silicon chip for optical interconnect based on SPPs.

Raman scattering in planar silicon on insulator (SOI) waveguides with 2 μm width, 220 nm height and 2 cm length is investigated. A cw Nd:YAP laser at 1340.6 nm with 7 GHz FWHM spectral width is used as the pump source. A lensed fiber of 2.5 μm focus diameter is used to couple the pump laser into the waveguide. The coupling efficiency is estimated to be around 10%. Spontaneous Raman scattering is observed with as low as 2.5 mW pump power inside the waveguide. The spontaneous Raman spectrum is measured by an optical spectrum analyzer. The first order Raman peak is measured at around 1441.4 nm corresponding to a Raman shift of 15.6 THz, while the FWHM of Raman spectrum is measured as around 100 GHz. Maximum Raman output of around 90 pW is obtained by around 22 mW pump. The stimulated Raman gain coefficient is estimated as around 56 cm/GW from the relationship between spontaneous Raman output power and pump power. A temperature dependence of Raman frequency shift of about 0.6 GHz/K is measured. The spontaneous anti-Stokes Raman scattering output peak at 1253 nm is also observed with around 35 mW pump. Stimulated Raman amplification measurement is carried out with a SLED white light source as probe signal. With 35 mW pump power, around 0.6 dB gain has been determined with both pump and probe being TE polarized.

The HELIOS project is a European funded program which focuses on the development and integration of the different photonic and electronic building block components required to form high performance photonic circuits with a variety of functionality. One of the key photonic building block components central to most photonic applications is the optical modulator which is required to write data onto an optical carrier. Within the project two designs of carrier depletion based phase modulator are under development, together with a means of enhancing the modulation effect using slow wave and ring resonator based structures. In this work modulation results from the two phase shifters are presented along with passive results from related slow wave and resonator structures.

A new technique pertaining to the optical contactless chip-to-board communication using a commercially available CMOS technology is under development. The main concept is to use mid-IR light from a small LED which will enter an IC from the underside, impinge upon one or more pn-junctions and be reflected by a metallic sheet so that it falls on an external, discrete photodetector. After propagation through the doped semiconductor, the light undergoes attenuation due to free carrier absorption. By varying the reverse bias across the pn-junction(s), the depletion region widths are changed and therefore modulation of light intensity can be achieved. Through this scheme, data readout can be realized optically, thus alleviating the need for galvanic contacts (most notably wirebonds).

A high speed silicon electro-optic modulator is proposed based on a hybrid-lattice mode-gap resonator. The device surface area is only 10 μm by 4.5 μm and both injection and depletion mode operation have been studied. Our full 3D optical and electrical numerical result shows the device is capable of a modulation speed of 238 Gb/s at a 10 dB extinction ratio when it is operated in the depletion mode by an embedded P⁺PNN⁺ diode. More importantly, its energy consumption is ultra-low at 26.6 fJ per bit. The fabricated hybrid-lattice resonator demonstrates a resonance peak around 1600 nm with quality factor ~7800, which agrees well with the optical numerical results from 3D FDTD methods. The dynamic characterization of the device is still in progress. The compact device dimension and ultra-low energy consumption are favorable to high density photonic integration.

The workhorse of future high speed short reach interconnect technology will be the optical modulator. These devices in silicon have experienced dramatic improvements over the last 6 years and the modulation bandwidth has increased from a few tens of MHz to over 30 GHz. However, the demands of optical interconnects are significant. Hence, the need for devices with compact real estate, broadband characteristics, operating at high speed and working for both polarisation is of outmost importance. Here we describe the approach taken at Surrey to meet these requirements from the early days to the more recent work where some initial data are introduced. The recent all-silicon optical modulator uses a CMOS compatible fabrication and demonstrates high data rate with large extinction ratio for TE and TM polarisations. This technology is not only compatible with conventional complementary MOS (CMOS) processing, but is also intended to facilitate a high yield, reliable fabrication process.

The performance of an electro-optic modulator based on quantum confined Stark effect in a SiGe filled metal stub, coupled to an underlying Si-waveguide, is investigated using finite element simulations. The transmission of the system is controlled by changing the absorption coefficient of the material filling the stub, which modifies both the power transmitted by the stub itself and the field profile, and hence the coupling of this field into the single-mode output waveguide. An extinction ratio of ~8.5 dB with an insertion loss of ~8.5 dB can be achieved via electro-absorption derived from the quantum confined Stark effect (QCSE), assuming that the stub is filled with Ge/SiGe multiple quantum wells (MQWs) or Ge quantum dots (QDs) in a silicon matrix. With the sub-wavelength dimensions of the device offering low power operation and high switching speeds, the effect is of potential interest for application in silicon platform integrated photonics. Comparison is then made with an alternative class of plasmonic modulators based on metal-gap-dielectric structures, relying on the sensitivity of the gap plasmon mode losses near the mode cutoff to the precise refractive index profile, which can be changed via free carrier accumulation. These devices offer reduced insertion losses and, in contrast to the stub structures, their insertion loss and modulation depth scale with device length.

Hybrid silicon platform provides a solution to integrate active components (lasers, amplifiers, photodetectors, etc.) with passive ones on the same silicon substrate, which can be used for building an optical interconnect system. Owing to the advantages in footprint, power consumption, and high-speed modulation, hybrid silicon microring lasers have been demonstrated as a potential candidate for on-chip silicon light source. In this paper we review the progress to improve the performance of recently demonstrated compact microring lasers with ring diameter of 50 μm. A simple approach to enhance optical mode and electron-hole recombination, which results in threshold reduction and efficiency improvement is developed. This is done by appropriately undercutting the multiple quantum well (MQW) region to force carriers to flow towards the outer edge of the microring for better gain/optical mode overlap. We observe a reduction of the threshold of over 20% and up to 80% output power enhancement. The model and the experimental results highlight the benefits, as well as the negative effects from excessive undercutting, including lower MQW confinement, higher modal loss and higher thermal impedance. A design rule for MQW undercutting is therefore provided. Application as on-chip optical interconnects is discussed from a system perspective.

We report on the fabrication, characterization and integration of semiconductor microtube lasers on silicon. These microtubes are fabricating using standard photolithography techniques on epitaxially grown strained bilayer films, and show remarkable spectral properties attributable to whispering-gallery-mode type optical resonances. We have demonstrated coherent emission coupled to the optical microcavity modes in both GaAs/InGaAs and InGaAsP microtubes with embedded quantum dots. Furthermore, the GaAs/InGaAs microtubes have shown room temperature, continuous wave lasing. The microtubes can be transferred to any foreign substrate without affecting their optical properties. Work is in progress to couple the tubes with integrated silicon-on-insulator waveguides.

SiO₂ films have been widely applied in the production of electronic devices, integrated devices, optical thin film devices, sensors because of their desirable properties, such as good insulation, high light transmittance, strong corrosion resistance, good dielectric properties, etc. Amorphous silicon dioxide was fabricated by plasma enhanced chemical deposition on GaAs substrate. The thickness and refractive index are obtained by optical transmittance of the film, which are measured by ellipsometer. The deposition rate of the film and the refractive index are studied at different time, pressure, and the ratio of SiH₄/N₂O. The SiO₂ thin film growth rate remained basically unchanged versus time. The reaction chamber pressure, which make the SiO₂ thin film growth rate getting the peak, should be about 105Pa. But the SiO₂ thin film growth rate and the refractive index are anti-related. The enormous changes of the gas flow rate do not have huge impact to the response rate. However, the refractive index of SiO₂ thin film changed greatly when the SiH₄flow increased the refractive index of the thin films is highest when the ratio of SiH₄/N₂O is 200:20

We studied a characteristics trimming technique in Si photonic-wire waveguide devices. In order to trimming device properties, we utilized refractive index change of amorphous silicon when it crystallizes by annealing. We fabricated MZI devices with amorphous silicon waveguides, and demonstrated the trimming of the transmission spectra by thermal annealing and also laser annealing after finished the device fabrication process. We observed 5.2 % of the refractive index change owing to crystallization by annealing in a nitrogen atmosphere and 5.8% of change by laser crystallization.

We fabricated wavelength tunable laser diodes consisting of ring resonator wavelength filters with Si-wire waveguides. More than 45 nm wavelength tuning operation was obtained by about 100 mW heating power. We also measured spectral linewidth of the tunable laser, and observed about 200 kHz of spectral linewidth.

Two-dimensional (2D) photonic crystal (PC) bars with 6 and 21 periods were fabricated by simultaneous photoelectrochemical etching of macropores and trenches in a pre-patterned silicon wafer. The structures had square lattice of cylindrical pores and were terminated by nonmodulated silicon pre-layers. The infrared reflection spectra of the PC bars have been simulated using scattering matrix method. In order to take into account the roughness of pore inner surface an additional silicon layer around the pores was introduced with a fitted complex refractive index. A comparison between the simulated refection spectra and those obtained experimentally demonstrates a satisfactory agreement in the region of secondary photonic band gaps.

In this paper we present a Deformable Mirror (DM) based on the continuous voltage distribution over a resistive layer. This DM can correct the low order aberrations (defocus, astigmatism, coma and spherical aberration) using only three electrodes with nine contacts leading to an ideal device for sensorless applications. We present a mathematical description of the mirror, a comparison between the simulations and the experimental results. In order to demonstrate the effectiveness of the device we compared its performance with the one of a multiactuator DM of similar properties in the correction of an aberration statistics. At the end of the paper an example of sensorless correction is shown.