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Athermal operation of silicon waveguides for the TM and TE mode is achieved using the bridged subwavelength grating (BSWG) waveguide geometry. For the TM mode the experimental results show that the temperature-induced wavelength shift (dλ/dT) is an order of magnitude smaller for the BSWG waveguides with grating duty cycle, waveguide and bridge widths of 42%, 490 nm and 220 nm, respectively, as compared to standard photonics wires (PW). For the TE mode similar results are achieved by using the bridge width of 200 nm and similar duty cycle and waveguide width. A temperature-induced shift of only -2.5 pm/°C is reported for the TM polarized light. Propagation losses of BSWG waveguides for both polarizations were measured to be about 8 dB/cm, comparable to that of PWs. © 2012 SPIE., Photonics North 2012, June 6-8, 2012, Montreal, QC, Canada, Series: Proceedings of SPIE; no. 8412

We report on the ultraclean emission from single quantum dots embedded in pure wurtzite nanowires. Using a two-step growth process combining selective-area and vapor–liquid–solid epitaxy, we grow defect-free wurtzite InP nanowires with embedded InAsP quantum dots, which are clad to diameters sufficient for waveguiding at λ ∼ 950 nm. The absence of nearby traps, at both the nanowire surface and along its length in the vicinity of the quantum dot, manifests in excitonic transitions of high spectral purity. Narrow emission line widths (30 μeV) and very-pure single photon emission with a probability of multiphoton emission below 1% are achieved, both of which were not possible in previous work where stacking fault densities were significantly higher.

We investigate the picosecond switching capabilities of a planar waveguide interferometric photonic device when used for all-optical wavelength conversion of one picosecond pulses. Our device comprises a subwavelength grating waveguide arm and a photonic wire waveguide arm in a Mach–Zehnder configuration, fabricated on the silicon-on-insulator material platform. No detrimental effects of pulse broadening for transient pulses were observed.

This Letter introduces an enhanced cavity-waveguide coupling architecture based upon slow-light engineering in a two-port photonic crystal system. After analyzing the system transmittance using coupled-mode theory, the system is probed experimentally and shown to have increased transmittance due to the enhanced cavity-waveguide coupling. Such a coupling architecture may facilitate next-generation planar lightwave circuitry such as onchip quantum information processing or high precision light-matter sensing applications.

We report a silicon-on-insulator ring resonator biosensor array with one output port, using wavelength division multiplexing as the addressing scheme. With the use of on-chip referencing for environmental drift cancellation, simultaneous monitoring of multiplexed molecular bindings is demonstrated, with a resolution of 0.3 pg/mm(2) (40 ag of total mass) for protein concentrations over 4 orders of magnitude down to 20 pM. Reactions are measured over time periods as long as 3 h with high stability.

Biomarkers such as the neuron-specific enolase (NSE) have been proposed as potential prognostic markers following traumatic brain injury (TBI) [1,2]. However, the use of NSE is not currently recommended for prognostic evaluation. Our objective was to systematically review the prognostic value of NSE levels following moderate or severe TBI.

We demonstrate a new microphotonic waveguide principle based on subwavelength gratings. We also present several practical implementations of subwavelength waveguides, including a microphotonic fiber-chip coupler with a coupling loss as small as -0.3 dB, a waveguide crossover with an excess loss of 0.02dB/crossing and a PDL of, 7th IEEE International Conference on Group IV Photonics (GFP), September 1-3, 2010, Beijing, China

The ability to control the nucleation site of a single quantum dot will have a profound effect on the development of quantum dot-based photonic devices. The deterministic approach will provide a truly scalable technology that can take full advantage of conventional semiconductor processing for device fabrication. In this review, we discuss the progress towards the integration of deterministically nucleated single quantum dots with top-down quantum optical devices targeting telecommunication wavelengths. Advances in site-controlled quantum dot nucleation using selective-area epitaxy now makes it possible to position quantum dots at predetermined positions on a substrate in registry with alignment markers. This, in turn, has allowed for devices fabricated in subsequent processing steps to be aligned to individual quantum dots. The specific devices being targeted are gated-single dots and coupled dot-cavity systems which are key components of efficient sources of single photons and entangled photon pairs.

We report on the experimental demonstration and analysis of a new waveguide principle using subwavelength gratings. Unlike other periodic waveguides such as line-defects in a 2D photonic crystal lattice, a subwavelength grating waveguide confines the light as a conventional index-guided structure and does not exhibit optically resonant behaviour. Subwavelength grating waveguides in silicon-on-insulator are fabricated with a single etch step and allow for flexible control of the effective refractive index of the waveguide core simply by lithographic patterning. Experimental measurements indicate a propagation loss as low as 2.1 dB/cm for subwavelength grating waveguides with negligible polarization and wavelength dependent loss, which compares favourably to conventional microphotonic silicon waveguides. The measured group index is nearly constant n(g) ~1.5 over a wavelength range exceeding the telecom C-band.

We demonstrate an ultracompact polarization mode converter based on a silicon-on-insulator waveguide with two longitudinal subwavelength trenches. An extinction ratio of 16 dB at 1.5 μm is achieved for a device length of 10 μm. © 2012 OSA., 2012 Conference on Lasers and Electro-Optics, CLEO 2012, 6 May 2012 through 11 May 2012, San Jose, CA

Results of experimental study of multiexcitonic emission related to the p-shell of single self-assembled InAs/GaAs quantum dots are presented. Optical properties of a first emission line to appear from the p-shell of a strongly excited quantum dots are investigated using low-temperature polarization- sensitive micro-photoluminescence measurements. The emission line is attributed to the recombination of a complex of three electrons and holes confined in a dot (neutral triexciton), 3X. It is found that the emission consists of two linearly polarized components and the fine structure splitting is larger than the respective splitting of a neutral exciton. The optical anisotropy of the 3X emission is related to the anisotropy of the quantum dot localizing potential. The axis of the 3X optical anisotropy changes from dot to dot covering broad range within ±50 degrees with respect to the axis defined by the optical anisotropy of a neutral exciton (X). Possible origin of the deviation is discussed.

We review our advances in diffractive and subwavelength grating coupler structures for microphotonic waveguides. We present a subwavelength grating fiber-chip edge coupler with a loss as low as 0.9 dB and with minimal wavelength dependence over a broad wavelength range exceeding 200 nm. We also present fiber-to-chip surface grating couplers based on subwavelength effective medium. The effective medium refractive index is engineered to control the strength of the grating and thereby maximize coupling efficiency, while mitigating back reflections at the same time. We analyze the fabrication tolerances of the coupler, which are of particular relevance for large scale photonic fabrication. Furthermore, we present the first grating coupler for micrometric silicon rib waveguides, which is particularly challenging since the coupler waveguide region is multimode. We experimentally demonstrate grating couplers in 1.5 μm thick silicon ridge waveguides with a coupling efficiency of 2.2 dB and a 3 dB bandwidth of 40 nm. An inverse taper is used to match the fundamental mode of the interconnection waveguide with the optimum grating coupler excitation field, with negligible higher order mode excitation. The coupler was fabricated using i-line stepper lithography and single etch step. © 2012 IEEE., 14th International Conference on Transparent Optical Networks, ICTON 2012, 2 July 2012 through 5 July 2012, Coventry

The fabrication and experimental characterisation of a two-stage bandpass filter based on curved waveguide sidewall gratings is reported for the silicon-on-insulator platform. At each cascaded filtering stage, the spectral components of the input signal are dispersed by the diffraction grating formed in the sidewall of a silicon strip waveguide. Different wavelengths are focused onto different positions along the Rowland circle and the filter central wavelength is selected by a specific receiver waveguide. By using two consecutive filtering stages, both the filter passband profile and the stopband rejection ratio are substantially increased. The grating is apodised and chirped to ensure a constant effective index along the grating length to minimise phase distortions. Blazed geometry is used to maximise the diffraction efficiency to the - 1st order. The device was fabricated with electron beam lithography and reactive ion etching using a single etch step. A bandwidth of 6.2 nm was measured near 1590 nm for the fabricated filter, with a roll-off of 4 dB/nm at the passband edge, and a stopband rejection of 40 dB.

We experimentally demonstrate a new type of waveguide multiplexer device designed for silicon photonics, with a crosstalk level as low as -35 dB and an operational wavelength range of 300 nm. A compact device footprint of only 100 × 160 μ m 2 offers an excellent potential for integration with other silicon nanophotonic circuits. © 2012 Optical Society of America.

Silicon photonic wire waveguides are usually highly birefringent, so they are generally designed to operate for one particular polarization. For commonly used waveguides with a silicon thickness of 220 nm, TE polarization is preferred since TM is only weakly guided. For waveguides with a silicon thickness larger than 250 nm, both TE and TM polarizations have been employed. Overall, the choice of polarization has largely appeared arbitrary. In this presentation we review the pertinent polarization-dependent waveguide properties, including losses, back-reflection, polarization conversion and fabrication tolerances, with the intent to suggest guidelines for choosing the proper polarization. Through experimental evidence, we show that TM polarization has several important advantages and can support high performance resonators with a radius down to 2 μm. © 2012 SPIE., Silicon Photonics VII, January 22-25, 2012, San Francisco, CA, USA, Series: Proceedings of SPIE; no. 8266

We present a method of engineering the waveguide core refractive index locally on a silicon photonic chip using subwavelength gratings. Applications such as efficient waveguide crossings, fiber-chip couplers and multiplexer circuits are discussed., The 2011 Photonics Society Winter Topicals, Keystone, Colorado, January 10-12, 2011

We use subwavelength gratings (SWGs) to engineer the refractive index in microphotonic waveguides, including practical components such as input couplers and multiplexer circuits. This technique allows for direct control of the mode confinement by changing the refractive index of a waveguide core over a range as broad as 1.6-3.5 by lithographic patterning. We demonstrate two experimental examples of refractive index engineering, namely, a microphotonic fiber-chip coupler with a coupling loss as small as -0.9dB and minimal wavelength dependence and a planar waveguide multiplexer with SWG nanostructure, which acts as a slab waveguide for light diffracted by the grating, while at the same time acting as a lateral cladding for the strip waveguide. This yields an operation bandwidth of 170nm for a device size of only approximately 160microm x100microm.

Optoelectronic devices based on single, self-assembled semiconductor quantum dots are attractive for applications in secure optical communications, quantum computation and sensing. In this paper we show how it is possible to dictate the nucleation site of individual InAs/InP quantum dots using a directed self-assembly process, to control the electronic structure of the nucleated dots and also how to control their coupling to the optical field by locating them within the high field region of a photonic crystal nanocavity. For application within fiber networks, these quantum dots are targeted to emit in the spectral region around 1550 nm., Quantum Sensing and Nanophotonic Devices VII, January 24, 2010, San Francisco, California, USA

Our progress in subwavelength structures in silicon waveguides is reviewed. Several practical implementations of subwavelength grating waveguides are discussed, including fibre-chip couplers, waveguide crossings and athermal waveguides. © 2011 IEEE., 8th IEEE International Conference on Group IV Photonics, GFP 2011, 14 September 2011 through 16 September 2011, London

In this paper, athermal subwavelength grating (SWG) waveguides are investigated. Both numerical simulations and experimental results show that a temperature independent behaviour can be achieved by combining two materials with opposite thermo-optic coefficients within the waveguide. SU-8 polymer with a negative thermo-optic coefficient (dn/dT = -1.1×10-4 K -1) is used in our silicon SWG waveguides to compensate for silicon's positive thermo-optic coefficient of 1.9×10-4 K-1. The grating duty ratio required to achieve an athermal behavior is reported to vary as a function of the operating wavelength and the waveguide dimensions. For example, for athermal waveguides of 260 nm in height, duty ratios of 61.3% and 83.3% were calculated for TE and TM polarized light respectively for a 450 nm wide waveguide, compared to ratios of 79% and 90% for a 350 nm wide waveguide. It is also reported that with increasing width, and increasing height, a smaller grating duty ratio is necessary to achieve an athermal behaviour. A smaller fraction of silicon would hence be needed to compensate for the polymer's negative thermo-optic effect in the waveguide core. Subwavelength sidewall grating (SWSG) waveguides are also proposed here as alternatives to high duty ratio SWG waveguides that are required for guiding TM polarized light. Assuming a duty ratio of 50%, the width of the narrow segments for temperature- independent behavior is found by numerical simulations to be 125 nm and 143 nm for TE and TM polarized light, respectively. © 2011 Copyright Society of Photo-Optical Instrumentation Engineers (SPIE)., Photonics North 2011, May 16-18, 2011, Ottawa, Ontario, Canada, Series: Proceedings of SPIE; no. 8007

A complete instrumentation system for interrogating silicon photonic wire waveguide sensor array chips has been built and demonstrated. The system is designed to read 16 or more photonic wire sensors on a single silicon chip simultaneously and in real time, while delivering sample fluid to the sensors through microfluidic channels fabricated monolithically on the chip. The chip can be inserted into the instrument, automatically aligned with input optics and fluid connection, and be ready for measurement in a few minutes. © 2011 IEEE., 8th IEEE International Conference on Group IV Photonics, GFP 2011, 14 September 2011 through 16 September 2011, London

I integrated photonic circuits, the refractive-index contrast is usually set by the choice of the material platform. For example, for silicon photonic circuits operating at a wavelength near l= 1.55 μm, the waveguide core and the cladding indices are given by the material constants of silicon (n = 3.5) and silicon dioxide (n = 1.44), and waveguide devices must be designed within the constraint of these fixed values. From free-space optics, we know that periodic dielectric structures with a periodicity smaller than one half of the wavelength do not diffract any light. Instead, such so-called subwavelength gratings (SWGs) act as homogeneous effective media with spatially averaged refractive index.1 We have recently demonstrated the first use of SWGs for refractive-index engineering in microphotonic waveguides, providing a powerful method for controlling the refractive index of a waveguide core in any specific location of a photonic chip. Importantly, our method only relies on standard fabrication techniques and can be implemented without any modifications to the chip fabrication process flow. The structure shown in (a) exemplifies refractive-index engineering of a silicon photonic wire waveguide. By etching periodic gaps of a well-defined width w and pitch L into a standard silicon photonic wire, an SWG waveguide is formed with an effective core index determined by the duty ratio w/L. Calculation of the dispersion relation of the segmented waveguide and comparison with the dispersion of an equivalent photonic wire waveguide with identical cross section and a core index of n = 2.65, as shown in (b) confirms theoretically the concept of spatial refractive-index averaging. Experimentally, we have observed waveguiding in such SWG structures with a propagation loss as low as 2.1 dB/cm, comparable to the best photonic wire waveguides reported, and with a low and nearly wavelengthindependent group index, as predicted by theory.2 Although consistent with Bloch theory, it is fascinating to observe light propagating almost unperturbedly through so many strong discontinuities.3 Among the applications of SWG waveguides4 is an SWG slab waveguide structure that simultaneously acts as a lateral cladding for a photonic wire waveguide in a novel microspectrometer design and an efficient in-plane fiberchip coupling structure. The coupler structure works by gradual modification of the waveguide core index, leading to mode-size transformation between a high-index photonic wire and the lowindex optical fiber. Measured coupling loss is 0.9 dB for TE and 1.2 dB for TM polarization. SWG waveguides were also implemented for highly efficient waveguide crossings,5 such as those shown in (c). (a) SEM image of an SWG waveguide. (b) Dispersion relation of an SWG waveguide and an equivalent photonic wire waveguide with core refractive index of 2.65 (TE polarization). (c) SWG waveguide crossings. (a)

We report on the experimental demonstration of ultrafast all-optical switching and wavelength down-conversion based on a novel nonlinear Mach-Zehnder interferometer with subwavelength grating and wire waveguides. Unlike other periodic waveguides such as line-defects in a 2D photonic crystal lattice, a subwavelength grating waveguide confines the light as a conventional index-guided structure and does not exhibit optically resonant behaviour. Since the device had no dedicated port to input optical signal to control switching a new approach was also implemented for all-optical switching control. © 2011 Optical Society of America.

Type-I interband laser diodes were developed for trace gas sensing applications in the 2–4um wavelength range. The devices were grown by molecular beam epitaxy on GaSb substrates using InGaAsSb/Al(In)GaAsSb active regions. Tunable, single-mode lasers were produced using distributed feedback grating processing or by incorporating Fabry-Perot lasers in an external cavity configuration. Sensitive gas detection was demonstrated using these lasers in tunable-diode laser absorption spectroscopy.

Photonic wire evanescent field (PWEF) sensor chips have been developed for multiplexed label free molecular detection. The sensors are made using 260 nm ×450 nm cross-section silicon waveguides folded into spirals less than 200 μm in diameter, but with an overall sensor length of more than a millimeter. The long propagation length gives a response to molecular binding much better than currently available tools for label-free molecular sensing. These sensors can be arrayed at densities up to ten or more per square millimeter. This talk reviews our ongoing work on the photonic wire sensor chip design and layout, on-chip integrated fluidics, optical coupling, and chip interrogation using arrays of grating couplers formed using sub-wavelength patterned structures. The goal is to develop a commercially viable sensor platform by addressing cost-of-instrumentation, cost per measurement, ease-of-use, and by increasing the number of sensors that can be simultaneously monitored. © 2011 IEEE., 2011 ICO International Conference on Information Photonics, IP 2011, 18 May 2011 through 20 May 2011, Ottawa, ON

We present a medium-dependent quantum optics approach to describe the influence of electron-acoustic phonon coupling on the emission spectra of a strongly coupled quantum-dot cavity system. Using a canonical Hamiltonian for light quantization and a photon Green function formalism, phonons are included to all orders through the dot polarizability function obtained within the independent Boson model. We derive simple user-friendly analytical expressions for the linear quantum light spectrum, including the influence from both exciton and cavity-emission decay channels. In the regime of semiconductor cavity-QED, we study cavity emission for various exciton-cavity detunings and demonstrate rich spectral asymmetries as well as cavity-mode suppression and enhancement effects. Our technique is nonperturbative, and non-Markovian, and can be applied to study photon emission from a wide range of semiconductor quantum dot structures, including waveguides and coupled cavity arrays. We compare our theory directly to recent and apparently puzzling experimental data for a single site-controlled quantum dot in a photonic crystal cavity and show good agreement as a function of cavity-dot detuning and as a function of temperature., Comment: Regular Paper, Submitted to PRB, Dec, 2010

We describe two different approaches to growing precisely positioned InP nanowires on InP wafers. Both of these approaches utilize the selective area growth capabilities of Chemical Beam Epitaxy, one using the Au catalysed Vapour-Liquid-Solid (VLS) growth mode, the other being catalyst-free. Growth is performed on InP wafers which are first coated with 20 nm of SiO 2. These are then patterned using e-beam lithography to create nanometer scale holes in the SiO 2 layer to expose the InP surface. For the VLS growth Au is then deposited into the holes in the SiO 2 mask layer using a self-aligned lift-off process. For the catalyst-free growth no Au is deposited. In both cases the deposition of InP results in the formation of InP nanowires. In VLS growth the nanowire diameter is controlled by the size of the Au particle, whereas when catalyst-free the diameter is that of the opening in the SiO 2 mask. The orientation of the nanowires is also different, B when using Au particles and A when catalyst-free. For the catalysed growth the effect of the Au particle can be turned off by modifying growth conditions allowing the nanowire to be clad, dramatically enhancing the optical emission from InAs quantum dots grown inside the nanowire. © 2011 Copyright Society of Photo-Optical Instrumentation Engineers (SPIE)., Quantum Dots and Nanostructures: Synthesis, Characterization, and Modeling VIII, January 25-26, 2011, San Francisco, CA, USA, Series: Proceedings of SPIE; no. 7947

In this paper, we present experimental results from site-selected single quantum dots that have undergone a number of intermixing process steps via rapid thermal annealing. We show that the intermixing process blueshifts the dot's emission spectrum without affecting the linewidth as well as decreasing its biexciton binding energy and s-p shell spacing. The anisotropic exchange splitting is shown to have undergone a sign inversion implying that the splitting had gone through zero. Intermixing provides another nanoengineering tool for the design of scalable solid-state photon and entangled photon pair sources. © 2011 Copyright Society of Photo-Optical Instrumentation Engineers (SPIE)., Quantum Dots and Nanostructures: Synthesis, Characterization, and Modeling VIII, January 25-26, 2011, San Francisco, CA, USA, Series: Proceedings of SPIE; no. 7947

We review recent advances in subwavelength and diffractive structures in planar waveguides. First, we present a new type of microphotonic waveguide, exploiting the subwavelength grating (SWG) effect. We demonstrate several examples of subwavelength grating waveguides and components made of silicon, operating at telecom wavelengths. The SWG technique allows for engineering of the refractive index of a waveguide core over a range as broad as 1.5-3.5 simply by lithographic patterning using only two materials, for example Si and SiO2. This circumvents an important limitation in integrated optics, which is the fixed value of the refractive indices of the constituent materials in the absence of an active tuning mechanism. A subwavelength grating fibre-chip microphotonic coupler is presented with a loss as low as 0.9 dB and with minimal wavelength dependence over a broad wavelength range exceeding 200 nm. It is shown that the SWG waveguides can be used to make efficient waveguide crossings with minimal loss and negligible crosstalk. We also present a diffractive surface grating coupler with subwavelength nanostructure, that has been implemented in a Si-wire evanescent field biological sensor. Furthermore, we discuss a new type of planar waveguide multiplexer with a SWG engineered nanostructure, yielding an operation bandwidth exceeding 170 nm for a device size of only 160 μm × 100 μm., Integrated Optics: Devices, Materials, and Technologies XV, January 24-26, 2011, San Francisco, CA, USA, Series: Proceedings of SPIE; no. 7941

We are developing a photonic wire evanescent field (PWEF) sensor chip using 260 nm x 450 nm cross-section silicon photonic wire waveguides. The waveguide mode is strongly localized near the silicon surface, so that light interacts strongly with molecules bound to the waveguide surface. The millimeter long sensor waveguides can be folded into tight spiral structures less than 200 micrometers in diameter, which can be arrayed at densities up to ten or more independent sensors per square millimeter. The long propagation length in each sensor element gives a response to molecular binding much better than currently available tools for label-free molecular sensing. Cost of instrumentation, cost per measurement, ease-of-use, and the number of sensors that can be simultaneously monitored on a sensor array chip are equally important in determining whether an instrument is practical for the end user and hence commercially viable. The objective of our recent work on PWEF sensor array chips and the associated instrumentation is to address all of these issues. This conference paper reviews our ongoing work on the photonic wire sensor chip design and layout, on-chip integrated fluidics, optical coupling, and chip interrogation using arrays of grating couplers formed using sub-wavelength patterned structures. © 2011 Copyright Society of Photo-Optical Instrumentation Engineers (SPIE)., SPIE BiOS, January 22-23, 2011, San Francisco, CA, USA, Series: Proceedings of SPIE; no. 7888

Self-assembled semiconductor quantum dots show great potential as efficient semiconductor-based non-classical light sources. However, due to the very nature of the self-assembled growth process, the characteristics of individual dots can vary widely and their spatial location is generally uncontrolled. Using a directed self-assembly process, the nucleation site of single quantum dots are designed through lithography. The site-control is used to facilitate the spatial alignment of single quantum dots to high finesse optical microcavities. The single dot-cavity device is a unique system to study the dot-cavity coupling where the presence of background emitters can be unambiguously ruled out. © 2011 IEEE., 2011 ICO International Conference on Information Photonics, IP 2011, 18 May 2011 through 20 May 2011, Ottawa, ON

We present a method for designing temperature independent silicon waveguide devices using the subwavelength grating effect. Photonic wire waveguides are patterned with periodic gaps and filled with SU-8 polymer to cancel the silicon thermo-optic effect., Integrated Photonics Research, Silicon and Nanophotonics, 12–15 June 2011, Toronto, ON, Canada

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., Silicon Photonics VI, January 23-26, 2011, San Francisco, CA, USA, Series: Proceedings of SPIE; no. 7943

In this paper we focus on the discussion of two recent unique applications of the finite-difference time-domain (FDTD) simulation method to the design and modeling of advanced nano- and bio-photonic problems. The approach that is adopted here focuses on the potential of the FDTD methodology to address newly emerging problems and not so much on its mathematical formulation. We will first discuss the application of a traditional formulation of the FDTD approach to the modeling of sub-wavelength photonics structures. Next, a modified total/scattered field FDTD approach will be applied to the modeling of biophotonics applications including optical phase contrast microscope (OPCM) imaging of cells containing gold nanoparticles (NPs) as well as its potential application as a modality for in vivo flow cytometry configurations. The conclusion provides a justification for the selection of the two specific examples and summarizes some of the insights that could open the opportunity for the application of the FDTD approach in new research areas. © 2011 Elsevier B.V. All rights reserved.

We review our work on silicon wire devices designed for evanescent field sensor arrays and ultra-compact dense optical comb filters, both taking advantage of a spiral cavity resonator design. Two sensor array configurations are described, and monitoring of biomolecular binding is demonstrated with a detection limit of 0.3 pg/mm2. On-chip temperature drift compensation is achieved by using a reference resonator. A novel grating coupler using subwavelength structures facilitates the coupling of light between the optical fiber and waveguide chips.

Micro-photonic SOI Mach-Zehnder interferometers were coated with solid-phase micro-extraction materials derived from polydimethylsiloxane to enable sensing of volatile organic compounds of the BTEX class in air. A different coating based on functionalized mesoporous silicates is used to detect lead Pb(II) with a detection limit of < 100 ppb in water.

We report on the design, simulation and experimental demonstration of a new type of waveguide crossing based on subwavelength gratings in silicon waveguides. We used 3D finite-difference time-domain simulations to minimize loss, crosstalk and polarization dependence. Measurement of fabricated devices show that our waveguide crossings have a loss as low as −0.023 dB/crossing, polarization dependent loss of < 0.02 dB and crosstalk

Site-selective epitaxy is used to deterministically control the nucleation site of a single quantum dot. A photonic crystal cavity is fabricated at the dot site for a true single quantum dot-cavity system which, by design, contains no background emitters. Cavity tuning at fixed temperature is used to measure the dot-cavity coupling over a large $(g15\text{ }\text{meV})$ detuning range using nonresonant excitation. The low-excitation spectra are modeled using a master equation model based on incoherent excitation. We find that pure phonon dephasing alone does not account for the observed nonresonant cavity emission and an additional cavity feeding mechanism, consistent with phonon-assisted dot-cavity coupling, must be included to reproduce the experimental spectra.

The gain media of the quantum dot lasers consist of InAs QDs in an InGaAsP matrix on an InP substrate. The quantum dot lasers have different free spacing ranges (FSRs) corresponding to Fabry-Perot (F-P) cavity lengths. A silicon ring resonator and a QD laser have been combined to form comb laser. The output characteristics of the combined comb laser were investigated. The measured FSR was about 2.8nm and the extinction ratio was about 10(dB) when the FSR of the QD laser was about 0.4nm and the FSR of the ring resonator was about 0.47nm. The experimental results show that the ring resonator had a strong control on the FSR and extinction ratio of the comb laser.

We report on a new waveguide principle using subwavelength gratings. It is known that diffraction effects are suppressed for waves propagating in materials structured at the subwavelength scale. Subwavelength gratings can create artificial media engineered using microscopic inhomogeneities to enact effective macroscopic behaviour. For the high-index-contrast waveguides, a subwavelength grating can be created by the combination of high-refractive-index and low-refractive-index materials, for example single crystal silicon and amorphous silica in silicon-on-insulator platform. These periodic structures frustrate diffraction provided they operate outside the Bragg condition and behave like a homogeneous medium. In a subwavelength grating (SWG) waveguide with a core consisting of a periodic arrangement of segments (Fig. 1), light excites a Bloch mode, which can theoretically propagate through the SWG waveguide with minimal scattering losses. Unlike other periodic waveguides such as line-defects in a 2D photonic crystal lattice, a subwavelength grating waveguide confines the light like a conventional index-guided structure and does not exhibit optically resonant behaviour.

Background Healthcare professionals are increasingly using wikis as collaborative tools to create, synthesize, share, and disseminate knowledge in healthcare. Because wikis depend on collaborators to keep content up-to-date, healthcare professionals who use wikis must adopt behaviors that foster this collaboration. This protocol describes the methods we will use to develop and test the metrological qualities of a questionnaire that will assess healthcare professionals' intentions and the determinants of those intentions to use wiki-based reminders that promote best practices in trauma care. Methods Using the Theory of Planned Behavior, we will conduct semi-structured interviews of healthcare professionals to identify salient beliefs that may affect their future use of wikis. These beliefs will inform our questionnaire on intended behavior. A test-retest of the survey will verify the questionnaire's stability over time. We will interview 50 healthcare professionals (25 physicians and 25 allied health professionals) working in the emergency departments of three trauma centers in Quebec, Canada. We will analyze the content of the interviews and construct and pilot a questionnaire. We will then test the revised questionnaire with 30 healthcare professionals (15 physicians and 15 allied health professionals) and retest it two weeks later. We will assess the internal consistency of the questionnaire constructs using Cronbach's alpha coefficients and determine their stability with the intra-class correlation (ICC). Discussion To our knowledge, this study will be the first to develop and test a theory-based survey that measures healthcare professionals' intentions to use a wiki-based intervention. This study will identify professionals' salient beliefs qualitatively and will quantify the psychometric capacities of the questionnaire based on those beliefs.

We discuss several applications of both resonant and non-resonant subwavelength gratings (SWGs) for silicon photonics. We present results of evanescent field molecular sensing using the transverse magnetic mode of a 0.22 mm thick silicon slab waveguide with a resonant SWG, which couples a free space laser beam to the silicon waveguide mode. The optical readout of this configuration is almost identical to the established surface plasmon resonance sensing technology. Using calibrated sucrose solutions, we demonstrate a bulk refractive index sensitivity of 111 nm/RIU in good agreement with rigorous coupled wave analysis calculations. The binding of a monolayer of streptavidin protein on the waveguide surface is monitored in real time with a signal-to-noise ratio of ~500. In another application, non-resonant SWGs are used to create effective dielectric media with a refractive index that can be tuned between the values of silicon (3.48) and SU-8 polymer used for the cladding (1.58). For example, we present SWG waveguides with an effective core index of approximately 2.65, which exhibit lower propagation loss than photonic wire waveguides of similar dimensions. We use these SWG waveguides to demonstrate highly efficient fiber-chip couplers., Silicon Photonics V, January 24-27, 2010, San Francisco, California, USA, Series: SPIE Proceedings

We present development of a compact, robust, waveguide Fourier-transform microspectrometer for high-resolution and high-throughput spectroscopy in space-based applications. The prototype device is being developed to monitor water vapor in the atmosphere from a micro-satellite platform. The instrument is based on a unique slab waveguide spatial heterodyne spectrometer (SHS) chip fabricated at the National Research Council Canada in silicon-on-insulator (SOI) technology.

Optoelectronic devices based on single, self-assembled semiconductor quantum dots are attractive for applications in secure optical communications, quantum computation and sensing. In this paper we show how it is possible to dictate the nucleation site of individual InAs/InP quantum dots using a directed self-assembly process, to control the electronic structure of the nucleated dots and also how to control their coupling to the optical field by locating them within the high field region of a photonic crystal nanoocavity. For application within fiber networks, these quantum dots are targeted to emit in the spectral region around 1550nm.

We report multiplexed label-free measurements of biomolecular interactions using silicon wire waveguide sensor arrays. The sensors are addressed using both wavelength division multiplexing and power broadcasting approaches. We demonstrate the real-time monitoring of antibody-antigen reactions using complementary and mismatched IgG receptor-analyte pairs and bovine serum albumin. The measured level of detection for each sensor element corresponds to a surface coverage of less than ~ 0.02% of a protein, OSA Integrated Photonics Research, Silicon and Nanophotonics (IPRSN), July 26-28, 2010, Monterey, USA

A new optical waveguide principle is proposed, exploiting subwavelength grating effect. We demonstrate first subwavelength grating waveguides, including practical components such as highly efficient fibre-chip couplers, waveguide crossings and microspectrometer chips.