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We demonstrate a silicon nanowire based radio frequency spectrum analyser based on cross-phase modulation. We show that the device is accurate, with cross-chirp from photogenerated free-carriers negligible and measure RF spectra for 640Gbaud on-off-keyed data., 2010 36th European Conference and Exhibition on Optical Communication, ECOC 2010, September 19-23, 2010, Torino, Italy

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

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.

This invited paper presents several passive devices containing long silicon photonic wires condensed into spirals. These devices present a large density factor due to their high ratio length over area that improves at the same time their efficiency and fabrication cost. The talk will present the basic equations of the waveguide shape as well as the design and performance of four passive devices under development at the Institute for Microstructural Sciences of the National Research Council Canada.

A method is developed for extracting the coupling and loss coefficients of ring resonators from the peak widths, depths, and spacings of the resonances of a single resonator. Although the formulas used do not distinguish which coefficient is coupling and which is loss, it is shown how these coefficients can be disentangled based on how they vary with wavelength or device parameters.

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 an SOI biosensor microarray chip that allows multiple molecular binding reactions to be simultaneously monitored. The individual biosensors are formed using 0.26 × 0.45 μm 2 silicon photonic wire waveguides, which are arranged in compact Mach-Zehnder interferometer geometries with near temperature independent response. The sharp bend radius permitted by the photonic wires is exploited to form dense spiral waveguide structures that provide several millimeters of path length in a compact 130 μm diameter circular area. This design provides the high sensitivity of a long waveguide, while maintaining compatibility with commercial microarray spotting tools. For low volume analyte delivery the sensor array chip contains a monolithically integrated microfluidic channel formed in an SU-8 overlayer. Multiple antibody-antigen reactions are observed in real-time by using an infrared camera to monitor the optical powers emerging from the sensor array output waveguides.

We calculate the π-power and rise time for several 1×1 y-branch MZI SOI thermo-optic switches as a function of device size. These switches consist of waveguide core thickness ranging from 10 to 0.22 μm. Upon scaling the core thickness, the best power and speed performance occurs at 0.7 μm. Further miniaturization results in an increased power and reduced speed, mainly due to the mode expansion from the core into the cladding. We show that varying the MZI arm separation is an effective approach to improve the performance of miniaturized thermo-optic switches.

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.

We show that thin silicon-on-insulator (SOI) microphotonic waveguides offer significant advantages over other material platforms for the applications of biological and chemical sensing. The high index contrast inherent to SOI waveguides allow an extremely large yet highly localized electric field to be supported in the evanescent tail of the waveguide mode, ideal for the probing of thin biological layers. Various sensing geometries including Mach-Zehnder interferometers and high quality factor ring resonators have been designed and fabricated and their performance is presented. SOI sensors are shown to be capable of providing higher intrinsic sensitivity over comparable sensor designs reported in all other lower index contrast planar waveguide material systems. Finally, the device design conditions for optimized sensitivity are examined for the sensing of both bulk solutions and thin adsorbed biomolecular layers.

We review recent advances in silicon photonic arrayed waveguide grating and sub-wavelength grating devices developed at the NRC Canada. We present three original microspectrometer concepts, namely a compact 50 channel AWG microspectrometer with a spectral resolution of 1 A and a total chip size of 8 x 8 mm", a Fourier- transform AWG with a markedly increased light gathering capability compared to conventional AWG devices, and an AWG with a resolution significantly increased by inserting a triangular photonic crystal waveguide region in the phased array. Various new sub-wavelength grating waveguide structures will also be presented, including monolithic fibre-chip couplers, anti-reflective waveguide facets and mirrors.

We demonstrate experimentally and by simulations the use of subwavelength grating patterns on the facets of planar waveguides as a means of modifying facet reflectivity over a wide range of values, from antireflective to highly reflective. An antireflective structure can be obtained from a gradient index effect with triangular gratings. Square gratings can be used to obtain either antireflective or highly reflective facets by an interference effect. Finite difference time domain simulations and calculations based on effective medium theory show that reflectivities well below 1% can be achieved with triangular gratings. Experimentally, facet reflectivities as low as 2.0% and 2.4% for the fundamental TE and TM waveguide modes, respectively, are demonstrated for light of 1.55 μm wavelength in silicon-on-insulator ridge waveguides. The experimental results are in good agreement with both effective medium theory and finite difference time domain simulations. The polarization dependence of the effects is also discussed in detail.

This paper reviews theory and experiments on silicon photonic wire waveguide evanescent field (PWEF) biosensors. Theoretical conside- rations and supporting calculations show that sensor response increases both with increasing core-cladding refractive index contrast, and with decreasing waveguide core thickness until a maximum sensor response is achieved. As a result, appropriately designed Si waveguide sensors can have the largest response to superstrate refractive index shifts, and also to surface molecular adsorption, of any commonly available waveguide system. Measurements of Si waveguide sensor response to fluid index change and biotin-avidin binding reactions confirm the predictions of theory.

Photonics is playing an increasingly important role in the field of medical diagnostics, genomics and drug discovery. With the advances in molecular biology which gives insight to the processes underlying diseases and drug response, there is a need for new biological sensors to rapidly detect and quantify these processes. Sensing of biological events using planar waveguide evanescent field (EVF) detection offers label-free, high sensitivity, and real time monitoring [1-4]. This is a competing technology with the commercially pervasive SPR (surface plasmon resonance) method, but with the advantage of portability and low cost.

We demonstrate a novel SOI photonic wire ring resonator that uses a MMI coupler which has a compact size of 3times9 mum2 The resonators exhibited quality factor of 5000, and resonance depth of 20 dB

Silicon photonic wire waveguides have a remarkably high response to surface molecular binding. Evanescent field waveguide sensors based on silicon can be interrogated using Mach-Zehnder interferometers, ring resonators, or by probing surface gratings in a reflection geometry. This paper compares these approaches from a theoretical viewpoint and through recent experimental results, with the goal of defining a path from our existing individual sensors to practical biosensor array chips.

We report a SOI ring resonator biosensor array with 1 reference ring and 4 sensing rings, using WDM as the addressing scheme. On-chip referencing and temperature shift cancellation are demonstrated, and the differential signal shows a low temperature sensitivity of ~ ± 0.8 pm/°C.

By exploiting the small bend radius achievable using high-index-contrast silicon photonic wire waveguides, we demonstrate a new low power thermo-optic switch arranged in a dense, double spiral geometry. Such a design permits the waveguide length to be extended for increased phase shift, without the need for increased heated volume. This provides an effective means to reduce the power consumption of thermo-optic switches, as well as a compact geometry desirable for the development of switch arrays. A low switching power of 6.5 mW was obtained for a spiral-path Mach-Zehnder interferometer device having a 10% - 90% rise time of 14 micros. The switching power is shown to be reduced by more than 5 times compared to a Mach-Zehnder interferometer employing a conventional straight waveguide geometry.

Silicon-on-insulator (SOI) is considered the most promising high-index-contrast waveguide platform for fabricating microphotonic devices with high integration density. However, there are fundamental challenges with this waveguide system related to the fixed values of the refractive indices of the constituent materials (Si and SiO 2 ). In this paper, we present a method that can potentially circumvent this limitation by using the sub-wavelength grating effect in SOI waveguides to effectively engineer materials with intermediate refractive indices by standard lithographic patterning. The first implementations of the SWG effect in SOI waveguides are discussed, including our latest results in fiber-chip couplers, anti-reflective and high-reflectivity waveguide facets, mode transformers between waveguides of different geometries, and microphotonic waveguide crossings.

We review our work developing label-free molecular sensors using silicon nanophotonic waveguides. We show that the high index contrast of these waveguides provides high surface sensitivity and enables compact sensor designs to be realized. We also describe new waveguide circuit geometries that allow photonic wire waveguide sensors to be conveniently arrayed in two dimensions for compatibility with commercial spotting tools, while simultaneously providing long interaction length and improved molecular capture efficiency. These sensor designs are shown to provide a practical route to the development of label-free, microarrayed biochips for multiparameter analysis.

The spectral characteristics of a ring resonator made of Si photonic wires are modeled using mode expansion of supermodes of the directional coupler. The influence of the coupling coefficient, loss factor and waveguide dispersion on the spectral features are analyzed in detail. The model is then compared with the experimental data of a ring resonator designed for sensing purposes. The model that includes a wavelength dependence on coupling length reproduces the large variations of the envelope of the experimental spectrum, when coupling coefficient cover its full range from 0 to 1. Fitting parameters explain the details of the experimental spectrum and contribute to the sensor optimization, as well as illustrating general guidelines for ring resonator design.

We present experimental and theoretical results of label-free molecular sensing with the TM mode of a 0.22 µm thick silicon slab waveguide used in a guided mode resonance configuration. Due to the strong overlap of the evanescent field of the waveguide mode with a molecular layer attached to the surface, these sensors exhibit high sensitivity, while their fabrication and packaging requirements are minimal. Experimentally, we demonstrate a resonance wavelength shift of ~1 nm when a monolayer of streptavidin is attached to the surface, in good agreement with calculations based on rigorous coupled wave analysis.

We report a compact high-resolution arrayed waveguide grating (AWG) interrogator system designed to measure the relative wavelength spacing between two individual resonances of a tilted fiber Bragg grating (TFBG) refractometer. The TFBG refractometer benefits from an internal wavelength and power reference provided by the core mode reflection resonance that can be used to determine cladding mode perturbations with high accuracy. The AWG interrogator is a planar waveguide device fabricated on a silicon-on-insulator platform, having 50 channels with a 0.18 nm wavelength separation and a footprint of 8 mm×8 mm. By overlaying two adjacent interference orders of the AWG we demonstrate simultaneous monitoring of two widely separated resonances in real time with high wavelength resolution. The standard deviation of the measured wavelength shifts is 1.2 pm, and it is limited by the resolution of the optical spectrum analyzer used for the interrogator calibration measurements.

We show by theoretical analysis and experiments on submicrometer silicon-on-insulator channel waveguides that the optical scattering loss of high-index-contrast planar waveguides is modified significantly by a thin-film interference effect, caused by boundary reflections.

Using silicon photonic wire waveguides we demonstrate highly sensitive and ultra-compact optical circuits for molecular sensing. The high-index-contrast of these structures is exploited to fabricate new folded waveguide geometries beneficial for sensing, as well as optical switching applications.

We review our work developing optical waveguide-based evanescent field sensors for the label-free, specific detection of biological molecules. Using high-index-contrast silicon photonic wire waveguides of submicrometer dimension, we demonstrate ultracompact and highly sensitive molecular sensors compatible with commercial spotting apparatus and microfluidic-based analyte delivery systems. We show that silicon photonic wire waveguides support optical modes with strong evanescent field at the waveguide surface, leading to strong interaction with surface bound molecules for sensitive response. Furthermore, we present new sensor geometries benefiting from the very small bend radii achievable with these high-index-contrast waveguides to extend the sensing path length, while maintaining compact size. We experimentally demonstrate the sensor performance by monitoring the adsorption of protein molecules on the waveguide surface and by tracking small refractive index changes of bulk solutions.

This paper reports the progress (design, fabrication and measurement) in label-free biological sensors based on ring resonator technology originally developed for telecommunication. These sensors are made in silicon-on-insulator (SOI), a high index contrast material platform that provides enhanced sensitivity and allows compact waveguide geometries by employing very small bend radii. A double spiral shape allows designing millimetre-long resonator in a compact size (100-150 mum) compatible with spotting technology used for large biochip assays. The detection limit estimated from the resonance shift measurement is ~5 fg of streptavidin adsorbed on the sensor surface functionalised with biotin.

We review two emerging concepts in planar waveguide multiplexers and spectrometers. The first concept is a planar waveguide demultiplexer with the wavelength dispersive properties provided by a diffraction grating formed in the sidewall of a curved Si waveguide. The phase errors are minimized using an apodized design with a chirped grating, yielding a crosstalk below -30 dB. The device has 15 channels with a wavelength spacing of 25 nm, thus a broad operational bandwidth of 375 nm suitable for coarse wavelength division multiplexing (CWDM) applications. The layout area occupies less then 0.005 mm2, which is the smallest footprint yet reported for a mux/demux device of similar performance. The second concept is a Fourier-transform Mach-Zehnder interferometer array. Multi-aperture input provides a markedly increased optical throughput. Unlike conventional Fourier-transform spectrometers, the device has no moving parts. Another advantage of this device is that phase and amplitude errors can be readily measured and numerically corrected with no need for costly modifications of the waveguide physical properties. An example of the spectrometer designed for the silicon-oninsulator platform with a spectral resolution of 0.025 nm is presented.

We demonstrate Mach-Zehnder interferometer and ring resonator evanescent field sensors fabricated on the silicon-on-insulator material platform. These devices exploit the strong evanescent field of the transverse magnetic mode of a high index contrast, submicron dimension waveguide to obtain strong interaction of the guided mode with biomolecules adsorbed to the waveguide surface. We utilize the extremely small bend radius achievable with silicon photonic wire waveguides to fabricate spiral and folded waveguide sensors that maintain the high sensitivity of a long waveguide, while providing compact footprint. These devices offer a suitable geometry for the development of sensor arrays and provide compatibility with commercial spotting functionalization systems. We demonstrate sensors containing waveguides of up to 5.5 mm length that are contained within a 150 μm × 150 μm area.

We demonstrate a method of canceling the temperature dependence of ring resonator sensors using a double ring configuration. Temperature calibration curves are provided for SOI photonic wire ring sensors with air and SU8 polymer cladding.

We demonstrate by numerical simulations and experiments that highly reflective (HR) facets can be formed on silicon waveguides with high reflectivity diffraction gratings. We use an HR grating with a plane wave reflectivity exceeding 99.99%, as calculated by rigorous coupled wave analysis. Experimentally, we demonstrate the HR effect for silicon-on-insulator waveguide facets patterned lithographically with grating structures. Due to a strong mode size dependence, the maximum facet reflectivity for 1.5 microm thick waveguide is 77%, but finite difference time-domain simulations show that modal reflectivies larger than 90% can be achieved for silicon waveguides with thicknesses of 4 microm or more.

We demonstrate a new silicon photonic wire waveguide evanescent field (PWEF) sensor that exploits the strong evanescent field of the transverse magnetic mode of this high-index-contrast, submicrometer-dimension waveguide. High sensitivity is achieved by using a 2 mm long double-spiral waveguide structure that fits within a compact circular area of 150 microm diameter, facilitating compatibility with commercial spotting apparatus and the fabrication of densely spaced sensor arrays. By incorporating the PWEF sensor element into a balanced waveguide Mach-Zehnder interferometer circuit, a minimum detectable mass of approximately 10 fg of streptavidin protein is demonstrated with near temperature-independent response.

We present theoretical and experimental results on an interference effect caused by boundary reflections on the optical scattering loss in high-index-contrast planar waveguides. Analytical expressions for the polarization-dependent scattering loss are derived using a surface Green's function. For high-index-contrast waveguides of submicrometer dimensions a significant deviation from accepted theory arises, including scattering loss suppression owing to a thin-film interference effect. Our theoretical predictions are confirmed by loss measurements on silicon-on-insulator channel waveguides.

The functionality and performance of many planar waveguide devices, including lasers and optical amplifiers, are critically affected by the reflectivity of the waveguide facets. For high index contrast waveguide devices, the Fresnel reflection at the facet is a significant contribution to the fibre-to-chip coupling loss and the return loss. Currently, the common method to control the facet reflectivity of planar waveguides is the deposition of anti-or high-reflective coatings.

We present recent theoretical and experimental results on silicon photonic wire evanescent field (PWEF) sensors that show such PWEF sensors have the highest response to bulk index change as well as surface molecular adsorption.

The design, simulation, and experimental performance of mode converters for coupling from single-mode silicon-on-insulator ridge waveguides to high aspect ratio channel waveguides are described. The converters consist of a two-level adiabatic taper structure. The final channel waveguide is 1.5 mum high by 0.8 mum wide. Simulations predict that for total coupler lengths longer than 20 mum, the coupling loss from the fundamental ridge mode to the slit mode is better than -0.2 dB. The couplers and waveguides were fabricated using a two-step self-aligned process. The measured coupling loss for fabricated mode converters is -0.4 dB

This paper presents the development of a microspectrometer and a surface plasmon waveguide sensor on a silicon platform derived from the expertise acquired in designing optical telecommunication components.

We demonstrate a new, highly sensitive evanescent field sensor using silicon-on-insulator (SOI) photonic wire waveguides. Theoretical analysis shows that thin SOI waveguides can provide higher sensitivity over devices based in all other common planar waveguide material systems for the probing of both thin adsorbed biomolecular layers and bulk homogeneous solutions. A Si photonic wire waveguide was incorporated into a Mach-Zehnder interferometer based sensor, configured to monitor the index change of a homogeneous solution. High effective index change of 0.31 per refractive index unit (RIU) change of the solution was measured, confirming theoretical predictions

The advantages of the silicon-on-insulator (SOI) waveguide platform are examined for evanescent field (EF) based biological sensing. It is suggested that the high index contrast (HIC) inherent to SOI waveguides allows sensors fabricated in this material to demonstrate improved sensitivity over that of all other common planar waveguide platforms for the probing of thin biological layers.

We propose a new method for waveguide mode transformation and coupling between an optical fiber and a sub-micrometer waveguide. The method is based on mode effective index modification by a subwavelength grating and it is demonstrated by FDTD simulations of coupling between an SMF-28 fiber and a thin SOI waveguide

We propose a new method for mode conversion and coupling between an optical fiber and a sub-micrometer waveguide using a subwavelength grating (SWG) with a period less than the 1st order Bragg period. The coupler principle is based on gradual modification of the waveguide mode effective index by the SWG effect that at the same time frustrates diffraction and minimizes reflection loss. We demonstrate the proposed principle by two-dimensional Finite Difference Time Domain (FDTD) calculations of various SWG structures designed for the silicon-on-insulator (SOI) platform with a Si core thickness of 0.3 microm. We found a coupling loss as small as 0.9 dB for a 50 microm-long SWG device and low excess loss due to fiber misalignment, namely 0.07 dB for a transverse misalignment of +/-1 microm, and 0.24 dB for an angular misalignment of +/-2 degrees. Scaling of the SWG coupler length down to 10 microm is also reported on an example of a 2D slab waveguide coupling structure including aspect ratio dependent etching and micro-loading effects. Finally, advantages of the proposed coupling principle for fabricating 3D coupling structures are discussed.

A silicon-on-insulator based evanescent field sensor using silicon photonic wire waveguides is reported. The unique properties of high index contrast, submicron structures are exploited to enhance electric field magnitude and localization near the sensor surface. The evanescent field sensor is demonstrated in a Mach Zehnder configuration.

An InP-based monolithically integrated triplexer chip comprising 1555 nm/1490 nm/1310 nm WDM, video/data receiver and transmitter monitor photodetectors, along with waveguide circuitry, is presented. A high-performance component with a footprint size of only 1 mm × 5.5 mm does not require active alignment and is compatible for flip-chip mounting on a silicon optical bench. (2 pages)

The advantages of monolithic integration of passive and active optoelectronic components into multifunctional PICs (photonic integrated circuits) are numerous and well known. In WDM transmission systems, where up to hundreds of wavelength channels may be present and must be manipulated on a per wavelength basis, the advantages of PICs containing wavelength (de)multiplexers and arrays of active components rapidly multiply. This has been exploited in our earlier reported SurePath family of InP-based PICs for optical channel monitoring / equalization, which contain an echelle grating demultiplexer and single-mode vertically integrated waveguide photodetectors / electroabsorption attenuators inserted into each of its output channels. Now, the same design principles and fabrication techniques have been utilized for the development of a dense WDM data receiver. This paper concentrates on the key building block of such a component, the single-mode vertically integrated waveguide photodetector. A detailed characterization and analysis of the device performance are presented.

Spot-size converter (SSC) is an important building block of InP-based photonic integrated circuits since it allows a standard single-mode fiber with a large and symmetric mode spot to be efficiently coupled with high displacement tolerance to a semiconductor waveguide with a small and asymmetric mode spot. Having an on-chip SSC integrated with a semiconductor waveguide is practically advantageous since such an element greatly simplifies the packaging process while increasing its reliability. In this paper, a SSC utilizing two-step lateral tapering is proposed for converting the semiconductor waveguide device mode into that suitable for fiber coupling without compromising the designs of the device and coupling waveguides. This is achieved by inserting a transient taper between the device and coupling waveguide as an impedance matcher. This paper describes the design principles and characterization results for such a two-step SSC, compatible with earlier reported InP-based photonic integrated circuits for WDM. Transmission, Fabry-Perot fringes and photoresponsivity measurements (the last - by using an on-chip waveguide photodetector monolithically integrated with the SSC) show excellent performance of the two-step SSC. In good agreement with simulations, it was experimentally demonstrated that using this integrated component for fiber coupling can reduce the coupling loss to below 1dB, which includes the taper radiation loss of ~0.2 dB.

In WDM optical networks, signals have to be manipulated and monitored on a per wavelength basis. This requires that (de)multiplexing and wavelength processing functions are combined in the same optical component. The most efficient solution from a footprint size, cost and reliability point of view would be a combination of both functions in one photonic integrated circuit (PIC), fabricated by photolithography. Given that processing / detecting of individual wavelengths is an active function, in S, C and L communication bands naturally realized by InP and related semiconductor materials, InP-based PICs are widely agreed to be the superior choice. This paper reports a practical design of such InP-based PICs. It is based on a building block approach, which allows a large variety of WDM optical components to be built from relatively few monolithically integrable elements, by using standard semiconductor fabrication technologies. These include: (i) (de)multiplexer based on a planar echelle diffractive grating with polarization compensation in the slab waveguide region; (ii) single-mode vertically integrated waveguide active devices with detecting, attenuating, amplifying and switching features, inserted in every (in)output waveguide channel of a planar (de)multiplexer, and (iii) passive waveguide circuitry required for coupling the light to and directing it through the InP-based photonic chip. Design and characterization examples of the building blocks and PICs for channel monitoring, variable attenuation / equalization and spatial switching are presented.

Two-step lateral tapering is proposed as a means for waveguide mode shaping for improved fiber coupling without compromising the waveguide design. Using this technique, on-chip spot-size converters integrated with shallow etched InP-based waveguides are reported.