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We proposed a simple noise model based on the photon transfer method for the testing of a hybrid optical sensor for imaging in short-wavelength infrared regime. The proposed testing procedure allowed us to separate the noise sources and then work on noise mitigation., 2019 IEEE Research and Applications of Photonics in Defense Conference, RAPID 2019, August 19-21, 2019, Miramar Beach, FL, USA

Background: Switchable glasses allow the control of light transmission—an attractive property for applications such as car sunroofs, aircraft windows, building windows, augmented reality, imaging, and displays. Commercialized switchable glasses have severe limitations, such as speed, cost, and operating conditions, among others. Microshutters, a type of switchable glass with very distinctive properties, are reviewed, as they are a technology that could significantly improve some or all of the shortcomings mentioned above. Aim: We will summarize the various types of microshutters and tentatively identify various critical designs, fabrication schemes, and performance criteria by the many research groups implementing them and investigating their properties. Approach: We will describe the various approaches used to control light transmission through microelectromechanical systems. It will compare their performances and comment on fabrication and implementation challenges. Conclusions: Microshutters have performance levels that could make them good candidates for switchable glasses. Many research groups have investigated various approaches to fabricate microshutters and have shown that they can be implemented reliably on a small scale, with fast actuation, low power, and high contrast and are relatively easy to manufacture. Work is needed to demonstrate that they can be scaled-up and still be economical to produce.

In this review, we summarize and discuss our recent studies of subwavelength grating (SWG) structures for engineering the refractive index of silicon microphotonic waveguides. The SWG effect allows control of the effective refractive index of a waveguide core over a range spanning the values of the cladding material and silicon by lithographic patterning. We demonstrate this effect with the example of segmented photonic wire waveguides, which are shown to exhibit low propagation loss, and can be used to make highly efficient waveguide crossings and in-plane fiber-chip coupling structures. Other applications of SWG structures in silicon photonic waveguide devices include surface grating couplers with enhanced performance and simplified fabrication requirements, as well as a novel curved waveguide sidewall grating micro-spectrometer, in which an SWG structure fulfills a dual purpose by acting as an effective slab waveguide for diffracted light and as a lateral cladding for a channel waveguide.

First implementations of subwavelength gratings (SWGs) in silicon-on-insulator (SOI) waveguides are discussed and demonstrated by experiment and simulations. The subwavelength effect is exploited for making antireflective and highly reflective waveguide facets as well as efficient fiber-chip coupling structures. We demonstrate experimentally that by etching triangular SWGs into SOI waveguide facets, the facet power reflectivity can be reduced from 31% to 94% facet reflectivity can be achieved with square SWGs for 5 μm thick SOI waveguides. Finally, SWG fiber-chip couplers for SOI photonic wire waveguides are introduced, including design, simulation, and first experimental results.

We review the use of the oxide cladding stress-induced photoelastic effect to modify the polarization dependent properties in silicon-on-insulator (SOI) waveguide components, and highlight characteristics particular to this high index contrast (HIC) systems. The birefringence in SOI waveguides has its origin in the electromagnetic boundary conditions at the waveguide boundaries, and can be further modified by the presence of stress in the waveguiding materials. With typical stress levels in SiO2 films, which are often used as the upper cladding, the waveguide effective index can be altered anisotropically up to the order of 10−3 for ridges with heights ranging from 1 μm to 5 μm. This effect can be used effectively to counter the waveguide geometrical birefringence, allowing the waveguide cross-section profiles to be optimized for design criteria other than null geometrical birefringence. Design strategies are developed for using stress engineering to achieve a variety of functions. Polarization insensitive arrayed waveguide gratings (AWGs), polarization insensitive ring resonators, and polarization splitters and filters are demonstrated using these design principles.

The applications of cladding stress in SOI waveguide components to enhance de- vice functionality and improve fabrication tolerance are reviewed. Assisted by FEM design tools, characteristics of stress-induced efiects are studied in depth. Design strategies are developed for using stress engineering to achieve a variety of functions. Polarization insensitive arrayed waveg- uide gratings (AWGs) and ring resonators, and polarization splitters and fllters are demonstrated using these design principles.

Surface grating couplers are fundamental components in chip-based photonic devices to couple light between photonic integrated circuits and optical fibers. In this work, we report on a grating coupler with sub-decibel experimental coupling efficiency using a single etch process in a standard 220-nm silicon-on-insulator (SOI) platform. We specifically demonstrate a subwavelength metamaterial refractive index engineered nanostructure with backside metal reflector, with the measured peak fiber-chip coupling efficiency of -0.69 dB (85.3%) and 3 dB bandwidth of 60 nm. This is the highest coupling efficiency hitherto experimentally achieved for a surface grating coupler implemented in 220-nm SOI platform.

This paper presents an overview of our recent work on several fundamental optical elements and their integration on the silicon-on-insulator (SOI) waveguide platform. Theory, design and experimental results are presented for monolithically integrated asymmetric graded-index waveguide couplers, as well as output couplers based on total internal reflection mirrors. Design strategies for dispersive elements on SOI, for example, ring resonators and arrayed waveguide gratings, are discussed with special emphasis on methods to eliminate the polarization sensitivity. Finally, the properties and applications of evanescent fields in SOI waveguides are reviewed

2006 ECS Meeting : Cancun, Mexico, Oct.29 -Nov.3, 2006, Series: ECS Transactions

We present a technique to lithographically define and fabricate all required optical facets on a silicon-on-insulator photonic integrated circuit by an inductively coupled plasma etch process. This technique offers 1μm positioning accuracy of the facets at any location within the chip and eliminates the need of polishing. Facet fabrication consists of two separate steps to ensure sidewall verticality and minimize attack on the end surfaces of the waveguides. Protection of the waveguides by a thermally evaporated aluminum layer before the 40–70μm deep optical facet etching has been proven essential in assuring the facet smoothness and integrity. Both scanning electron microscopy analysis and optical measurement results show that the quality of the facets prepared by this technique is comparable to the conventional facets prepared by polishing.

We examine, both experimentally and theoretically, the feasibility of positioning and sizing self-assembled InAs quantum dots on a variety of patterned InP templates. Such templates are fabricated using either chemically assisted ion beam etching or selective oxide patterning, and subsequent chemical beam epitaxial overgrowth. For templates of trapezoidal cross-section, we demonstrate experimentally how quantum dot formation can be localised on the top (0 0 1) surface of the structure. For templates of triangular cross-section, in which the (0 0 1) top surface has been eliminated and strained quantum wells have been embedded, we use finite element modeling of the stress distribution and elastic strain energy to examine the positioning and sizing of self-assembled InAs quantum dots on the sidewalls. We show that dots can be located near the intersection of the quantum well stressors with the template sidewalls, whilst the lateral dot dimension is influenced by the extent of the local strain distribution.

We demonstrate compact multimode interference (MMI) couplers on silicon-on-insulator that exhibit both high performance and relaxed tolerances. The devices are fabricated with a single shallow etch step on 1.5-mum-thick silicon, and have a footprint of 12.8 mum times 456 mum, including 100-mum-long tapers at input and output. In a Mach-Zehnder configuration, we achieve an extinction ratio larger than 22 dB for transverse-electric polarization and larger than 20 dB for transverse-magnetic polarization. This extinction ratio is maintained in the full 1520- to 1580-nm band and for MMI width variations in a range of 0.45 mu m. We also show appreciable tolerance differences between paired and general excitation MMIs.

InGaAs/InP layers are grown on (1 0 0) substrates patterned using chemically assisted ion beam etching (CAIBE) to produce undercut mesas aligned along the 〈0 1 1〉 direction. Undercut mesas are used to avoid any interaction between growth on the etched and non-etched regions of the substrate. We show that optimised growth conditions for InP produce (1 1 1)B facets on the sides of the ridges which are atomically smooth along their full length. These ridges form an excellent template for the diffusion of the group III species onto the (1 0 0) plane in the ridge centre. The success of this technique relies heavily on the quality of the growth template used since the diffusion of group III species off the higher-order (n 1 1) planes onto the (1 0 0) is plane specific. The formation of this template by growth rather than wet chemical etching results in atomically smooth facets of a well-defined orientation and height, which is well suited to our application.

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 describe the development of a waveguide Fourier-transform spectrometer for space-borne high-resolution sensing. A prototype device is designed to monitor the water vapor absorption band near 1,364 nm with a resolution of 0.05 nm. It has no moving parts and is based on a unique concept of arrayed interferometers implemented in silicon-on-insulator planar waveguide chip. The optical input is formed by many independent waveguides, providing a significantly increased light gathering capability (etendue) compared to single-waveguide input configurations. Enhancements of the spectrometer capabilities are achieved by stacking planar waveguide layers and by using surface gratings to couple light into the waveguides.

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 use of grating couplers in high index contrast waveguides like silicon on insulator (SOI) offers several advantages over other coupling approaches, including better alignment tolerances and allowing for wafer-scale testing. The grating couplers were developed for nanometric SOI waveguides (Si-wires), and recently also for micrometric rib waveguides. In this paper we review our work in fiber-to-chip grating couplers for thick SOI rib waveguides, where a coupling efficiency of −2.2 dB was demonstrated experimentally. We also discuss the use of grating couplers to improve optical throughput (etendue) of a planar waveguide Fourier-Transform (FT) spectrometer implemented in thick rib waveguides.

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.

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

We present the development of a compact planar waveguide Fourier-transform spectrometer for high-resolution and high-throughput spectroscopy. The prototype device is designed to monitor the water vapor absorption band near λ= 1364 nm in the atmosphere from an Earth-orbiting satellite. The instrument is fully static (i.e. no moving parts) and it is based on a unique slab waveguide Fourier-transform spectrometer concept implemented with silicon-on-insulator (SOI) technology. The spectrometer input is formed by an array of N independent waveguide apertures, thereby significantly (Nx) increasing light gathering capability (étendue) compared to conventional single-aperture devices. We also discuss a practical implementation of the multi-aperture concept based on an array of surface grating couplers. © 2011 IEEE., 2011 13th International Conference on Transparent Optical Networks, ICTON 2011, 26 June 2011 through 30 June 2011, Stockholm

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

Multiple Aperture Transform Chip Heterodyne (MATCH) spectrometers have been developed for targeted remote sensing applications in harsh environments. These waveguide-based Fourier Transform Spectrometers (FTS) offer significant improvements in resource efficiency over monolithic glass implementations, but are relatively limited in terms of input coupling efficiency and fill factor of the input facet. Integrated optics spectrometers have significant resource advantages for space applications. Monolithic Spatial Heterodyne Spectrometers are insensitive to vibration and do not require frequent calibration. In addition, Fourier Transform Spectrometers are known to provide significant performance advantages for emission spectroscopy. Ongoing work will improve the MATCH spectrometer input coupling efficiency from free space. This paper discusses the signal to noise improvements expected by incorporation of surface gratings, or back-thinning and stacking of slabs. We show that the use of surface gratings can increase the throughput over coupling to bare waveguides alone (in a single polarization), and provide close to 100% fill factor, albeit with limited field. Étendue improvements associated with stacked slabs are limited only by the sensing area available, but the fill factor of the input facet is limited to ∼10%. The impact of these improvements is assessed in the context of two space-based applications: 1) Atmospheric remote sensing in the context of Spatial Heterodyne Observations of Water (solar occultation absorption spectroscopy) near 1.3 μm and 2) Point emission spectroscopy (LIBS/Raman/fluorescence) for mineral identification on a planetary rover. © 2011 Copyright Society of Photo-Optical Instrumentation Engineers (SPIE)., Reliability, Packaging, Testing, and Characterization of MEMS/MOEMS and Nanodevices X, January 24-25, 2011, San Francisco, CA, USA, Series: Proceedings of SPIE; no. 7928

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

The LOCOS technique for formation of SOI optical waveguides has been extended to produce low-loss photonic wire channel waveguides with deep submicron dimensions using a very simple process. © 2011 IEEE., 8th IEEE International Conference on Group IV Photonics, GFP 2011, 14 September 2011 through 16 September 2011, London

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

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.

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.

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.

The six-port reflectometer technique enables simple and accurate measurement of optical reflection coefficients in both magnitude and phase. The reflection coefficient is computed from four power measurements of linear combinations of the waves incident and reflected from the device under test. While the six-port technique is very successful at microwave frequencies and conceptually related to coherent optical phase diversity receivers, no optical implementations have been reported so far. In this paper, we present an experimental characterization of an optical six-port reflectometer composed of three multimode interference couplers, fabricated with a single etch step in silicon on insulator. Measurements are performed using a novel technique with a simple setup. The six-port combines the incident and reflected waves with magnitude and phase errors less than plusmn0.5 dB and plusmn6deg in the 1485-1575 nm band.

We show that integrated optical star couplers can be useful characterization devices to measure the sidewall roughness-induced scattering losses of planar waveguides. We describe the detailed fabrication processes of these star couplers on the silicon-on-insulator (SOI) platform and the process improvements implemented to reduce the waveguide sidewall roughness and scattering loss. We report the main process challenges, particularly to assure a clear gap between any adjacent waveguides of the dense and closely spaced output waveguide array. These challenges are addressed by optimizing the exposure dose of the resist and adding an oxygen ashing treatment to eliminate waveguide footings. We demonstrate further improvement on the waveguide profile and sidewall roughness through the use of a thin Cr hardmask for the dry plasma etching. This optimized fabrication process is capable of producing approximately a 3 nm root-mean-square sidewall roughness, measured using both scanning electron microscopy (SEM) and atomic force microscopy (AFM). Using the fabricated star couplers, we manage to measure the relative scattering losses of various waveguides with the width varying from 0.2 to 2.0 μm in a single measurement, and show that the measured losses agree with the measured sidewall roughness.

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.

Integrated Optoelectronic Devices 2007, 2007, San Jose, California, United States, Series: Proceedings of SPIE; no. 6477

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.

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.

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.

This invited talk presents the evolution of the planar waveguide dispersive devices developed in our laboratory for spatial heterodyne spectroscopy. The basic concepts are introduced and then applied to a Mach-Zehnder interferometer array capable of a resolution of 0.1 nm over a bandwidth of 2.5 nm.

We present miniature spectrometers that offer high resolution, increased optical throughput (etendue), and are compatible with a microsatellite platform. The spectrometers are implemented using arrays of singlemode planar optical waveguides and use a Fourier technique for spectra retrieval. We discuss design, fabrication, and first experimental results for these multiaperture spectrometers implemented in silicon-on-insulator (SOI) waveguides.

We use star couplers to measure the relative scattering losses of silicon-on-insulator (SOI) ridge waveguides of various widths over the range of 1.75 to 0.2 mum in a single measurement. The scattering loss data obtained for waveguides fabricated by different photolithography and e-beam base processes correlate well with the measured root-mean-square roughness of the waveguide sidewalls obtained using SEM image analysis, and are in qualitative agreement with the prediction of simple scattering loss theory.

We present multiaperture stationary spectrometers in planar optical waveguides. The devices are based on the spatial heterodyning technique, do not require moving parts, and use Fourier transformation for spectra retrieval. The design is based on arrays of waveguide interferometers with linearly increasing optical path delay. The spectrometers have increased optical throughput due to multiple input waveguides. We discuss design, fabrication, and first experimental results for these multiaperture spectrometers implemented in silicon-on-insulator (SOI) ridge waveguides.

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.

An integrated polarization compensator for wavelength-division-multiplexed waveguide demultiplexers is proposed and experimentally demonstrated. It is simple to fabricate, has many advantages over previously reported polarization compensation schemes, and is effective in both etched diffraction grating and arrayed waveguide grating based devices.

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.