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Using photonic devices, we developed a new approach to traditional spectroscopy where the spectral cross-correlation with a template spectrum can be done entirely on-device. By creating photonic devices with a carefully designed, modulated transmission spectrum, the cross-correlation can be carried out optically without requiring any dispersion, vastly simplifying the instrument and reducing its cost. The measured correlation lag can be used for detecting atomic/molecular species within and determining the radial velocity of a particular astrophysical object. We present an overview of two design approaches that are currently being developed that use different photonic platforms: silicon and fibre-based photonics. The silicon photonic approach utilizes ring resonators that can be thermo-optically modulated to carry out the cross-correlation. The fibre approach uses customized fibre Bragg gratings (FBGs) with transmission spectra that can be strain-modulated. Both approaches have been able to detect molecular gas in a lab setting, and we are now in the process of on-sky testing. Lastly, we discuss the future for these types of devices as their simplicity opens up the possibility of developing low-cost, purpose-built multi-object or integral field spectroscopic instruments that could make significant contributions to scientific programs requiring stellar RV measurements and exoplanet detections., Comment: SPIE Proceedings, Astronomical Telescopes and Instrumentation, July 2022, 10 pages, 7 figures

We present a novel, to the best of our knowledge, remote gas detection and identification technique based on correlation spectroscopy with a piezoelectric tunable fiber-optic Fabry–Perot filter. We show that the spectral correlation amplitude between the filter transmission window and gas absorption features is related to the gas absorption optical depth, and that different gases can be distinguished from one another using their correlation signal phase. Using a previously captured telluric-corrected high-resolution near-infrared spectrum of Venus, we show that the radial velocity of Venus can be extracted from the phase of higher order harmonic lock-in signals. This correlation spectroscopy technique has applications in the detection and radial velocity determination of weak spectral features in astronomy and remote sensing. We experimentally demonstrate a remote C O 2 detection system using a lock-in amplifier, fiber-optic Fabry–Perot filter, and single channel avalanche photodiode.

The absorption spectra of distant targets can be used for remote gas detection. However, the detection of very faint absorption features is difficult since noise can dominate the molecular signal in the acquired spectrum. Rather than using typical dispersive spectroscopy, high sensitivity remote gas sensing is possible by correlation spectroscopy using a spectral matching filter. In this work, we use a thermo-optically tunable nanophotonic silicon waveguide ring resonator as an integrated spectral filter to obtain a correlation signal proportional to the absorption spectrum of a specific gas. We demonstrate the ability to resolve very small absorption depth changes using integrated photonics at the level required for the characterization of exoplanet atmospheres during transits of their host stars., 2021 Photonics North (PN), May 31 - June 2, 2021, Toronto, ON, Canada

The instrument group of the Herzberg Astronomy and Astrophysics has been subcontracted by Australian Astronomical Optics (AAO) at Macquarie University to design and build the bench spectrograph for the Gemini High-Resolution Optical SpecTrograph (GHOST) instrument. The GHOST instrument is being developed for the Gemini telescope and is a collaboration between AAO, the Herzberg Astronomy and Astrophysics (HAA) in Canada and the Australian National University (ANU). The instrument is a fiber fed spectrograph with R, Ground-based and Airborne Instrumentation for Astronomy VIII, December 14-18, 2020, Online Only, United States, Series: Proceedings of SPIE

Exoplanetary biosignatures, molecular compounds which indicate a likelihood of extraterrestrial life, can be detected by highly sensitive spectroscopy of starlight which passes through the atmospheres of exoplanets towards the Earth. Such sensitive measurements can only be accomplished with the next generation of telescopes, leading to a corresponding increase in cost and complexity spectrometers. Integrated astrophotonic instruments are well-suited to address these challenges through their low-cost fabrication and compact geometries. We propose and characterize an integrated photonic gas sensor which detects the correlation between the near-infrared quasi-periodic vibronic absorption line spectrum of a gas and a silicon waveguide ring resonator transmittance comb. This technique enables lock-in amplification detection for real-time detection of faint biosignatures for reduced observation timescales and rapid exoplanetary atmosphere surveys using highly compact instrumentation.

The Herzberg Astronomy and Astrophysics Research Centre has established a comprehensive and versatile vibration measurement capability. In recent years, HAA personnel have executed a number of diverse vibration measurement projects, including recent vibration transmission measurements at Gemini South. In this paper we describe the HAA’s vibration measurement capabilities, including the equipment and experimental approaches that have been used. We will provide some illustrative examples of recent applications and results, and highlight plans for further development of our capabilities., Ground-based and Airborne Telescopes VIII, December 14-18, 2020, Online Only, United States, Series: Proceedings of SPIE

Absorption spectroscopy is widely used in sensing and astronomy to understand molecular compositions on microscopic to cosmological scales. However, typical dispersive spectroscopic techniques require multichannel detection, fundamentally limiting the ability to detect extremely weak signals when compared to direct photometric methods. We report the realization of direct spectral molecular detection using a silicon nanophotonic waveguide resonator, obviating dispersive spectral acquisition. We use a thermally tunable silicon ring resonator with a transmission spectrum matched and cross-correlated to the quasi-periodic vibronic absorption lines of hydrogen cyanide. We show that the correlation peak amplitude is proportional to the number of overlapping ring resonances and gas lines, and that molecular specificity is obtained from the phase of the correlation signal in a single detection channel. Our results demonstrate on-chip correlation spectroscopy that is less restricted by the signal-to-noise penalty of other spectroscopic approaches, enabling the detection of faint spectral signatures.

We present an integrated photonic correlation filter for the detection of remote HCN gas. We demonstrate sensing of absorption due to HCN using thermo-optic tuning of the drop port transmission spectrum in a silicon waveguide ring resonator., 2020 IEEE Photonics Conference (IPC), September 28 - October 1, 2020, Vancouver, BC, Canada

We present the design of integrated astrophotonic instruments for high background atmospheric gas detection. Such instruments can be fibre-coupled to long focal length space telescopes as compact, flexure-free, instruments., Conference on Lasers and Electro-Optics/Pacific Rim 2020, August 3-5, 2020, Sydney Australia

Absorption spectroscopy is a powerful technique for characterizing remote gas composition where direct interaction with a target it not possible. While dispersive spectroscopy is typically used to acquire a spectrum with which the gas presence is determined, correlation spectroscopy can directly detect such spectral features in a single detection channel. Here we present a novel integrated photonics correlation technique on an integrated photonic platform which uses real-time spectral processing to generate a multiline gas specific detection signal., 2020 Photonics North (PN), May 26-28, 2020, Niagara Falls, ON, Canada

In this work, the authors evaluated the access resistance of InP high electron mobility transistors (HEMTs) and their degradation during wafer processing. The transfer resistance, which was rarely separated from other components of the total access resistance of InP HEMTs in the literature, was found to be the dominant component of the access resistance. It was also found that the transfer resistance degraded during wafer processing. The selection of the ohmic metal stack and its impact on both the metal-cap contact resistance and the transfer resistance was also investigated. The observations in their experiments and relevant discussions in the report are expected to be useful in the identification of improvement opportunities in both material growth and wafer fabrication of InP HEMTs.

Astronomical instrumentation is traditionally costly, large, and alignment-sensitive owing to the use of bulk optics. The use of integrated photonic devices in astronomical instrumentation can mitigate such drawbacks in certain applications where high light throughput and spectral bandwidth are less crucial. In this work, we present an ultra-compact carbon dioxide detection scheme using a single silicon waveguide ring resonator. The comb-like absorption line spectrum of CO2 around 1580 nm wavelength can closely match the comb spectrum of an appropriately designed ring resonator. By actively correlating such a ring spectrum with the CO2 absorption lines, a specific detection signal can be generated. We design the free spectral range of a ring resonator to match the absorption line spacing of carbon dioxide lines in the range from 1575 to 1585 nm. Using thermo-optic modulation, the ring resonator drop or through port transmission spectrum can be shifted back and forth across the incoming CO2 light spectrum, resulting in a modulated signal with an amplitude proportional to the CO2 absorption line strength. Furthermore, high frequency modulation and lock-in detection can result in a significant improvement in the signal to noise ratio. We demonstrate that such a device can provide real-time carbon dioxide detection for applications in ground- and satellite-based astronomy, as well as remote atmospheric sensing, in a compact package. In future work, such a sensor can be adapted to a range of gases and used to determine radial velocities and compositional maps of astronomical objects.

We present a correlation spectrometer using a silicon waveguide ring resonator for the identification of molecules in stellar and planetary atmospheres. We tailor the free spectral range of a ring resonator to the vibronic overtones of carbon dioxide in the near infrared. The ring resonator spectrum is modulated via the thermo-optic effect and produces a detection signal unique to carbon dioxide. This spectrometer can be used for real-time remote gas detection and radial velocities of exoplanets in a narrow spectral band., 2019 Photonics North (PN), May 21-23, 2019, Quebec City, QC, Canada

NFIRAOS (Narrow-Field InfraRed Adaptive Optics System) will be the first-light multi-conjugate adaptive optics system for the Thirty Meter Telescope (TMT). NFIRAOS houses all of its opto-mechanical sub-systems within an optics enclosure cooled to precisely -30°C in order to improve sensitivity in the near-infrared. It supports up to three client science instruments, including the first-light InfraRed Imaging Spectrograph (IRIS). Powering NFIRAOS is a Real Time Controller that will process the signals from six laser wavefront sensors, one natural guide star pyramid WFS, up to three low-order on-instrument WFS and up to four guide windows on the client instrument’s science detector in order to correct for atmospheric turbulence, windshake, optical errors and plate-scale distortion. NFIRAOS is currently preparing for its final design review in late June 2018 at NRC Herzberg in Victoria, British Columbia in partnership with Canadian industry and TMT., Adaptive Optics Systems VI, June 10-15, 2018, Austin, United States, Series: Proceedings of SPIE; no. 10703

The Narrow Field InfraRed Adaptive Optics System (NFIRAOS) will be the first-light facility Adaptive Optics (AO) system for the Thirty Meter Telescope (TMT). NFIRAOS will be able to host three science instruments that can take advantage of this high performance system. NRC Herzberg is leading the design effort for this critical TMT subsystem. As part of the final design phase of NFIRAOS, we have identified multiple subsystems to be sub-contracted to Canadian industry. The scope of work for each subcontract is guided by the NFIRAOS Work Breakdown Structure (WBS) and is divided into two phases: the completion of the final design and the fabrication, assembly and delivery of the final product. Integration of the subsystems at NRC will require a detailed understanding of the interfaces between the subsystems, and this work has begun by defining the interface physical characteristics, stability, local coordinate systems, and alignment features. In order to maintain our stringent performance requirements, the interface parameters for each subsystem are captured in multiple performance budgets, which allow a bottom-up error estimate. In this paper we discuss our approach for defining the interfaces in a consistent manner and present an example error budget that is influenced by multiple subsystems.

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.

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

The design, fabrication, and performance of an InP-based monolithically integrated optical power monitor are presented. It contains 44 wavelength channels separated by 100 GHz and demonstrates record small footprint size. The device's major components, which include the echelle diffractive grating demultiplexer, passive waveguide circuitry and single-mode vertically integrated waveguide PIN photodetectors, are characterized and discussed as generic building blocks of InP-based planar lightwave technology for DWDM.

A new InP-based waveguide photodetector utilizing single-mode vertical integration of a p-i-n structure atop of a low-loss optical waveguide is reported. Over all states of polarization, in a spectral range across the C-band, the device exhibits high on-chip responsivities of /spl sim/1.1 A/W, which remains nearly constant at a reverse bias above 5 V and optical powers up to 1 mW. If integrated within the output channels of a planar demultiplexer, it enables a very compact optical spectral analyzer to be realized.

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 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.

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

Surface grating couplers enable efficient coupling of light between optical fibers and planar waveguide circuits. While traditional grating designs require two etch steps for efficient coupling to silicon-on-insulator waveguides, recently proposed subwavelength structured gratings can achieve the same coupling efficiencies with a single etch step, thereby significantly reducing fabrication complexity. Here we demonstrate that such couplers can be fabricated on a large scale with ultra-violet lithography, achieving a 5 dB coupling efficiency at 1,550 nm. Through both simulations and experiments we give physical insight on how pattern fidelity impacts the performance of these couplers, and propose strategies to deal with inevitable process variations.

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 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

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 demonstrate silicon-chip-based instantaneous chromatic dispersion monitoring (GVD) for an ultrahigh bandwidth 640 Gbit/s differential phase-shift keying (DPSK) signal. This monitoring scheme is based on cross-phase modulation in a highly nonlinear silicon nanowire. We show that two-photon absorption and free-carrier-related effects do not compromise the GVD monitoring performance, making our scheme a reliable on-chip CMOS-compatible, all-optical, and real-time impairment monitoring approach for up to Terabit/s DPSK signals.

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 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

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

Fibre-to-chip grating couplers are an efficient means for injecting and extracting light from silicon-wire waveguides. Here we present the design of single-etch couplers, based on effective media implemented with sub-wavelength gratings. We show that the pitch of these sub-wavelength structures can be increased to make their fabrication compatible with deep-ultraviolet lithography, without compromising their effective medium behavior. We experimentally demonstrate fully-etched grating couplers fabricated with DUV lithography. © 2011 IEEE., 2011 ICO International Conference on Information Photonics, IP 2011, 18 May 2011 through 20 May 2011, Ottawa, ON

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.

We describe a new label-free biosensor array chip developed for the real-time, simultaneous monitoring of multiple molecular binding reactions. It is composed of monolithically integrated grating couplers, microfluidic channels and spiral cavity silicon photonic wire sensors. The grating couplers use a novel design for coupling to the transverse magnetic mode of a silicon photonic wire. They contain arrays of subwavelength dimension holes, which allow the local refractive index to be engineered in the grating region. They can be fabricated with the photonic wires in a single etch step, an important advantage over other vertical couplers. The coiled waveguides are configured as ring resonators with extended cavity length for high sensitivity and small footprint for compatibility with microarray spotting. For analyte delivery, microfluidic channels were formed in an SU-8 overlayer.