Showing papers by "Pavel Cheben published in 2009"
TL;DR: A silicon waveguide-fiber grating coupler that uses a subwavelength microstructure to achieve a continuously variable grating strength yet can be fabricated using only a single etch step is proposed.
Abstract: We propose a silicon waveguide-fiber grating coupler that uses a subwavelength microstructure to achieve a continuously variable grating strength yet can be fabricated using only a single etch step. By adjusting the subwavelength microstructure at every point along the grating, the grating coupler can be optimized to give high field overlap with the optical fiber mode and also minimize backreflections along the incident waveguide path. Our design example is optimized for quasi-TM mode in a silicon photonic-wire waveguide, as required for waveguide evanescent-field-sensing applications. A field overlap of up to 94% with a standard single-mode optical fiber (SMF-28) is achieved by coupler apodization. Backreflection from the grating is reduced to ~0.1%, and the total predicted photonic wire to fiber coupling efficiency is 50%.
207 citations
TL;DR: The real-time monitoring of antibody-antigen reactions using complementary and mismatched immunoglobulin G receptor-analyte pairs and bovine serum albumin is demonstrated.
Abstract: We demonstrate a silicon photonic wire waveguide biosensor array chip for the simultaneous monitoring of different molecular binding reactions. The chip is compatible with automated commercial spotting tools and contains a monolithically integrated microfluidic channel for sample delivery. Each array sensor element is a 1.8-mm-long spiral waveguide folded within a 130 microm diameter spot and is incorporated in a balanced Mach-Zehnder interferometer with a near temperature independent response. The sensors are arranged in a 400 microm spacing grid pattern and are addressed through cascaded 1x2 optical power splitters using light from a single input fiber. We demonstrate the real-time monitoring of antibody-antigen reactions using complementary and mismatched immunoglobulin G receptor-analyte pairs and bovine serum albumin. The measured level of detection for each sensor element corresponds to a surface coverage of less than 0.3 pg/mm(2).
197 citations
TL;DR: Efficient, low power, continuous-wave four-wave mixing in the C-band is demonstrated using a high index doped silica glass micro ring resonator having a Q-factor of 1.2 million, and theoretically that the characteristic low dispersion enables phase-matching over a tuning range > 160 nm.
Abstract: We demonstrate efficient, low power, continuous-wave four-wave mixing in the C-band, using a high index doped silica glass micro ring resonator having a Q-factor of 1.2 million. A record high conversion efficiency for this kind of device is achieved over a bandwidth of 20nm. We show theoretically that the characteristic low dispersion enables phase-matching over a tuning range > 160nm.
147 citations
TL;DR: A new low power thermo-optic switch arranged in a dense, double spiral geometry that permits the waveguide length to be extended for increased phase shift, without the need for increased heated volume is demonstrated.
Abstract: 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.
117 citations
TL;DR: The design and numerical simulation results for a silicon waveguide modulator based on carrier depletion in a linear array of periodically interleaved PN junctions that are oriented perpendicular to the light propagation direction are presented.
Abstract: We present the design and numerical simulation results for a silicon waveguide modulator based on carrier depletion in a linear array of periodically interleaved PN junctions that are oriented perpendicular to the light propagation direction. In this geometry the overlap of the optical waveguide mode with the depletion region is much larger than in designs using a single PN junction aligned parallel to the waveguide propagation direction. Simulations predict that an optimized modulator will have a high modulation efficiency of 0.56 V.cm for a 3V bias, with a 3 dB frequency bandwidth of over 40 GHz. This device has a length of 1.86 mm with a maximum intrinsic loss of 4.3 dB at 0V bias, due to free carrier absorption. (C) 2009 Optical Society of America
112 citations
TL;DR: Experimental and theoretical results of label-free molecular sensing using the transverse magnetic mode of a 0.22 mum thick silicon slab waveguide with a surface grating implemented in a guided mode resonance configuration show high sensitivity and good agreement with calculations based on rigorous coupled wave analysis.
Abstract: We present experimental and theoretical results of label-free molecular sensing using the transverse magnetic mode of a 0.22 μm thick silicon slab waveguide with a surface grating implemented 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 modest. Experimentally, we demonstrate a resonance wavelength shift of ~1 nm when a monolayer of the protein streptavidin is attached to the surface, in good agreement with calculations based on rigorous coupled wave analysis. In our current optical setup this shift corresponds to an estimated limit of detection of 0.2% of a monolayer of streptavidin.
73 citations
TL;DR: This work reports on several new types of sub-wavelength grating (SWG) gradient index structures for efficient mode coupling in high index contrast slab waveguides, and proposes an implementation of SWG structures to reduce loss and higher order mode excitation between a slab waveguide and a phase array of an array waveguidegrating (AWG).
Abstract: We report on several new types of sub-wavelength grating (SWG) gradient index structures for efficient mode coupling in high index contrast slab waveguides. Using a SWG, an adiabatic transition is achieved at the interface between silicon-on-insulator waveguides of different geometries. The SWG transition region minimizes both fundamental mode mismatch loss and coupling to higher order modes. By creating the gradient effective index region in the direction of propagation, we demonstrate that efficient vertical mode transformation can be achieved between slab waveguides of different core thickness. The structures which we propose can be fabricated by a single etch step. Using 3D finite-difference time-domain simulations we study the loss, polarization dependence and the higher order mode excitation for two types (triangular and triangular-transverse) of SWG transition regions between silicon-on-insulator slab waveguides of different core thicknesses. We demonstrate two solutions to reduce the polarization dependent loss of these structures. Finally, we propose an implementation of SWG structures to reduce loss and higher order mode excitation between a slab waveguide and a phase array of an array waveguide grating (AWG). Compared to a conventional AWG, the loss is reduced from -1.4 dB to < -0.2 dB at the slab-array interface.
37 citations
TL;DR: In this paper, the spectral characteristics of a ring resonator made of Si photonic wires are modeled using mode expansion of supermodes of the directional coupler, and the influence of the coupling coefficient, loss factor and waveguide dispersion on the spectral features are analyzed in detail.
Abstract: 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.
36 citations
TL;DR: Simple fabrication procedures are reported for the preparation of Ag/Au nanoalloys on Si/SiO(x) substrates, with tunable plasmon resonances, for surface-enhanced Raman scattering (SERS) spectroscopy.
35 citations
TL;DR: This paper presents a novel method to recover the original device characteristics from the measured power transmission in the presence of curious reflections, which uses minimum phase techniques to reconstruct time domain information which is filtered to remove the reflection artifacts.
Abstract: Spurious reflections can preclude the accurate experimental characterization of integrated optical devices. This is particularly important for facet reflections in high refractive index platforms such as Indium Phosphide (InP) or Silicon-on-Insulator (SOI) when no anti-reflective (AR) coating is used. In this paper we present a novel method to recover the original device characteristics from the measured power transmission in the presence of such reflections. Our approach uses minimum phase techniques to reconstruct time domain information which is filtered to remove the reflection artifacts. A criterion to assess if a certain device exhibits the minimum phase characteristics required to apply the technique is given. Simulated and experimental results for multi-mode interference couplers (MMICs) in SOI without AR coating validate the technique.
22 citations
TL;DR: In this paper, the authors proposed a new class of volume hologram recording materials, sol-gel nanocomposites, with important advantages for various holographic applications, including data storage.
Abstract: The research into new photosensitive materials with advanced performance for holographic applications is an active branch in material science and photonics, still challenging the field. We proposed a new class of volume hologram recording materials, sol-gel nanocomposites, with important advantages for various holographic applications, including data storage. Here we review several aspects of different types of photosensitive sol-gel glasses that we have developed. Our photopolymerizable glasses exhibit high refractive index modulation, diffraction efficiencies close to the theoretical maxima, along with low scattering and negligible shrinkage. Beside these and other practical advantages discussed in this paper, our recently developed nanocomposite glass incorporating high refractive index species has enabled fundamental studies of new optical phenomena such as the Pendellosung effect, which was observed for the first time in the optical band.
TL;DR: In this paper, the authors demonstrate compact multimode interference couplers on silicon-on-insulator that exhibit both high performance and relaxed tolerances, achieving an extinction ratio larger than 22 dB for transverse-electric polarization and larger than 20 dB for Transverse-magnetic polarization.
Abstract: 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.
07 May 2009
TL;DR: In this article, the authors present miniature spectrometers that offer high resolution, increased optical throughput (etendue), and are compatible with a microsatellite platform using arrays of singlemode planar optical waveguides.
Abstract: 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.
09 Feb 2009
TL;DR: In this article, a multi-aperture stationary spectrometers in planar optical waveguides are presented, which are based on the spatial heterodyning technique, do not require moving parts and use Fourier transformation for spectra retrieval.
Abstract: 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
12 Feb 2009
TL;DR: In this paper, a spatial heterodyne waveguide spectrometer with a stationary Fourier technique is employed to reconstruct the input spectrum from the array of outputs, which can be readily implemented in the spectral retrieval algorithm.
Abstract: We present a novel micro-interferometer implemented using arrays of single-mode planar optical waveguides. The spatial heterodyne waveguide spectrometer offers high resolution and increased optical throughput (etendue) and is compatible with a microsatellite platform. A stationary Fourier technique is employed to reconstruct the input spectrum from the array of outputs. Calibration mitigates waveguide fabrication errors and input illumination non-uniformities and can be readily implemented in the spectral retrieval algorithm. Signal to noise performance is estimated for a remote sensing application using a classical telescope front end with comparison to classical techniques.
TL;DR: In this paper, 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, is presented.
Abstract: 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.
TL;DR: Polarization properties of transmission volume holographic phase gratings recorded in a photopolymerizable glass modified with high refractive index species are reported and phase analysis of the transmitted light reveals a phase discontinuity of pi at the Bragg angle.
Abstract: Polarization properties of transmission volume holographic phase gratings recorded in a photopolymerizable glass modified with high refractive index species are reported. The gratings are recorded by the interference of two parallel s-polarized writing beams with orthogonal propagation directions. High optical quality, low scattering, and diffraction efficiency of 99.4% are achieved. Degrees of polarization of 0.987 and 0.999 are obtained for transmitted and diffracted light, respectively. Furthermore, phase analysis of the transmitted light reveals a phase discontinuity of π at the Bragg angle.
17 Nov 2009
TL;DR: In this paper, the authors compare different approaches from a theoretical viewpoint and through experimental results, with the goal of defining a path from existing individual sensors to practical biosensor array chips.
Abstract: 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.
12 Feb 2009
TL;DR: In this paper, a subwavelength grating gradient index structure for efficient mode coupling in high-index slab waveguides was proposed, where the SWG transition region minimizes both mode mismatch loss and coupling to higher order modes.
Abstract: We report on new types of sub-wavelength grating gradient index structures for efficient mode coupling in high index
contrast slab waveguides. Using sub-wavelength gratings (SWGs), an adiabatic transition can be formed at the interface
between slab waveguides of different core thicknesses. The SWG transition region minimizes both mode mismatch loss
and coupling to higher order modes. By creating the adiabatic gradient effective index region in the direction of
propagation, we demonstrate that vertical mode size transformation is readily achieved in structures that can be
fabricated using a single etch step. Using 3D finite-difference time-domain simulations we study the loss, polarization
dependence and the higher order mode excitation for two types (triangular and triangular-transverse) of SWG transition
regions between silicon-on-insulator slab waveguides of different core thicknesses. We also demonstrate two solutions to
mitigate polarization dependent loss, namely using a partial transverse SWG and a SWG in the region between the
triangular teeth. Our mode transformer designs are optimized for applications in polarization compensator in echelle
grating and arrayed waveguide grating (AWG) multiplexers and a gradient index interface between the ridge waveguide
and the slab combiner region in a curved waveguide grating demultiplexer.
31 Jul 2009
TL;DR: In this article, the authors present the evolution of the planar waveguide dispersive devices developed in our laboratory for spatial heterodyne spectroscopy and apply them to a Mach-Zehnder interferometer array capable of a resolution of 0.1 nm over a bandwidth of 2.5 nm.
Abstract: 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.
01 Dec 2009
TL;DR: In this article, a zero-dispersive and two-photon adsorption free micro-ring resonator was used to achieve a nonlinear wavelength conversion with an internal efficiency as high as −26dB over a tuning range of 18nm.
Abstract: We report ultra low power four-wave mixing in a zero-dispersive and two-photon adsorption free micro-ring resonator. A nonlinear wavelength conversion with an internal efficiency as high as −26dB has been experimentally achieved over a tuning range of 18nm. The theoretical model predicts a phase-matching range larger than 100nm.
12 Jul 2009
TL;DR: In this article, a densely folded spiral cavity resonator with Q > 20,000 and an area of 30?m × 30 m was presented, and the authors showed that extended cavity length increases Q and improves the fabrication robustness of resonators.
Abstract: We demonstrate densely folded spiral cavity resonator with Q > 20,000 and an area of 30 ?m × 30 ?m. We show that extended cavity length increases Q and improves the fabrication robustness of resonators.
31 Jul 2009
TL;DR: In this article, the sub-wavelength grating effect in SOI waveguides is exploited for fabricating materials with intermediate refractive indices by standard lithographic patterning.
Abstract: 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.
TL;DR: The properties of a photopolymerizable glass modified with high refractive index species incorporated at molecular level, including a wide range of spatial frequencies and the recording kinetics, are analyzed in this paper.
Abstract: The properties of a photopolymerizable glass modified with high refractive index species incorporated at molecular level, including a wide range of spatial frequencies and the recording kinetics, are analyzed. Implementation of emerging applications is proposed.
17 Nov 2009
TL;DR: In this paper, a SOI ring resonator biosensor array with 1 reference ring and 4 sensing rings, using WDM as the addressing scheme, is presented, and the differential signal shows a low temperature sensitivity of ~ ± 0.8 pm/°C.
Abstract: 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.
14 Jun 2009
TL;DR: In this paper, the authors demonstrate a simple method to localize reflections occurring inside the chip using only wavelength-swept power transmission measurements, which does not require a special measurement setup and is based on minimum phase techniques.
Abstract: Spurious reflections can be a problematic issue in integrated optical devices, such as lasers [1], detectors [2], or multi-mode interference (MMI) couplers [3]. Here we demonstrate a simple method to localize such faint reflections occurring inside the chip, using only wavelength-swept power transmission measurements. The method does not require a special measurement setup and is based on minimum phase techniques, which were recently proposed for integrated optical device characterization [4].
12 Jul 2009
TL;DR: In this article, the authors 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.
Abstract: 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.
12 Jul 2009
TL;DR: In this paper, the authors introduce several types of new waveguide spectrometers, including a high-resolution 50-channel AWG spectrometer, a 40-channel broadband AWG and a Si-wire sidewall grating multiplexer.
Abstract: We introduce several types of new waveguide spectrometers, namely a high-resolution 50-channel AWG spectrometer, a 40-channel broadband AWG spectrometer, a Si-wire sidewall grating multiplexer, and the first planar waveguide Fourier-transform spectrometer.
10 Feb 2009
TL;DR: In this article, the authors developed label-free molecular sensors using silicon nanophotonic waveguides and showed that the high index contrast of these waveguide provides high surface sensitivity and enables compact sensor designs to be realized.
Abstract: 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.
10 May 2009
TL;DR: In this paper, the authors present an overview of the main properties and emerging implementations corresponding to a photopolymerizable glass modified with high refractive index species (HRIS) incorporated at molecular level.
Abstract: We present an overview of the main properties and the emerging implementations corresponding to a photopolymerizable glass modified with high refractive index species (HRIS) incorporated at molecular level. The main characteristic of the HRIS photopolymerizable glass is the codirectional diffusion enhancement of monomer and HRIS species upon inhomogeneous illumination, yielding an increased dynamic range, along with low coherent and incoherent scattering noise, high optical quality and dimension stability[1-2-3]. The study concerns to transmission and reflection holograms in Bragg and Raman-Nath regimens for standard and over-modulated gratings[4] with spatial frequencies range from 50 to 6000 lines/mm. Polarization properties of gratings with high spatial frequencies are also analyzed demonstrating a strong dependence of the refractive index modulation with the polarization state of the reading beam [5].