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P.V.S. Pham Van So

Bio: P.V.S. Pham Van So is an academic researcher. The author has contributed to research in topics: Slow light & Optical cavity. The author has an hindex of 1, co-authored 1 publications receiving 7 citations.

Papers
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DissertationDOI
01 Jun 2012
TL;DR: In this article, the authors demonstrate the versatility of a silicon nitride grated waveguide (GWG) optical cavity as a compact IO sensor for bulk-index concentration sensing, label-free protein sensing and mechano-optical gas sensing.
Abstract: Integrated Optical Sensors utilizing Slow-light Propagation in Grated-waveguide Cavities Owing to the small size of integrated optical (IO) devices many basic functions can be integrated on one single IO chip. IO sensors are suitable candidates for accurate detection of small changes of physical or chemical parameters. The integration offers advantages such as enabling a high density of functionalities, automatic and stable alignment of elements, a high potential for mass production with in principle low production costs, and the possibility for the realization of sensor arrays for multi-parameter detection. The main goal of this PhD project is firstly to design, fabricate and demonstrate functioning IO devices based on grated waveguides for sensing applications. A grated waveguide (GWG) is a waveguide with a finite-length grated section, being a structure with a periodic variation of the dielectric constant. Such a structure acts as both a 1-dimensional photonic crystal (PhC) and, owing to modal reflections at the waveguide-GWG transitions, an optical resonator, as evidenced by fringes in the transmission spectrum. In particular near the band edge these fringes can be extremely sharp, which is related to both the near band edge shape of the dispersion curve, corresponding to slow light propagation, and high modal reflectance due to mode mismatch between WG and GWG modes. Both effects lead to strong light-matter interaction, which can be exploited for sensing applications. In this thesis, we demonstrate the versatility of a silicon nitride GWG optical cavity as a compact IO sensor for bulk-index concentration sensing, label-free protein sensing and mechano-optical gas sensing. For concentration sensing, the sensing principle is based on the bulk index change of the GWG top cladding. The principle of the label-free protein sensing relies on the growth and measurement of an ad-layer on the GWG surface, owing to the antigen-antibody interaction. The mechano-optical gas sensing is based on stress-induced deflections of a microcantilever (μCL) suspended above the GWG, which are due to H2 gas absorption by the palladium receptor layer coated on the μCL surface. In the first chapter of this thesis an overview is given of bio- and gas-sensors. In chapter 2, the background of slow light propagation in GWGs and its utilization for sensing applications are discussed. In chapter 3, results related to the first 2 sensing applications (concentration sensing and label-free protein sensing) are presented; here, sensitivity and limit of detection of the sensors are analyzed in detail. The design and fabrication of the GWG-CL integrated readout, and the demonstration of the integrated mechano-optical sensor for gas sensing, are presented in chapter 4 and chapter 5, respectively. Results of an optimization study of the integrated mechano-optical readout principle, on the basis of numerical calculations, is presented in chapter 6. In chapter 7, conclusions and outlook, based on the results presented in this thesis, are given.

7 citations


Cited by
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04 Apr 2001
TL;DR: In this paper, a review of the most relevant developments in the field of integrated optical (IO) sensors is presented, where strong and weak points of principle and configuration based on these principles are indicated and main performance data of the IO sensing platforms, especially the obtained resolution, are indicated.
Abstract: During the last decade there has been a rapidly growing interest in integrated optical (IO) sensors, expecially because many of them principally allow for sensitive, real time, label-free-on-site measurements of the concentration of (bio-)chemical species. This review aims at giving an overview of the most relevant developments in this area. After a general introduction into the field of IO sensors for the chemical domain, relevant aspects of integrated optics and chemical sensing are presented in short. A large variety of IO sensing platforms are introduced and discussed: interferometers, resonators, coupling-based devices such as grating couplers and surface plasmon resonance based sensors and finally a new class of sensors based on chemically induced field profile changes. Strong and weak points of principle and of configuration based on these principles are indicated and the main performance data of the IO sensing platforms, especially the obtained resolution, are indicated. Best resolutions of the chemically induced refractive indices on the order of magnitude $10^{-6}-10^{-8}RIU$ can be obtained, corresponding to a resolution of $10^{-3}-10^{-5}$nm in the chemically induced growth of layer thickness of chemo-optical transducer materials. Depending on the anlalyte and the type of transduction layer chemical concentrations down to some ppb or some pg $ml^{-1}$can be determined. Several IO sensing systems are commercially available. Extension of individual sensors to sensor arrays is treated and finally an outlook for the future is given.

215 citations

01 Jun 2011
TL;DR: In this paper, the authors used Bragg-grating cavities inscribed into optical waveguides for label-free sensing of antibody-antigen protein reactions and H2 gas sensing by stress-induced Pd-receptor microcantilever deflections.
Abstract: Use of optical principles for the detection and analysis of biomolecules and biotissue has a long-standing tradition, and highly sensitive optical methods have been developed. Integration on a microchip offers cost reduction and instrument miniaturization, thus enabling novel applications, but also allows reduced biosample volumes, higher sensitivity, and faster acquisition times. We demonstrate optical sensing with Bragg-grating cavities inscribed into optical waveguides for label-free sensing of antibody-antigen protein reactions and H2 gas sensing by stress-induced Pd-receptor microcantilever deflections. Furthermore, we introduce the method of modulation-frequency-encoded multi-wavelength fluorescent DNA analysis in an optofluidic chip during capillary electrophoresis separation, enabling detection down to the single-molecule level and allowing simultaneous analysis of DNA fragments from independent human genomic segments, associated with genetic predispositions to breast cancer and anemia, in a single experiment. Finally, by integrating wavelength-selective arrayed-waveguide gratings on a microchip, we demonstrate on-chip Raman spectroscopy and spectral-domain optical coherence tomography of biotissue.

3 citations

01 Aug 2009
TL;DR: In this article, the 2D bidirectional eigenmode propagation (BEP) method has been applied to analyze the effect of cantilever displacement on the optical transmission spectrum of the Si3N4 grated waveguide (GWG).
Abstract: We present results related to the simulation and fabrication of a novel and highly sensitive mechano-optical sensor for gas detection (i.e., hydrogen gas) based on microcantilevers, supplied with a selective gas absorption layer, suspended above a Si3N4 grated waveguide (GWG). The presence of a dielectric object, in this case a suspended cantilever, in the evanescent field region of the GWG may lead to the occurrence of propagating modes for wavelengths inside the stop band of the grating, and so to defect modes inside the stop band. These modes introduce sharp features in the transmission spectrum of the device. These features are quite suitable to monitor stress induced bending of the cantilever owing to concentration changes of the gas for which the absorptive layer is sensitive. The 2D bidirectional eigenmode propagation (BEP) method has been applied to analyze the effect of cantilever displacement on the optical transmission spectrum of the GWG. The simulation results show that as the cantilever approaches the grating, the first near band-edge resonance peak is pulled inside the stop band and its spectral width decreases. The resolution of displacement measurement is estimated to be 0.2 nm for a 200 nm thick cantilever at a 200 nm initial gap, assuming a signal-to-noise ratio (SNR) of 20 dB. Integrated microcantilever-GWG devices have been fabricated successfully using MEMS techniques. Uniform gratings have been defined with laser interference lithography. SiO2 cantilevers with low initial bending (i.e., low stress) have been fabricated by combining the tetra-ethyl-ortho-silicate chemical vapor deposition (TEOS-CVD) and plasma-enhanced chemical vapor deposition (PE-CVD) oxides, and by releasing them using a tetramethylammonium hydroxide (TMAH) wet-etching solution to remove the sacrificial poly-Si layer, followed by a freeze-drying process. Currently we are optimizing the fabrication process to achieve cantilevers with low initial bending. Detailed results, also discussing the potential of the integrated microcantilever-GWG as a novel and compact mechano-optical sensor for hydrogen gas, will be presented during the conference.

2 citations

01 Oct 1990
TL;DR: In this paper, surface plasmon resonance is applied for sensing concentrations of ammonia in air, using a thin bromo-cresol purple layer as a chemo-optical interface.
Abstract: Surface plasmon resonance is applied for sensing concentrations of ammonia in air, using a thin bromo-cresol purple layer as a chemo-optical interface. The sensor shows a dynamic range of 0.5–15 mbar, a resolution of about 5% and a response time smaller than 1 min.

2 citations

27 Nov 2009
TL;DR: In this article, the authors presented results related to the fabrication of a novel and highly sensitive mechano-optical sensor for hydrogen gas, based on microcantilevers, supplied with a selective gas absorbing layer (Pd), suspended above a Si3N4 grated waveguide (GWG).
Abstract: We present results related to the fabrication of a novel and highly sensitive mechano-optical sensor for hydrogen gas, based on microcantilevers, supplied with a selective gas absorbing layer (Pd), suspended above a Si3N4 grated waveguide (GWG). Integrated microcantilever-GWG devices have been fabricated successfully using MEMS techniques. Several technical problems encountered during the preparation of such integrated devices (i.e., grating production, surface roughness, facet quality) will be discussed and solutions to address these issues will be given as well.

2 citations