Optical Slot-Waveguide Based Biochemical Sensors

Slot-waveguides allow light to be guided and strongly confined inside a nanometer-scale region of low refractive index. Thus stronger light-analyte interaction can be obtained as compared to that achievable by a conventional waveguide, in which the propagating beam is confined to the high-refractive-index core of the waveguide. In addition, slot-waveguides can be fabricated by employing CMOS compatible materials and technology, enabling miniaturization, integration with electronic, photonic and fluidic components in a chip, and mass production. These advantages have made the use of slot-waveguides for highly sensitive biochemical optical integrated sensors an emerging field. In this paper, recent achievements in slot-waveguide based biochemical sensing will be reviewed. These include slot-waveguide ring resonator based refractometric label-free biosensors, label-based optical sensing, and nano-opto-mechanical sensors

Classical and fluctuation-induced electromagnetic interactions in micronscale systems: designer bonding, antibonding, and Casimir forces

Whether intentionally introduced to exert control over particles and macroscopic objects, such as for trapping or cooling, or whether arising from the quantum and thermal fluctuations of charges in otherwise neutral bodies, leading to unwanted stiction between nearby mechanical parts, electromagnetic interactions play a fundamental role in many naturally occurring processes and technologies. In this review, we survey recent progress in the understanding and experimental observation of optomechanical and quantum-fluctuation forces. Although both of these effects arise from exchange of electromagnetic momentum, their dramatically different origins, involving either real or virtual photons, lead to different physical manifestations and design principles. Specifically, we describe recent predictions and measurements of attractive and repulsive optomechanical forces, based on the bonding and antibonding interactions of evanescent waves, as well as predictions of modified and even repulsive Casimir forces between nanostructured bodies. Finally, we discuss the potential impact and interplay of these forces in emerging experimental regimes of micromechanical devices.Comment: Review to appear on the topical issue "Quantum and Hybrid Mechanical Systems" in Annalen der Physi

Fully integrated transducer platform with cavity optomechanical readout

Research and development of transducers based on cavity optomechanics is a topic of high interest particularly because these transducers enable measurement of mechanical motion down to the fundamental limit of precision imposed by quantum mechanics. The development of an on-chip cavity optomechanical transducer platform that combines high bandwidth and sensitivity near the standard quantum limit with compactness, robustness, small size, and potential for low cost batch fabrication inherent in MEMS is demonstrated as a proof of concept study. Design, fabrication and characterization of fully integrated and fiber pigtailed transducers is presented. The devices combine high sensitivity (0.14 - 40 fm·Hz^(-1/2), high bandwidth optomechanical readout and built-in thermal and electrostatic actuation. It is implemented by a double-side wafer-scale microfabrication process combining one e-beam, six stepper, and three contact mask aligner lithography steps. The SiN probes can be actuated using an electrical signal supplied to an integrated thermal or electrostatic actuator. The probe is evanescently coupled to a high-Q (10^5 - 2 x 10^6) optical whispering gallery mode of the optical microdisk cavity and the motion is detected by measuring the resonance frequency shift of the optical cavity mode. The actuator can be used to dynamically move the probe as well as to tune the distance between the cantilever and the optical cavity, to change the sensitivity and range of measurement of the cantilever. One side of the probe overhangs the edge of the chip, where it can be easily coupled to a variety of off-chip samples and physical systems of interest. The modular design of the transducer allows for parallelization, which enables the possibility of sensor arrays for simultaneous detection of multiple forces or other physical properties. Parallelization is shown on a 2x1 array, which can be easily extended to larger array architectures. The application of the probe arrays and single probes in a commercial scanning probe microscope is shown. In addition the flexibility of this transducer approach is demonstrated with membrane transducers and acceleration sensors. The performance of all presented transducers is studied, focusing on displacement sensitivity, frequency stability and readout gain tuning.Forschung und Entwicklung von Wandlern basierend auf kavität- optomechanischen Elementen ist ein Forschungsgebiet von hohem Interesse. Sie kombiniert hohe Bandbreiten und Empfindlichkeit nahe dem Standardquantumlimit mit Kompaktheit, Robustheit, kleinen Abmessungen und dem Potential für eine wirtschaftliche Massenproduktion systemimmanent bei mikroelektromechanischen Systemen. Vollintegrierte Wandler erlauben demnach Bewegungsmessungen bis hin zum fundamentalen Quantenlimit. In dieser Arbeit werden Design, Herstellung und Charakterisierung eines vollintegrierten und glasfasergekoppelten Wandlers in einer Machbarkeitsstudie dargestellt. Das System kombiniert hohe Verschiebungsauflösungen 0.14 - 40 fm· Hz^(-1/2), optomechanische Detektion mit hoher Bandbreite und eine eingebaute thermische und elektrostatische Anregung. Die Herstellung erfolgt in einem doppelseitigen mikro- und nanotechnischen Fertigungsverfahren auf Waferbasis, in einer Kombination aus einem Elektronenstrahllithographieschritt, sechs Projektionslithographieschritten und drei Kontaktlithographie Schritten. Die Siliziumnitrid-Sonden können mittels eines elektrischen Signals, angelegt an den integrierten thermischen oder elektrostatischen Aktuator, angeregt werden. Sie sind optisch über das evanecente Feld mit einer optischen Kavität hoher Güte (10^5 - 2 x 10^6) gekoppelt. Die Bewegung der Sonde wird detektiert über eine Veränderung der Resonanzfrequenz der Kavität. Die eingebauten Aktuatoren ermöglichen die Einstellung des Abstandes zwischen Sonde und optischer Kavität, welche die Einstellung der Sensitivität ermöglicht. Eine Seite der Sonde steht über die Kante des Siliziumchips, um die Kopplung mit einer Vielzahl von Proben und physikalischen Systemen zu erlauben. Die modulare Bauweise des Wandlers schafft die Grundlage zur Parallelisierung der Sonden für die gleichzeitige Messung mehrerer Kräfte oder physikalischer Eigenschaften. Die Parallelisierung wird in dieser Arbeit am Beispiel eines 2x1 Array gezeigt, welche mit geringem Aufwand auf größere Arrayarchitekturen angepasst werden kann. Zur Demonstration der Funktion von Einzelsonden und Sondenarrays, wird die Sondenanwendung in der Rasterkraftmikroskopie präsentiert. Des Weiteren wird die Flexibilität der Wandlerbauweise an der Herstellung von Membrane- und Beschleunigungswandlern belegt. Das Verhalten aller hergestellten Wandler wird hinsichtlich der Bewegungsempfindlichkeit, Frequenzstabilität, und Einstellbarkeit der Auslesung analysiert

MEMS Technology for Biomedical Imaging Applications

Biomedical imaging is the key technique and process to create informative images of the human body or other organic structures for clinical purposes or medical science. Micro-electro-mechanical systems (MEMS) technology has demonstrated enormous potential in biomedical imaging applications due to its outstanding advantages of, for instance, miniaturization, high speed, higher resolution, and convenience of batch fabrication. There are many advancements and breakthroughs developing in the academic community, and there are a few challenges raised accordingly upon the designs, structures, fabrication, integration, and applications of MEMS for all kinds of biomedical imaging. This Special Issue aims to collate and showcase research papers, short commutations, perspectives, and insightful review articles from esteemed colleagues that demonstrate: (1) original works on the topic of MEMS components or devices based on various kinds of mechanisms for biomedical imaging; and (2) new developments and potentials of applying MEMS technology of any kind in biomedical imaging. The objective of this special session is to provide insightful information regarding the technological advancements for the researchers in the community

MEMS tunable infrared metamaterial and mechanical sensors

Sub-wavelength resonant structures open the path for fine controlling the near-field at the nanoscale dimension. They constitute into macroscopic “metamaterials” with macroscale properties such as transmission, reflection, and absorption being tailored to exhibit a particular electromagnetic response. The properties of the resonators are often fixed at the time of fabrication wherein the tunability is demanding to overcome fabrication tolerances and afford fast signal processing. Hybridizing dynamic components such as optically active medium into the device makes tunable devices. Microelectromechanical systems (MEMS) compatible integrated circuit fabrication process is a promising platform that can be merged with photonics or novel 2D materials. The prospect of enormous freedom in integrating nanophotonics, MEMS actuators and sensors, and microelectronics into a single platform has driven the rapid development of MEMS-based sensing devices. This thesis describes the design and development of four tunable plasmonic structures based on active media or MEMS, two graphene-based MEMS sensors and a novel tape-based cost-effective nanotransfer printing techniques. First of all, we present two tunable plasmonic devices with the use of two active medium, which are electrically controlled liquid crystals and temperature-responsive hydrogels, respectively. By incorporating a nematic liquid crystal layer into quasi-3D mushroom plasmonic nanostructures and thanks to the unique coupling between surface plasmon polariton and Rayleigh anomaly, we have achieved the electrical tuning of the properties of plasmonic crystal at a low operating electric field. We also present another tunable plasmonic device with the capability to sense environmental temperature variations. The device is bowtie nanoantenna arrays coated with a submicron-thick, thermos-responsive hydrogel. The favorable scaling of plasmonic dimers at the nanometer scale and ionic diffusion at the submicron scale is leveraged to achieve strong optical resonance and rapid hydrogel response, respectively. Secondly, we present two MEMS -based tunable near-to-mid infrared metamaterials on a silicon-on-insulator wafer via electrically and thermally actuating the freestanding nanocantilevers. The two devices are developed on the basis of the same fabrication process and are easy-to-implement. The electrostatically driven metamaterial affords ultrahigh mechanical modulation (several tens of MHz) of an optical signal while the thermo-mechanically tunable metamaterial provides up to 90% optical signal modulation at a wavelength of 3.6 õm. Next, we present MEMS graphene-based pressure and gas flow sensors realized by transferring a large area and few-layered graphene onto a suspended silicon nitride thin membrane perforated with micro-through-holes. Due to the increased strain in the through-holes, the pressure sensor exhibits a very high sensitivty outperformed than most existing MEMS-based pressure sensors using graphene, silicon, and carbon nanotubes. An air flow sensor is also demonstrated via patterning graphene sheets with flow-through microholes. The flow rate of the air is measured by converting the mechanically deflection of the membrane into the electrical readout due to the graphene piezeroresistors. Finally, we present a tape-based multifunctional nanotransfer printing process based on a simple stick-and-peel procedure. It affords fast production of large-area metallic and dielectric nanophotonic sensing devices and metamaterials using Scotch tape

Multiscale optical patterning: using micro and nano periodic structures to create novel optical devices with applications to biosensing

Patterning, the utilisation and manipulation of geometric properties, is important both for the rational design of technological devices and also to the understanding of many natural phenomena. In this thesis I examine the way in which micro and nano patterning can alter optical properties across a large range of wavelength scales and how these novel phenomena can be utilised. Micro patterned electrodes can tune the geometry of radio frequency electric fields to generate dielectrophoretic microfluidic devices. These devices use the dielectrophoretic force to sort, position and characterise the properties of micro and nano particles.. I develop a new image processing algorithm that radically improves experimental efficiency allowing for real-time supervisor free dielectrophoretic characterisation of nanoparticles. Metamaterials are composite structures that have repeating units that are much smaller than the wavelength of radiation they are designed to work with. The optical properties of the materials are derived from these units rather than the bulk characteristics of the materials they are composed of. I demonstrate the development of novel THz metamaterial absorber devices. These devices provide a means to design and control the absorption of THz radiation, modulating bandwidth, polarization dependence and frequency in a form that is readily integrable with other standard fabrication processes. Finally by periodically patterning materials on the nanometer scale I demonstrate the development of novel photonic crystal devices and complementary optical components. In these devices the periodicity of the electromagnetic wave is modulated by the periodicity of the structures themselves resulting in band gaps and resonances analogous to the band gaps and defect states found commonly in semi-conductor physics. I demonstrate the theory, fabrication and measurement of these devices using novel broadband supercontinuum sources and propose a future application for biosensing. Further topics covered in the appendix include the development of a spin out technology, a $100 open source atomic force microscope developed while spending time in China. Finally I examine the role of patterning for optimising the performance of nanomechanical cantilever biosensors, and show how geometrical effects on the microscopic scale are crucial to understanding the workings of the vancomycin family of antibiotics, as screened using microcantilevers. Portions of this report are edited extracts from published articles resulting from this work, a full list of which is given in Appendix A

Hybrid Micro-Electro-Mechanical Tunable Filter

While advantages such as good thermal stability and processing-chemical compatibilities exist for common monolithic-integrated micro-electro-mechanically tunable filters (MEM-TF) and MEM-tunable vertical cavity surface emitting lasers (MT-VCSEL), they often require full processing to determine device characteristics. Alternatively, the MEM actuators and the optical parts may be fabricated separately, then subsequently bonded. This hybrid approach potentially increases design flexibility. Since hybrid techniques allow integration of heterogeneous material systems, best of breed compound optoelectronic devices may be customized to enable materials groups to be optimized for tasks they are best suited. Thus, as a first step toward a hybrid (AlxGa1-xAs-polySi) MT-VCSEL, this dissertation reports the design, fabrication, and demonstration of an electrostatically actuated hybrid MEM-TF. A 250x250-µm2, 4.92-µm-thick, Al0.4Ga0.6As-GaAs distributed Bragg reflector was successfully flip-bonded to a polySi piston electrostatic actuator using SU-8 photoresist as bonding adhesive. The device demonstrated 53nm (936.5 - 989.5nm) of resonant wavelength tuning over the actuation voltage range of 0 to 10 V