Mode dynamics in coupled disk optical microresonators

Die vorliegende Dissertation beschäftigt sich mit gekoppelten optischen Flüstergalerieresonatoren in Form von Mikrodiskresonatoren und deren kollektiven resonanten Anregungen, den sogenannten Flüstergaleriemoden. Im Mittelpunkt der Arbeit stehen die umfassende theoretische und experimentelle Charakterisierung gekoppelter Mikrodiskresonatoren, wobei gezeigt wird, dass durch die Kopplung mehrerer Resonatoren deren herausragende Eigenschaften, wie etwa die hohe optische Güte, nur geringfügig beeinflusst werden. Der Nachweis der optischen Kopplung der Moden in den vorliegenden Strukturen wird anhand der charakteristischen spektralen Resonanzaufspaltung erbracht, die von der Anzahl als auch der Anordnung der einzelnen Mikroresonatoren abhängt. Es wird eine Methode vorgestellt, mit welcher erstmals die Intensitätsverteilung der kollektiven Anregungen in gekoppelten Scheibenresonatoren mit einer räumlichen Auflösung im Nanometerbereich gemessen werden kann. Aufbauend auf der Realisierung gekoppelter Mikroresonatoren erfolgt die Untersuchung des Einflusses thermischer nichtlinearer Effekte auf die Resonatormoden. Diese dynamische Licht-Materie-Wechselwirkung wird durch Absorption des Lichts in den Mikroresonatoren und der thermischen Relaxationszeit des Resonatorsystems bestimmt. In diesem Zusammenhang wird eine anregungsleistungsabhängige Resonanzverschiebungen und optische Bistabilität in gekoppelten Mikrodiskresonatoren untersucht. Durch Kombination der thermischen Nichtlinearität und der charakteristischen Intensitätsverteilung der einzelnen Moden kann somit in gekoppelten Mikrodiskresonatoren eine differentielle opto-optische Resonanzverstimmung realisiert werden. Des Weiteren erlaubt die detaillierte Kenntnis der thermo-optischen Eigenschaften der Mikrodiskresonatoren die Realisierung einer Methode zur Kompensation der thermisch induzierten Resonanzverstimmungen, wodurch die Resonanzwellenlänge für einen großen Bereich der Anregungsleistung stabilisiert werden kann

Estudio y diseño de dispositivos ópticos biosensores depositados con películas delgadas basados en detección de longitud de onda de resonancias

A lo largo de esta tesis se presenta el estudio y diseño de varias plataformas de guía-ondas ópticas, con el fin de ver su viabilidad a la hora de usarlas como biosensores sobre fibra óptica u otros sustratos fotónicos. En este trabajo se depositan estructuras ópticas como una fibra monomodo desnuda, un estrechamiento en fibra óptica o una fusión de fibras mono – multi – monomodo (SMS) con películas delgadas de materiales usando técnicas nanotecnológicas como el ensamblado capa a capa (LbL-assembly) o el sputtering. Además, se dedica un capítulo al estudio de microresonadores toroidales depositados por rotación (spin-coating). El objetivo es generar o mejorar las prestaciones en resolución y sensibilidad de los fenómenos resonantes que se pueden obtener en estas estructuras ópticas, para luego detectar reacciones biológicas que den lugar a un futuro diagnóstico precoz de enfermedades.Along this thesis, the study and design of several optical waveguide platforms is presented, in order to check their viability when used as biosensors based on either optical fiber or other photonic substrates. In this work, some fiber-optic-based structures such as cladding removed multimode structures, tapered single-mode fibers and single-mode – multimode – single-mode fibers are deposited with thin-films of materials, using nanotechnology-based methods such as layer-by-layer assembly (LbL-assembly) or sputtering. Moreover, a brief chapter is focused on the study of toroidal microring resonators deposited by spin-coating. The final objective is to generate or enhance the parameters of the resonant phenomena obtained in these structures, in terms of resolution and sensitivity. Then, a biological detection is addressed and characterized, to see if they are able to perform a future early diagnosis for illnesses.La realización de este trabajo ha sido posible gracias a las aportaciones económicas recibidas por parte de la Universidad Pública de Navarra (UPNA), así como del patrocinio de la UPNA y del Ministerio de Economía y Competitividad, a través de los proyectos CICYT fondos FEDER TEC2010-17805, TEC2013-43679-R e IPT-2011-1212-920000 (PMEL).Programa Oficial de Doctorado en Ingeniería y Arquitectura (RD 1393/2007)Ingeniaritzako eta Arkitekturako Doktoretza Programa Ofiziala (ED 1393/2007

Akinetic Tuneable Optical Sources with Applications

Optical Coherence Tomography (OCT) is a modern, non-invasive imaging technique in biomedical research and medical diagnostics. It was initially developed for clinical applications in ophthalmology, providing high-resolution, cross-sectional images of the retina, retinal nerve fibre layer and the optic nerve head. Today, OCT is used for in vivo imaging of almost every type of tissue and it also branched out in fields outside medicine, like industrial or pharmaceutical applications. OCT is a continuously improving imaging technique, benefiting from the development of advanced optical components and broadband optical sources. The objective of the work presented in the thesis was the development of both short and, respectively, long cavity akinetic optical devices, employing several types of dispersive optical fibre components in the cavity, like chirped fibre Bragg gratings, single mode or dispersion compensating fibre, and actively radio-frequency tuned semiconductor optical amplifiers, used as gain media. The use of external modulators, like Fabry-Perot assemblies, rotating mirrors and other mechanical devices is therefore completely eliminated, while versatility is added in the control of the coherence length, output bandwidth, repetition rate and power. The short cavity source was developed in the 1060 nm region, the output power and bandwidth showing a slow decay with the increase of repetition rate up to 250 kHz. Without any booster, the power achieved was 2 mW at 100 kHz. A novel dual-mode-locking mechanism was developed in order to tune an akinetic swept source based on dispersive cavities at a repetition rate close to, but different from the inverse of the cavity roundtrip. Several optical source configurations emitting in the 1060 nm or 1550 nm wavelength region were developed, characterised and tested in OCT applications. For the 1550 nm swept source employing a Faraday Rotating Mirror in a dispersive cavity, sweeping rates in the range of MHz were achieved, from 782 kHz to up to 5 times this value, with proportional decrease in the tuning bandwidth. Linewidths smaller than 60 pm and output powers exceeding 10 mW were measured. OCT topographic imaging was demonstrated. The thesis ends with a proposed broadband investigation of microresonators written in silica glass employing akinetic optical sources at 1550 nm. The work presented in this thesis resulted in several peer reviewed papers, one patent application and several conference presentations, listed after the final conclusions

A New Silicon-Based Dielectric Waveguide Technology for Millimeter-Wave/Terahertz Devices and Integrated Systems

In recent decades, the millimeter-Wave (mmWave)/THz band has attracted great attention in the research community. The Terahertz frequency band runs from approximately 300 GHz to 3 THz, an incredible 2700 GHz of bandwidth. The Terahertz frequency range has traditionally been considered as the RF "no man's land", between electronic and optical technologies. Many efforts have been made to extend existing active and passive devices to take advantage of these higher frequencies. The development of a universal technology for integrating various functionalities in the THz region is the ultimate goal of many researchers. The primary focus of this research is to develop a novel silicon waveguide-based technology for implementing various structures and devices in the mmWave and THz range of frequencies. The structures introduced in this study are designed based on High Resistivity Silicon (HRS). Two technologies are developed and investigated at the Centre for Intelligent Antenna and Radio Systems (CIARS): Silicon-On-Glass (SOG) and Silicon Image Guide (SIG) technologies. The proposed technologies provide a low-cost, highly efficient, and integratable platform for realization a variety of mmWave/THz systems suitable for various applications such as sensing, communication, and imaging. A comprehensive study is conducted for functionality and error analysis of the proposed technologies. Also, a vast range of passive structures such as bends, dividers, and couplers are designed, fabricated and successfully tested with desired performance at the mmWave range of frequencies. Additionally, three types of dielectric waveguide antennas are designed and optimized: parasitic tapered antenna, groove grating antenna, and strip grating antenna. Another focus of this thesis is to investigate the behavior of resonance structures, operating based on Whispering Gallery Modes (WGMs). The WG mode is a special type of high order mode of a circular shaped resonator, and offers very unique properties, which make it very suitable for sensing applications. In this research, an efficient algorithm is developed for analyzing the WGM resonators. Then, the proposed HRS platforms are used for implementing various WGM resonance configurations. The introduced WGM structures are employed for two major applications: DNA sensing and resonance tuning. The results for DNA testing are quite impressive in being able to distinguish between different kinds of DNA. To demonstrate the usefulness of the developed HRS structures, a number of complex systems including, a Butler matrix network, a finger-shaped phase shifter, and tunable WGM resonance structures are designed, optimized, and realized in this report. As part of this research, a novel Microwave-Photonic idea is proposed for sensing purposes. The core of the system is based on the WGM resonance structures implemented on the HRS platforms. The proposed system is tested and promising results are achieved.4 month

Nanoparticle-coated Optical Microresonators for Whispering-gallery Lasing and Other Applications

The purpose of this study is to explore the properties of high quality optical microsphere resonators in combination with various types of nanoparticles deposited on their surfaces. Optical whispering-gallery modes of the silica microspheres were pumped efficiently by tapered optical fibers. For whispering-gallery lasing, the microspheres were coated with HgTe and HgCdTe quantum dots. Gold nanorods were grown on the surface of the microspheres nucleated by HgTe nanoparticles. Lasing in HgTe was demonstrated for the first time and record low thresholds were measured in these devices. Interesting effect on enhancement of evanescent coupling was observed with microsphere resonators with gold nanorods grown on their surfaces. We develop a new procedure that uses semiconductor nanoparticles as seeds for growth of gold nanorods.Department of Physic

Glassy Materials Based Microdevices

Microtechnology has changed our world since the last century, when silicon microelectronics revolutionized sensor, control and communication areas, with applications extending from domotics to automotive, and from security to biomedicine. The present century, however, is also seeing an accelerating pace of innovation in glassy materials; as an example, glass-ceramics, which successfully combine the properties of an amorphous matrix with those of micro- or nano-crystals, offer a very high flexibility of design to chemists, physicists and engineers, who can conceive and implement advanced microdevices. In a very similar way, the synthesis of glassy polymers in a very wide range of chemical structures offers unprecedented potential of applications. The contemporary availability of microfabrication technologies, such as direct laser writing or 3D printing, which add to the most common processes (deposition, lithography and etching), facilitates the development of novel or advanced microdevices based on glassy materials. Biochemical and biomedical sensors, especially with the lab-on-a-chip target, are one of the most evident proofs of the success of this material platform. Other applications have also emerged in environment, food, and chemical industries. The present Special Issue of Micromachines aims at reviewing the current state-of-the-art and presenting perspectives of further development. Contributions related to the technologies, glassy materials, design and fabrication processes, characterization, and, eventually, applications are welcome

Non-Invasive Blood Glucose Monitoring Using Electromagnetic Sensors

Monitoring glycemia levels in people with diabetes has developed rapidly over the last decade. A broad range of easy-to-use systems of reliable accuracies are now deployed in the market following the introduction of the invasive self-monitoring blood glucose meters (i.e., Glucometers) that utilize the capillary blood samples from the fingertips of diabetic patients. Besides, semi-invasive continuous monitors (CGM) are currently being used to quantify the glucose analyte in interstitial fluids (ISF) using an implantable needle-like electrochemical sensors. However, the limitations and discomforts associated with these finger-pricking and implantable point-of-care devices have established a new demand for complete non-invasive pain-free and low-cost blood glucose monitors to allow for more frequent and convenient glucose checks and thereby contribute more generously to diabetes care and prevention. Towards that goal, researchers have been developing alternative techniques that are more convenient, affordable, pain-free, and can be used for continuous non-invasive blood glucose monitoring. In this research, a variety of electromagnetic sensing techniques were developed for reliably monitoring the blood glucose levels of clinical relevance to diabetes using the non-ionizing electromagnetic radiations of no hazards when penetrating the body. The sensing structures and devices introduced in this study were designed to operate in specific frequency spectrums that promise a reliable and sensitive glucose detection from centimeter- to millimeter-wave bands. Particularly, three different technologies were proposed and investigated at the Centre for Intelligent Antenna and Radio Systems (CIARS): Complementary Split-Ring Resonators (CSRRs), Whispering Gallery Modes (WGMs) sensors, and Frequency-Modulated Continuous-Wave (FMCW) millimeter-Wave Radars. Multiple sensing devices were developed using those proposed technologies in the micro/millimeter-wave spectrums of interest. A comprehensive study was conducted for the functionality, sensitivity, and repeatability analysis of each sensing device. Particularly, the sensors were thoroughly designed, optimized, fabricated, and practically tested in the laboratory with the desired glucose sensitivity performance. Different topologies and configurations of the proposed sensors were studied and compared in sensitivity using experimental and numerical analysis tools. Besides, machine learning and signal processing tools were intelligently applied to analyze the frequency responses of the sensors and reliably identify different glucose levels. The developed glucose sensors were coupled with frequency-compatible radar boards to realize small mobile glucose sensing systems of reduced cost. The proposed sensors, beside their impressive detection capability of the diabetes-spectrum glucose concentrations, are endowed with favourable advantages of simple fabrication, low-power consumption, miniaturized compact sizing, non-ionizing radiation, and minimum health risk or impact for human beings. Such attractive features promote the proposed sensors as possible candidates for development as mobile, portable/wearable gadgets for affordable non-invasive blood glucose monitoring for diabetes. The introduced sensing structures could also be employed for other vital sensing applications such as liquid type/quantity identification, oil adulteration detection, milk quality control, and virus/bacteria detection. Another focus of this thesis is to investigate the electromagnetic behavior of the glucose in blood mimicking tissues across the microwave spectrum from 200 MHz to 67 GHz using a commercial characterization system (DAK-TL) developed by SPEAG. This is beneficial to locate the promising frequency spectrums that are most responsive to slight variations in glucose concentrations, and to identify the amount of change in the dielectric properties due to different concentrations of interest. Besides, the effect of the blood typing and medication was also investigated by measuring the dielectric properties of synthetic “artificial” as well as authentic “human” blood samples of different ABO-Rh types and with different medications. Measured results have posed for other factors that may impact the developed microwave sensors accuracy and sensitivity including the patient’s blood type, pre-existing medical conditions, or other illnesses