A Microring Resonator Based Negative Permeability Metamaterial Sensor

Metamaterials are artificial multifunctional materials that acquire their material properties from their structure, rather than inheriting them directly from the materials they are composed of, and they may provide novel tools to significantly enhance the sensitivity and resolution of sensors. In this paper, we derive the dispersion relation of a cylindrical dielectric waveguide loaded on a negative permeability metamaterial (NPM) layer, and compute the resonant frequencies and electric field distribution of the corresponding Whispering-Gallery-Modes (WGMs). The theoretical resonant frequency and electric field distribution results are in good agreement with the full wave simulation results. We show that the NPM sensor based on a microring resonator possesses higher sensitivity than the traditional microring sensor since with the evanescent wave amplification and the increase of NPM layer thickness, the sensitivity will be greatly increased. This may open a door for designing sensors with specified sensitivity

Radio-Frequency Sensors for High Performance Liquid Chromatography Applications

As a fast-developing analytical technique for separation, purification, identification and quantification of components in a mixture, high performance liquid chromatography (HPLC) has been widely used in various fields including biology, food, environment, pharmacy and so on. As a critical part in the HPLC system, the detector with the feature of high sensitivity, universal detection and gradient-elution compatibility is highly desired. In this dissertation, two types of radio-frequency (RF) sensors for HPLC gradient applications are presented: a tunable interferometer (TIM) and a modified square ring loaded resonator (SRLR). For the TIM-based sensor, the sensitivity is evaluated by measuring a few common chemicals in DI water at multiple frequencies from 0.98 GHz to 7.09 GHz. Less than 84 ppm limit of detection (LOD) is demonstrated. An algorithm is provided and used to obtain sample dielectric permittivity at each frequency point. When connected to a commercial HPLC system and injected with a 10 μL aliquot of 10000 ppm caffeine DI-water solution, the sensor yields a signal-to-noise ratio (SNR) up to 10 under isocratic and gradient elution operations. Furthermore, the sensor demonstrates a capability to quantify co-eluted vitamin E succinate (VES) and vitamin D3 (VD3). For the SRLR-based sensor, where a transmission line and a ring are electrically shorted with a center gap, the detection linearity is characterized by measuring water-caffeine samples from 0.77 ppm to 1000 ppm when connected to the HPLC system. A 0.231 ppm limit of detection (LOD) is achieved, revealing a comparable sensitivity with commercial ultraviolet (UV) detectors. The compatibility of the proposed sensor to gradient elution is also demonstrated. Besides, this work presents a method for the measurement of liquid permittivity without using liquid reference materials or calibration standards. The method uses a single transmission line and a single microfluidic channel which intercepts the line twice. As a result, two transmission line segments are formed with channel sections to measure liquid samples. By choosing a 2:1 ratio for the two line segment lengths, closed-form formulas are provided to calculate line propagation constants directly from measured S-parameters. Then, sample permittivity values are obtained. A coplanar waveguide is built and tested with de-ionized water, methanol, ethanol and 2-propanol from 0.1 GHz to 9 GHz. The obtained performance agrees with simulation results. The obtained sample permittivity values agree with commonly accepted values. Radiofrequency (RF) non-thermal (NT) bio-effects have been a subject of debate and attracted significant interests due to the potential health risks or beneficial applications. A miniature transverse electro-magnetic (TEM) device is designed for broadband investigation of RF NT effects on Saccharomyces cerevisiae growth, a common yeast species. The frequency-dependent yeast permittivity, obtained by measuring the difference between the medium and yeast in the medium, was used to select the applied RF frequencies, i.e., 1.0 MHz, 3.162 MHz, 10 MHz and 905 MHz. The results showed that the RF field at 3.162 MHz reduced yeast growth rates by 11.7%; however, the RF fields at 1.0 MHz and 10 MHz enhanced cell growth rates by 16.2% and 4.3%, respectively. In contrast, the RF field at 905 MHz had no effect on the growth rates

Two-dimensional alignment and displacement sensor based on movable broadside-coupled split ring resonators

This paper proposes a two-dimensional alignment and displacement sensor based on movable broadside-coupled split ring resonators (BC-SRRs). As a basis for this sensor, a one-dimensional displacement sensor based on a microstrip line loaded with BC-SRRs is presented firstly. It is shown that compared to previously published displacement sensors, based on SRR-loaded coplanar waveguides, the proposed one-dimensional sensor benefits from a much wider dynamic range. Secondly, it is shown that with modifications in the geometry of the BC-SRRs, the proposed one-dimensional sensor can be modified and extended by adding a second element to create a high-dynamic range two-dimensional displacement sensor. Since the proposed sensors operate based on a split in the resonance frequency, rather than the resonance depth, they benefit from a high immunity to environmental noise. Furthermore, since the sensors' principle of operation is based on the deviation from symmetry, they are more robust to ambient conditions such as changes in the temperature, and thus they can be used as alignment sensors as well. A prototype of the proposed two-dimensional sensor is fabricated and the concept and simulation results are validated through experiment

Microdisk Resonator With Negative Thermal Optical Coefficient Polymer for Refractive Index Sensing With Thermal Stability

In this paper, we propose a microdisk resonator with negative thermal optical coefficient (TOC) polymer for refractive index (RI) sensing with thermal stability. The transmission characteristics and sensing performances by using quasi-TE01 and quasi-TM01 modes are simulated by a three-dimensional finite element method. The influences of the TOC, RI, and thickness of the polymer on the sensing performances are also investigated. The simulation results show that the RI sensitivity Sn and temperature sensitivity ST with different polymers are in the ranges of 25.1-26 nm/RIU and 67.3-75.2 pm/K for the quasi-TE01 mode, and 94.5-110.6 nm/RIU and 1.2-51.3 pm/K for the quasi-TM01 mode, respectively. Moreover, figure-of-merit of the temperature sensing for the quasi-TM01 mode is in the range of 2 × 10-4-8 × 10-3, which can find important application in the implementation of the adiabatic devices

Doctor of Philosophy

dissertationPhotonic integration circuits (PICs) have received overwhelming attention in the past few decades due to various advantages over electronic circuits including absence of Joule effect and huge bandwidth. The most significant problem obstructing their commercial application is the integration density, which is largely determined by a signal wavelength that is in the order of microns. In this dissertation, we are focused on enhancing the integration density of PICs to warrant their practical applications. In general, we believe there are three ways to boost the integration density. The first is to downscale the dimension of individual integrated optical component. As an example, we have experimentally demonstrated an integrated optical diode with footprint 3 Ã- 3 m2, an integrated polarization beamsplitter with footprint 2.4 Ã- 2.4 m2, and a waveguide bend with effective bend radius as small as 0.65 m. All these devices offer the smallest footprint when compared to their alternatives. A second option to increase integration density is to combine the function of multiple devices into a single compact device. To illustrate the point, we have experimentally shown an integrated mode-converting polarization beamsplitter, and a free-space to waveguide coupler and polarization beamsplitter. Two distinct functionalities are offered in one single device without significantly sacrificing the footprint. A third option for enhancing integration density is to decrease the spacing between the individual devices. For this case, we have experimentally demonstrated an integrated cloak for nonresonant (waveguide) and resonant (microring-resonator) devices. Neighboring devices are totally invisible to each other even if they are separated as small as /2 apart. Inverse design algorithm is employed in demonstrating all of our devices. The basic premise is that, via nanofabrication, we can locally engineer the refractive index to achieve unique functionalities that are otherwise impossible. A nonlinear optimization algorithm is used to find the best permittivity distribution and a focused ion beam is used to define the fine nanostructures. Our future work lies in demonstrating active nanophotonic devices with compact footprint and high efficiency. Broadband and efficient silicon modulators, and all-optical and high-efficiency switches are envisioned with our design algorithm

Lab-on-a-Chip Optical Biosensor Platform: Micro Ring Resonator Integrated with Near-Infrared Fourier Transform Spectrometer

A micro-ring-resonator (MRR) optical biosensor based on the evanescent field sensing mechanism has been extensively studied due to its high sensitivity and compact device size. However, a suitable on-chip integrated spectrometer device has to be demonstrated for the lab-on-a-chip applications, which can read the resonance wavelength shift from MRR biosensors based on minuscule changes in refractive index. In this paper, we demonstrated the design and experimental results of the near-infrared lab-on-a-chip optical biosensor platform that monolithically integrates the MRR and the on-chip spectrometer on the silicon-on-insulator (SOI) wafer, which can eliminate the external optical spectrum analyzer for scanning the wavelength spectrum. The symmetric add-drop MRR biosensor is designed to have a free spectral range (FSR) of ~19 nm, and a bulk sensitivity of ~73 nm/RIU; then the drop-port output resonance peaks are reconstructed from the integrated spatial-heterodyne Fourier transform spectrometer (SHFTS) with the spectral resolution of ~3.1 nm and bandwidth of ~50 nm, which results in the limit of detection of 0.042 RIU. The MRR output spectrum with air- and water-claddings are measured and reconstructed from the MRR-SHFTS integrated device experimentally to validate the wavelength shifting measurement.Comment: 23 pages, 9 figures including supplementar