Browsing by Subject "Optical resonators"

Now showing 1 - 20 of 26

Open Access
Asymmetric chiral metamaterial circular polarizer based on four U-shaped split ring resonators
(Optical Society of America, 2011-04-28) Mutlu, M.; Akosman, A. E.; Serebryannikov, A. E.; Özbay, Ekmel
An asymmetric chiral metamaterial structure is constructed by using four double-layered U-shaped split ring resonators, which are each rotated by 90° with respect to their neighbors. The peculiarity of the suggested design is that the sizes of the electrically and magnetically excited rings are different, which allows for equalizing the orthogonal components of the electric field at the output interface with a 90° phase difference when the periodic structure is illuminated by an x-polarized wave. As a result, left-hand circular polarization and right-hand circular polarization are obtained in transmission at 5:1 GHz and 6:4 GHz, respectively. The experiment results are in good agreement with the numerical results.
Open Access
Chiral metamaterials with negative refractive index based on four "U" split ring resonators
(American Institute of Physics, 2010-08-23) Li, Z.; Zhao, R.; Koschny, T.; Kafesaki, M.; Alici, K. B.; Colak, E.; Caglayan, H.; Özbay, Ekmel; Soukoulis, C. M.
A uniaxial chiral metamaterial is constructed by double-layered four "U" split ring resonators mutually twisted by 90°. It shows a giant optical activity and circular dichroism. The retrieval results reveal that a negative refractive index is realized for circularly polarized waves due to the large chirality. The experimental results are in good agreement with the numerical results.
Open Access
Coupling enhancement of split ring resonators on graphene
(Pergamon Press, 2014-12) Cakmakyapan, S.; Caglayan, H.; Özbay, Ekmel
Metallic split ring resonator (SRR) structures are used in nanophotonics applications in order to localize and enhance incident electromagnetic field. Electrically controllable sheet carrier concentration of graphene provides a platform where the resonance of the SRRs fabricated on graphene can be tuned. The reflectivity spectra of SRR arrays shift by applying gate voltage, which modulates the sheet carrier concentration, and thereby the optical conductivity of monolayer graphene. We experimentally and numerically demonstrated that the tuning range can be increased by tailoring the effective mode area of the SRR and enhancing the interaction with graphene. The tuning capability is one of the important features of graphene based tunable sensors, optical switches, and modulator applications. © 2014 Elsevier Ltd. All rights reserved.
Open Access
Effect of disorder on magnetic resonance band gap of split-ring resonator structures
(Optical Society of American (OSA), 2004) Aydın, K.; Güven, K.; Katsarakis, N.; Soukoulis, C. M.; Özbay, Ekmel
We investigated the influence of periodicity, misalignment, and disorder on the magnetic resonance gap of split-ring resonators (SRRs) which are essential components of left handed-metamaterials (LHMs). The resonance of a single SRR which is induced by the split is experimentally demonstrated by comparing transmission spectra of SRR and closed ring resonator. Misaligning the SRR boards do not affect the magnetic resonance gap, while destroying the periodicity results in a narrower band gap. The disorder in SRR layers cause narrower left-handed pass band and decrease the transmission level of composite metamaterials (CMMs), which may significantly affect the performance of these LHMs. © 2004 Optical Society of America.
Open Access
An electromagnetic sensing system incorporating multiple probes and single antenna for wireless structural health monitoring
(IEEE, 2017) Özbey, Burak; Altıntaş, Ayhan; Demir, Hilmi Volkan; Ertürk, Vakur B.; Kurç, Ö.
In this study, a wireless and passive displacement/strain sensing system is proposed for structural health monitoring (SHM). The wireless and passive interrogation of the sensing unit [a variant of a nested split-ring resonator (NSRR)] is achieved through the near-field interaction and electromagnetic coupling between the single antenna in the system and the multiple sensors called the NSRR probes. It is demonstrated that the system can acquire data from more than one NSRR probe simultaneously in a real-life scenario, where the probes are confined within concrete inside a beam, while the antenna monitors them from outside.
Open Access
Ferroelectric based tuneable SRR based metamaterial for microwave applications
(IEEE, 2007) Özbay, Ekmel; Aydın, Koray; Bütün, Serkan; Kolodziejak, K.; Pawlak, D.
We discuss the possibility of achieving tunable split ring resonators at microwave frequencies. One method is to use varying capacitance values to tune the magnetic resonance frequency. As another method ferroelectric thin films can be employed to obtain active response from the split ring resonators. We report the experimental measurements that are performed for single split ring resonators at microwave frequencies.
Open Access
High resolution dielectric characterization of single cells and microparticles using integrated microfluidic microwave sensors
(Institute of Electrical and Electronics Engineers, 2023-03-01) Seçme, Arda; Tefek, Uzay; Sarı, Burak; Pisheh, Hadi Sedaghat; Uslu, H. Dilara; Akbulut, Özge; Küçükoğlu, Berk; Erdoğan, R. Tufan; Alhmoud, Hashim; Şahin, Özgür; Hanay, M. Selim
Microwave sensors can probe intrinsic material properties of analytes in a microfluidic channel at physiologically relevant ion concentrations. While microwave sensors have been used to detect single cells and microparticles in earlier studies, the synergistic use and comparative analysis of microwave sensors with optical microscopy for material classification and size tracking applications have been scarcely investigated so far. Here we combined microwave and optical sensing to differentiate microscale objects based on their dielectric properties. We designed and fabricated two types of planar sensor: a Coplanar Waveguide Resonator (CPW) and a Split-Ring Resonator (SRR). Both sensors possessed sensing electrodes with a narrow gap to detect single cells passing through a microfluidic channel integrated on the same chip. We also show that standalone microwave sensors can track the relative changes in cellular size in real-time. In sensing single 20-micron diameter polystyrene particles, Signal-to-Noise ratio values of approximately 100 for CPW and 70 for SRR sensors were obtained. These findings demonstrate that microwave sensing technology can serve as a complementary technique for single-cell biophysical experiments and microscale pollutant screening.
Open Access
Integrated micro ring resonator displacement sensor for scanning probe microscopies
(Institute of Physics Publishing, 2004) Kiyat, I.; Kocabas, C.; Aydınlı, Atilla
We describe a novel displacement sensor for scanning probe microscopies using an integrated optical micro ring resonator. This device operates by means of monitoring the changes in the transmission spectrum of a high finesse micro ring resonator. Finite element method simulations were carried out to obtain the optimum sensor design and finite difference time domain simulation was used to obtain the transfer characteristics of micro ring resonators. Operation principles and sensitivity calculations are discussed in detail. To achieve high sensitivity, we have studied different types of ring resonator. The highest sensitivity is obtained in a race-track resonator. This new design should provide sensitivities as high as ∼10 -4 Å -1.
Open Access
Light-controlled microwave whispering-gallery-mode quasi-optical resonators at 50W LED array illumination
(American Institute of Physics Inc., 2015) Yurchenko V.B.; Ciydem, M.; Altintas, A.
We present experimental observations of light-controlled resonance effects in microwave whispering-gallery-mode quasi-optical dielectric-semiconductor disk resonators in the frequency band of 5 GHz to 20 GHz arising due to illumination from a light emitting diode (LED) of 50W power range. We obtain huge enhancement of photo-sensitivity (growing with the resonator Q-factor) that makes light-microwave interaction observable with an ordinary light (no laser) at conventional brightness (like an office lighting) in quasi-optical microwave structures at rather long (centimeter-scale) wavelength. We also demonstrate non-conventional photo-response of Fano resonances when the light suppresses one group of resonances and enhances another group. The effects could be used for the optical control and quasi-optical switching of microwave propagation through either one or another frequency channel. © 2015 Author(s).
Open Access
Metamaterial-based wireless RF-MEMS strain sensors
(IEEE, 2010) Melik, Rohat; Ünal, Emre; Perkgoz, Nihan Kosku; Puttlitz, C.; Demir, Hilmi Volkan
Approximately 10% of the fractures do not heal properly because of the inability to monitor fracture healing. Standard radiography is not capable of discriminating whether bone healing is occurring normally or aberrantly. We propose and develop an implantable wireless sensor that monitors strain on implanted hardware in real time telemetrically. This enables clinicians to monitor fracture healing. Here we present the development and demonstration of metamaterial-based radiofrequency (RF) micro-electro-mechanical system (MEMS) strain sensors for wireless strain sensing to monitor fracture healing. The operating frequency of these sensors shifts under mechanical loading; this shift is related to the surface strain of the implantable test material. In this work, we implemented metamaterials in two different architectures as bio-implantable wireless strain sensors for the first time. These custom-design metamaterials exhibit better performance as sensors than traditional RF structures (e.g., spiral coils) because of their unique structural properties (splits). They feature a low enough operating frequency to avoid the background absorption of soft tissue and yield higher Q-factors compared to the spiral structures (because their gaps have much higher electric field density). In our first metamaterial architecture of an 5x5 array, the wireless sensor shows high sensitivity (109kHz/kgf, 5.148kHz/microstrain) with low nonlinearity-error (<200microstrain). Using our second architecture, we then improved the structure of classical metamaterial and obtained nested metamaterials that incorporate multiple metamaterials in a compact nested structure and measured strain telemetrically at low operating frequencies. This novel nested metamaterial structure outperformed classical metamaterial structure as wireless strain sensors. By employing nested metamaterial architecture, the operating frequency is reduced from 529.8 MHz to 506.2 MHz while the sensitivity is increased from 0.72 kHz/kgf to 1.09 kHz/kgf. ©2010 IEEE.
Open Access
A Miniaturized Patch Antenna by Using a CSRR Loading Plane
(Hindawi Publishing Corporation, 2015) Ramzan, M.; Topalli, K.
This paper presents a design methodology for the implementation of a miniaturized square patch antenna and its circuit model for 5.15 GHz ISM band. The miniaturization is achieved by employing concentric complementary split ring resonator (CSRR) structures in between the patch and ground plane. The results are compared with the traditional square patch antenna in terms of area, bandwidth, and efficiency. The area is reduced with a ratio of 1/4 with respect to the traditional patch. The miniaturized square patch antenna has an efficiency, bandwidth, and reflection coefficient of 78%, 0.4%, and -16 dB, respectively. The measurement and circuit modeling results show a good agreement with the full-wave electromagnetic simulations. © 2015 Mehrab Ramzan and Kagan Topalli.
Open Access
Multi-gap individual and coupled split-ring resonator structures
(Optical Society of American (OSA), 2008) Penciu, R.S.; Aydin, K.; Kafesaki, M.; Koschny Th.; Özbay, Ekmel; Economou, E.N.; Soukoulis, C.M.
We present a systematic numerical study, validated by accompanied experimental data, of individual and coupled split ring resonators (SRRs) of a single rectangular ring with one, two and four gaps. We discuss the behavior of the magnetic resonance frequency, the magnetic field and the currents in the SRRs, as one goes from a single SRR to strongly interacting SRR pairs in the SRR plane. We show that coupling of the SRRs along the E direction results to shift of the magnetic resonance frequency to lower or higher values, depending on the capacitive or inductive nature of the coupling. Strong SRR coupling along propagation direction usually results to splitting of the single SRR resonance into two distinct resonances, associated with peculiar field and current distributions. © 2008 Optical Society of America.
Open Access
Multiband one-way polarization conversion in complementary split-ring resonator based structures by combining chirality and tunneling
(OSA - The Optical Society, 2015) Serebryannikov, A. E.; Beruete, M.; Mutlu, M.; Özbay, Ekmel
Multiband one-way polarization conversion and strong asymmetry in transmission inspired by it are demonstrated in ultrathin sandwiched structures that comprise two twisted aperture-type arrays of complementary split-ring resonators (CSRRs), metallic mesh, and dielectric layers. The basic features of the resulting mechanism originate from the common effect of chirality and tunneling. The emphasis is put on the (nearly) perfect polarization conversion of linear incident polarization into the orthogonal one and related diodelike asymmetric transmission within multiple narrow bands. Desired polarization conversion can be obtained at several resonances for one of the two opposite incidence directions, whereas transmission is fully blocked for the other one. The resonances, at which the (nearly) perfect conversion takes place, are expected to be inherited from similar structures with parallel, i.e., not rotated CSRR arrays that do not enable chirality and, thus, polarization conversion. It is found that the basic transmission and polarization conversion features and, thus, the dominant physics are rather general, enabling efficient engineering of such structures. The lowest-frequency resonance can be obtained in structures made of conventional materials with total thickness less than λ?/ 50 and up to ten such resonances can correspond to thickness less than λ ?/ 20 . ©2015 Optical Society of America.
Open Access
Nested metamaterials for wireless strain sensing
(IEEE, 2009-12-28) Melik, R.; Unal, E.; Perkgoz, N. K.; Santoni, B.; Kamstock, D.; Puttlitz, C.; Demir, Hilmi Volkan
We designed, fabricated, and characterized metamaterial-based RF-microelectromechanical system (RF-MEMS) strain sensors that incorporate multiple split ring resonators (SRRs) in a compact nested architecture to measure strain telemetrically. We also showed biocompatibility of these strain sensors in an animal model. With these devices, our bioimplantable wireless metamaterial sensors are intended, to enable clinicians, to quantitatively evaluate the progression of long-bone fracture healing by monitoring the strain on the implantable fracture fixation hardware in real time. In operation, the transmission spectrum of the metamaterial sensor attached to the implantable fixture is changed when an external load is applied to the fixture, and from this change, the strain is recorded remotely. By employing telemetric characterizations, we reduced the operating frequency and enhanced the sensitivity of our novel nested SRR architecture compared to the conventional SRR structure. The nested SRR structure exhibited a higher sensitivity of 1.09 kHz/kgf operating at lower frequency compared to the classical SRR that demonstrated a sensitivity of 0.72 kHz/kgf. Using soft tissue medium, we achieved the best sensitivity level of 4.00 kHz/kgf with our nested SRR sensor. Ultimately, the laboratory characterization and in vivo biocompatibility studies support further development and characterization of a fracture healing system based on implantable nested SRR.
Open Access
Novel integrated optical displacement sensor for scanning force microscopies
(IEEE, 2003) Aydınlı, Atilla; Kıyat, İsa; Kocabaş, Coşkun
A novel displacement sensor for scanning force microscoples using an integrated optical micro-ring resonator is described. Device operates by monitoring the changes in transmission spectrum of micro-ring resonator. This design provides sensitivities about ∼10-4 Å-1.
Open Access
Novel SIW based interdigital bandpass filter with harmonic suppression
(IEEE, 2014) Kurudere, S.; Ertürk, Vakur B.
A novel configuration for substrate integrated waveguide (SIW) based bandpass filter with interdigital type resonators is presented. In the proposed structure, interdigital type resonators consisting of vias and circular caps at top of them are combined into a bowtie SIW structure. SIW is fed by a tapered microstrip line transition providing low loss and good matching. In order to improve harmonic suppression performance of the filter, the dumbbell shaped defected ground structure (DGS) is etched to the ground side of the microstrip line feeding section. The proposed filter structure is put in a conducting box in order to improve attenuation levels at the band edges and prevent radiation to the outside. The prototype is designed at 9 GHz center frequency with 500 MHz bandwidth, analyzed and fabricated for verification. The measurement results are in good agreement with the simulations, and the filter exhibits more than 30 dB harmonic suppression.
Open Access
Observation of negative refraction and negative phase velocity in true left-handed metamaterials
(SPIE, 2005) Özbay, Ekmel
We report a true left-handed (LH) behavior in a composite metamaterial consisting of periodically arranged split ring resonator (SRR) and wire structures. The magnetic resonance of the SRR structure is demonstrated by comparing the transmission spectra of SRRs with that of closed SRRs. We confirmed experimentally that the effective plasma frequency of the LH material composed of SRRs and wires is lower than the plasma frequency of the wires. A well-defined left-handed transmission band with a peak value of -1.2 dB (-0.3 dB/cm) is obtained. We also report the transmission characteristics of a 2D composite metamaterial (CMM) structure in free space. At the frequencies where left-handed transmission takes place, we experimentally confirmed that the CMM structure has effective negative refractive index. Phase shift between consecutive numbers of layers of CMM is measured and phase velocity is shown to be negative at the relevant frequency range. Refractive index values obtained from the refraction experiments and the phase measurements are in good agreement. The experimental results agree extremely well with the theoretical calculations.
Open Access
Photonic magnetic metamaterial basics
(Elsevier, 2010-07-21) Alici, K. B.; Serebryannikov, A. E.; Özbay, Ekmel
In the present study, we provide a detailed analysis for the study of photonic metamaterials. We demonstrate the polarization and orientation dependent transmission response of split ring resonators at the infrared and visible band. We provided optical measurements only for one case, in which electric component of the incident field was coupled to planar split ring resonator array. We consecutively studied (i) frequency tuning, (ii) effect of resonator density, (iii) shifting magnetic resonance frequency by changing the resonator shape, and (iv) effect of metal loss and plasma frequency. The study provides an overlook for the candidate applications such as the enhancement of power passing through an electrically small hole, negative index metamaterials and optical metamaterial absorbers.
Open Access
Polarization characteristics of compact SOI rib waveguide racetrack resonators
(IEEE, 2005) Kiyat, I.; Aydınlı, Atilla; Dagli, N.
We report on the development of compact optical racetrack resonators on silicon-on-insulator (SOI) rib waveguides. We make use of large-cross-section waveguides instead of photonic wire waveguides. We fabricated resonators with bending radii down to 20 μm and characterized for both transverse-electric and transverse-magnetic polarizations. Different polarization characteristics were analyzed and related to the modal shape of the SOI waveguide. These compact resonators show large free spectral ranges (3.0 nm), high finesse (19), and Q-factor (28 000) values.
Open Access
Radiation properties and coupling analysis of a metamaterial based, dual polarization, dual band, multiple split ring resonator antenna
(Taylor and Francis, 2012-04-03) Alici, K. B.; Serebryannikov, A. E.; Özbay, Ekmel
We demonstrate an electrically small antenna that operates at two modes, which correspond to two orthogonal polarizations. The antenna was single fed and composed of perpendicularly placed metamaterial elements and a monopole. One of the metamaterial elements was a multi split ring resonator (MSRR), and the other one was a split ring resonator (SRR). The elements' physical sizes were the same while the electrical sizes differed nearly by 1 GHz. This variety resulted in the dual mode operation at the 4.72 GHz and 5.76 GHz frequencies. When the antenna operated in the MSRR mode at 4.72 GHz for one polarization, it simultaneously operated for the SRR mode at 5.76 GHz, but for the perpendicular polarization. The efficiencies of the modes were 15% and 40%, and electrical sizes were λ/11.2 and λ/9.5, correspondingly. Finally, we numerically demonstrate the effect of coupling of the two resonators on the operation frequencies.