Browsing by Subject "Ring resonators"
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Item Open Access Explorations on optomechanical devices for energy sink applications(Bilkent University, 2023-01) Lee, ChulHyeongResonance energy dissipation mechanism has been gaining importance in the interest of sensing applications. As such, the capacity for precise and fast measurement of the transient phase of motion has been desirable. The development of optomechanics in recent years has enabled such a fast scheme. Here a design, setup, and measurement of a silicon nitride optomechanical system is explored. Fundamental parameters of the design are investigated with simulation analysis. Grating structures, waveguides, and resonator parameters are explored. A series of optical resonance responses are observed, and the resonance characteristics are analyzed for optomechanical devices of combinations of design parameters. Measurements on devices of different nanomechanical beam modulation schemes are performed. To translate the technique from the optical to microwave domain, an integration of a split ring resonator (SRR) cavity and NEMS device is explored. Mode simulation of the modified cavity design is done. A technique of alignment of EBL to an existing pattern on an insulating surface is optimized. The studied designs leave possibilities for applications in real-time mass sensing and fundamental studies on energy dissipation mechanisms.Item Open Access Monolithic and hybrid silicon-on-insulator integrated optical devices(Bilkent University, 2005) Kiyat, İsaSilicon, the basic material of electronics industry is rediscovered nowadays for its potential use in photonics and integrated optics. The research activity in silicon integrated optics have been speeding up during the last decade and even attracting interest of leading industrial companies. As a contribution to this world wide effort, we have designed, fabricated and characterized a class of monolithic and hybrid silicon integrated optical devices. These devices were realized on high-quality silicon-on-insulator (SOI) wafers. Beam propagation method (BPM) based simulations and analytical calculations were employed for the design. We have demonstrated for the first time an SOI device that splits light into its TE and TM components. An SOI rib waveguide becomes birefringent as its size reduced. This idea is used to design and fabricate a directional coupler polarization splitter based on geometrical birefringence. The device uses 1 µm sized SOI waveguides. This compact device (only 110 µm in length) shows extinction ratios larger than 20 dB. SOI waveguides with the same geometry was used to realize a batch of single and double bus racetrack resonators having radii in the range of 20 to 500 µm. Design of these racetrack resonators are presented in detail. The bending loss and coupling factor calculations were performed using BPM. During the design and analysis of waveguide resonators, we proposed a novel displacement sensor that can be used for scanning probe microscopies. The sensor operates by means of monitoring the changes in transmission spectrum of a high finesse micro-ring resonator due to stress induced by displacement. Operation principles and sensitivity calculations are discussed in detail. SOI resonators with quality factors (Q) as high as 119000 have been achieved. This is the highest Q value for resonators based on SOI rib waveguides to date. Finesse values as large as 43 and modulation depths of 15 dB were observed. Free spectral ranges increased from 0.2 nm to 3.0 nm when radius was decreased from 500 to 20 µm. The thermo-optical tunability of these resonators were also studied. A high-Q racetrack resonator is used to develop a wavelength selective optical switch. The resonator was thermo-optically scanned over its full free spectral range applying only 57 mW of electrical power. A low power of 17 mW was enough to tune from resonance to off-resonance state. The device functioned as a wavelength selective optical switch with a 3 dB cutoff frequency of 210 kHz. We have also demonstrated wavelength add/drop filters using the same racetrack resonators with double bus. Asymmetric lateral coupling was used in order to get better filter characteristics. Filters with crosstalks as low as -10.0 dB and Q-factors of as high as 51000 were achieved. Finally, we introduce the use of a layer transfer method for SOI wafers. Such a layer transfer results in the possibility of using the back side of the silicon layer in SOI structure for further processing. With this method, previously fabricated SOI waveguides were transferred to form hybrid silicon-polymer waveguides. Benzocyclobutene (BCB) polymer was used as the bonding agent. The method is also applied to SOI M-Z interferometers to explore the possibilities of the technology. We additionally studied asymmetric vertical couplers (AVC) based on polymer and silicon waveguides and fabricated them using a hybrid technology.Item 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.Item Open Access Particle sensing with narrowband microwave split-ring resonators(Bilkent University, 2021-09) Küçükoğlu, BerkA new microwave sensor with concentric split-ring resonator (CSRR) topology is designed and integrated with microfluidics. While the resonator is being driven at its resonant frequency, cells passing through the channel shift this frequency. Information regarding the cell (or microparticle) can be extracted from the am-plitude of this shift. The design is based strongly on simulations and shows good agreement with the theory. Experiments are performed to evaluate the sensor’s performance with polystyrene particles. These experiments show that the sensor gives an outstanding SNR value: around 140kHz mean signal amplitude com-pared to a 1.2kHz average noise amplitude. To further evaluate the performance, single-cell experiments are performed. A target cell is selected and passed through the sensing region repeatedly. Frequency shifts are recorded. The mean frequency shift is 44kHz, and the signal-to-noise ratio is over 140. The ensemble standard deviation for the frequency shifts is 9.33kHz, and the variance in the results can be further improved with creative microfluidic designs. Work has been directed towards improving the measurement setup for split-ring resonators. A split-ring resonator sensor is designed and integrated into an oscillator loop, designed from scratch. The design criteria for this project are; faster acquisition times, control-loop parameter independence, and improved cost-effectiveness. It is shown that the new oscillator setup satisfies all the design criteria. The design process is once again simulation-driven. Real-life experiments are also performed with the oscillator boards for performance evaluation. Allan deviation experiments show promising results (1.49 × 10−6) regarding oscillator stability. Polystyrene experiments show a lower response compared to the CSRR sensors.