Добірка наукової літератури з теми "IO Resonators"

Ultra-Low-Frequency (ULF) waves provide a means for the rapid propagation of energy and field-aligned current in planetary magnetospheres. At Earth, the ULF frequency range is usually defined as including waves with periods of 0.2–600 s; however, at Jupiter these waves can extend to periods of tens of minutes. In both magnetospheres, shear mode Alfvén waves can form field line resonances that exist between the ionospheres, with periods of a few minutes at Earth and a few tens of minutes at Jupiter. A major distinction between these two magnetospheres is in the density distribution. Earth has a dense ionosphere full of heavy ions, an extended, cold plasmasphere and a relatively low-density plasma sheet. In contrast, at Jupiter, the ionosphere is largely hydrogen (both in atomic form and in the H3+ molecular ion), there is no appreciable plasmasphere and the plasma disk is dense and populated with heavy ions (largely sulfur and oxygen) originating at the moon Io and to some extent from other moons. As at Earth, the sharp Alfvén speed gradient above the ionosphere forms an ionospheric Alfvén resonator at Jupiter with periods of seconds. Furthermore, the high-latitude lobes at Jupiter have very low density and a resonant structure can be formed by waves bouncing between the ionosphere and the dense plasma disk. This structure leads to periods of tens of seconds. Finally, the dense Io plasma torus and plasma sheet provide conditions for compressional cavity modes to form in this region. Thus, the structure of the field line resonance modes is quite different at the two planets. Implications of these resonances on auroral particle acceleration will be discussed.

Microring resonators have rapidly emerged in the past few years as a new sensing platform for miniaturization of modern integrated optical devices. Ring resonator are having advantages of compactness, stability with respect to back reflections, do not need facets or gratings for optical feedback, strong optical field enhancement inside cavities, high wavelength selectivity, narrow line width, high Q-factor and high sensitivity. These unique characteristics made microring resonator as promising platform for integrated photonics.. A generic ring resonator consists of an optical waveguide which is looped back on it self and coupled with a single or double bus waveguide. In this thesis, a compact microring resonator (MRR) is proposed and optimized to exhibit high sensitivity and quality factor. Also, force and acceleration sensing applications of MRR are discussed. Electromagnetic computations are done using Finite Difference Time Domain (FDTD) method. Fabrication and characterization of microring is also carried out. While the main emphasis is on design and analysis, this experimental work supports better understanding of practical issues in study of microring resonators. Then, the force sensing application of the optimized microring resonator is presented. The design and modeling of the devices, including the mechanical properties of the microcantilever beam, are done by using a Finite Element Method (FEM). The force sensing characteristics are presented for the force range of 0 to 1 μN. The drawbacks of single MRR can be overcome by using serially coupled double microring resonator(SC-DMRR) and serially coupled double racetrack resonator (SC-DRTR) with vernier effect. They provide, high FSR, low FWHM, high Q-factor and high sensitivity. By using SC-DMRR as an optical sensing element, a novel IO MEMS SC-DMRR based force sensor is proposed, resulting in high Q-factor of 19000 and force sensitivity of 100 pm/ 1μN. Further, in order to increase the sensitivity, a novel SCDRTR based force sensor is proposed. The study is expanded to photonic crystal microring resonator (PC-MRR) structures, where a PCMRR is designed in a hexagonal lattice of air holes on a silicon slab. A novel approach is used to optimize PC-MRR to achieve high Q-factor. A high sensitive force sensor based on PC-MRR integrated with silicon micro cantilever is presented. The force sensing characteristics are presented for forces in the range of 0 to 1 μN. For forces which are in the range of few tens of μN, a force sensor with bilayer cantilever is considered. Further, the PC-MRR equivalent microring resonator is designed and analyzed for comparison between the force sensors. Finally, a novel IO MEMS serially coupled racetrack resonator based accelerometer is proposed and the required characteristics like sensitivity and dynamic range are reported. In conclusion, IO micro ring resonators are the best candidates to design and develop force and acceleration sensors in the sub-μN sensitivities.

We have demonstrated a new mechanism for bistability in integrated optics, viz., light-induced-desorption of molecules from the waveguide surface by which the effective guide index N is changed. Bistability occurs if the desorption rate depends linearly on the incoupled power P' in an input coupler device (see Fig.1), and on the intracavity power in an IO Fabry Perot or ring resonator. This follows theoretically from an analysis analogous to that of the bistable radiation pressure driven waveguide pendulum.1