Mode coupling control in a resonant device: application to solid-state ring lasers

A theoretical and experimental investigation of the effects of mode coupling in a resonant macro- scopic quantum device is achieved in the case of a ring laser. In particular, we show both analytically and experimentally that such a device can be used as a rotation sensor provided the effects of mode coupling are controlled, for example through the use of an additional coupling. A possible general- ization of this example to the case of another resonant macroscopic quantum device is discussed

Studies in fiber-optic couplers and resonators

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1993.Title as it appears in the Feb. 1993 MIT Graduate List: Studies in polished couplers and resonators. Vita.Includes bibliographical references.Robert Paul Dahlgren.M.S

Thin-Film AlN-on-Silicon Resonant Gyroscopes: Design, Fabrication, and Eigenmode Operation

Resonant MEMS gyroscopes have been rapidly adopted in various consumer, industrial, and automotive applications thanks to the significant improvements in their performance over the past decade. The current efforts in enhancing the performance of high-precision resonant gyroscopes are mainly focused on two seemingly contradictory metrics, larger bandwidth and lower noise level, to push the technology towards navigation applications. The key enabling factor for the realization of low-noise high-bandwidth resonant gyroscopes is the utilization of a strong electromechanical transducer at high frequencies. Thin-film piezoelectric-on-silicon technology provides a very efficient transduction mechanism suitable for implementation of bulk-mode resonant gyroscopes without the need for submicron capacitive gaps or large DC polarization voltages. More importantly, in-air operation of piezoelectric devices at moderate Q values allows for the cointegration of mode-matched gyroscopes and accelerometers on a common substrate for inertial measurement units. This work presents the design, fabrication, characterization, and method of mode matching of piezoelectric-on-silicon resonant gyroscopes. The degenerate in-plane flexural vibration mode shapes of the resonating structure are demonstrated to have a strong gyroscopic coupling as well as a large piezoelectric transduction coefficient. Eigenmode operation of resonant gyroscopes is introduced as the modal alignment technique for the piezoelectric devices independently of the transduction mechanism. Controlled displacement feedback is also employed as the frequency matching technique to accomplish complete mode matching of the piezoelectric gyroscopes.Ph.D

Developing highly symmetric Microelectromechanical systems (MEMS) based butterfly gyroscopes

Microelectromechanical systems (MEMS) is the technology combining electrical components with mechanical systems at a micro scale. The combination of these two technologies allowed devices to interact with each other and build complex structures. System on the chips are built with components such as masses, electrodes, anchors, actuators and detectors. Reducing the size, weight, energy usage and cost is key while maintaining the sensors integrity. Sensitivity is an important factor when evaluating a gyroscope’s performance. This research presents beam modeling techniques for maximizing mechanical sensitivity of the butterfly resonator for gyroscopic applications. It investigates the geometric aspects of synchronizing beam that connects the wings of a butterfly resonator. The results show that geometric variation in the synchronizing beam can have a large effect on the frequency split and sensitivity of the device. The model simulation demonstrates a sensitivity of 10e-12 (m/°/sec) for a frequency split of 10 Hz, resulting from the optimized synchronous beam. Out of plane actuation was developed to drive and sense the resonators displacement. A butterfly sensor chip was fabricated to capture the dynamic responses of the resonator and to observe the theoretical and experimental results. Two butterfly resonators were tested, and the experimental results show a frequency split of 305 Hz and 400 Hz, while the model illustrated a split of 195 Hz and 220 Hz, respectively. The design and analysis presented in this thesis can further aid the development of MEMS butterfly resonators for inertial sensing applications

High-Q Fused Silica Micro-Shell Resonators for Navigation-Grade MEMS Gyroscopes

This research aims to develop the resonator for a navigation-grade microelectromechanical system (MEMS) Coriolis vibratory gyroscope (CVG) that will bring inertial navigation capabilities to a wider range of applications by reducing gyroscope size and cost. To achieve the desired gyroscope performance, the gyroscope resonator must have low energy dissipation and a highly symmetric structure. Several challenges arise at the micro-scale due to the increased sensitivity to imperfections and increased susceptibility to energy loss mechanisms. This work investigates the lower limit on energy dissipation in a micro-shell resonator known as the birdbath (BB) resonator. The BB resonator is designed to mitigate the energy loss mechanisms that commonly limit MEMS resonators, including anchor loss and thermoelastic dissipation, through a unique shape and fabrication process and through the use of fused silica as the structural material. A blowtorch molding process is used to form high aspect ratio fused silica shells with a range of wall profiles, providing a high level of control in three dimensions that is not possible with conventional micromachining techniques. Prototype BB resonators were developed prior to this dissertation work but they achieved low quality factors (Q) and low ring-down time constants (T) on the order of 100 thousand and 1 s, respectively. The goal of this work is to drastically increase performance above these initial results. Each relevant energy loss mechanism is considered in order to identify the dominant loss mechanism for a given device. Process improvements are implemented to mitigate each loss mechanism, including improved thermal management during blowtorch molding, cleaner lapping and polishing, reduced upfront surface contamination, and methods to remove contaminants after fabrication. Following optimization, Qs up to 10 million and Ts up to 500 s are measured, representing a marked improvement over the prototype resonators. It is found that BB resonators are now limited by surface loss, as indicated by the observed inverse relationship between Q and surface-to-volume ratio. The surface-loss-limited regime results in a high sensitivity to added surface layers. The addition of a conductive layer to enable electrostatic transduction is found to have a large impact, decreasing Q by 50% with the addition of only 30 angstroms of metal. It is suggested that the origin of this loss may be interfacial slippage due to a large increase in stress that occurs at the interface during oscillation. Experimental investigation into the dependence of Q on conductive layer composition, thickness, deposition conditions, and post-deposition treatments is carried out. Following treatments to removed adsorbed contaminants from the surface, resonators with a 15/50 angstrom Ti/Pt layer are found to maintain 60% of their initial Qs. Indium tin oxide (ITO) is identified as a promising conductive layer candidate, with initial experiments producing shells that maintain 70% of their initial Q. The values of Q and T produced in this work are unprecedented for MEMS resonators. Even accounting for the losses that accompany conductive layer deposition, birdbath resonator gyroscopes are expected to achieve navigation-grade performance.PHDElectrical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttps://deepblue.lib.umich.edu/bitstream/2027.42/146096/1/taln_1.pd

Nonlinear enhanced microresonator gyroscope

Optical gyroscopes based on the Sagnac effect have been the mainstay of inertial navigation in aerospace and shipping for decades. These gyroscopes are typically realized either as ring-laser gyroscopes (RLGs) or fiber-optic gyroscopes (FOGs). With the recent rapid progress in the field of ultrahigh-quality optical whispering-gallery mode and ring microresonators, attention has been focused on the development of microresonator-based Sagnac gyroscopes as a more compact alternative to RLGs and FOGs. One avenue that has been explored is the use of exceptional points in non-Hermitian systems to enhance the responsivity to rotation. We use a similar phenomenon, namely, the critical point of a spontaneous symmetry-breaking transition between counterpropagating light, to demonstrate a microresonator gyroscope with a responsivity enhanced by a factor of around 104. We present a proof-of-principle rotation measurement as well as a characterization of the system’s dynamical response, which shows the universal critical behaviors of responsivity enhancement and critical slowing down, both of which are beneficial in an optical gyroscope. We believe that this concept could be used to realize simple and cheap chip-based gyroscopes with sensitivities approaching those of today’s RLGs and FOGs

Fiber optic sensor based on dual ring resonator system

A comprehensive study of fiber optic sensors based on a dual ring resonator system has been conducted. A new theoretical model is established for a single fiber optic ring resonator. The performance of fiber optic sensors based on the dual ring resonator system is then analyzed, based on this model. The best configuration for the dual ring resonator system is determined in terms of the shot-noise-limited minimum detectable phase change, as well as the environmental stability when polarization crosstalk is present. The relationship between the coherence length of semiconductor light sources and the resonator loop lengths is investigated, with the aim of eliminating phase noise effects. Moreover, the effect of length mismatch between the two resonator loops is discussed. Finally, the fundamental output characteristics of fiber optic sensors based on dual ring resonator system are verified experimentally. Some recommendations are also given for further possible improvement

Vektorisuunnistukseen perustuva sisätilapaikannusjärjestelmä

In this thesis a positioning system, that can provide accurate reference coordinates for indoor usage is described and analysed. Those coordinates are needed in the development of various indoor positioning systems. Satellite navigation systems such as GPS can provide accurate positioning outdoors but their accuracy is poor when used indoors. Inertial navigation can provide accurate positioning indoors using accelerometers and gyroscopes but an accurate system is extremely expensive. Accurate indoor positioning is also achievable using a floor plan, a measuring tape or both but these methods are prone to human errors. The system presented in this thesis is designed to overcome the aforementioned problems using dead reckoning navigation. Dead reckoning is a positioning method, that starts always from a known location and attitude. In dead reckoning, gyroscope and odometer measurements are used to obtain position by updating the previous position. The dead reckoning system uses a micro electro mechanical (MEMS) gyroscope and two odometers to measure attitude and travelled distance, respectively. A data acquisition program was written to save their measurements to log files on a PC and position was computed by post processing those. The system has been mounted on a cart for easy transportation. Before testing accuracy of the system the gyro and odometers were calibrated. The gyro was attached to a turn table to calibrate its scale factor and bias. From the turn table study it became obvious that the gyro needs to be calibrated just before testing accuracy of the system. Odometers were calibrated by driving the cart in a known straight line distance several times. Based on the drives a scale factor was calculated to compensate the difference in odometer readings. The gyro scale factor was calibrated just before accuracy test of the system by turning the cart around several times. The accuracy of the system was tested in a test drive lasting 30 minutes. During the test the gyro bias was calibrated whenever the system was stopped at reference positions for positioning accuracy estimation. Positioning error of less than 30 cm was achieved in the test drive.Tässä työssä kehitettiin ja analysoitiin tarkka sisätilapaikannusjärjestelmä. Sitä voidaan käyttää tarkkojen koordinaattien määrittämiseen, joita tarvitaan kehitettäessä muita sisätilapaikannusjärjestelmiä. Satelliittipaikannusjärjestelmiä, kuten GPS:ää, voidaan käyttää ulkotiloissa tarkkojen koordinaattien määrittämiseksi, mutta sisällä niiden tarkkuus on heikko. Tarkkaan sisätilapaikannukseen soveltuvat esimerkiksi gyroskooppeja ja kiihtyvyysantureita käyttävät inertiapaikannusjärjestelmät, mutta ne ovat erittäin kalliita. Pohjapiirustusta, mittanauhaa tai molempia voidaan käyttää tarkkaan sisätilapaikannukseen, mutta niitä käytettäessä tulee tehtyä helposti virheitä. Työssä esitetty vektorisuunnistusjärjestelmä on suunniteltu ratkaisuksi edellä mainittuihin ongelmiin. Vektorisuunnistus on paikannusmenetelmä, joka alkaa aina tunnetusta sijainnista ja suunnasta. Siinä käytetään gyroskoopin ja matkamittarin mittauksia paikan määrittämiseksi päivittämällä edellinen sijainti. Työssä esitetty järjestelmä käyttää mikromekaanista (MEMS) gyroskooppia suunnan määrittämiseksi ja kahta matkamittaria kuljetun matkan mittaamiseksi. Mittausten lukemiseksi antureilta kirjoitettiin tietokoneohjelma, joka tallensi ne lokitiedostoihin. Järjestelmän sijainti määritettiin jälkikäteen käyttäen lokitiedostoihin tallennettuja mittauksia. Järjestelmä on kiinnitetty kärryyn, jotta sitä on helppo kuljettaa sisätiloissa. Järjestelmän gyroskooppi ja matkamittarit kalibroitiin ennen sen tarkkuuden tutkimista. Skaalauskertoimen ja biaksen määrittämiseksi gyroskooppi kiinnitettiin pyörityspöytään. Kalibrointituloksista kävi ilmi, että gyroskooppi täytyy kalibroida juuri ennen järjestelmän tarkkuuden tutkimista. Matkamittarit kalibroitiin työntämällä kärryä suoraan tunnetun pituinen matka, jonka mittaus toistettiin useampia kertoja. Mittausten perusteella määritettiin skaalauskerroin, jolla kompensoitiin matkamittareiden lukemissa havaittu ero. Gyroskoopin skaalauskerroin kalibroitiin juuri ennen järjestelmän tarkkuuden tutkimista pyörittämällä kärryä useampi kerta ympäri. Järjestelmän tarkkuutta tutkittiin koeajossa, joka kesti 30 minuuttia. Koeajon aikana gyroskoopin bias kalibroitiin aina pysähdyttäessä tunnetuissa sijainneissa paikannustarkkuuden tutkimiseksi. Paikannusvirhe koeajon aikana oli alle 30 cm