Technologies for single chip integrated optical gyroscopes

Optical gyroscopes are being employed for navigational purposes for decades now and have achieved comparable or better reliability and performance than rotor-based gyroscopes. Mechanical gyros are however generally bulky, heavy and consume more power which make them unsuitable for miniaturized applications such as cube satellites and drones etc. Therefore, much effort is being expended worldwide to fabricate optical gyros having tactical grade robustness and reliability, small size, weight, cost and power consumption with minimal sacrifice of sensitivity. Integrated optics is an obvious approach to achieving this. This work comprises detailed comparative analysis of different types and structures of integrated optical gyroscopes to find out the suitable option for applications which require a resolution of <10 o/h. Based on the numerical analysis, Add-drop ring resonator-based gyro is found to be a suitable structure for integration which has a predicted shot noise limited resolution of 27 o/h and 2.71 o/h for propagation losses of 0.1 dB/cm and 0.01 dB/cm respectively. An integrated gyro is composed of several optical components which include a laser, 3dB couplers, phase/frequency modulators, sensing cavity and photodetectors. This requires hybrid integration of multiple materials technologies and so choices about which component should be implemented in which technology. This project also undertakes theoretical optimization of few of the above-mentioned optical components in materials systems that might offer the most convenient/tolerant option, this including 3dB coupler, thermo-optic phase modulator and sensing cavity (resonator and waveguide loop). In particular, the sensing element requires very low propagation loss waveguides which can best be realised from Si3N4 or Ta2O5. The optimised Si3N4 or Ta2O5 waveguides however are not optimal for other functions and this is shown and alternatives explored where the Si3N4 or Ta2O5 can easily be co-integrated. The fabrication process of low loss Si3N4 and Ta2O5 waveguides are also reported in this thesis. Si3N4 films were grown by using low pressure chemical vapor deposition (LPCVD) technique. Dry etching of Si3N4 films have been optimized to produce smooth and vertical sidewalls. Experimental results predicted that the propagation loss of 0.009 dB/cm is achievable by using optimum waveguide dimensions and silica cladding with the relatively standard processes available within the Laser Physics Centre at the Australian National University. A CMOS back end of line compatible method was developed to deposit good quality Ta2O5 films and silica claddings through ion beam sputtering (IBS) method. Plasma etching of Ta2O5 waveguides has been demonstrated by using a gas combination of CHF3/SF6/Ar/O2. Oxygen was introduced into the chamber to produce non-vertical sidewalls, so the waveguides could be cladded without voids with IBS silica. Average propagation losses of 0.17 dB/cm were achieved from Ta2O5 waveguides which appeared after extensive investigation to be limited by the spatial inhomogeneity of the processing. Lastly, a detailed theoretical and experimental analysis was performed to find out the possible causes of the higher average propagation loss in Ta2O5 waveguides, some sections being observed with 0.02 dB/cm or lower losses

Integrated Optical Delay Line Circuits on a Ultra-low Loss Planar Waveguide Platform

Photonic integrated circuits (PICs) play a major role in the advancement of optical networks. One of the constraints of PICs is the high propagation loss of optical waveguides. As the complexity in PICs increases, so does the power usage and heat generation; therefore, bringing “fiber-like” losses on-chip would not only allow for the improvement of chip performance, but it would also revolutionize delay line technologies allowing longer delay lines to be integrated on chip, otherwise not practically feasible. The design of such waveguides and optical circuits requires a balance of numerous tradeoffs between mode-size, bending radius, and footprint, to name a few. Herein, we present the design and fabrication of optical delay line circuits using an ultra-low loss waveguide platform, which utilizes a high aspect ratio buried Si3N4 core planar waveguide. Optical delay line circuits are defined here as any optical circuit that requires the optical signal to be delay by a certain amount of time for its proper functionality. Such devices are used in many applications ranging from medical to sensing and national defense. In this dissertation we present the integration of three optical delay line circuits: Tunable true time delay for broadband phased array antennas application, a programmable dispersion compensation filter, and an optical gyroscope waveguide coil. The design tradeoff, fabrication, and results for each circuit are present and highlighted in detail

Towards a high-precision atomic gyroscope

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Physics, 2013.Cataloged from PDF version of thesis.Includes bibliographical references (pages 69-72).In this thesis, I report on the design and construction of the Rubidium Atomic Gyroscope Experiment (RAGE) at Draper Lab.by Mackenzie A. Van Camp.S.M

Recent advances in miniaturized optical gyroscopes

Low-cost chip-scale optoelectronic gyroscopes having a resolution ≤ 10 °/h and a good reliability also in harsh environments could have a strong impact on the medium/high performance gyro market, which is currently dominated by well-established bulk optical angular velocity sensors. The R&amp;D activity aiming at the demonstration of those miniaturized sensors is crucial for aerospace/defense industry, and thus it is attracting an increasing research effort and notably funds.  In this paper the recent technological advances on the compact optoelectronic gyroscopes with low weight and high energy saving are reviewed. Attention is paid to both the so-called gyroscope-on-a-chip, which is a novel sensor, at the infantile stage, whose optical components are monolithically integrated on a single indium phosphide chip, and to a new ultra-high Q ring resonator for gyro applications with a configuration including a 1D photonic crystal in the resonant path. The emerging field of the gyros based on passive ring cavities, which have already shown performance comparable with that of optical fiber gyros, is also discussed

Hybrid Integrated Photonics Using Bulk Acoustic Resonators

Microwave frequency acousto-optic modulation is realized by exciting high overtone bulk acoustic wave resonances (HBAR resonances) in the photonic stack. These confined mechanical stress waves transmit exhibit vertically transmitting, high quality factor (Q) acoustic Fabry Perot resonances that extend into the Gigahertz domain, and offer stress-optical interaction with the optical modes of the microresonator. Although HBAR are ubiquitously used in modern communication, and often exploited in superconducting circuits, this is the first time they have been incorporated on a photonic circuit based chip. The electro-acousto-optical interaction observed within the optical modes exhibits high actuation linearity, low actuation power and negligible crosstalk. Using the electro-acousto-optic interaction, fast optical resonance tuning is achieved with sub-nanosecond transduction time. By removing the silicon backreflection, broadband acoustic modulation at 4.1 and 8.7 GHz is realized with a 3 dB bandwidth of 250 MHz each. The novel hybrid HBAR nanophotonic platform demonstrated here, allowing on chip integration of micron-scale acoustic and photonic resonators, can find immediate applications in tunable microwave photonics, high bandwidth soliton microcomb stabilization, compact opto-electronic oscillators, and in microwave to optical conversion schemes. Moreover the hybrid platform allows implementation of momentum biasing, which allows realization of on chip non-reciprocal devices such as isolators or circulators and topological photonic bandstructures.Comment: 41 pages, 4 figure

MEMS Technology for Biomedical Imaging Applications

Biomedical imaging is the key technique and process to create informative images of the human body or other organic structures for clinical purposes or medical science. Micro-electro-mechanical systems (MEMS) technology has demonstrated enormous potential in biomedical imaging applications due to its outstanding advantages of, for instance, miniaturization, high speed, higher resolution, and convenience of batch fabrication. There are many advancements and breakthroughs developing in the academic community, and there are a few challenges raised accordingly upon the designs, structures, fabrication, integration, and applications of MEMS for all kinds of biomedical imaging. This Special Issue aims to collate and showcase research papers, short commutations, perspectives, and insightful review articles from esteemed colleagues that demonstrate: (1) original works on the topic of MEMS components or devices based on various kinds of mechanisms for biomedical imaging; and (2) new developments and potentials of applying MEMS technology of any kind in biomedical imaging. The objective of this special session is to provide insightful information regarding the technological advancements for the researchers in the community

Modelling and characterization of hybrid integrated lasers in 2 to 3 µm wavelength band

Hybrid integrated silicon photonic lasers functioning at mid-IR wavelengths have recently emerged as a solution for developing compact optical sensors targeted at trace gas spectroscopy. This thesis concerns a measurement and simulation combined approach to characterize Silicon Nitride photonic integrated circuits (PICs) equipped to work as such lasers. Seven PICs from the same process are first aligned in an end-fire coupling scheme with the III-V gain chip using a closed-loop piezo stage. The gain chip consists of an AlGaInAsSb/GaSb type-I quantum well reflective semiconductor optical amplifier (RSOA). The PICs contain narrow-band long rectangular spiral and round spiral shaped distributed Bragg reflectors (DBRs) which work as external cavities allowing periodic feedback to the gain element. Intensity vs. current sweeps and measurements of the spectra of the uncooled 2 µm lasers demonstrate narrow full-width half-maximum (FWHM) linewidths and remarkable power outputs in continuous wave operation at room temperature. The measurements also give insight into process variation and design reliability, and have led to a recent submission to Optica for publication. A commercial eigenmode expansion solver is used to verify the experimental results as well as to explore the design space for Bragg reflectors at 2 µm and 2.7 µm with a view to optimizing the packing ratio, linewidth and side-mode suppression ratio of the devices for improved laser performance. The rapid and efficient end-fire based optical testing method presented in this work is expected to set a base-line for optimization of mid-IR tunable hybrid lasers

RF-MEMS Technology for High-Performance Passives (Second Edition) - 5G applications and prospects for 6G

The focus of this book develops around hardware, and in particular on low-complexity components for Radio Frequency (RF) applications. To this end, microsystem (MEMS) technology for RF passive components, known as RF-MEMS, is employed, discussing its potentialities in the application frame of 5G. The approach adopted is practical, and a significant part of the content can be directly used by scientists involved in the field, to put their hand on actual design, optimization and development of innovative RF passive components in MEMS technology for 5G and beyond applications. This update (which includes a review of the main approaches to the modelling and simulations of MEMS and RF-MEMS devices) is timely and will find a wider readership as it crosses into the translational aspects of applied research in the subject. Key features • With over 50 pages of new content, the book will be 1/3 larger than the 1st edition. • New chapter on simulation and modelling techniques. • Practical approach to the design and development of RF-MEMS design concepts for 5G and upcoming 6G. • Includes case studies. • Video figures. • Includes a review of the business landscape

Fabrication of high aspect ratio vibrating cylinder microgyroscope structures by use of the LIGA process

Inertial grade microgyroscopes are of great importance to improve and augment inertial navigation systems based on GPS for industrial, automotive, and military applications. The efforts by various research groups worldwide to develop inertial grade microgyroscopes have not been successful to date. In 1994, the Department of Mechanical Engineering at Louisiana State University and SatCon Technology Corporation (Boston, Massachusetts) proposed a series of shock tolerant micromachined vibrating cylinder rate gyroscopes with aspect ratios of up to 250:1 to meet the needs of inertial navigation systems based on existing conventional vibrating cylinder gyroscopes. Each microgyroscope consisted of a tall thin shell metallic cylinder attached to a substrate at one end and surrounded by four drive- and four sense-electrodes. The proposed drive- and sense-mechanisms were capacitive-force and capacitance-change, respectively. Since the high aspect ratio metallic microgyroscope structures could not be fabricated by using traditional silicon-based MEMS processes, a LIGA-based two layer fabrication process was developed. A wiring layer was constructed by using a combination of thick film photolithography and electroplating (nickel and gold) on a silicon substrate covered with silicon nitride and a tri-layer plating base; aligned X-ray lithography and nickel electroplating were used to build the high aspect ratio cylinders and electrodes. Deficiencies in the LIGA process were also addressed in this research. Three types of X-ray mask fabrication processes for multi-level LIGA were developed on graphite, borosilicate glass and silicon nitride substrates. Stable and reliable gold electroplating methods for X-ray masks were also established. The plating rate and internal stress of deposits were thoroughly characterized for two brands of commercially available sulfite-based gold electroplating solutions, Techni Gold 25E and NEUTRONEX 309. The gaps between the cylinders and electrodes, which are defined by thin PMMA walls during electroplating, were found to be smaller than designed and deformed in many of the microgyroscope structures. The lateral dimensional loss (LDL) and deformation were identified to be related to the overall thickness and lateral aspect ratio (LAR) of the thin PMMA walls