The doctoral dissertations of the former Helsinki University of Technology (TKK) and Aalto University Schools of Technology (CHEM, ELEC, ENG, SCI) published in electronic format are available in the electronic publications archive of Aalto University - Aaltodoc.
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Optical Microsystems Based on Integrated Optics and Micromechanics
Pekka Katila
Dissertation for the degree of Doctor of Science in Technology to be presented with due permission of the Department of Electrical and Communications Engineering for public examination and debate in Auditorium S1 at Helsinki University of Technology (Espoo, Finland) on the 20th of August, 2004, at 12 o'clock noon.
Dissertation in PDF format (ISBN 951-22-7207-5) [8469 KB]
Dissertation is also available in print (ISBN 951-22-7206-7)
Abstract
Optical microsystems based on silicon technology have been studied in this work. Components applying integrated optical structures and microelectromechanical systems (MEMS) have been developed. New functionality, lower component costs, and improved reliability have been aimed at by the integration and miniaturization of the novel concepts. The four components studied in this work represent new ideas based on well established material technologies and manufacturing schemes. The first three components are based silicon integrated optics and the fourth component is based on silicon micromechanics.
A novel architecture for a surface plasmon resonance (SPR) sensor based on a silicon nitride slab waveguide structure was proposed and studied. Industrial aspects and feasibility for the practical sensor design of the introduced concept were considered. As a main result a proof-of-concept was shown by demonstrating the device sensitivity to humidity. A surface plasmon sensor fabricated with a silicon nitride waveguide technology has applications as a chemical and biochemical sensor.
A thermally tunable integrated optical ring resonator device was developed to study the optical characteristics of a ring resonator, waveguide quality, and electrical characteristics of thermo-optical control with in situ temperature sensing. The device was based on Si3N4 waveguides. The ring perimeter of the resonator was 6.76 mm and the free spectral range was 26 GHz. The thermal control was implemented by using poly-silicon resistive heaters integrated on top of the waveguide layer. The thermal tuning was demonstrated to be a feasible tool for an accurate optical phase control. The measured temperature coefficient of Si3N4 rib waveguide can be applied in the design of future devices based on similar structures. This type of ring resonator structures are suitable for sensing applications, as high refractive index difference enables flexible designs with small radius waveguide bends.
New type of integrated optical beam combiner circuits were proposed, designed and fabricated based on a silicon oxynitride waveguide technology, to provide a replacement for optical fiber coupler components in a phased array antenna demonstrator. The insertion loss of the pigtailed devices turned out to be moderately high but the coupling ratio of the 3 dB couplers were better than 47:53, and polarization extinction ratio was above 10 dB. Based on the results of the fabricated test devices the specified optical requirements for a practical application were considered achievable with the proposed SiON technology by further reducing the propagation loss of the waveguide and the excess loss of the 3 dB couplers.
Lastly, microelectromechanical variable optical attenuators (VOA) based on the silicon-on-insulator (SOI) technology were developed for optical fiber networks. Two novel VOA architectures were proposed and developed. As a result both configurations were shown to have optical performance satisfying the general requirements set by modern fiber optical networks for VOAs. The major achievement was a reflective type VOA device with low insertion loss below 0.8 dB, ultra-low polarization sensitivity below 0.1 dB, 30 dB dynamic attenuation range, and with optical repeatability better than 0.03 dB.
Keywords: optical microsystem, integrated optic, waveguide, MEMS, MST, micromechanics, surface plasmon resonance, ring resonator, variable optical attenuator
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© 2004 Helsinki University of Technology
Last update 2011-05-26