High quality nanophotonic structures fabricated on silicon nitride substrates and operating in the visible range of the spectrum are investigated. As most biological sensing applications, such as Raman and fluorescence sensing, require visible light pumping and analysis, extending the nanophotonics concepts to the visible range is essential. Traditionally, CMOS compatible processes are used to make compact silicon nanophotonics structures. While the high index contrast of silicon on insulator (SOI) wafers offer a high integration capability, the high absorption loss of silicon renders it unusable in the visible range. In this research high quality factor microdisk and photonic crystal resonators and high resolution arrayed waveguide grating and superprism spectrometers are fabricated and characterized in the visible range and integrated with fluidic structures and their application in biosensing and athermal operations is investigated.

The purpose of this work is the development of MEMS-based resonant sensors for liquid-phase biochemical sensing applications. Specifically, the sensors developed here are aimed at embedded or point-of-sampling applications: (1) when there is not enough time to send a sample to a lab for analysis, (2) in resource-poor settings, (3) when collecting analyte and shipping it to a lab would damage the sample, or (4) for in-situ monitoring. To this end, a bulk micromachined resonant cantilever sensor and a surface micromachined sensor based on the spring-softening effect are investigated as transducer elements. The developed cantilever resonators are operated in an in-plane vibration mode to reduce fluid damping and mass loading by the surrounding fluid. The surface of the resonator is either coated with a chemically sensitive polymer film for chemical sensing or with a layer of protein or antibody for biosensor testing. Chemical tests for sensing volatile organic compounds using polymer-coated in-plane resonators in the liquid-phase give estimated limits of detection below 100 ppb. In addition, biosensor tests for the detection of anti-IgG yield estimated limits of detection around 100 ng/ml. In an attempt to further improve sensor reliability and to further lower the limits of detection, a second sensing concept has been investigated. The presented sensing scheme is capacitive with a resonator acting as an analog-to-digital converter. The resonator and the sensing capacitors are coupled via the spring softening effect. Through this mechanism a change in capacitance causes a shift in resonant frequency. Extensive device modeling has been performed and a process has been developed allowing for fabrication and on-chip packaging of these sensor structures. Initial mechanical characterization data show that the resonators do in fact vibrate.

Kyoto University (京都大学) / 0048 / 新制・課程博士 / 博士(工学) / 甲第18990号 / 工博第4032号 / 新制||工||1621 / 31941 / 京都大学大学院工学研究科電気工学専攻 / (主査)教授 引原 隆士, 教授 北野 正雄, 准教授 山田 啓文 / 学位規則第4条第1項該当

Cavity quantum electrodynamics provide a platform to form a quantum network which connects individual quantum bits (qubits) via photon. Optical cavity, a device which traps photons in a confined volume can enhance the interaction between photons and the qubits serves as fundamental building block for a quantum network. Nitrogen vacancy (NV) centers in diamond has emerged as one of the leading solid-state qubits because of its long spin coherence time and single photon emission properties at room temperature. Diamond optical micro-cavities are highly sought after for coupling with NV centers. Fabrication of optical cavities from nano-crystalline diamond film has been demonstrated previously. The quality factor (Q) of such devices was limited by the material properties of the nano-crystalline diamond film. Fabrication of single-crystal diamond photonic cavities is challenging because there is no trivial way to form thin diamond film with optical isolation. In this thesis, we describe an approach to fabricate high quality single-crystal diamond optical cavities for coupling to NV centers in diamond. ingle-crystal diamond membranes were generated using an ion-slicing method. Whispering gallery modes were observed for the first time from microdisk cavities made from such material. However, the cavity Q (∼ 500) was limited by the ion damage created during processing. By using an homo-epitaxial overgrowth method, a high quality diamond film can be grown on the ion damaged membranes. Microdisk cavities with Q ∼ 3,000 were fabricated on these improved materials. Diamond membranes with a delta-doped layer of NV can be made using a slow overgrowth process which demonstrate the position and density of NV centers can be controlled in these membranes. Photonic crystal cavities with Q ∼ 4,000 were fabricated from the delta-doped membranes with cavity resonance near the zero phonon line of NV centers. Different color centers can also be introduced during the overgrowth process, and optical coupling of an ensemble of silicon vacancy centers is demonstrated by coupling to a diamond microdisk cavity. We believe the techniques developed in this thesis could contribute to building of a quantum photonic network using diamond as a platform. / Engineering and Applied Sciences

Το κύριο αντικείμενο αυτής της διατριβής είναι να δοθεί απάντηση στο ιστορικό ερώτημα: ήταν αποτελεσματικοί οι συντονιστές; Και αν ναι, μπορούν να χρησιμοποιηθούν για την βελτιστοποίηση της ακουστικής ενός χώρου μόνοι τους ή με τη συμβολή κάποιας άλλης τεχνικής; Εδώ χρησιμοποιείται η τεχνική της σύζευξης, η οποία και αναλύεται διεξοδικά. Όπως αναπτύσσεται στα κεφάλαια της διατριβής στους χώρους λατρείας για αρκετούς αιώνες εντοίχιζαν συντονιστές που είχαν τη μορφή αγγείων [1.4-7], [1.9-10], [1.12], [1.15] [1.18] [1-25]. Για την αποτελεσματικότητα αυτής της τεχνικής αυτής έχουν διατυπωθεί αρκετές αντικρουόμενες απόψεις. Για ορισμένους ερευνητές (όπως π.χ. ο Bulle κ.α.) οι συντονιστές δεν προσέφεραν καμία βελτίωση στην ακουστική των κλειστών χώρων [1.3]. Κύριο επιχείρημα τους ήταν η εγκατάλειψη της τεχνικής αυτής γύρω στον 19ο αιώνα. Άλλοι ερευνητές όπως για παράδειγμα ο Knudsen πίστευαν ότι οι συντονιστές χρησιμοποιούνταν ως απορροφητές [1.28]. Για άλλους (όπως π.χ. o Junker), οι συντονιστές χρησιμοποιούνταν για την ενίσχυση του ήχου ή τη βελτίωση της ακουστικής ποιότητας των χώρων. Κύριο επιχείρημα της ομάδας αυτής είναι η εξάπλωση της τεχνικής αυτής σε ολόκληρο σχεδόν τον τότε πολιτισμένο κόσμο [1.19 – 20]. Στη συνέχεια παρουσιάζονται οι δείκτες και οι τρόποι με τους οποίους αξιολογούνται ακουστικά οι χώροι. Χωρίζονται σε κατηγορίες, αξιολογούνται και δίνεται έμφαση σε αυτούς που θα χρησιμοποιηθούν, σε όσους είναι πιο σημαντικοί και σε όσους μπορούν να παρουσιάσουν διαφοροποιήσεις μετρήσιμες και αξιοσημείωτες ανάλογα με τις αλλαγές που επιφέρονται στους εκάστοτε χώρους. Έχοντας παρουσιάσει τη χρήση των συντονιστών σε χώρους λατρείας με πολλά παραδείγματα και φωτογραφίες, επιχειρείται μια παρουσίασή τους πιο θεωρητική. Παρουσιάζονται τα χαρακτηριστικά τους, η λειτουργία τους, τα μοντέλα τους και όλη η θεωρεία που τους συνοδεύει με αρκετές αναφορές ιστορικές και επιστημονικές από διάφορους ερευνητές και μελετητές από τον Helmholtz μέχρι σήμερα. Το δεύτερο μεγάλο κομμάτι περιλαμβάνει τη θεωρεία της σύζευξης μέσα από τα μοντέλα που έχουν αναπτυχθεί κατά καιρούς, τις έρευνες που έχουν γίνει και τα αποτελέσματα των μελετών που έχουν κατά καιρούς ασχοληθεί με αυτή. Τα πιο σημαντικά κομμάτια είναι οι απαντήσεις στα παρακάτω ερωτήματα: ποιοι είναι συζευγμένοι χώροι, πόσο ισχυρά ή ασθενώς συζευγμένοι είναι, ποια μοντέλα τους προσδιορίζουν καλύτερα, ποιες εξισώσεις μπορούν να αποδώσουν καλύτερα τις διαδικασίες που λαμβάνουν χώρα κατά τη σύζευξη κ.α. Στο τέλος παρουσιάζεται το προτεινόμενο μοντέλο για τη σύζευξη που λαμβάνει υπόψη του τη λειτουργία των συντονιστών και το κατά πόσο μπορούν να αλλάξουν τη συμπεριφορά των συζευγμένων χώρων. Τα θεωρητικά αποτελέσματα του μοντέλου συγκρίνονται με πραγματικές μετρήσεις σε χώρους λατρείας στους οποίους στήθηκαν πειραματικές διατάξεις για να καταγράψουν τη συμπεριφορά αυτών με τη παρουσία των συντονιστών και χωρίς. Γενικότερα, για να πραγματοποιηθούν τα παραπάνω, η έρευνα προχώρησε σε τρεις κατευθύνσεις. Η πρώτη κατεύθυνση ήταν η μελέτη και η καταγραφή της τεχνικής εντοίχισης της μορφής των αγγείων, του αριθμού των αγγείων και όλων των λοιπών στοιχείων που σχετίζονται με τους συντονιστές. Η δεύτερη κατεύθυνση ήταν στη μέτρηση της ακουστικής συμπεριφοράς των χώρων με την παρουσία συντονιστών και χωρίς αυτούς. Η τρίτη κατεύθυνση αφορά την κατασκευή ενός στατιστικού μοντέλου που να περιλαμβάνει τη λειτουργία των συντονιστών. Οι προβλεπόμενες τιμές από το μοντέλο συγκρίθηκαν με μετρήσεις σε ναούς. Το μοντέλο που αναπτύχθηκε ουσιαστικά αποτελεί την επέκταση της θεωρίας της σύζευξης, διότι στους χώρους λατρείας υπάρχουν ισχυρά φαινόμενα σύζευξης, ώστε να περιλάβει συστήματα σκέδασης όπως είναι οι συντονιστές. / This thesis tries to answer to the question: Was resonators effective? If yes, can be used to improve the acoustics of a room or has to be used combined to some other technique? Here is used the coupling method. A lot of resonators have been found in church's walls but the effectiveness of this method has been discussed a lot by specialists. Some researchers say that resonators do not effect the acoustics of a church, some others support that resonators were used to enlarge voice or as absorbers. Many useful rates are being introduced and most of them are going to be used to evaluate the acoustics of the questioned rooms. The theory of resonators is being introduced analytically. How and when resonators have been used, which are their characteristics and their models and lastly many papers are being referred. The theory of coupling is the next important issue and is being introduced in detail. Most of the models and papers referred to coupling method are being presented and the most important questions are: which are the coupling rooms, how strong or weak is coupling and which models describe better the coupling procedure. In the end the proposed model is being presented. This model takes into account the coupling method and the resonator's function in order to evaluate the behaviour of the room. The outcomes of the model are being compared to measured values from churches. Three steps have been followed. Firstly, the vessels used as enwalled resonators were examined and marked. Then, the acoustics of rooms with resonators was evaluated and lastly a statistic model was constructed to anticipate the behaviour of coupling rooms with resonators.

Optimal utilization of microwave energy requires more basic knowledge of the dielectric properties of the material under investigation. The dielectric properties of materials subjected to microwaves are known to depend on moisture content, temperature and density of the material as well as the frequency of the applied microwave field. This thesis is focussed on the development and evaluation of the new Permittivity Analyser to measure the dielectric properties of agri-food materials at 915 and 2450 MHz using cavity perturbation concept. / In this study, the dielectric properties measuring system was designed and developed using cavity perturbation concept to measure the essential and fundamental parameters of microwave-material interaction; dielectric constant and dielectric loss factor of selected agri-food substances and organic solvents. The TM010 mode of electromagnetic energy was selected and configured to operate at the peakresonant condition for both ISM (Industrial, Scientific and Medical) approved frequencies of .915 and 2450 MHz frequencies. The resonant perturbation cavities were designed, fabricated and tested using the network analyser and the permittivity analyser. High Q (ratio of energy supplied to absorbed) values were reported for both frequencies. Basic calibration of the measurement system was performed using standard media such as air, water and alcohol. Necessary mathematical steps and algorithms were written and integrated into a user-friendly software program (Visual basic 6.0) to carry out the entire measurement. / The dielectric properties (epsilon' & epsilon ″) of materials such as; edible oils---canola, soya and sunflower oils, neem oil/pulp, homogenized milk (1, 2 and 3.25% fat), organic solvents such as ethanol, hexane and their mixtures were determined at various temperatures and frequency (915, 2450 MHz) combinations, using cavity perturbation technique. Linear relationships between the dielectric properties and temperature found in the literature were confirmed to be valid for certain ranges in case of edible oils, organic solvents and milk samples tested with the cavity perturbation method. Repeatibility and variability aspects of the permittivity analyzer at both the frequencies are presented.

A low-temperature (<300°C) method to fabricate electrostatically actuated microelectromechanical (MEM) clamped-clamped beam resonators has been developed. It utilizes an amorphous silicon carbide (SiC) structural layer and a thin polyimide spacer. The resonator beam is constructed by DC sputtering a tri-layer composite of low-stress SiC and aluminum over the thin polyimide sacrificial layer, and is then released using a microwave O 2 plasma etch. Deposition parameters have been optimized to yield low-stress films (<50MPa), in order to minimize the chance of stress-induced buckling or fracture in both the SiC and aluminum. Characterization of the deposited SiC was performed using several different techniques including scanning electron microscopy, EDX and XRD. / Several different clamped-clamped beam resonator designs were successfully fabricated and tested using a custom built vacuum system, with measured frequencies ranging from 5MHz to 25MHz. A novel thermal tuning method is also demonstrated, using integrated heaters directly on the resonant structure to exploit the temperature dependence of the Young's modulus and thermally induced stresses.

No description available.

The dynamics of atomic scale structures during structural change can be studied by Ultrafast Electron Diffraction (UED). The time resolution needed to reveal the fastest dynamics is 100 fs. Sub-angstrom structural resolution becomes possible with 1-1000 pC of charge necessary for diffraction pattern analysis during subtle structural changes. This combination of requirements cannot currently be realized due to the space-charge temporal broadening inherent to bunches of electrons of high fluence and short temporal duration. Simulations show that the incorporation of a specially designed Radio-Frequncy (RF) cavity into the UED apparatus removes this technical limitation. The RF cavity reverses the near linear position-momentum distribution of the temporally broadened electron bunch, causing the bunch to recompress itself as it propagates. It is found that our proposed method allows for sub-100 fs bunches with maximum charge of 0.6 pC, almost 3 orders of magnitude improvement over today's state of the art.

No description available.