Designing coupled-resonator optical waveguides based on high-Q tapered grating-defect resonators

We present a systematic design of coupled-resonator optical waveguides (CROWs) based on high-Q tapered grating-defect resonators. The formalism is based on coupled-mode theory where forward and backward waveguide modes are coupled by the grating. Although applied to strong gratings (periodic air holes in single-mode silicon-on-insulator waveguides), coupled-mode theory is shown to be valid, since the spatial Fourier transform of the resonant mode is engineered to minimize the coupling to radiation modes and thus the propagation loss. We demonstrate the numerical characterization of strong gratings, the design of high-Q tapered grating-defect resonators (Q>2 × 10^6, modal volume = 0.38•(λ/n)^3), and the control of inter-resonator coupling for CROWs. Furthermore, we design Butterworth and Bessel filters by tailoring the numbers of holes between adjacent defects. We show with numerical simulation that Butterworth CROWs are more tolerant against fabrication disorder than CROWs with uniform coupling coefficient

"Ideal" optical delay lines based on tailored-coupling and reflecting, coupled-resonator optical waveguides

We present a design of "ideal" optical delay lines (i.e., constant amplitude and constant group delay over the desired bandwidth). They are based on reflection from coupled-resonator optical waveguides (CROWs). The inter-resonator coupling coefficients are tailored and decrease monotonically with the distance from the input to realize all-pass Bessel filters. The tailored coupling coefficients result in a frequency-dependent propagating distance which compensates for the group velocity dispersion of CROWs. We present a simple formalism for deriving the time-domain coupling coefficients and convert these coefficients to field coupling coefficients of ring resonators. The reflecting CROWs possess a delay-bandwidth product of 0.5 per resonator, larger than that of any kind of transmitting CROW. In the presence of uniform gain, the gain enhanced by slow light propagation and the constant group delay result in efficient and dispersion-free amplifiers

Grating induced transparency (GIT) and the dark mode in optical waveguides

We propose and describe a new class of optical modes consisting of superposition of three waveguide modes which can be supported by a few-mode waveguide spatially modulated by two co-spatial gratings. These supermodes bear a close, but not exact, formal analogy to the three-level quantum states involved in EIT and its attendant slow light propagation characteristics. Of particular interest is the supermode which we call the dark mode in which, in analogy with the dark state of EIT, one of the three uncoupled waveguide modes is not excited. This mode has unique dispersion characteristics that translate into a slow light propagation which possesses high bandwidth-delay product and can form the basis for a new generation of optical resonators and lasers

Synthesis of high-order bandpass filters based on coupled-resonator optical waveguides (CROWs)

We present a filter design formalism for the synthesis of coupled-resonator optical waveguide (CROW) filters. This formalism leads to expressions and a methodology for deriving the coupling coefficients of CROWs for the desired filter responses and is based on coupled-mode theory as well as the recursive properties of the coupling matrix. The coupling coefficients are universal and can be applied to various types of resonators. We describe a method for the conversion of the coupling coefficients to the parameters based on ring resonators and grating defect resonators. The designs of Butterworth and Bessel CROW filters are demonstrated as examples

Substantial gain enhancement for optical parametric amplification and oscillation in two-dimensional χ(2) nonlinear photonic crystals

We have analyzed optical parametric interaction in a 2D NPC. While in general the nonlinear coefficient is small compared to a 1D NPC, we show that at numerous orientations a multitude of reciprocal vectors contribute additively to enhance the gain in optical parametric amplification and oscillation in a 2D patterned crystal. In particular, we have derived the effective nonlinear coefficients for common-signal amplification and common-idler amplification for a tetragonal inverted domain pattern. We show that in the specific case of signal amplification with QPM by both G10 and G11, symmetry of the crystal results in coupled interaction with the corresponding signal amplification by G10 and G1,-1. As a consequence, this coupled utilization of all three reciprocal vectors leads to a substantial increase in parametric gain. Using PPLN we demonstrate numerically that a gain that comes close to that of a 1D QPM crystal could be realized in a 2D NPC with an inverted tetragonal domain pattern. This special mechanism produces two pairs of identical signal and idler beams propagating in mirror-imaged forward directions. In conjunction with this gain enhancement and multiple beams output we predict that there is a large pulling effect on the output wavelength due to dynamic signal build-up in the intrinsic noncollinear geometry of a 2D NPC OPO

The potential of social innovation in rural revitalisation : a comparative case study from Taiwan

Social innovations have been frequently discussed in the context of rural development and even viewed as a key toward rural revitalisation, promising to cope with such societal challenges. However, to what extent and how social innovation can contribute to rural development, especially under the future challenge of rural decline, still remains an ongoing concern. This research aims to explore the potential of social innovation in rural revitalisation by clarifying the actors roles in social innovation processes. In particular, the study made use of four cases of rural development practice in Taiwan. The special attention of these case studies draws on the four objectives, which are: (1) to explore the role of actors in community-driven social innovation; (2) to clarify the role of actors in external support-driven rural social innovation; (3) to provide recommendations for integrating the concept of social innovation into rural development policies and programmes; (4) to further theoretical and methodological insights for the study of rural social innovation. The study concludes that the internal actors may not aim to innovate society they intend to solve practical local issues. Therefore, the outcomes of social innovation can be unintentional; tangible and material outcomes are crucial for internal actors, which may challenge the literatures perspective that treats material outcomes as supplementary results. Furthermore, external actors could play a key role as helpers in fuelling social innovation only if they get sufficient support from rural areas and the public sector, resulting in their growth while facing upcoming challenges. The study also discussed the pros, cons, and differences between community-driven and external support-driven approaches. These two approaches―are like two sides of the same coin―while the former is more local-oriented in terms of local targeted problems and local joint actors, the latter is rather issue-oriented that can focus on the targeted problems and the joint actors without geographical boundaries. In addition, the external support-driven approach conducted by this research to a certain degree reflects the nexogenous approach. From the empirical experiences of this study, this approach might not guarantee the success of rural social innovation―however, it did provide a bright chance for the public sector to participate not only as a partner or sponsor in rural areas but they can actively be as a bridge to link potential partners somewhere beyond geographical boundaries. Three strategies are provided for the public sector, encompassing: (1) the public sector should actively play a bridging role to provide opportunities for connecting external actors; (2) the public sector could use programmes, such as village competitions or other innovative activities, to provide a reachable share vision for people to participate; (3) rural development related programmes should draw more attentions om educational and learning types of programmes to develop self-learning mechanism in local communities. For theoretical and methodological insights, the ANT can be better used to explore research with inequality consideration and without initial social explanation assumptions. The actor-oriented approach may be suitably used to study interactions among clear differentiation of social actors with initial social explanation assumptions. From the findings of this case study, it can be concluded that social innovation in terms of rural revitalisation is valuable in its outcomes, uncertain in its emergence, challenged by the marginalising rural reality, and promising on external connections without geographical boundaries. Since the future of rural marginalisation is considered inevitable, to survive in its effects is essential. In other words, rural social innovation may not be able to eliminate the causes of rural marginalisation; however, it provides an approach to adapt its effects, that is, to weave a future that rural areas might not have many inhabitants―however, they have more self-organisation―initiators, actors, more external partners and connections are driven by needs to solve common societal problems―without geographical boundaries.Soziale Innovationen werden häufig im Zusammenhang mit der Entwicklung des ländlichen Raums diskutiert und sogar als Schlüssel zu deren Wiederbelebung angesehen und zur Bewältigung solcher gesellschaftlichen Herausforderungen. Inwieweit und wie soziale Innovationen zur Entwicklung des ländlichen Raums beitragen, und insbesondere einem negativen Trend entgegenwirken können, ist jedoch nach wie vor eine offene Frage. Ziel dieser Untersuchung ist es, das Potenzial der sozialen Innovation für die Wiederbelebung des ländlichen Raums über die Klärung der Rollen der Akteure in sozialen Innovationsprozessen zu erforschen. Für die Studie wurden vier Fälle aus der Praxis der ländlichen Entwicklung in Taiwan herangezogen. Die besondere Aufmerksamkeit, mit der die vier Fallstudien untersucht wurde, beruht auf den folgenden vier Zielen: (1) Untersuchung der Rolle von Akteuren bei gemein-schaftsgetriebenen sozialen Innovationen; (2) Klärung der Rolle von Akteuren bei extern unterstützten sozialen Innovationen im ländlichen Raum; (3) Erarbeitung von Empfehlungen für die Integration des Konzepts der sozialen Innovation in politische Maßnahmen und Programme zur Entwicklung des ländlichen Raums; (4) Förderung theoretischer und methodologischer Erkenntnisse für die Untersuchung sozialer Innovationen im ländlichen Raum. Die Studie kommt zu dem Schluss, dass die internen Akteure möglicherweise nicht darauf abzielen, die Gesellschaft zu erneuern - sie beabsichtigen, praktische lokale Probleme zu lösen. Daher können die Ergebnisse sozialer Innovation unbeabsichtigt sein; greifbare und materielle Ergebnisse sind für interne Akteure von entscheidender Bedeutung, was eine in der Literatur verbreitete Sichtweise in Frage stellt, die materielle Ergebnisse als zusätzliche Ergebnisse behandelt. Darüber hinaus könnten externe Akteure nur dann eine Schlüsselrolle bei der Förderung sozialer Innovation spielen, wenn sie ausreichend Unterstützung aus dem ländlichen Raum und dem öffentlichen Sektor erhalten, was zu ihrem Wachstum bei gleichzeitiger Bewältigung der anstehenden Herausforderungen führt. Die Studie erörtert auch die Vor- und Nachteile sowie die Unterschiede zwischen gemeinschaftsorientierten und auf externe Unterstützung ausgerichteten Ansätzen. Diese beiden Ansätze sind wie zwei Seiten derselben Medaille - während der erste Ansatz eher lokal orientiert ist, was die anvisierten Probleme und die lokalen gemeinsamen Akteure betrifft, ist der zweite Ansatz eher themenorientiert und konzentriert sich auf die Probleme und die gemeinsamen Akteure ohne geografische Grenzen zu setzen. Darüber hinaus spiegelt der von dieser Studie verfolgte Ansatz der externen Unterstützung bis zu einem gewissen Grad den "nexogenen Ansatz" wider. Aus den empirischen Erfahrungen dieser Studie geht hervor, dass dieser Ansatz keine Garantie für den Erfolg sozialer Innovationen im ländlichen Raum ist - er bietet jedoch eine gute Chance für den öffentlichen Sektor, nicht nur als Partner oder Sponsor in ländlichen Gebieten aufzutreten, sondern aktiv als Brücke zu fungieren, um potenzielle Partner über geografische Grenzen hinweg miteinander zu verbinden. Drei Strategien für den öffentlichen Sektor vorgeschlagen: (1) der öffentlichen Sektor sollte aktiv eine Brücken¬funktion übernehmen, um Möglichkeiten für die Einbindung externer Akteure zu schaffen; (2) der öffentliche Sektor könnte Programme wie Dorfwettbewerbe oder andere innovative Aktivitäten nutzen, um den Menschen eine erreichbare gemeinsame Vision zu bieten, an der sie sich beteiligen können; (3) Programme zur Entwicklung des ländlichen Raums sollten mehr Aufmerksamkeit auf Bildungs- und Lernprogramme lenken, um Selbst¬lernmechanismen in lokalen Gemeinschaften zu entwickeln. Für theoretische und methodologische Einsichten kann die ANT besser genutzt werden, um Forschung unter Berücksichtigung von Ungleichheit und ohne anfängliche soziale Erklärungsannahmen zu betreiben. Der akteursorientierte Ansatz eignet sich für die Untersuchung von Interaktionen zwischen klar differenzierten sozialen Akteuren mit anfänglichen sozialen Erklärungsannahmen. Aus den Ergebnissen dieser Fallstudie lässt sich schließen, dass soziale Innovation im Hinblick auf die Wiederbelebung des ländlichen Raums in ihren Ergebnissen wertvoll, in ihrer Entstehung unsicher, durch die Marginalisierung des ländlichen Raums herausgefordert und auf externe Beziehungen ohne geografische Grenzen angewiesen ist. Da ländliche Marginalisierung in der Zukunft unvermeidlich scheint, ist es wichtig, ein Leben mit deren Auswirkungen zu gestalten. Soziale Innovation bietet dazu einen Ansatz, wie die abnehmende Zahl der Einwohner in ländlichen Räumen über mehr Selbstorganisation und externe Partner und Beziehungen gemeinsame gesellschaftliche Probleme lösen können ohne geographische Grenzen

Conservación del paisaje cultural de irrigación en Taiwan como lugar potencial de Patrimonio Mundial: una aportunidad para un paisaje rural

The Wushantou Reservoir and Jianan Irrigation System was designed by Hatta Yoichi and built by many workers in 1920s. The reservoir was built with the condition of natural environment, and the agriculture production was also changed due to this irrigation system. In 2009, the system was registered as “cultural landscape” under Cultural Heritage Preservation Act. It also designated as one of the Potential World Heritage Sites of Taiwan. Due to the nature of cultural landscape, the conservation concepts should be different to those of monuments or historical buildings which were mostly derived from a single point. Furthermore, the conservation of an irrigation cultural landscape should not be limited to the structure – objects or cannels – only. The whole irrigated agricultural land is essential. The opportunities provided for agricultural production to local people may be the important concept for the conservation of a rural landscape. Agriturism in this sense may become a good possibility to combine agricultural production and heritage conservation, by which local people may be economically sustainable, while the function and features of irrigation system may be also kept. Food made from local agricultural products also connected tangible and intangible part of heritage, while a virtuous circle would be derived from this connection. In this paper, the irrigation system and its heritage value would be explored. The status of rural development in the area, development and possibilities of agritourism, and relation between food and local production, would be discussed and analyzed.La Reserva Wushantou y el Sistema de Irrigación Jianan fueron diseñados por Hatta Yoichi y construido por numerosos constructores en los años 20. La Reserva fue construida con la condición de un entorno natural, y la producción agrícola también cambió debido a este sistema de irrigación. En 2009, el sistema fue registrado como un “paisaje cultural” bajo la Ley de Conservación del Patrimonio Cultural. Esta también lo declaró como uno de los potenciales lugares de Patrimonio Mundial de Taiwán. Debido a la naturaleza del paisaje cultural, los conceptos de conservación deberían ser diferentes a los de monumentos o edificios históricos, que deriva principalmente de un punto único. Además, la preservación de un paisaje cultural de irrigación no debería estar únicamente limitada a la estructura-objetos o canales. Toda la tierra agrícola irrigada es esencial. Las oportunidades dadas por la producción agrícola a la población local pueden ser el concepto importante para la conservación de un paisaje rural. El agroturismo en este sentido puede convertirse en una buena posibilidad para combinar la producción agrícola y la conservación patrimonial, por la que la población local puede ser económicamente sostenible, al tiempo que la función y los elementos del sistema de irrigación pueden ser también mantenidos. La comida preparada a partir de productos agrícolas también conectan la parte material e inmaterial del patrimonio, mientras que un círculo virtuoso se derivaría de esta conexión. En este trabajo, el sistema de irrigación y su valor patrimonial serán considerados. El estatus del desarrollo rural en el área, el desarrollo y las posibilidades del agroturismo, y la relación entre la comida y la producción loca serán discutidas y analizadas.Depto. de Prehistoria, Historia Antigua y ArqueologíaFac. de Geografía e HistoriaTRUEMinisterio de Economía y Competitividad (MINECO)pu

A Simple Technique Using a Modified Nance Appliance as Anchorage for Maxillary Molar Distalization—Two Case Reports

Maxillary molar distalization to correct a dental Class II molar relationship and to create space to relieve crowding has been a long-lasting subject of debate in orthodontics. Generally, to distalize maxillary molars, an intra-arch distalization appliance is favored over an inter-arch appliance since it does not utilize mandibular dentition as an anchorage, so some unwanted side effects on mandibular incisors can be avoided. A variety of intra-arch appliances have been developed to distalize maxillary molars, such as the pendulum, Jones jig, first class appliance, distal jet, and modified C-palatal plate. Although they could achieve efficient molar distalization, the learning curve of proper appliance insertion and activation is relatively long. In addition, the appliances are not comfortable for the patients due to the bulky activation units, especially when the activation units are designed in the palatal area. The current manuscript describes a novel and effective maxillary intra-arch molar distalization appliance—a modified Nance appliance technique, which consists of: (1) palatally, a big acrylic button against the palatal rugae and connected to the premolars with wide mesh pads; (2) buccally, regular brackets on maxillary premolars and first molars with sectional round stainless steel archwires and open coil springs between the second premolar and first molar. Either bilateral or unilateral maxillary molar distalization can be achieved with this appliance, and the Class II elastics are not needed. It is simple to be fabricated, delivered, and activated, and it is comfortable for patients. © 2022 by the authors. Licensee MDPI, Basel, Switzerland