Integrated GHz silicon photonic interconnect with micrometer-scale modulators and detectors

We report an optical link on silicon using micrometer-scale ring-resonator enhanced silicon modulators and waveguide-integrated germanium photodetectors. We show 3 Gbps operation of the link with 0.5 V modulator voltage swing and 1.0 V detector bias. The total energy consumption for such a link is estimated to be ~120 fJ/bit. Such compact and low power monolithic link is an essential step towards large-scale on-chip optical interconnects for future microprocessors

Controlling photonic structures using optical forces

The downscaling of optical systems to the micro and nano-scale results in very compliant systems with nanogram-scale masses, which renders them susceptible to optical forces. Here we show a specially designed resonant structure for enabling efficient static control of the optical response with relatively weak repulsive and attractive optical forces. Using attractive gradient optical forces we demonstrate a static mechanical deformation of up to 20 nanometers in the resonator structure. This deformation is enough to shift the optical resonances by roughly 80 optical linewidths.Comment: Body: 7 pages, 3 figures; Appendix: 14, 5 figure

Large optical nonlinearity of nanoantennas coupled to an epsilon-near-zero material

The size and operating energy of a nonlinear optical device are fundamentally constrained by the weakness of the nonlinear optical response of common materials1. Here, we report that a 50-nm-thick optical metasurface made of optical dipole antennas coupled to an epsilon-near-zero material exhibits a broadband (∼400 nm bandwidth) and ultrafast (recovery time less than 1 ps) intensity-dependent refractive index n2 as large as −3.73 ± 0.56 cm2 GW−1. Furthermore, the metasurface exhibits a maximum optically induced refractive index change of ±2.5 over a spectral range of ∼200 nm. The inclusion of low-Q nanoantennas on an epsilon-near-zero thin film not only allows the design of a metasurface with an unprecedentedly large nonlinear optical response, but also offers the flexibility to tailor the sign of the response. Our technique removes a longstanding obstacle in nonlinear optics: the lack of materials with an ultrafast nonlinear contribution to refractive index on the order of unity. It consequently offers the possibility to design low-power nonlinear nano-optical devices with orders-of-magnitude smaller footprints.PostprintPeer reviewe

Combinatoria léxica, polisemia y polisemia regular en una base de conocimiento léxico conceptual : el caso de "Redes diccionario combinatorio del español contemporáneo" y functional grammar knowledge base

This dissertation attempts to link the linguistic information contained in REDES Diccionario combinatorio del español contemporáneo (Bosque, 2004), or REDES, to the ontological framework of Functional Grammar Knowledge Base, or FunGramKB. REDES is a dictionary that gathers systematic restrictions imposed by some 4,000 Spanish predicates to their selection of lexical arguments, while FunGramKB is a multilingual and multipurpose lexical conceptual knowledge base (KB) designed for Natural Language Processing (NLP). This work is thus part of the field known as electronic lexicography for the XXIst century or the third millennium (Fuertes and Tarp, 2011).This new lexicography comprises electronic lexicographical resources which are much more complex than the commonly used digitalized versions of traditional dictionaries. It is composed of lexical databases or lexical knowledge bases, of variable complexity and depth, built on electronic platforms. Even though electronic lexicography can also serve the typical dictionary queries posed by humans, the best-known NLP applications include machine translation (MT), question and answer systems, information extraction, and voice recognition programs. However, the main problem facing NLP continues to be Word Sense Disambiguation (WSD). Most words in a language are polysemic and a successful NLP application will depend on its ability to assign the correct sense to each word in a given context. A great deal of the work that is taking place in NLP is therefore focused on finding strategies to effectively disambiguate words in their context.In working with REDES and FunGramKB, it could seem at first glance that we are dealing with two distant fields –print lexicography and knowledge engineering, respectively–, but this thesis assumes that linking these resources would yield significant benefits for both. Furthermore, it would combine two sources of valuable linguistic and theoretical data: on the one hand, REDES contributes thousands of patterns of systematic predicate-argument word combinations, taken from real use in Spanish-language corpora. These combinations are not presented as “collocations”, that is, combinations between a single predicate and a single argument, or vice versa, but rather, between predicates and “lexical classes”, groups of arguments that share a common semantic basis. On the other hand, FunGramKB contributes a multilevel electronic platform designed for NLP, which includes a conceptual, a lexical and a grammatical model, and has been built around a hierarchical and taxonomical ontology of universal cognitive concepts