47 research outputs found
All-optical conditional logic with a nonlinear photonic crystal nanocavity
We demonstrate tunable frequency-converted light mediated by a chi-(2)
nonlinear photonic crystal nanocavity. The wavelength-scale InP-based cavity
supports two closely-spaced localized modes near 1550 nm which are resonantly
excited by a 130 fs laser pulse. The cavity is simultaneously irradiated with a
non-resonant probe beam, giving rise to rich second-order scattering spectra
reflecting nonlinear mixing of the different resonant and non-resonant
components. In particular, we highlight the radiation at the sum frequencies of
the probe beam and the respective cavity modes. This would be a useful,
minimally-invasive monitor of the joint occupancy state of multiple cavities in
an integrated optical circuit.Comment: 4 pages, 4 figure
Ultra-high-Q TE/TM dual-polarized photonic crystal nanocavities
We demonstrate photonic crystal nanobeam cavities that support both TE- and
TM-polarized modes, each with a Quality factor greater than one million and a
mode volume on the order of the cubic wavelength. We show that these
orthogonally polarized modes have a tunable frequency separation and a high
nonlinear spatial overlap. We expect these cavities to have a variety of
applications in resonance-enhanced nonlinear optics.Comment: 4 pages, 4 figure
Efficient Terahertz Generation in Triply Resonant Nonlinear Photonic Crystal Microcavities
We propose a scheme for efficient cavity-enhanced nonlinear THz generation
via difference-frequency generation (DFG) processes using a triply resonant
system based on photonic crystal cavities. We show that high nonlinear overlap
can be achieved by coupling a THz cavity to a doubly-resonant,
dual-polarization near-infrared (e.g. telecom band) photonic-crystal nanobeam
cavity, allowing the mixing of three mutually orthogonal fundamental cavity
modes through a chi(2) nonlinearity. We demonstrate through coupled-mode theory
that complete depletion of the pump frequency - i.e., quantum-limited
conversion - is possible in an experimentally feasible geometry, with the
operating output power at the point of optimal total conversion efficiency
adjustable by varying the mode quality (Q) factors.Comment: 8 pages, 3 figure
Large expert-curated database for benchmarking document similarity detection in biomedical literature search
Document recommendation systems for locating relevant literature have mostly relied on methods developed a decade ago. This is largely due to the lack of a large offline gold-standard benchmark of relevant documents that cover a variety of research fields such that newly developed literature search techniques can be compared, improved and translated into practice. To overcome this bottleneck, we have established the RElevant LIterature SearcH consortium consisting of more than 1500 scientists from 84 countries, who have collectively annotated the relevance of over 180 000 PubMed-listed articles with regard to their respective seed (input) article/s. The majority of annotations were contributed by highly experienced, original authors of the seed articles. The collected data cover 76% of all unique PubMed Medical Subject Headings descriptors. No systematic biases were observed across different experience levels, research fields or time spent on annotations. More importantly, annotations of the same document pairs contributed by different scientists were highly concordant. We further show that the three representative baseline methods used to generate recommended articles for evaluation (Okapi Best Matching 25, Term Frequency–Inverse Document Frequency and PubMed Related Articles) had similar overall performances. Additionally, we found that these methods each tend to produce distinct collections of recommended articles, suggesting that a hybrid method may be required to completely capture all relevant articles. The established database server located at https://relishdb.ict.griffith.edu.au is freely available for the downloading of annotation data and the blind testing of new methods. We expect that this benchmark will be useful for stimulating the development of new powerful techniques for title and title/abstract-based search engines for relevant articles in biomedical research