Photonic Crystal Nanocavities and Waveguides

Fabrication of optical structures has evolved to a precision which allows us to control light within etched nanostructures. Nano-optic cavities can be used for efficient and flexible concentration of light in small volumes, and control over both emission wavelength and frequency. Conversely, if a periodic pattern is defined in the top semitransparent metal layer by lithography, it is possible to efficiently couple out the light out of a semiconductor and to simultaneously enhance the spontaneous emission rate. Here we demonstrate the use of photonic crystals for efficient light localization and light extraction

Photonic Crystals and their Applications to Efficient Light Emitters

When combined with high index contrast slabs in which light can be efficiently guided, microfabricated two-dimensional photonic bandgap mirrors provide us with the geometries needed to confine and concentrate light into extremely small volumes and to obtain very high field intensities. Fabrication of optical structures has now evolved to a precision which allows us to control light within such etched nanostructures. Sub-wavelength nano-optic cavities can be used for efficient and flexible control over both emission wavelength and frequency, and nanofabricated optical waveguides can be used for efficient coupling of light between devices. The reduction of the size of optical components leads to their integration in large numbers and the possibility to combine different functionalities on a single chip. We show uses of such crystals in functional nonlinear optical devices, such as lasers, modulators, add/drop filters, polarizers and detectors

Reliability of judging in DanceSport

Purpose The aim of this study was to assess the reliability and validity of the new judging system in DanceSport. Methods Eighteen judges rated the 12 best placed adult dancing couples competing at an international competition. They marked each couple on all judging criteria on a 10 level scale. Absolute agreement and consistency of judging were calculated for all main judging criteria and sub-criteria. Results A mean correlation of overall judging marks was 0.48. Kendall’s coefficient of concordance for overall marks (W = 0.58) suggesting relatively low agreement among judges. Slightly lower coefficients were found for the artistic part [Partnering skills (W = 0.45) and Choreography and performance (W = 0.49)] compared to the technical part [Technical qualities (W = 0.56) and Movement to music (W = 0.54)]. ICC for overall criteria was low for absolute agreement [ICC(2,3) = 0.62] but higher for consistency [ICC(3,3) = 0.80]. Conclusion The relatively large differences between judges’ marks suggest that judges either disagreed to some extent on the quality of the dancing or used the judging scale in different ways. The biggest concern was standard error of measurement (SEM) which was often larger than the difference between dancers scores suggesting that this judging system lacks validity. This was the first research to assess judging in DanceSport and offers suggestions to potentially improve both its objectivity and validity in the future

Photonic Crystal Cavities and Waveguides

Recently, it has also become possible to microfabricate high reflectivity mirrors by creating two- and three-dimensional periodic structures. These periodic "photonic crystals" can be designed to open up frequency bands within which the propagation of electromagnetic waves is forbidden irrespective of the propagation direction in space and define photonic bandgaps. When combined with high index contrast slabs in which light can be efficiently guided, microfabricated two-dimensional photonic bandgap mirrors provide us with the geometries needed to confine and concentrate light into extremely small volumes and to obtain very high field intensities. Here we show the use of these "artificially" microfabricated crystals in functional nonlinear optical devices, such as lasers, modulators, and waveguides

Entangled photons from a strongly coupled quantum dot-cavity system

A quantum dot strongly coupled to a photonic crystal has been recently proposed as a source of entangled photon pairs [R. Johne et al., Phys. Rev. Lett. 100, 240404 (2008)]. The biexction decay via intermediate polariton states can be used to overcome the natural splitting between the exciton states coupled to the horizontally and vertically polarized light modes, so that high degrees of entanglement can be expected. We investigate theoretically the features of realistic dot-cavity systems, including the effect of the different oscillator strength of excitons resonances coupled to the different polarizations of light. We show that in this case, an independent adjustment of the cavity resonances is needed in order to keep a high entanglement degree. We also consider the case when the biexciton-exciton transition is also strongly coupled to a cavity mode. We show that a very fast emission rate can be achieved allowing the repetition rates in the THz range. Such fast emission should however be paid for by a very complex tuning of the many strongly coupled resonances involved and by a loss of quantum efficiency. Altogether a strongly coupled dot-cavity system seems to be very promising as a source of entangled photon pairs.Comment: 7 pages, 5 figure

Photonic bandgap microcavity devices

Modern semiconductor microfabrication techniques can be used to define the high quality optical components needed in nanophotonic integrated circuits. Here we show our work on design, fabrication and characterization of ultrasmall lasers, filters, modulators and waveguides in photonic crystals

A photonic crystal cavity-optical fiber tip nanoparticle sensor for biomedical applications

We present a sensor capable of detecting solution-based nanoparticles using an optical fiber tip functionalized with a photonic crystal cavity. When sensor tips are retracted from a nanoparticle solution after being submerged, we find that a combination of convective fluid forces and optically-induced trapping cause an aggregation of nanoparticles to form directly on cavity surfaces. A simple readout of quantum dot photoluminescence coupled to the optical fiber shows that nanoparticle presence and concentration can be detected through modified cavity properties. Our sensor can detect both gold and iron oxide nanoparticles and can be utilized for molecular sensing applications in biomedicine.Comment: 13 pages, 5 figure