Biomedical subjects

Daniel Erni

Publications and source records attributed to Daniel Erni.

8 recordsLinked to original sources

PubMed2005

Energy-time entanglement preservation in plasmon-assisted light transmission.

We report on experimental evidence of the preservation of the energy-time entanglement of a pair of photons after a photon-plasmon-photon conversion. This preservation is observed in two different plasmon conversion experiments, namely, extraordinary optical transmission through subwavelength metallic hole arrays and long range surface plasmon propagation in metallic waveguides. Plasmons are shown to coherently exist at two different times separated by much more than their lifetimes. This kind of entanglement involving light and matter is expected to be useful for future processing and storing of quantum information.

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PubMed2005

Quasi-analytic formalism for mode characteristics in highly overmoded rectangular dielectric waveguide bends.

A fast and simple quasi-analytic method to simulate mode characteristics in highly overmoded rectangular dielectric waveguide bends is presented. Fast mode-based bend models are necessary, since overmoded rectangular waveguides have become very popular in optical interconnects on printed circuit boards. The proposed method combines a simple mode solver with the formalism that was proposed by Melloni et al. [J. Lightwave Technol. 16, 571 (2001)], yielding to a very convenient and accurate quasi-analytic formalism for the bend transfer function based on matrix notation. For that purpose, a simple method to approximate leaky modes is introduced. The model offers the ability to predict individual modal phases and amplitudes within a given bend as well as the calculation of coupling losses and was validated using three-dimensional beam-propagation-method simulation software.

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PubMed2004

Theory of plasmon-assisted transmission of entangled photons.

The recent surface plasmon entanglement experiment [Nature (London) 418, 304 (2002)]] is theoretically analyzed. The entanglement preservation upon transmission in the nonfocused case is found to provide information about the interaction of the biphoton and the metallic film. The entanglement degradation in the focused case is explained in the framework of a fully multimode model. This phenomenon is a consequence of the polarization-selective filtering behavior of the metallic nanostructured film. It is shown that the "which-way" labels that degrade entanglement are not located in the degrees of freedom of the metallic film but rather in the spatial degrees of freedom of the photon field.

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PubMed2004

Efficient coupling into and out of high-Q resonators.

The temporal-coupled-mode theory is directly applied to the design of devices that feature a resonator with a high quality factor. For the temporal-coupled-mode theory we calculate the decay rate of the resonator to determine the transmission properties of the device. The analysis using the decay rates requires little computational effort, and therefore the optimum device properties can be determined quickly. Two examples, a wavelength filter and a resonator crossing, are presented to illustrate the use of the analysis.

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PubMed2004

Optimization of photonic crystal structures.

We report on the numerical structural optimization of two-dimensional photonic crystal (PhC) power dividers by using two different classes of optimization algorithms, namely, a modified truncated Newton (TN) gradient search as deterministic local optimization scheme and an evolutionary optimization representing the probabilistic global search strategies. Because of the severe accuracy requirements during optimization, the proper PhC device has been simulated by using the multiple-multipole program that is contained in the MaX-1 software package. With both optimizer classes, we found reliable and promising solutions that provide vanishing power reflection and perfect power balance at any specified frequency within the photonic bandgap. This outcome is astonishing in light of the discrete nature inherent in the underlying PhC structure, especially when the optimizer is allowed to intervene only within a very small volume of the device. Even under such limiting constraints structural optimization is not only feasible but has proven to be highly successful.

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PubMed2002

Modeling of discontinuities in photonic crystal waveguides with the multiple multipole method.

A method for the simulation of discontinuities in photonic crystal defect waveguides is presented. This frequency domain technique is based on the multiple multipole method. In contrast with other known techniques, spurious reflections (due to the impedance mismatch at the waveguide terminations) are avoided. The absence of spurious reflections allows one to characterize precisely the intrinsic behavior of the sole discontinuity, reducing at the same time the size of the simulation domain. To achieve a perfect impedance matching, the guided modes of infinitely long waveguides corresponding to the input and output channels of the discontinuity are first computed using a supercell approach. Then, the discontinuity is fed with one of the previously computed modes, and the fields transmitted or reflected towards the discontinuity arms are matched to the modal fields corresponding to each output waveguide. This method allows one to compute the intrinsic transmission and reflection coefficients of the discontinuity (i.e., coefficients not altered by additional effects such as finite crystal size, etc.). The procedure is presented in detail using some simple discontinuities as test cases. Then, it is applied to the computation of the coupling from a waveguide to free space and for the analysis of a filtering T junction.

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PubMed2002

Prevention of deep-vein thrombosis in ambulatory arthroscopic knee surgery: A randomized trial of prophylaxis with low--molecular weight heparin.

PURPOSE: The risk of deep vein thrombosis (DVT) in patients undergoing arthroscopic knee surgery is not well known. The purpose of this study was to determine the incidence of DVT, to demonstrate the efficacy of a perioperative and postoperative prophylaxis against thromboembolism with use of low--molecular weight heparin (LMWH), and to show the safety and feasibility of LMWH administration. TYPE OF STUDY: Prospective, single-blind, randomized clinical trial. METHODS: There were 218 consecutive outpatients scheduled for ambulatory arthroscopic knee surgery eligible. Of these, 130 patients were randomized to a treatment group with LMWH (dalteparin: 2,500 IU less-than-or-equal70 kg and 5,000 IU >70 kg, started perioperatively and given once daily for 4 weeks; n = 66) and a control group (n = 64) with no prophylaxis. To detect DVT, all patients underwent bilateral compression ultrasonography before and 12 and 31 days after surgery. RESULTS: Among the 130 patients studied, thromboembolism was significantly lower in the treatment than in the control group: 1 of 66 (1.5%) versus 10 of 64 (15.6%); 95% confidence interval, 7.8% to 26.8%; P =.004. Eighty percent of DVT occurred within the first 14 postoperative days. No severe side effects of LMWH were observed. Only 5% of patients refused continued subcutaneous LMWH injections. CONCLUSIONS: In patients undergoing ambulatory arthroscopic knee surgery without antithrombotic prophylaxis, the risk of DVT is high. Perioperative and postoperative prophylaxis with dalteparin is an effective and safe means of reducing this risk.

Adult↗

PubMed2002

Multiple multipole method with automatic multipole setting applied to the simulation of surface plasmons in metallic nanostructures.

Highly accurate computations of surface plasmons in metallic nanostructures with various geometries are presented. Calculations for cylinders with irregular cross section, coupled structures, and periodic gratings are shown. These systems exhibit a resonant behavior with complex field distribution and strong field enhancement, and therefore their computation requires a very accurate numerical method. It is shown that the multiple multipole (MMP) method, together with an automatic multipole setting (AMS) procedure, is well suited for these computations. An AMS technique for the two-dimensional MMP method is presented. It relies on the global topology of each domain boundary to generate a distribution of numerically independent multipole expansions. This technique greatly facilitates the MMP modeling.

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