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Search Results: 1 - 10 of 760 matches for " Christi Madsen "
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Electrical Signal-to-Noise Ratio Enhancement in Detection of Mid-IR Signals by Four-Wave Mixing in As2S3-on-LiNbO3 Waveguides  [PDF]
Qi Chen, Christi Madsen
Optics and Photonics Journal (OPJ) , 2016, DOI: 10.4236/opj.2016.65010
Abstract: Mid-infrared (mid-IR) signals can be converted to near-infrared (near-IR) wavelengths in As2S3-on-LiNbO3 waveguides by high efficiency four-wave mixing. It provided us a solution to detect mid-IR signals indirectly by state-of-the-art near-IR detectors. High efficiency four-wave mixing was demonstrated and electrical signal-to-noise ratio (eSNR) improvement was also investigated. Compared to direct detection by PbSe and HgCdTe (MCT) mid-IR detectors, the calculation indicated that, at room temperature, the indirect detection to mid-IR signals increased the electrical signal-to-noise ratio up to 67 dB.
Demonstration of an As2S3 Grating Coupler on Thin Film LiNbO3  [PDF]
Chen Zhang, Christi K. Madsen
Optics and Photonics Journal (OPJ) , 2018, DOI: 10.4236/opj.2018.84011
Abstract: We present both design and experimental results for an As2S3 grating coupler on a thin film LiNbO3 substrate. A basic grating coupler structure is designed with coupling efficiency of 53% to a single mode fiber. A maximum simulated coupling efficiency of 78.8% is achieved, assuming a polymer bonding process. The basic structure was fabricated, and the coupling efficiency was measured to be at least 23.4% at 1540 nm. Some of the loss may be attributable to non-grating sources, such as waveguide tapers and testing fiber tails. A grating cavity was then measured using the grating couplers. The cavity waveguide propagation loss was 2.0 dB/cm. For a 400 nm thick As2S3 on 500 nm thin film LiNbO3 on insulator, the confinement factor in the LiNbO3 crystal is 82.3% when the As2S3 waveguide width is 400 nm, showing that As2S3-on-thin film LiNbO3 is an excellent candidate for thin film electro-optic applications.
Phase-Matching and Parametric Conversion for the Mid-Infrared in As2S3 Waveguides  [PDF]
Qi Chen, Xin Wang, Christi Madsen
Optics and Photonics Journal (OPJ) , 2012, DOI: 10.4236/opj.2012.24031

We illustrate two As2S3 waveguide designs for four-wave mixing, which can generate 3.03 μm mid-infrared light from a 1.55 μm near-infrared signal source and a 2.05 μm pump source. Through simulations, we verify that four-wave mixing phase-matching efficiencies up to 100% can be achieved using dispersion engineering to maintain the dispersion at 2.05 μm near to zero. The best conversion efficiency is –10 dB. When the waveguide length is 1 cm, the parametric conversion bandwidth is 1525 nm. We also evaluated the shift of 100% phase-matching efficiency wavelengths based upon fabrication tolerances.

Analysis of As2S3-Ti: LiNbO3 Taper Couplers Using Supermode Theory  [PDF]
Xin Xia, Yifeng Zhou, Christi K. Madsen
Optics and Photonics Journal (OPJ) , 2012, DOI: 10.4236/opj.2012.24043

In this work, we develop a simulation method based on supermode theory and transfer matrix formalism, and then apply it to the analysis and design of taper couplers for vertically integrated As2S3 and Ti: LiNbO3 hybrid waveguides. Test structures based on taper couplers are fabricated and characterized. The experimental results confirm the validity of the modeling method, which in turn, is used to analyze the fabricated couplers.

Chalcogenide As2S3 Sidewall Bragg Gratings Integrated on LiNbO3 Substrate  [PDF]
Xin Wang, Aiting Jiang, Christi Madsen
Optics and Photonics Journal (OPJ) , 2013, DOI: 10.4236/opj.2013.31013

This paper introduces the design and applications of integrated As2S3 sidewall Bragg gratings on LiNbO3 substrate. The grating reflectance and bandwidth are analyzed with coupled-mode theory. Coupling coefficients are computed by taking overlap integration. Numerical results for uniform gratings, phase-shifted gratings and grating cavities as well as electro-optic tunable gratings are presented. These integrated As2S3 sidewall gratings on LiNbO3 substrate provide an approach to the design of a wide range of integrated optical devices including switches, laser cavities, modulators, sensors and tunable filters.

Madsen Christi K,Dragoman Daniela,Aza?a José
EURASIP Journal on Advances in Signal Processing , 2005,
Autocodecovergen: Prototype Of Data Driven Unit Test Genration Tool That Guarantees 100% Code Coverage For C#
Arpit Christi
Advanced Computing : an International Journal , 2012,
Abstract: Unit testing has become an integral part of software development process as it ensures all your individualfunctions behave in a way they should behave. Obtaining 100% code coverage out of unit test suit isessential to ensure that all code paths are covered. This paper proposes a tool AutoCodeCoverGen thatguarantees 100% code coverage. It also discusses the core idea behind tool and evolution of the tool.Also, it shows how the tool differs from existing tools and what benefits it reaps for its users.
Arpit Christi
Indian Journal of Computer Science and Engineering , 2012,
Abstract: Concurrent access issue is one of the most frequently encountered issues in performance testing. The issue is a classic case of producer consumer problem where multiple clients try to access same code on the server at the same time, resulting in collision in accessing the code/data. Readily available solutions to producer consumer problem are applied with proper implementation to solve the above mentioned issue. Relative pros and cons of each solution are also discussed.
Evolutionary Determinants of Genetic Variation in Susceptibility to Infectious Diseases in Humans
Christi Baker, Janis Antonovics
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0029089
Abstract: Although genetic variation among humans in their susceptibility to infectious diseases has long been appreciated, little focus has been devoted to identifying patterns in levels of variation in susceptibility to different diseases. Levels of genetic variation in susceptibility associated with 40 human infectious diseases were assessed by a survey of studies on both pedigree-based quantitative variation, as well as studies on different classes of marker alleles. These estimates were correlated with pathogen traits, epidemiological characteristics, and effectiveness of the human immune response. The strongest predictors of levels of genetic variation in susceptibility were disease characteristics negatively associated with immune effectiveness. High levels of genetic variation were associated with diseases with long infectious periods and for which vaccine development attempts have been unsuccessful. These findings are consistent with predictions based on theoretical models incorporating fitness costs associated with the different types of resistance mechanisms. An appreciation of these observed patterns will be a valuable tool in directing future research given that genetic variation in disease susceptibility has large implications for vaccine development and epidemiology.
"Realismo científico" se dice de muchas maneras, al menos de 1111: una elucidación del término "realismo científico"
Carman, Christián Carlos;
Scientiae Studia , 2005, DOI: 10.1590/S1678-31662005000100003
Abstract: i propose to offer an elucidation of the expression "scientific realism". i will proceed in two steps. in the first i will offer an a priori elucidation, in which i will state that there are two basic thesis envolved in the realist approach, but that only one is discussed. in the second step i will propose a definitional scheme that accounts for the great variety of senses of "scientific realism". in a future paper i will try to offer a general account of this great diversity of senses.
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