Abstract: Inventive systems and methods for the generation of energy using thermophotovoltaic cells are described. Also described are systems and methods for selectively emitting electromagnetic radiation from an emitter for use in thermophotovoltaic energy generation systems. In at least some of the inventive energy generation systems and methods, a voltage applied to the thermophotovoltaic cell (e.g., to enhance the power produced by the cell) can be adjusted to enhance system performance. Certain embodiments of the systems and methods described herein can be used to generate energy relatively efficiently.

Abstract: A nonlinear harmonic generation system is provided. The nonlinear harmonic generation system includes a waveguide channel receives and propagates electromagnetic signals. A resonant cavity is coupled to the waveguide channel. The resonant cavity structure includes a plurality of resonant modes into which electromagnetic energy is coupled during the operation of the system. One of the resonant modes includes a resonant frequency that changes during operation of the system to reach either an input-signal frequency or a harmonic frequency for a majority of the time in which harmonic generation is occurring. Both reflected and harmonic fields are emitted back into the waveguide channel so as to allow efficient harmonic generation at a specified critical input power.

Abstract: A nonlinear harmonic generation system is provided. The nonlinear harmonic generation system includes a waveguide channel receives and propagates electromagnetic signals. A resonant cavity is coupled to the waveguide channel. The resonant cavity structure includes a plurality of resonant modes into which electromagnetic energy is coupled during the operation of the system. One of the resonant modes includes a resonant frequency that changes during operation of the system to reach either an input-signal frequency or a harmonic frequency for a majority of the time in which harmonic generation is occurring. Both reflected and harmonic fields are emitted back into the waveguide channel so as to allow efficient harmonic generation at a specified critical input power.

Abstract: According to one example embodiment, there is provided a method and an apparatus to evaluate the credit of a healthcare patient. The example embodiment provides methods and computer systems programmed to use multiple variables that are known about a patient prior to a service being rendered to segment the patient population into finer grained groupings. These finer grained groupings allow financial factors, such as a credit score, to be a more accurate predictor. Also, according to another example embodiment, the model is not a generic model for all patients, but the variables and their parameters are specific to a particular healthcare organization's or facility's patient population. This creates a custom model that further enhances its predictiveness.

Abstract: A solar cell includes a thin film photovoltaic material structure used in absorbing light of a selective bandwidth. A multitude of dielectric front coatings are positioned on the thin film photovoltaic material structure so as to maximize admittance over the selected bandwidth. The thicknesses and indices of each of the front coatings are chosen by a global-optimization procedure to maximize the short-circuit current of the solar cell.

Abstract: A fiber structure for propagating one or more zero group-velocity modes is provided. The fiber structure includes a cladding arrangement comprising a photonic crystal having a complete bandgap at a specified index. A core is formed in a selective region of the cladding arrangement. The core allows the propagation of the one or more group-velocity modes.

Abstract: A doubly-resonant cavity structure includes at least one cavity structures so as to allow total frequency conversion for second or third-harmonic generation using ?(2) and ?(3) nonlinearities between the at least one cavity structures. The total frequency conversion is efficiently optimized by determining a critical power allowing for such total frequency conversion to occur depending on the cavity parameters of the at least one cavity structures.

Abstract: A doubly-resonant cavity structure includes at least one cavity structures so as to allow total frequency conversion for second or third-harmonic generation using ?(2) and ?(3) nonlinearities between the at least one cavity structures. The total frequency conversion is efficiently optimized by determining a critical power allowing for such total frequency conversion to occur depending on the cavity parameters of the at least one cavity structures.

Abstract: A system and a method for generating terahertz (THz) radiation are provided. The system includes a photonic crystal structure comprising at least one nonlinear material that enables optical rectification. The photonic crystal structure is configured to have the suitable transverse dispersion relations and enhanced density photonic states so as to allow THz radiation to be emitted efficiently when an optical or near infrared pulse travels through the nonlinear part of the photonic crystal.

Abstract: A periodic electromagnetic medium is disclosed that includes a surface that provides an interface with an ambient medium and a periodic structure that provides negative refraction within the medium of an incident electromagnetic field incident on the surface. In various embodiments the incident electromagnetic field is within a range of frequencies, the medium may include dielectric or metallic material, and has either a positive or negative effective index.

Abstract: A nano-electromechanical optical switch includes an input optical waveguide that is provided with an optical signal. At least two output optical waveguides are coupled to the input optical waveguide. The deflection of the input optical waveguide aligns with one of either of the two output optical waveguides so as to allow transmission of the optical signal to one of either of the two output optical waveguides.

Abstract: In general, in one aspect, the invention features an apparatus that includes a photonic crystal fiber configured to guide a mode of electromagnetic radiation at a wavelength, ?, along a waveguide axis. The fiber includes a core extending along the waveguide axis, and a confinement region extending along the waveguide axis and surrounding the core. The confinement region includes alternating layers of a first and a second dielectric material having thicknesses d1 and d2 and different refractive indices n1 and n2, respectively. The thickness of at least one of the alternating layers of the first material differs from thickness d1QW or at least one of the alternating layers of the second material differs from thickness d2QW, where d1QW and d2QW correspond to a quarter-wave condition for the two dielectric materials given by d1QW=?/(4?{square root over (n12?1)}) and d2QW=?/(4?{square root over (n22?1)}), respectively.

Abstract: The present invention provides a micro-resonator including a plurality of waveguides forming optic junctions therebetween, with adjacent waveguides having different core permittivities and different cladding permittivities. Adjacent waveguides are mode-matched through adjustments of the core permittivities and the cladding permittivities of the waveguides to reduce or eliminate junction radiation, thereby providing high performance.

Abstract: A periodic structure is disclosed that includes an array of point defects within the periodic structure. The array includes point defects in a least two dimensions of the periodic structure. Each point defect permits electromagnetic fields of a first wavelength that is otherwise within a band gap range of the periodic structure to exist in each of the point defects.

Abstract: An on-chip silicon-based optical coupler used to guide light from an optical fiber to a waveguide. The incoming wave is confined vertically by stacks of graded index materials. In the lateral direction, a linear taper formed by etched holes or trenches confines the wave.

Abstract: A photonic bandgap microcavity is provided. The microcavity includes a membrane structure that can experience strain. A photonic bandgap waveguide element is formed on the membrane structure having a defect so that when the membrane structure is strained, the photonic bandgap waveguide element is tuned to a selective amount.

Abstract: A device for converting frequency of electromagnetic radiation includes a nonlinear medium that forms a moving grating in the nonlinear medium by introducing at opposite ends of the nonlinear medium a first set of electromagnetic radiation having varying frequencies. Electromagnetic radiation is inputted into the nonlinear medium at a first frequency and extracted at a second frequency from the nonlinear medium. The moving grating in the nonlinear medium allows for electromagnetic radiation to be converted into the second frequency.

Abstract: A coupling element includes a first stage having a dielectric waveguide that is transitioned to a waveguide having a sequence of resonators with a fixed period. A second stage transitions the waveguide to a photonic crystal waveguide by gradually bringing closer at an angle the cladding bulk of the photonic crystal to the waveguide.

Abstract: An optical waveguide including: a dielectric core region extending along a waveguide axis; and a dielectric confinement region surrounding the core about the waveguide axis, the confinement region comprising a photonic crystal structure having a photonic band gap, wherein during operation the confinement region guides EM radiation in at least a first range of frequencies to propagate along the waveguide axis, wherein the core has an average refractive index smaller than about 1.3 for a frequency in the first range of frequencies, and wherein the core a diameter in a range between about 4? and 80?, wherein ? is a wavelength corresponding to a central frequency in the first frequency range.

Abstract: A photonic crystal includes a plurality of photonic crystal slabs that is suited for confining TE polarizations and TM polarizations. The photonic crystal slabs include alternating slabs of dielectric rods and air holes. The alternating slabs create a lateral symmetry plane. The alternating slabs of dielectric rods and air holes further include planar line defects resulting in the formation of defect bands inside the bandgap of the photonic crystal.