Abstract: An absorption spectroscopy apparatus including an elliptical mirror centered on the midpoint between a source/detector and a mirror. The cavity between the elliptical mirror and the source/bolometer and mirror defines an interior volume of a sample cell. Electromagnetic radiation from the source/detector travels along a multi-segment path starting from the source/bolometer toward the elliptical mirror, reflecting off of the elliptical mirror and traveling toward the mirror, reflecting off of the mirror and traveling back toward the elliptical mirror and finally reflecting off the elliptical mirror for a second time and returning toward the source/bolometer. The multiple reflections combined with the focusing effects of the elliptical mirrored surface result in an efficient sampling device. Among other aspects and advantages, the apparatus of the present disclosure is able to use incoherent, non-collimated light sources while maintaining high optical throughput efficiencies.

Abstract: Methods and apparatus for providing a tunable absorption band in a wavelength selective surface are disclosed. A device for selectively absorbing incident electromagnetic radiation includes an electrically conductive surface layer including an arrangement of multiple surface elements. The surface layer is disposed at a nonzero height above a continuous electrically conductive layer. An electrically isolating intermediate layer defines a first surface that is in communication with the electrically conductive surface layer. The continuous electrically conductive backing layer is provided in communication with a second surface of the electrically isolating intermediate layer. The arrangement of surface elements couples at least a portion of the incident electromagnetic radiation between itself and the continuous electrically conductive backing layer, such that the resonant device selectively absorbs incident radiation, and reflects a portion of the incident radiation that is not absorbed.

Abstract: Methods and apparatus for providing a tunable absorption-emission band in a wavelength selective device are disclosed. A device for selectively absorbing incident electromagnetic radiation includes an electrically conductive surface layer including an arrangement of multiple surface elements. The surface layer is disposed at a nonzero height above a continuous electrically conductive layer. An electrically isolating intermediate layer defines a first surface that is in communication with the electrically conductive surface layer. The continuous electrically conductive backing layer is provided in communication with a second surface of the electrically isolating intermediate layer. When combined with an infrared source, the wavelength selective device emits infrared radiation in at least one narrow band determined by a resonance of the device. In some embodiments, the device includes a control feature that allows the resonance to be selectively modified.

Abstract: An absorption spectroscopy apparatus including a sample cell having a central axis, and a side wall coaxially positioned about the axis. The side wall defines a generally circular cross-section of the cell as taken along a plane extending perpendicular to the axis, wherein the generally circular cross-section of the sample cell has an average radius. The side wall includes a plurality of light reflective segments arrayed about the axis, wherein each reflective segment has a cross-section taken along a plane extending perpendicular to the axis of the cell that is concave with respect to the axis. The concave cross-section of each segment has an average radius that is unequal to the average radius of the generally circular cross-section of the sample cell. Among other aspects and advantages, the apparatus of the present disclosure is able to use incoherent, non-collimated light sources while maintaining high optical throughput efficiencies.

Abstract: An infrared emitter, which utilizes a photonic bandgap (PBG) structure to produce electromagnetic emissions with a narrow band of wavelengths, includes a semiconductor material layer, a dielectric material layer overlaying the semiconductor material layer, and a metallic material layer having an inner side overlaying the dielectric material layer. The semiconductor material layer is capable of being coupled to an energy source for introducing energy to the semiconductor material layer. An array of holes are defined in the device in a periodic manner, wherein each hole extends at least partially through the metallic material layer. The three material layers are adapted to transfer energy from the semiconductor material layer to the outer side of the metallic material layer and emit electromagnetic energy in a narrow band of wavelengths from the outer side of the metallic material layer.

Abstract: An infrared emitter, which utilizes a photonic crystal (PC) structure to produce electromagnetic emissions with a narrow band of wavelengths, includes a semiconductor material layer, a dielectric material layer overlaying the semiconductor material layer, and a metallic material layer having an inner side overlaying the dielectric material layer. The semiconductor material layer is capable of being coupled to an energy source for introducing energy to the semiconductor material layer. An array of surface features are defined in the device in a periodic manner or quasi-periodic. The emitter device is adapted to emit electromagnetic energy having spectral characteristics determined by parameters of the periodically distributed surface features, the parameters including shape, size, depth, distribution geometry, periodicity, material properties and defects.

Abstract: An absorption spectroscopy apparatus including a sample cell having a central axis, and a side wall coaxially positioned about the axis. The side wall defines a generally circular cross-section of the cell as taken along a plane extending perpendicular to the axis, wherein the generally circular cross-section of the sample cell has an average radius. The side wall includes a plurality of light reflective segments arrayed about the axis, wherein each reflective segment has a cross-section taken along a plane extending perpendicular to the axis of the cell that is concave with respect to the axis. The concave cross-section of each segment has an average radius that is unequal to the average radius of the generally circular cross-section of the sample cell. Among other aspects and advantages, the apparatus of the present disclosure is able to use incoherent, non-collimated light sources while maintaining high optical throughput efficiencies.