In one aspect, a method of detecting a trace gas is disclosed. The method includes containing the trace gas in an optical cavity. The method further includes injecting a first laser light from a first laser into the optical cavity causing the trace gas to transition from an energy state lower that a first excited energy state to the first excited energy state, and injecting a second laser light from a second laser into the optical cavity causing the trace gas to transition from the first excited energy state to a second excited energy state. The method includes measuring, by a detector, a first cavity ringdown intensity as a function of time after turning off the second laser with the first laser on, and a second cavity ringdown intensity as a function of time after turning off the second laser with the first laser off.

An imaging spectropolarimeter for examining targets with polarized light, the spectropolarimeter including a light source adapted to produce polarized light directed at a target. Embodiments also include a three-camera camera system defining a three-camera camera axis with a first camera unit comprising a first analyzer set at 0°, a lens and a first multi-pixel sensor, a second camera unit comprising a second analyzer set at 45°, a lens and a second multi-pixel sensor, and a third camera unit comprising a third analyzer set at 90°, a lens and a third multi-pixel sensor. At least two beam splitters adapted to direct a portion of polarized light reflected from the target to each of the first, second and third camera units. Preferred systems include a processor adapted to produce polarimetric images of the target utilizing intensity information collected by the multi-pixel sensors.

A spectroscopy system is disclosed, and includes a resonant cavity, a first conduit configured to couple at a first end thereof to a gas source, and at a second end thereof to a first end of a sorbent tube containing a sample for analysis, and a second conduit configured to couple at a first end thereof to a second end of the sorbent tube, and at a second end thereof to the resonant cavity.

A spectroscopy system is disclosed, and includes a resonant cavity, a first conduit configured to couple at a first end thereof to a gas source, and at a second end thereof to a first end of a sorbent tube containing a sample for analysis, and a second conduit configured to couple at a first end thereof to a second end of the sorbent tube, and at a second end thereof to the resonant cavity.

An optical system (150) is disclosed and includes an optical sensor (154), a plurality of photosensitive pixels (178) disposed on the optical sensor, a wavelength-selective optical filter (158) in optical communication with the photosensitive pixels, the wavelength-selective optical filter being disposed remotely from the optical sensor, and a plurality of spatially-variant areas (220, 224, 228, 232) disposed in the optical filter, at least one area of the plurality of spatially-variant areas including a downconverter (400, 500).

An optical system (150) is disclosed and includes an optical sensor (154), a plurality of photosensitive pixels (178) disposed on the optical sensor, a wavelength-selective optical filter (158) in optical communication with the photosensitive pixels, the wavelength-selective optical filter being disposed remotely from the optical sensor, and a plurality of spatially-variant areas (220, 224, 228, 232) disposed in the optical filter, at least one area of the plurality of spatially-variant areas including a downconverter (400, 500).

Various embodiments relate to an optical detection element and GOI (Ge-on-insulator) device for ultra-small on-chip optical sensing, and a manufacturing method of the same. According to various embodiments, the optical detection element and the GOI device may be implemented on a GOI structure comprising a germanium (Ge) layer, and the GOI device may be implemented to have an optical detection element. Specifically, the GOI device may include a GOI structure with a waveguide region comprising a germanium layer, a light source element configured to generate light for the waveguide region, and at least one optical detection element configured to detect light coming from the waveguide region. At least one slot configured to collect light from the light source element may be formed in the germanium layer in the waveguide region. The light source element may generate light so as to be coupled to the germanium layer in the waveguide region. The optical detection element may detect heat generated as light is propagated from the germanium layer.

In an illustrative configuration, a method for monitoring air quality is disclosed. The method includes accepting analyte gas into a cell and reflecting light rays into the analyte gas repeatedly across the cell into at least one sensor. The light scattered by particulate matter in the analyte gas and amount of spectra-absorption due to presence of a gaseous chemical is then measured. Based on the determined amount of spectra-absorption and the measured scattered light the gaseous chemical is then measured.

A reflectometry instrument includes a light source for emitting an illumination beam that illuminates the macula. A portion of the illumination beam is reflected from the macula and forms a detection beam. The detection beam is indicative of macular pigment in the macula. The instrument also includes a first mirror for reflecting the illumination beam toward the macula and for reflecting the detection beam from the macula. The instrument is configured so that the illumination beam and the detection beam remain separated between the macula and the first mirror.

A reflectometry instrument includes a light source for emitting an illumination beam that illuminates the macula. A portion of the illumination beam is reflected from the macula and forms a detection beam. The detection beam is indicative of macular pigment in the macula. The instrument also includes a first mirror for reflecting the illumination beam toward the macula and for reflecting the detection beam from the macula. The instrument is configured so that the illumination beam and the detection beam remain separated between the macula and the first mirror.