Abstract: A surface-emitting quantum cascade laser of an embodiment includes a semiconductor stacked body, an upper electrode, and a lower electrode. The semiconductor stacked body includes an active layer that includes a quantum well layer and emits infrared laser light, a first semiconductor layer that includes a photonic crystal layer in which pit parts constitute a rectangular grating, and a second semiconductor layer. The upper electrode is provided on the first semiconductor layer. The lower electrode is provided on a lower surface of a region of the second semiconductor layer overlapping at least the upper electrode. The photonic crystal layer is provided on the upper surface side of the first semiconductor layer. In plan view, the semiconductor stacked body includes a surface-emitting region including the photonic crystal layer and a current injection region. The upper electrode is provided on the current injection region.

Abstract: A surface emitting quantum cascade laser includes an active layer and a first semiconductor layer. The active layer includes a plurality of quantum well layers and is capable of emitting laser light by intersubband transition. The first surface includes an internal region and an outer peripheral region. Grating pitch of the first pits is m times grating pitch of the second pits. The outer peripheral region surrounds the internal region. A first planar shape of an opening end of the first pit is asymmetric with respect to a line passing through barycenter of the first planar shape and is parallel to at least one side of the first two-dimensional grating. A second planar shape of an opening end of the second pit is symmetric with respect to each of lines passing through barycenter of the second planar shape and is parallel to either side of the second two-dimensional grating.

Abstract: A substrate including a photonic crystal has a compound semiconductor, dielectric layers, and a first semiconductor layer. The dielectric layers are provided on a surface of the compound semiconductor substrate and disposed at each grating point of a two-dimensional diffraction grating, each of the dielectric layers having an asymmetric shape in relation to at least one edge of the two-dimensional diffraction grating and having a refractive index lower than a refractive index of the compound semiconductor substrate. The first semiconductor layer includes a flat first face covering the dielectric layers and the surface of the compound semiconductor substrate, a layer constituting the first face containing a material capable of being lattice matched to a material constituting the compound semiconductor substrate.

Abstract: A quantum cascade laser has an active layer, a first and second cladding layer, and an optical guide layer. The active layer has a plurality of injection quantum well regions and a plurality of light-emitting quantum well regions. The each of the injection quantum well regions and the each of the light-emitting quantum well regions are alternatively stacked. The first and second cladding layers are provided to interpose the active layer from both sides, and have a refractive index lower than an effective refractive index of the each of the light-emitting quantum well regions. The optical guide layer is disposed to divide the active layer into two parts. The optical guide layer has a refractive index higher than the effective refractive index of the each of the light-emitting quantum well regions, and has a thickness greater than the thickness of all well layers of quantum well layers.

Abstract: A surface-emitting quantum cascade laser of an embodiment comprises a substrate, an active layer, and a photonic crystal layer. The active layer has optical nonlinearity, and is capable of emitting a first and a second infrared laser light. The photonic crystal layer includes a first and a second region. The rectangular grating of the first region is orthogonal to the rectangular grating of the second region. The first infrared laser light has a wavelength corresponding to a maximum gain outside a first photonic bandgap in a direction parallel to a first side of two sides constituting the rectangular grating. The second infrared laser light has a wavelength corresponding to a maximum gain outside a second photonic bandgap in a direction parallel to a second side of the two sides of the rectangular grating.

Abstract: A surface-emitting quantum cascade laser of an embodiment includes a semiconductor stacked body, an upper electrode, and a lower electrode. The semiconductor stacked body includes an active layer that includes a quantum well layer and emits infrared laser light, a first semiconductor layer that includes a photonic crystal layer in which pit parts constitute a rectangular grating, and a second semiconductor layer. The upper electrode is provided on the first semiconductor layer. The lower electrode is provided on a lower surface of a region of the second semiconductor layer overlapping at least the upper electrode. The photonic crystal layer is provided on the upper surface side of the first semiconductor layer. In plan view, the semiconductor stacked body includes a surface-emitting region including the photonic crystal layer and a current injection region. The upper electrode is provided on the current injection region.

Abstract: A terahertz quantum cascade laser device includes a substrate, q semiconductor stacked body and a first electrode. The semiconductor stacked body includes an active layer and a first clad layer. The active layer is provided on the substrate and is configured to emit infrared laser light by an intersubband optical transition. The first clad layer is provided on the active layer. A ridge waveguide is provided in the semiconductor stacked body. A first distributed feedback region and a second distributed feedback region are provided at an upper surface of the first clad layer to be separated from each other along an extension direction of the ridge waveguide. The first electrode is provided at the upper surface of the first clad layer. A planar size of the first distributed feedback region is smaller than a planar size of the second distributed feedback region.

Abstract: A distributed feedback semiconductor laser of includes a semiconductor stacked body and a first electrode. The semiconductor stacked body includes a first layer, an active layer that is provided on the first layer and is configured to emit laser light by an intersubband optical transition, and a second layer that is provided on the active layer. The semiconductor stacked body has a first surface including a flat portion and a trench portion; the flat portion includes a front surface of the second layer; the trench portion reaches the first layer from the front surface; the flat portion includes a first region and a second region; the first region extends along a first straight line; the second region extends to be orthogonal to the first straight line; and the trench portion and the second region outside the first region form a diffraction grating having a prescribed pitch along the first straight line. The first electrode is provided in the first region.

Abstract: A semiconductor laser device includes an active layer, a first layer, and a surface metal film. Multiple quantum well layers are stacked in the active layer; and the active layer is configured to emit laser light of a terahertz wave by an intersubband transition. The first layer is provided on the active layer and includes a first surface in which multiple pits are provided to form a two-dimensional lattice. The surface metal film is provided on the first layer and includes multiple openings. Each of the pits is asymmetric with respect to a line parallel to a side of the lattice. The laser light passes through the multiple openings and is emitted in a direction substantially perpendicular to the active layer.

Abstract: A surface emitting quantum cascade laser includes an active layer and a first semiconductor layer. The active layer includes a plurality of quantum well layers and is capable of emitting laser light by intersubband transition. The first surface includes an internal region and an outer peripheral region. Grating pitch of the first pits is m times grating pitch of the second pits. The outer peripheral region surrounds the internal region. A first planar shape of an opening end of the first pit is asymmetric with respect to a line passing through barycenter of the first planar shape and is parallel to at least one side of the first two-dimensional grating. A second planar shape of an opening end of the second pit is symmetric with respect to each of lines passing through barycenter of the second planar shape and is parallel to either side of the second two-dimensional grating.

Abstract: A quantum cascade laser device includes a substrate, a semiconductor stacked body and a first electrode. The semiconductor stacked body includes an active layer and a first clad layer. The active layer is configured to emit infrared laser light by an intersubband optical transition. A ridge waveguide is provided in the semiconductor stacked body. A distributed feedback region is provided along a first straight line. The ridge waveguide extends along the first straight line. The first electrode is provided at an upper surface of the distributed feedback region. A diffraction grating is arranged along the first straight line. The distributed feedback region includes a an increasing region where a length of the diffraction grating along a direction orthogonal to the first straight line increases from one end portion of the distributed feedback region toward another end portion of the distributed feedback region.

Abstract: A terahertz quantum cascade laser device includes a substrate, q semiconductor stacked body and a first electrode. The semiconductor stacked body includes an active layer and a first clad layer. The active layer is provided on the substrate and is configured to emit infrared laser light by an intersubband optical transition. The first clad layer is provided on the active layer. A ridge waveguide is provided in the semiconductor stacked body. A first distributed feedback region and a second distributed feedback region are provided at an upper surface of the first clad layer to be separated from each other along an extension direction of the ridge waveguide. The first electrode is provided at the upper surface of the first clad layer. A planar size of the first distributed feedback region is smaller than a planar size of the second distributed feedback region.

Abstract: A gas measuring apparatus includes a cell portion, a light source portion, a detection portion, and a control portion. The cell portion includes a space into which a sample gas containing breath containing a first isotope of carbon dioxide and a second isotope of carbon dioxide is introduced. The light source portion changes a wavelength of the light in a band of 4.345 ?m or more and 4.384 ?m or less. The detection portion performs an operation including first detection of an intensity of the light passing through the space and second detection of an intensity of the light passing through the space into which the sample gas is not introduced. The control portion calculates a ratio of an amount of the second isotope to an amount of the first isotope based on a result of the first detection and a result of the second detection.

Abstract: A surface emitting quantum cascade laser includes an active layer, a first semiconductor layer, and first electrode. The active layer has a plurality of quantum well layers stacked therein. The active layer is capable of emitting laser light by inter-subband transition. The first semiconductor layer is provided on the active layer and having a first surface provided with a plurality of pits so as to constitute a two-dimensional lattice. The first electrode is provided on the first semiconductor layer and having a periodic opening. Each pit is asymmetric with respect to a line parallel to a side of the lattice. The laser light is emitted in a direction generally perpendicular to the active layer from a pit exposed to the opening.

Abstract: A breath analyzer includes a light source, a gas cell, a detection unit and a data processing unit. The light source emits infrared light of a wavelength band including an absorption line for acetone. A breath containing sample gas is introduced to the gas cell. The infrared light is incident on the gas cell. The detection unit receives transmitted light emerging from the gas cell, and outputs a sample signal value corresponding to an acetone discharge amount. The data processing unit determines an approximation formula of dependence of fat oxidation rate on acetone discharge amount in advance, and calculates a fat oxidation rate for individual sample signal values using the approximation formula. When the acetone discharge amount (microliter/min) is x, the fat oxidation rate (milligram/min) y is approximated by a following formula: y=Ax+B (where A and B are constants).

Abstract: A gas measuring apparatus includes a cell portion, a light source portion, a detection portion, and a control portion. The cell portion includes a space into which a sample gas containing breath containing a first isotope of carbon dioxide and a second isotope of carbon dioxide is introduced. The light source portion changes a wavelength of the light in a band of 4.345 ?m or more and 4.384 ?m or less. The detection portion performs an operation including first detection of an intensity of the light passing through the space and second detection of an intensity of the light passing through the space into which the sample gas is not introduced. The control portion calculates a ratio of an amount of the second isotope to an amount of the first isotope based on a result of the first detection and a result of the second detection.

Abstract: A surface emitting quantum cascade laser includes an active layer, a first semiconductor layer, and first electrode. The active layer has a plurality of quantum well layers stacked therein. The active layer is capable of emitting laser light by inter-subband transition. The first semiconductor layer is provided on the active layer and having a first surface provided with a plurality of pits so as to constitute a two-dimensional lattice. The first electrode is provided on the first semiconductor layer and having a periodic opening. Each pit is asymmetric with respect to a line parallel to a side of the lattice. The laser light is emitted in a direction generally perpendicular to the active layer from a pit exposed to the opening.

Abstract: A breath analyzer includes a light source, a gas cell, a detection unit and a data processing unit. The light source emits infrared light of a wavelength band including an absorption line for acetone. A breath containing sample gas is introduced to the gas cell. The infrared light is incident on the gas cell. The detection unit receives transmitted light emerging from the gas cell, and outputs a sample signal value corresponding to an acetone discharge amount. The data processing unit determines an approximation formula of dependence of fat oxidation rate on acetone discharge amount in advance, and calculates a fat oxidation rate for individual sample signal values using the approximation formula. When the acetone discharge amount (microliter/min) is x, the fat oxidation rate (milligram/min) y is approximated by a following formula: y=Ax+B (where A and B are constants).

Abstract: A gas analysis method includes irradiating a sample gas introduced into a gas cell with infrared light tuned to a wavelength corresponding to one absorption line of a target gas contained in the sample gas, measuring a sample signal value corresponding to intensity of transmitted light of the infrared light transmitted through the gas cell, evacuating the sample gas in the gas cell and then replacing by a reference gas, measuring a reference signal value corresponding to intensity of transmitted light of the infrared light transmitted through the reference gas, and calculating gas concentration at the one absorption line from ratio of the sample signal value to the reference signal value.

Abstract: An exhalation diagnostic devise includes a cell portion, a light source, a detector and a controller. The cell portion includes space into which a sample gas containing first and second substances is introduced. The detector detects an intensity of the light transmitted through the space. The controller, at a time of a first operation, causes the light source to change a wavelength, and calculates a ratio of an amount of the second substance to an amount of the first substance. And the controller, at a time of a second operation performed in one respiration, causes the light source to set the wavelength of the light to a third wavelength, determines whether concentration of at least one of the first substance and the second substance exceeds a set value or not, and starts the first operation when the concentration exceeds the set value.