Abstract: An optical device comprises an optical filter having a substrate and a multilayer film having layers with different refractive indexes formed on at least one side of the substrate; and an infrared light emitting and receiving device having a first conductive-type semiconductor layer, an active layer, and a second conductive-type semiconductor layer. The multilayer film has alternatively stacked first second layers each having refractive indexes of 1.2 or more and 2.5 or less, and 3.2 or more and 4.2 or less, respectively, in a wavelength range of 2400 nm to 6000 nm. The optical filter includes a wavelength range having an average transmittance of 70% or more with a width of 50 nm or more in a wavelength range of 2400 nm to 6000 nm, and has a maximum transmittance of 5% or more in a wavelength range of 6000 nm to 8000 nm.

Abstract: An optical filter for an optical device comprises a substrate and a multilayer film having a plurality of layers with different refractive indexes formed on at least one side of the substrate. The multilayer film has a structure in which a first layer and a second layer are alternately stacked. The first layer has a refractive index of 1.2 or more and 2.5 or less, and the second layer has a refractive index of 3.2 or more and 4.3 or less in a wavelength range of 6 ?m to 10 ?m. The optical filter includes a wavelength range having an average transmittance of 70% or more with a width of 50 nm or more in a wavelength range of 6 ?m to 10 ?m, and has a maximum transmittance of 10% or more in a wavelength range of 12.5 ?m to 20 ?m.

Abstract: Provided is a risk information provision device including: an information acquisition unit configured to acquire risk information related to a risk depending on a status of leakage of a refrigerant in a determination target and risk handling information for handling the risk, wherein the status is determined on a basis of a concentration of the refrigerant in the determination target; a provision unit configured to provide at least one of the risk information or the risk handling information; and a date information acquisition unit configured to acquire date information of a date on which at least one of the risk information or the risk handling information is acquired. The risk handling information includes recipient information related to one or more recipients that receive the risk information. The provision unit is configured to provide at least one of the risk information or the date information to the one or more recipients.

Abstract: An optical device comprises an optical filter having a substrate and a multilayer film, and an infrared light emitting and receiving device having a first conductive-type semiconductor layer, an active layer, and a second conductive-type semiconductor layer. The multilayer film has layers with different refractive indexes formed on at least one side of the substrate, in which first and second layers having refractive indexes of 1.2 or more and 2.5 or less, and 3.2 or more and 4.3 or less, respectively, in a wavelength range of 6 ?m to 10 ?m are alternately stacked. The optical filter includes a wavelength range having an average transmittance of 70% or more with a width of 50 nm or more in a wavelength range of 6 ?m to 10 ?m, and has a maximum transmittance of 10% or more in a wavelength range of 12.5 ?m to 20 ?m.

Abstract: An optical device comprises an optical filter having a substrate and a multilayer film having layers with different refractive indexes formed on at least one side of the substrate; and an infrared light emitting and receiving device having a first conductive-type semiconductor layer, an active layer, and a second conductive-type semiconductor layer. The multilayer film has alternatively stacked first second layers each having refractive indexes of 1.2 or more and 2.5 or less, and 3.2 or more and 4.2 or less, respectively, in a wavelength range of 2400 nm to 6000 nm. The optical filter includes a wavelength range having an average transmittance of 70% or more with a width of 50 nm or more in a wavelength range of 2400 nm to 6000 nm, and has a maximum transmittance of 5% or more in a wavelength range of 6000 nm to 8000 nm.

Abstract: An optical device comprises an optical filter having a substrate and a multilayer film, and an infrared light emitting and receiving device having a first conductive-type semiconductor layer, an active layer, and a second conductive-type semiconductor layer. The multilayer film has layers with different refractive indexes formed on at least one side of the substrate, in which first and second layers having refractive indexes of 1.2 or more and 2.5 or less, and 3.2 or more and 4.3 or less, respectively, in a wavelength range of 6 ?m to 10 ?m are alternately stacked. The optical filter includes a wavelength range having an average transmittance of 70% or more with a width of 50 nm or more in a wavelength range of 6 ?m to 10 ?m, and has a maximum transmittance of 10% or more in a wavelength range of 12.5 ?m to 20 ?m.

Abstract: This disclosure provides a highly accurate NDIR gas sensor and a highly accurate optical device even using a simplified optical filter. The NDIR gas sensor and the optical device include: an optical filter having a substrate and a multilayer film on the substrate; and an infrared light emitting and receiving device; where the multilayer film has a structure in which a first layer and a second layer are alternately stacked; the active layer contains AlxIn1-xSb or InAsySb1-y; and the optical filter includes a wavelength range having an average transmittance of 70% or more with a width of 50 nm or more in 2400-6000 nm, and has a maximum transmittance of 5% or more in 6000-8000 nm and an average transmittance of 2% or more and 60% or less in 6000-8000 nm.

Abstract: This disclosure provides a NDIR gas sensor comprising: an optical filter having a substrate and a multilayer film; and an infrared light emitting and receiving device having a semiconductor layer of a first conductive type, an active layer, and a semiconductor layer of a second conductive type; where the multilayer film has a structure in which a first layer and a second layer are alternately stacked; the active layer contains InAsySb1-y (0.1?y?0.2); and the optical filter includes a wavelength range having an average transmittance of 70% or more with a width of 50 nm or more in a wavelength range of 6 ?m to 10 ?m, and has a maximum transmittance of 10% or more in a wavelength range of 12.5 ?m to 20 ?m and an average transmittance of 5% or more and 60% or less in a wavelength range of 12.5 ?m to 20 ?m.

Abstract: Provided are a semiconductor wafer, a semiconductor device, and a gas concentration measuring device having a size reduced by reducing warpage to be even smaller than the sizes that can be achieved by conventional techniques. The semiconductor wafer includes: a wafer substrate, a semiconductor stacked portion formed on a first surface of the wafer substrate, the semiconductor stacked portion being capable of emitting or receiving infrared light of 2 ?m to 10 ?m; and an optical filter formed on a second surface of the wafer substrate that is opposite to the first surface of the wafer substrate. The thickness Twaf [?m] of the wafer substrate and the thickness Topt [?m] of the optical filter satisfy the relations of Topt?4 and Topt?0.000053× Twaf2.0488.

Abstract: This disclosure provides a NDIR gas sensor comprising: an optical filter having a substrate and a multilayer film; and an infrared light emitting and receiving device having a semiconductor layer of a first conductive type, an active layer, and a semiconductor layer of a second conductive type; where the multilayer film has a structure in which a first layer and a second layer are alternately stacked; the active layer contains InAsySb1-y (0.1?y?0.2); and the optical filter includes a wavelength range having an average transmittance of 70% or more with a width of 50 nm or more in a wavelength range of 6 ?m to 10 ?m, and has a maximum transmittance of 10% or more in a wavelength range of 12.5 ?m to 20 ?m and an average transmittance of 5% or more and 60% or less in a wavelength range of 12.5 ?m to 20 ?m.

Abstract: This disclosure provides a highly accurate NDIR gas sensor and a highly accurate optical device even using a simplified optical filter. The NDIR gas sensor and the optical device include: an optical filter having a substrate and a multilayer film on the substrate; and an infrared light emitting and receiving device; where the multilayer film has a structure in which a first layer and a second layer are alternately stacked; the active layer contains AlxIn1-xSb or InAsySb1-y; and the optical filter includes a wavelength range having an average transmittance of 70% or more with a width of 50 nm or more in 2400-6000 nm, and has a maximum transmittance of 5% or more in 6000-8000 nm and an average transmittance of 2% or more and 60% or less in 6000-8000 nm.