A wavelength conversion element according to an embodiment of the present disclosure includes: a phosphor layer; a refrigerant; a refrigerant transport member; and a housing. The phosphor layer includes a plurality of phosphor particles. The phosphor layer has a gap therein. The refrigerant cools the phosphor layer. The refrigerant transport member is provided in contact with the phosphor layer. The refrigerant transport member circulates the refrigerant. The phosphor layer, the refrigerant, and the refrigerant transport member are encapsulated in the housing.

A light source device, including: a reflective member including a plurality of reflective surfaces including a first reflective surface and a second reflective surface, and one or more transmissive surfaces including a first transmissive surface that connects between the first reflective surface and the second reflective surface; a plurality of light-emitting elements including a first light-emitting element emitting first light that travels in a direction in which the reflective member is arranged to be incident on the first reflective surface, and a second light-emitting element emitting second light that travels in a direction in which the reflective member is arranged to be incident on the second reflective surface; and a first photodetector having a first light-receiving surface on which the first light that travels in the direction in which the reflective member is arranged and is transmitted through the first transmissive surface is irradiated.

A photoconversion device includes a first wavelength converter and a long-pass filter. The first wavelength converter receives excitation light from an output portion and emits fluorescence having a longer wavelength than the excitation light. The long-pass filter transmits the fluorescence emitted by the first wavelength converter and reflects the excitation light transmitted through or reflected from the first wavelength converter to enter the first wavelength converter.

A photoconversion device includes a first wavelength converter and a long-pass filter. The first wavelength converter receives excitation light from an output portion and emits fluorescence having a longer wavelength than the excitation light. The long-pass filter transmits the fluorescence emitted by the first wavelength converter and reflects the excitation light transmitted through or reflected from the first wavelength converter to enter the first wavelength converter.

A phosphor coating material containing phosphor particles and a curable resin component. A viscosity of the phosphor coating material, measured at 25° C. and a rotation speed of 20 rpm using a B-type viscometer, is equal to or more than 60 dPa.Math.s and equal to or less than 450 dPa.Math.s.

A reflector includes a reflector body that reflects light emitted from a light source and a phosphor layer that is provided on the reflector body and includes a phosphor excited by the light emitted from the light source.

There is provided a wavelength conversion member including: a fluorescent body and a reflective film. The fluorescent body is configured to emit fluorescence by an excitation light and has an incident surface into which the excitation light comes and a rear surface which faces the incident surface. The reflective film is arranged on a side of the rear surface of the fluorescent body and includes a metal layer and ceramic particles dispersed in the metal layer. The ceramic particles are crystalline, and a melting point of the ceramic particles is higher than a melting point of a metal constructing the metal layer.

There is provided a wavelength conversion member including: a fluorescent body and a reflective film. The fluorescent body is configured to emit fluorescence by an excitation light and has an incident surface into which the excitation light comes and a rear surface which faces the incident surface. The reflective film is arranged on a side of the rear surface of the fluorescent body and includes a metal layer and ceramic particles dispersed in the metal layer. The ceramic particles are crystalline, and a melting point of the ceramic particles is higher than a melting point of a metal constructing the metal layer.

A wavelength conversion member converts a wavelength of laser light. The wavelength conversion member includes a substrate having reflectivity with respect to the laser light, and a phosphor layer including a phosphor for converting the laser light into light having a longer wavelength than that of the laser light, the phosphor layer being on the substrate. The phosphor layer includes a plurality of concave parts, each having a depth of 50% or more and 80% or less with respect to a film thickness of the phosphor layer and an opening width of 50 μm or more, on a surface of the phosphor layer, the surface irradiated with the laser light. A distance between adjacent concave parts of the plurality of concave parts is smaller than a spot diameter of the laser light to be emitted to the surface of the phosphor layer.

A wavelength conversion member converts a wavelength of laser light. The wavelength conversion member includes a substrate having reflectivity with respect to the laser light, and a phosphor layer including a phosphor for converting the laser light into light having a longer wavelength than that of the laser light, the phosphor layer being on the substrate. The phosphor layer includes a plurality of concave parts, each having a depth of 50% or more and 80% or less with respect to a film thickness of the phosphor layer and an opening width of 50 μm or more, on a surface of the phosphor layer, the surface irradiated with the laser light. A distance between adjacent concave parts of the plurality of concave parts is smaller than a spot diameter of the laser light to be emitted to the surface of the phosphor layer.