OPTICAL WAVELENGTH CONVERSION MATERIAL, OPTICAL WAVELENGTH CONVERSION DEVICE, AND LIGHT EMITTING DEVICE
An optical wavelength conversion member according to one aspect of the present disclosure includes a ceramic sintered body, wherein the ceramic sintered body has a fluorescent phase containing, as a main. component, fluorescent crystal grains that generate fluorescence in response to incident light, and a translucent phase containing translucent crystal grains as a main component. The optical wavelength conversion member includes a metal layer having light reflectivity and provided on a side of the ceramic sintered body opposite the side on which the light is incident, and a dielectric multilayer film including dielectric layers having different optical refractive indices and provided between the ceramic sintered body and the metal layer.
1 . An optical wavelength conversion member comprising a ceramic sintered body, wherein the ceramic sintered body has
a fluorescent phase containing, as a main component, fluorescent crystal grains that generate fluorescence in response to incident light, and
a translucent phase containing translucent crystal grains as a main component, wherein the optical wavelength conversion member further comprises
a metal layer having light reflectivity and provided on a side of the ceramic sintered body opposite the side on which the light is incident, and
a dielectric multilayer film including dielectric layers having different optical refractive indices and provided between the ceramic sintered body and the metal layer.
2 . An optical wavelength conversion member according to claim 1 , wherein the crystal grains of the fluorescent phase have a composition represented by formula A 3 B 5 O 12 :Ce, and each of elements A and B is at least one element selected from the following element groups:
A: Sc, Y, and lanthanoids exclusive of Ce, and
B: Al and Ga.
3 . An optical wavelength conversion member according to claim 1 , wherein the crystal grains of the translucent phase have a composition of Al 2 O 3 .
4 . An optical wavelength conversion member according to claim 1 , wherein the metal layer contains Ag and/or Al as a component.
5 . An optical wavelength conversion member according to claim 4 , further comprising an Ni layer and/or an Au layer provided on a side of the metal layer opposite the light incident side.
6 . An optical wavelength conversion member according to claim 1 , wherein
the dielectric multilayer film is formed by alternate stacking of a high-refractive-index film that exhibits a refractive index “a” upon incidence of light having a wavelength of 550 nm and a low-refractive-index film that exhibits a refractive index “b” upon incidence of light having a wavelength of 550 nm, the refractive index b being lower than the refractive index a, wherein the refractive index a and the refractive index b satisfies a relation of 1.3<a/b, and
a relation of 1<a/c is satisfied wherein c represents the refractive index of the ceramic sintered body upon incidence of light having a wavelength of 550 nm on the ceramic sintered body.
7 . An optical wavelength conversion member according to claim 6 , wherein the high-refractive-index film contains at least one element selected from among Ti, Zr, Hf, Ta, and Nb, and the low-refractive-index film is formed of SiO 2 or MgF 2 .
8 . An optical wavelength conversion member according to claim 1 , wherein the dielectric multilayer film has an overall thickness of 300 nm or less.
9 . An optical wavelength conversion device comprising an optical wavelength conversion member as recited in claim 1 , and a heat dissipation member joined to the metal layer of the optical wavelength conversion member on a side opposite the light incident side.
10 . A light-emitting device comprising an optical wavelength conversion device as recited in claim 9 and a light-emitting element which emits the light.