Wavelength conversion element, light source device, projector, and method of manufacturing wavelength conversion element

A method of manufacturing a wavelength conversion element, the method comprising:

• a first step of providing a dichroic layer to a first surface of a substrate;
• a second step of forming an intermediate layer on a third surface different from a second surface opposed to the first surface of the substrate out of two surfaces of the dichroic layer, or so as to be opposed to a fourth surface of a wavelength conversion layer;
• a third step of providing a first bonding layer to a first member including the substrate;
• a fourth step of providing a second bonding layer to a second member including the wavelength conversion layer;
• and
• a fifth step of bonding the first bonding layer and the second bonding layer to each other, wherein
• the dichroic layer has two or more types of refractive index layers having respective refractive indexes different from each other, and
• when denoting a refractive index of the wavelength conversion layer by nm, a refractive index of the intermediate layer by nLm, a refractive index of a refractive index layer having a first refractive index out of the two or more types of refractive index layers by nL, and a refractive index of a refractive index layer having a second refractive index out of the two or more types of refractive layers by nH, and nH is higher than nL,
• θB≥θC is fulfilled with respect to θB obtained by a formula (1) described below and θC obtained by a formula (2) described below:
• θ
• B
• =
• sin
• -
• 1
• ⁢
• n
• L
• 2
• ⁢
• n
• H
• 2
• n
• m
• 2
• (
• n
• L
• 2
• +
• n
• H
• 2
• )
• (
• 1
• )
• θ
• C
• =
• sin
• -
• 1
• (
• n
• L
• ⁢
• m
• n
• m
• )
• ,
• (
• 2
• )
• wherein the θB corresponds to an angle that satisfies Brewster's condition at an interface between the wavelength conversion layer and the dichroic layer, and
• the θC is an total reflection angle at an interface between the wavelength conversion layer and the intermediate layer.

A wavelength conversion element comprising:

• a substrate;
• a dichroic layer provided to a first surface of the substrate;
• an intermediate layer disposed so as to be opposed to the substrate via the dichroic layer;
• and
• a wavelength conversion layer disposed so as to be opposed to the dichroic layer via the intermediate layer, and configured to convert light in a first wavelength band into light in a second wavelength band different from the first wavelength band, wherein
• the dichroic layer has two or more types of refractive index layers having respective refractive indexes different from each other, and
• when denoting a refractive index of the wavelength conversion layer by nm, a refractive index of the intermediate layer by nLm, a refractive index of a refractive index layer having a first refractive index out of the two or more types of refractive index layers by nL, and a refractive index of a refractive index layer having a second refractive index out of the two or more types of refractive layers by nH, and nH is higher than nL,
• θB≥θC is fulfilled with respect to θB obtained by a formula (1) described below and θC obtained by a formula (2) described below:
• θ
• B
• =
• sin
• -
• 1
• ⁢
• n
• L
• 2
• ⁢
• n
• H
• 2
• n
• m
• 2
• (
• n
• L
• 2
• +
• n
• H
• 2
• )
• (
• 1
• )
• θ
• C
• =
• sin
• -
• 1
• (
• n
• L
• ⁢
• m
• n
• m
• )
• (
• 2
• )
• wherein the intermediate layer is formed of a material including at least one of silicon oxide, magnesium fluoride, lithium fluoride, and calcium fluoride.