Wavelength conversion element, light source device, and projector for reducing heat damage in the wavelength conversion element

A wavelength conversion element comprising:

• a wavelength conversion layer having a first surface which excitation light enters, and a second surface opposed to the first surface, and adapted to perform wavelength conversion on the excitation light;
• a substrate disposed so as to be opposed to the second surface;
• and
• a bonding layer adapted to bond the wavelength conversion layer and the substrate to each other, wherein
• the bonding layer has a first bonding material disposed in a first region opposed to an incident area of the excitation light in the second surface, and a second bonding material disposed in at least a second region located on an outer periphery of the first region and lower in Young's modulus than the first bonding material,
• the first bonding material and the second bonding material are formed of the same material including voids, and
• a void ratio in the first bonding material is lower than a void ratio in the second bonding material.

A wavelength conversion element comprising:

• a wavelength conversion layer having a first surface which excitation light enters, and a second surface opposed to the first surface, and adapted to perform wavelength conversion on the excitation light;
• a substrate disposed so as to be opposed to the second surface;
• and
• a bonding layer adapted to bond the wavelength conversion layer and the substrate to each other, wherein
• the bonding layer has a first bonding material disposed in a first region opposed to an incident area of the excitation light in the second surface, and a second bonding material disposed in at least a second region located on an outer periphery of the first region and lower in Young's modulus than the first bonding material,
• the first bonding material includes a side surface that intersects the second surface, and
• the second bonding material is disposed on the side surface and is in contact with the side surface.