Wavelength converter, light source apparatus, and projector

A wavelength converter comprising:

• a base having a first surface;
• a wavelength conversion part that has a second surface facing the first surface and converts first light that belongs to a first wavelength band into second light that belongs to a second wavelength band different from the first wavelength band;
• a junction that joins the wavelength conversion part and the base to each other;
• and
• an air layer located in a region that the first light enters and surrounded by the wavelength conversion part, the base, and the junction,
• wherein the first surface of the base has a first region curved in a first direction,
• the second surface of the wavelength conversion part has a second region facing the first region and curved in the first direction,
• the wavelength converter emits the second light toward the same side as the side on which the first light is incident, and
• the wavelength conversion part includes a plurality of protrusions in a region where the wavelength conversion part is in contact with the junction.