EXCITATION LIGHT IRRADIATION DEVICE AND EXCITATION LIGHT IRRADIATION METHOD

An excitation light irradiation device includes a substrate having a color center. The color center is excited by an excitation light incident to the substrate. The substrate includes first and second reflection surfaces facing each other, and first and second end surfaces facing each other. When the excitation light enters into the substrate, the incident excitation light travels from the first end surface to the second end surfaces while repeatedly reflecting between the first and second reflection surfaces. The second end surface is inclined. The second end surface reflects the incident excitation light so as to cause the incident excitation light to be emitted from one of the first and second reflection surfaces.