Abstract: An optical component according to the present disclosure includes a substrate, which contains sapphire and includes a first main face and a second main face on opposite sides from each other. The inclination of the first main face and of the second main face with respect to a c-plane of the sapphire is 15° or less, and a heat dissipating portion is provided on at least one of the first main face or the second main face.

Abstract: An optical component according to the present disclosure includes a substrate containing sapphire. The substrate is provided with a functional portion and a heat dissipating portion. An inclination of a main face of the substrate is 75° or greater with respect to a c-plane of the sapphire. The functional portion and the heat dissipating portion are provided so that an angle formed by a c-axis of the sapphire and a line segment connecting the functional portion and the heat dissipating portion is 15° or less.

Abstract: The composite substrate of the present disclosure has a piezoelectric substrate having a first surface and a second surface opposing the first surface, a support substrate having a third surface in contact with the second surface and a fourth surface opposing the third surface, and a through hole penetrating from the first surface to the fourth surface. The through hole has a tapered shape having a diameter decreasing from the first surface to the fourth surface and has a stepped surface having a decreasing diameter in the support substrate. The piezoelectric device of the present disclosure comprises the composite substrate and a conductor located within the through hole.