a tube-shaped base formed from a metal and provided therein with a through hole;

an optical waveguide received inside the through hole of the base, the optical waveguide being an optical fiber member; and

a sensor head bonded to the base via a bonding member to be optically connected with the optical waveguide, the sensor head being formed from monocrystalline alumina, wherein

the sensor head comprises a first cavity comprising: a first reflection surface configured to reflect a part of light introduced through the optical waveguide; and a second reflection surface provided facing the first reflection surface and configured to reflect a part of the light introduced through the optical waveguide, the first cavity being a cavity from which a first interference light produced by an interference between the light reflected by the first reflection surface and the light reflected by the second reflection surface is output to the optical waveguide, and

the base is formed from one of titanium, nickel alloy, titanium alloy, and steel use stainless (SUS).