Abstract: An optical resonator includes a waveguide (12) formed by using an incidence side reflection film (93) and an emission side reflection film (94) arranged in parallel with each other and adapted to resonate light entering it by way of the incidence side reflection film (93) and adapted to propagate light formed and resonated so as to run through from the incidence side reflection (93) to the emission side reflection film (94), a substrate (11) for forming the optical waveguide (12) on the top surface thereof and a first protection member (86) and a second protection member (87) corresponding to the material of the substrate (11) provided at an upper part of the waveguide (12) so as to make at least an end facet of each of the members form a plane (91) or (92) identical with the first end facet (84) or the second end facet (85), whichever appropriate, of the substrate (11) including the light incidence end or the light emission end, whichever appropriate, of the optical waveguide (11) and the incidence side refl

Abstract: A resonance system (14, 15) is formed by a light incident side reflection mirror and a light exiting side reflecting mirror, arranged parallel to each other. The light incident on an incident side reflective mirror (14) is propagated in the outward path direction or in the backward path direction so that the light is set in a resonant state. The light in the resonant state in the resonance system (14, 15) is phase-modulated, responsive to a modulating signal supplied from an oscillating device (16) by a light modulation device (2) arranged between the light incident side reflective mirror (14) and the light exiting side reflective mirror (15). The oscillating device oscillates the modulating signal of a frequency fm.