OPTICAL ELEMENT, LASER BEAM OSCILLATION DEVICE AND LASER BEAM AMPLIFYING DEVICE

An optical element 20A which is composed of a light transmission characteristic medium, that has a refractive index higher than a refractive index of air, the optical element causes an incident laser beam to be propagated inside while reflecting the laser beam by a wall surface 20a a plurality of times, the optical element includes an incident window 21 which is located in a part of the wall surface 20a, that is for allowing the laser beam to be incident, an emitting window 22 which is located in a part of the wall surface 20a, that is for allowing the laser beam propagated inside to be emit, and wavelength dispersion compensating units 31 and 32 which are integrally located in parts of the medium, the wavelength dispersion compensating units compensate for wavelength dispersion by causing the laser beam to be transmitted or reflected at least twice.