OPTICAL RESONATOR, AND LASER PROCESSING DEVICE

An optical resonator 1 of wavelength beam combining type includes the laser diode array 11 having the plurality of laser elements 11a arranged along the predetermined X-direction and configured to emit light beams having wavelengths different from one another. The optical resonator 1 further includes the diffraction grating 40 that diffracts the light beam emitted from each of the laser elements 11a at the diffraction angle corresponding to the wavelength of the light beam. The optical resonator 1 further includes the output coupler 60 that reflects a part of the light beam diffracted by the diffraction grating 40 toward each of the laser elements 11a. The optical resonator 1 further includes the optical system 30 provided between the laser diode array 11 and the diffraction grating 40 and configured to align the light beams emitted from the laser elements 11a with one another. The optical system 30 includes, in a sequence from the laser diode array 11 toward the diffraction grating 40, the first lens element 31 having the negative power only in the predetermined X-direction and the second lens element 32 having the positive power only in the predetermined X-direction.