Abstract: The laser device includes a first mirror and a second mirror forming a resonator, a gain medium disposed between the first mirror and the second mirror and having a light emitting surface, an antireflection film provided on the light emitting surface of the gain medium, at least one optical element disposed between the gain medium and the second mirror, and a diffraction grating disposed between the optical element and the second mirror. The gain medium is a semiconductor layered body including an active layer and having a varying gain distribution in at least a first direction within the light emitting surface, and includes no waveguide.

Abstract: An external-cavity semiconductor laser includes a semiconductor laser element containing a gallium nitride material, a first lens disposed in an optical path of light emitted from the semiconductor laser element, a wavelength selective element disposed in an optical path of light transmitted through the first lens and configured to selectively transmit light having a predetermined wavelength, a second lens disposed in an optical path of light transmitted through the wavelength selective element, an output coupler disposed in an optical path of light condensed through the second lens, and a light-transmissive protective member bonded to at least one surface of the output coupler. The second lens is configured to cause light transmitted through the second lens and incident on the output coupler to form an image on a surface of the output coupler. The protective member covers the surface of the output coupler on which the image is formed.

Abstract: A vertical external-cavity surface-emitting laser includes: a resonator comprising at least two mirrors; a semiconductor laser medium disposed in the resonator; and a Q switch provided in the resonator.

Abstract: A Q switch resonator includes: an optical resonator comprising at least two mirrors, and configured to accumulate power of a continuous wave or an intermittent continuous wave incident from an outside; and a switching element provided in the optical resonator. The switching element is configured such that, when the power accumulated in the optical resonator increases to a predetermined level, the switching element outputs an optical pulse by lowering a Q factor from a first level to a second level lower than the first level.

Abstract: A laser device includes: a traveling wave type resonator comprising a first mirror and a second mirror; and a laser medium disposed between the first mirror and the second mirror. The first mirror and the second mirror are disposed such that round-trip light that travels in round trips in the resonator has a focus inside the laser medium. The laser device is configured such that: excitation light incident on the resonator is superimposed on the round-trip light at the focus and narrowed to be thinner than the round-trip light, ZR×?<0.5 is satisfied, where ZR is a Rayleigh length of the excitation light and ? is an absorption coefficient of the laser medium with respect to the excitation light, and a round-trip Gouy phase shift of the resonator has a value excluding 2?×n/m where m is an integer of less than 15 and n is an integer of equal to or less than m.

Abstract: An external-cavity semiconductor laser includes a semiconductor laser element containing a gallium nitride material, a first lens disposed in an optical path of light emitted from the semiconductor laser element, a wavelength selective element disposed in an optical path of light transmitted through the first lens and configured to selectively transmit light having a predetermined wavelength, a second lens disposed in an optical path of light transmitted through the wavelength selective element, an output coupler disposed in an optical path of light condensed through the second lens, and a light-transmissive protective member bonded to at least one surface of the output coupler. The second lens is configured to cause light transmitted through the second lens and incident on the output coupler to form an image on a surface of the output coupler. The protective member covers the surface of the output coupler on which the image is formed.