National Institute of Information and Communications Technology, Incorporated

National Institute of Information and Communications Technology, Incorporated Administrative Agency

Communications Research Laboratory, Independent Administrative Institution

National Institute of Information and Incorporated Administrative Agency

Mitsuo Ishizu

A laser oscillator, including an optical resonator, an optical amplifier element on an optical path inside the optical resonator, (i) the optical path in the optical resonator having an even number of optical reflections per resonator circuit or round-trip, (ii) the transverse mode pattern of the laser light in the optical resonator rotating with each resonator circuit or round-trip by a rotation angle other than zero degrees, 90 degrees or 180 degrees, the cumulative rotation angle increasing or decreasing monotonically as the number of circuits or round-trips increases, and (iii) polarization maintaining means that maintains the polarization direction of the laser light through one resonator circuit or round-trip.

Laser oscillator incorporating transverse mode rotation in the laser resonator

A laser apparatus has a multipath solid-state slab laser rod and an excitation source that excites it, and uses a solid-state slab laser rod that has a trapezoid or parallelogram-shaped cross section along the optical path, that is provided with six or more faces and that has a light amplifying effect or a nonlinear optical effect. The light that is incident to the laser rod is totally reflected at the incident-light end face and exit end face of the laser rod, passes back through the interior of the laser rod a plurality of times, e.g., three times, and then exits. For light amplification, excitation light is irradiated from the side face. In addition, for nonlinear optical effects, the z-axis of a nonlinear optical crystal is disposed so as to be orthogonal to the plane of the optical path, and the temperature of the solid-state slab laser rod is kept at the phase-matching temperature. This laser apparatus of this configuration solves drawbacks of prior-art laser rods so that the high conversion rate from excitation light to laser light is obtained at a high laser gain.

Multipath laser apparatus using a solid-state slab laser rod

A laser oscillator is provided that makes it possible to stably obtain a laser beam output in continuous or pulsed oscillation that has an intensity distribution of a top-hat profile or a fundamental transverse mode profile. An optical resonator is used that maintains the polarization of a laser beam traveling in the resonator but rotates the transverse mode pattern thereof. The resonator can be a ring resonator that includes an image rotating element, a nonplanar ring resonator, a diagonally crossed right-angle prism resonator or other such resonator. A combination of a polarizer, and a half-wave plate or Faraday rotator is used to preserve the polarization in the resonator. The optical path of the laser resonator can be intersected with another resonator of a conventional Fabry-Perot or planar ring resonator, and the optical paths coupled, using a beam-splitter or polarizer. A laser output beam from a counterclockwise or clockwise traveling wave in the laser oscillator is reflected back into the resonator by a reflector, suppressing such traveling laser oscillation.

A diode-pumped solid-state laser oscillator optically pumps a laser medium. The oscillator has at least one pumping light source that emits light in a predetermined wavelength band, and a laser medium that absorbs light in the wavelength band. In the wavelength band, the optical absorption index of the laser medium increases with an increase in wavelength, and the optical radiation energy of the light source decreases with an increase in wavelength. Thus, with respect to wavelength changes, an increase in the optical absorption index is cancelled out by a decrease in the radiation energy, making the stability of the laser output less dependent on the temperature of the optical pumping medium or laser medium.

Diode-pumped solid-state laser oscillator

A laser oscillator comprises a laser medium, an optical excitation laser diode that irradiates the laser medium with light, a polarizer disposed on an optical path of the laser medium at a first end thereof, a first Porro prism disposed with the optical path coinciding with a point on a ridgeline thereof and with the ridgeline parallel or perpendicular to a plane of incidence of the polarizer, and a second Porro prism disposed on the optical path of the laser medium at a second end thereof with the optical path coinciding with a point on a ridgeline thereof. An angle formed by the two ridgelines of the first and second Porro prisms is a predetermined angle other than 0 degrees, 90 degrees, 60 degrees, 45 degrees and 36 degrees, 30 degrees.

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Koganei, Japan

Mitsuo Ishizu