Internally Folded Scalable Laser.
Patent, Filed 21 May 92, patented 28 Sep 93,
DEPARTMENT OF THE NAVY WASHINGTON DC
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An internally folded scalable laser has a gain medium with an internal face and an external face and at least one internal-fold face subtending an angle which may be about 90 deg. An output coupler that is partially reflective of the resonator mode is oriented to receive and reflect resonator mode in a direction normal to the internal face to avoid resonator mode astigmatism and to define a folded hemispherically-shaped resonator cavity extending from the output coupler and through an active volume in the gain medium to the external face. A pumping mode source disposed adjacent to the external face is oriented to focus a first pumping mode in a direction normal to the external face in a boom waist at or inside the external face in the folded resonator cavity to define an active volume in the gain medium and to avoid pumping mode astigmatism. Other pumping mode sources direct more pumping mode through the internal-fold faces into portion of the active volume to partially or completely overlap the pumping and resonator modes. Simultaneously pumping the gain medium along more than one axis for each fold surface assures scaling and physical separation of the pumped regions reduces thermal lensing problems. Other angles between the external and internal faces could be formed in multifaceted configurations of the gain medium so long as the pumping mode beam is normal to the external face and the resonator mode beam is normal to the internal face.
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