Hollow cylindrical solid state laser medium and a laser system using the medium

A laser device, comprising:

• a hollow cylindrical solid state laser medium;
• pumping means for exciting the laser medium;
• an optical resonator arranged on both ends in the axial direction of the cylinder of the laser medium, for causing the radiation emitted into the laser medium to travel back and forth along the axial direction of the cylinder of the laser medium;
• and
• cooling means for cooling the hollow cylindrical solid state laser medium from both of the outer longitudinal surface and the inner longitudinal surface of the hollow cylinder, in which said cooling means comprises:
• (a) an outer shielding member made of a transparent material for covering the outer surface of said hollow cylindrical laser medium, said outer shielding member having a predetermined spacing from the outer surface;
• (b) an inner shielding member which serves also as an inner reflector for the emitted light, said inner shielding member having an outer diameter that is slightly smaller than the inner diameter of said laser medium, said inner shielding member being inserted in the cavity of the laser medium;
• and
• (c) a coolant that is flowed in the channel formed between said medium and the outer shielding member and also in the channel formed between said laser medium and the inner shielding member.

A laser device, comprising:

• (a) a hollow circular cylindrical solid state laser medium;
• (b) pumping means for exciting the laser medium;
• and
• (c) an optical resonator having a rear mirror and output mirror unit that are arranged on both ends in the axial direction of said laser medium, for causing the light emitted into said laser medium to travel back and forth along the axial direction of the laser medium;
• said output mirror unit having
• (i) an output mirror that is semi-transparent and arranged on the front end of the laser medium in the axial direction of said hollow circular cylindrical laser medium, said output mirror being separated by a predetermined distance away from the front end of said laser medium, and
• (ii) an axicon mirror assembly that is inserted between said laser medium and output mirror for producing a laser beam having substantially full beam cross-section from a laser beam having an annular beam cross-section,
• said axicon mirror assembly comprising
• (1) an outer reflecting member, formed with a truncated-conical bore having a truncated-conical inner reflecting surface whose mean radius is substantially the same as that of the cylinder of the laser medium and which is directed to the front end of the laser medium, for reflecting the laser beam emitted from the laser medium by the truncated-conical reflecting surface and focussing the laser beam on the central longitudinal axis of the laser medium, and
• (2) an inner reflecting member, having conical outer reflecting surface whose means radius is smaller than that of said outer reflecting member, and being disposed in the bore of said outer reflecting member in such a manner that the reflecting surface of said inner reflecting member is directed to said output mirror through the bore of said outer reflecting member, for reflecting the laser beam impinged from said outer reflecting member toward said output mirror along the central longitudinal axis of the laser medium by the conical reflecting surface so that the laser beam focussed by the outer reflecting member is defocussed to be a parallel pencil of rays having a substantially full beam cross-section.