Multi-pass light amplifier

A multiple pass light amplifier comprising:

• an optical gain medium to amplify a light beam having a selected wavelength that passes through the gain medium;
• an optical cavity containing the gain medium and including N reflective surfaces or mirrors (N.gtoreq.3), consecutively numbered i=1, 2, . . . , N and positioned so that a light beam introduced into the cavity will be reflected from each mirror in consecutive order and will pass through the gain medium at least once, then will be reflected from at least one of the mirrors numbered 2, ..., N a second time before the light beam is reflected from mirror number 1 a second time and so that the light beam will execute two or more approximately closed path cycles within the cavity, where the light beam has approximately the same beam diameter each time the beam passes through the gain medium;
• beam translation means, positioned between two of the N reflective surfaces so that the translation means does not lie on the cavity axis, for receiving and translating a light beam by a small, controllable amount in a direction approximately perpendicular to the immediately preceding direction of travel of the light beam immediately before the light beam is received by the translation means, so that, when the light beam issues from the translation means, the light beam travels substantially parallel to the immediately preceding direction;
• light beam insertion means for introducing a light beam produced by a light source into the cavity so that the beam propagates toward one of the mirrors;
• and
• light beam removal means for removing a light beam from the cavity.

A multiple-pass light amplifier comprising:

• a confocal resonator including first and second curvilinearly shaped mirrors facing each other along a resonator axis and having a common optical focal point positioned between the mirrors, the two mirrors being arranged so that a light beam that passes through the common focal point is subsequently received by either of the mirrors and is reflected toward the other mirror in a direction that is approximately parallel to the resonator axis;
• an optical gain medium, having a diameter that is small compared the distance between the two mirrors and being positioned at the common focal point of the two mirrors;
• beam translation means, positioned between two of the mirrors so that the translation means does not lie on the cavity axis, for receiving and translating a light beam by a small, controllable amount in a direction approximately perpendicular to the immediately preceding direction of travel of the light beam immediately before the light beam is received by the translation means, so that, when the light beam issues from the translation means, the light beam travels substantially parallel to the immediately preceding direction;
• light beam insertion means for introducing a light beam produced by the light source into the region between the first and second mirrors;
• and
• light beam removal means for removing a light beam from the region between the first and second mirrors,
• whereby a light beam introduced into the region between the first and second mirrors has approximately the same diameter each time the beam passes through the gain medium.