Reflex ring laser amplifier system

Claim 2

An unstable ring resonator laser amplifier system for amplifying an input laser pulse, comprising: a large-aperture laser amplifier having an input aperture to which the input laser pulse is injected for amplification by said laser amplifier and having an output aperture at which an amplified laser pulse is produced; means, optically aligned with the amplifier, for spatially filtering and expanding the laser pulse; means for recirculating the laser pulse through the amplifier to produce an expanded amplified laser pulse, successive pulses passing through concentric non-overlapping regions of the gain medium on each successive pass; means for coupling the expanded amplified laser pulse out of the unstable resonator when the laser pulse has reached a predetermined spatial extent.

Claim 3

The laser amplifier system of claim 1 wherein the means for spatially filtering and expanding the laser pulse is positioned after the amplifier.

Claim 4

The laser amplifier system of claim 1 wherein the means for spatially filtering and expanding the laser pulse is positioned before the amplifier.

Claim 5

The laser amplifier system of claim 1 wherein the means for recirculating the expanded amplified laser pulse comprises a plurality of mirrors forming a ring resonator.

Claim 6

The laser amplifier of claim 4 wherein the number of mirrors is four.

Claim 7

The laser amplifier of claim 4 wherein the mirrors are optically flat.

Claim 8

The laser amplifier of claim 4 wherein a pair of adjacent mirrors are focusing mirrors which spatially expand the pulse.

Claim 9

The laser amplifier of claim 7 further including a pinhole at the focal point between the pair of focusing mirrors for spatially filtering the pulse.

Claim 10

The laser amplifier of claim 1 wherein the means for spatially filtering and expanding the pulse comprises a pair of lenses forming an astronomical telescope and a pinhole at the focal point between the pair of lenses.

Claim 11

The laser amplifier system of claim 1 wherein the means for recirculating the expanded laser pulse includes an input mirror having an aperture formed therein to permit the input laser pulse to enter the unstable ring resonator and to remove the central portion of the expanded beam on the first pass.

Claim 12

The laser amplifier system of claim 1 further including an auxiliary mirror to permit the input laser pulse to be coupled into the unstable ring resonator and to remove the central portion of the expanded beam on the first pass.

Claim 13

The laser amplifier system of claim 1 wherein the means for coupling out the expanded, amplified and filtered laser pulse comprises an output mirror having dimensions such that the laser pulse, when it reaches a predetermined spatial extent, passes around the output mirror and exits the unstable ring resonator.

Claim 14

The laser amplifier system of claim 1 wherein the large aperture laser amplifier comprises a plurality of cascaded amplifiers.

Claim 15

The laser amplifier of claim 1 wherein the means for spatially filtering and expanding the beam has a magnification greater than one.

Claim 16

The laser amplifier of claim 1 wherein the gain (G) of the amplifier, the transmission (T) of the ring resonator and the magnification (M) of the means for expanding the pulse satisfy the condition for isofluence G=M 2 T whereby a pulse has substantially the same fluence (energy density) on the components for each pass.

Claim 17

The laser amplifier of claim 1 where the gain (G) of the amplifier, the single pass transmission (T) of the ring resonator and the magnification (M) of the means for expanding the pulse satisfy the condition G>M 2 T.

Claim 18

The laser amplifier of claim 1 where the gain (G) of the amplifier, the single pass transmission (T) of the ring resonator and the magnification (M) of the means for expanding the pulse satisfy the condition G<M 2 T.

Claim 19

An unstable ring resonator laser amplifier system comprising: a large-aperture laser amplifier having input and output apertures; a beam expanding spatial filter with magnification greater than 1 coupled to the output aperture of the laser amplifier and optically aligned with the laser amplifier; a plurality of mirrors forming a ring structure for the laser amplifier and spatial filter, the plurality of mirrors including an input mirror having a small aperture formed therein for injection of an input laser pulse into the unstable ring resonator, said plurality of mirrors providing a path for the laser pulse to make a series of passes around the ring structure and increase in spatial extent, the expanding pulse passing through different concentric nonoverlapping regions of the amplifier on each pass the plurality of mirrors also including an output mirror having dimensions such that on the final pass through the ring structure the laser pulse passes around the output mirror and exits the ring resonator structure.

Claim 20

An unstable ring resonator laser amplifier system comprising: a large-aperture laser amplifier having input and output apertures; a beam expanding spatial filter with magnification greater than 1 coupled to the output aperture of the laser amplifier and optically aligned with the laser amplifier; a plurality of mirrors forming a ring structure for the laser amplifier and spatial filter, the plurality of mirrors including an input mirror having a small aperture formed therein for injection of an input laser pulse into the unstable ring resonator, said plurality of mirrors providing a path for the laser pulse to make a series of passes around the ring structure and increase in spatial extent, the expanding pulse passing through different concentric nonoverlapping regions of the amplifier on each pass the plurality of mirrors also including an output mirror having dimensions such that on the final pass through the ring structure the laser pulse passes around the output mirror and exits the ring resonator structure.

Claim 23

The method of claim 19 wherein the steps of injecting a laser pulse into the unstable ring resonator includes injecting the laser pulse through an aperture formed in a mirror used for recirculating the amplified, expanded laser pulse.

Claim 24

The method of claim 19 wherein the step of coupling out the expanded, amplified pulse includes passing the pulse around an output mirror used for recirculating the expanded pulse.

Claim 25

The method of claim 19 wherein the recirculating pulse is amplified by passing through concentric non-overlapping regions of gain medium in an amplifier on each successive pass around the ring resonator.