Optically pumped external-cavity semiconductor laser with multiple gain structures

1. A laser, comprising:

a laser-resonator;

a plurality of OPS-structures located in said laser-resonator, each of said OPS-structures including a mirror-structure surmounted by a gain-structure;

an optical pumping arrangement for energizing said gain-structures of said OPS-structures thereby causing a beam of laser radiation to circulate in said laser resonator; and

a plurality of fold-mirrors, at least one of which has finite optical power; and

wherein said laser-resonator is folded by said plurality of fold-mirrors and said mirror-structures of said plurality of OPS-structures and wherein said fold-mirrors and said OPS-structures are configured and arranged such that said beam of laser radiation has about the same dimensions on a plurality of said OPS-structures.

2. The laser of claim 1 , wherein said laser resonator includes an additional OPS-structure having a mirror-structure surmounted by a gain-structure and said laser resonator is terminated by said mirror-structure of said additional OPS structure.

3. The laser of claim 1 , wherein said laser resonator is terminated by first and second end mirrors.

4. The laser of claim 3 , wherein said first end-mirror is a plane mirror and said second end mirror is a concave mirror.

5. The laser of claim 4 , wherein said second end-mirror and said fold-mirrors have the same radius of curvature.

6. The laser of claim 5 , wherein the number of said OPS-structures is equal to the number of said fold-mirrors.

7. The laser of claim 6 , wherein each of said OPS-structures is spaced apart from a corresponding one said fold-mirrors.

8. The laser of claim 7 , wherein said OPS-structures and said fold-mirrors are about equally spaced apart.

9. A laser, comprising:

a folded laser-resonator said laser-resonator being terminated by first and second end-mirrors, and having a resonator axis;

a plurality of OPS-structures located in said laser-resonator, each of said OPS-structures including a mirror-structure surmounted by a gain-structure;

an optical pumping arrangement for energizing said gain-structures of said OPS-structures thereby causing a beam of laser radiation to circulate in said laser resonator;

a plurality of concave fold-mirrors equal in number to said plurality of OPS structures, and each thereof having about the same radius of curvature; and

wherein said resonator axis is folded by said fold-mirrors and said mirror-structures of said OPS-structures with said beam, in one direction of circulation, propagating from said first end-mirror, alternately via a said fold-mirror and a said OPS-structure, to said second end mirror and wherein said fold-mirrors and said OPS-structures are configured and arranged such that said beam of laser radiation has about the same dimensions on a plurality of said OPS-structures.

10. The laser of claim 9 , wherein the axial distance between each of said fold-mirrors and an axially adjacent OPS-structure is about the same.

11. A laser comprising:

a laser-resonator;

a plurality of OPS-structures located in said laser-resonator, each of said OPS-structures including a mirror-structure surmounted by a gain-structure;

an optical pumping arrangement for energizing said gain-structures of said OPS-structures thereby causing a beam of laser radiation to circulate in said laser resonator; and

a plurality of fold-mirrors positioned such that said laser-resonator is folded by said plurality of fold-mirrors and said mirror-structures of said OPS-structures and wherein the spacing and the curvature of the fold mirrors is selected such that the size of the circulating beam is substantially the same at each OPS structure.

12. A laser comprising:

N substantially identical modules, wherein N is equal to at least three, each module including a base upon which is mounted a heat sink, said module further including an OPS chip having a mirror structure surmounted by a gain structure, said OPS chip mounted on said heat sink, each said module further including a laser diode pump source mounted to said base for generating an output beam for exciting the OPS chip, said modules being assembled in a side to side relationship so that the OPS-chips are aligned in an array in a substantially common plane;

at least N−1 fold mirrors aligned opposite said array of OPS chips, each fold mirror being concave with substantially the same radius of curvature; and

a pair of resonator mirrors cooperating with the OPS chips and the fold mirrors to create a resonant cavity which propagates a laser beam from one end of the resonator to the other end and alternatively between the OPS chips and the fold mirrors in zigzag fashion.

13. The laser as recited in claim 12 , wherein the spacing and curvature of the fold mirror mirrors is selected so that the size of the circulating beam at each OPS chip is substantially the same.

14. The laser as recited in claim 12 , wherein the laser diode pump source is in the form of two laser diode arrays, the arrays being positioned so that two respective output beams are emitted therefrom are directed at an angle to the surface of the OPS chip and wherein the two output beams lie in a common plane leaving open a planar path normal to said common plane to permit the beam to circulate in the resonator without interference with the pump beam.