Ultra-High Power Single Mode Fiber Laser System With Non-Uniformly Configured Fiber-to-Fiber Rod Multimode Amplifier

Patent metadata

Field	Value
Publication number	US-2016285228-A1
Application number	US-201414199638-A
Country	US
Kind code	A1
Filing date	Mar 6, 2014
Priority date	Mar 6, 2013
Publication date	Sep 29, 2016
Grant date	—

Abstract

A high power single mode (“SM”) laser system includes an amplifier configured with a monolithic fiber to rod fiber waveguide which is structured with a multimode (“MM”) core and at least one cladding surrounding the core. The MM core is configured with a small diameter uniform input region receiving and guiding a SM signal light, a mode-transforming frustoconical core region expanding outwards from the input region and a relatively large diameter uniform output portion. The high power laser system is further structured with a MM pump light delivery fiber having a numerical aperture NA 2 , which is at most equal to that one of the output core portion. The amplifier and pump light output fiber traverse an unconfined delivery cable and terminate upstream from a mirror which is configured to focus the incident pump light into the core of the amplifier in a counter-propagating direction. The mirror is further structured with an opening aligned with the optical axis of the amplifier and configured to provide a lossless passage of amplified signal light in a propagating direction.

First claim

1 . An ultra-high power fiber laser system, comprising:
a base laser console enclosing:
a single mode (“SM”) seed source emitting SM signal,
a SM passive fiber receiving and guiding the SM signal light in a propagating direction,
a fiber pigtailed laser diode pump outputting pump light, and
a utility assembly configured to support a laser system operation including control and safety electronics;
an optical laser head spaced from the base laser console; at least one flexible delivery cable extending between the console and laser head; a fiber to fiber rod booster amplifier having a major length traversing the delivery cable and provided with an output end which is directly coupled to the laser head, the booster amplifier being configured with an all doped multimode (MM″) monolithic core configured with at least: a uniformly dimensioned input core region coupled to a downstream end of a core of the SM passive fiber, the cores of respective input core region and SM fiber being configured with respective mode field diameters (“MFD”) which substantially match one another, a mode transforming core region expanding from the input core section and configured to expand the MFD of the SM while preventing an excitation of high order modes, an output amplifying uniformly dimensioned core region extending from the mode transforming core region and having a diameter larger than that of the input core region, wherein the booster fiber amplifier is operative to emit system output light in substantially the SM with a power varying in a kW-MW range; a mirror mounted in the laser head and spaced downstream from the booster amplifier; and a least one MM pump light delivery fiber extending through the delivery cable and guiding the pump light so that the pump light is incident on the mirror configured to redirect the pump light in a counter-propagating direction to end-pump the MM core of the booster amplifier.

2 . An ultra-high power single mode (“SM”) booster stage, comprising:
a fiber to fiber rod amplifier extending through free space and configured with a multimode (“MM”) non-uniformly dimensioned core, which guides and amplifies signal light, and a cladding coextending with and surrounding the core;
a MM pump light output fiber extending through free space and including a terminal region coextending with a terminal region of the amplifier;
a laser head receiving the terminal regions of respective amplifier and pump light output fibers; and
a mirror provided in the laser head and having a central opening, which is dimensioned to be traversed by the amplified signal light in the propagating direction, and the mirror being configured to redirect the pump light incident thereon in a counter-propagating direction so that the pump light is coupled into the core of the amplifier.

3 . The booster stage of claim 2 further comprising an unconfined delivery cable traversed by the amplifier and pump light output fiber, the terminal regions of respective output fiber and amplifier extending substantially parallel to one and projecting over a downstream end of the delivery cable into the laser head.

4 . The booster stage of claim 2 , wherein the MM core is doped with light emitters and structured with:
a small diameter uniform input region configured to guide a single mode (“SM”) signal light along a fiber part of the amplifier in a propagating direction, and a mode transforming region bridging the input and output portions.

5 . The booster stage of claims 4 , wherein the MM core further includes a large diameter uniform output region extending from the mode transforming region and guiding the SM signal light along the terminal region of the amplifier,

6 . The booster stage of claims 2 through 4 further comprising:
a buffer fused to the terminal regions of respective amplifier and output fiber and mounted to the laser head, and
a sleeve enclosing at least a part of the terminal regions of respective amplifier and pump fiber, buffer and mirror and coupled thereto, wherein the mirror and terminal regions of respective amplifier and output fiber are adjustable relative to one another so as to couple the pump light into the MM core of the amplifier while outputting the amplified SM signal light through the opening in the propagating direction

7 . The booster stage of claims 2 and 3 , wherein a numerical aperture of the pump light is at most equal to a numerical aperture of the output core region of the amplifier.

8 . The booster stage of claim 2 , wherein the mirror is spherical or aspherical.

9 . The booster stage of claims 2 through 5 further comprising an air supply system operative to introduce an air stream into the sleeve so as to carry out impurities out of the sleeve as the air stream exits through the hole of the mirror.

10 . The booster stage of claim 2 further comprising an actuator operative displace the mirror and the terminal regions of respective amplifier and delivery fiber in XYZ planes relative to one another.

11 . The booster stage of claim 2 , wherein the fiber to fiber rod amplifier is continuous between input and output terminal regions thereof.

12 . The booster stage of claim 2 , wherein the fiber to fiber rod amplifier includes fiber and fiber rod parts fused together.

13 . The booster stage of claims 2 through 5 , wherein the sleeve includes two cup-shaped parts insertable one into another and coupled to one another so as to provide an impurities-fee interior of the laser head.

14 . An ultra-high power fiber laser system comprising:
a seed laser source configured to deliver a signal; the booster stage of any one of claims 2 - 12 .

15 . The ultra-high power fiber laser system of claim 14 further comprising a housing enclosing a system operative to generate a high harmonic of a fundamental frequency of the amplified SM signal light, the system being configured with a housing optically and mechanically coupled to the laser head at a distance from the terminal regions of respective amplifier and pump light output fiber.

16 . The ultra-high power fiber laser system of claim 15 , wherein the laser head and housing are configured with respective passages aligned with the opening of the mirror and guiding the amplified signal light in the propagating direction from the laser head into the housing.

17 . The ultra-high power fiber laser system of claim 14 further comprising a main console spaced from the laser head and housing the seed laser source, the seed source being provided with a SM passive seed output fiber fused to an upstream region of the amplifier within the main console, the seed output fiber being provided with a core configured with a mode field diameter which substantially matches that one of the input region of the MM core of the amplifier.

18 . The ultra-high power fiber laser system of claim 17 further comprising a utility assembly enclosed within the main console and configured to support a laser system operation, the utility assembly including control and safety electronics.

19 . The ultra-high power fiber laser system of claim 17 further comprising a cooling system configured to reduce thereto-dynamic stresses produced by the signal and pump lights within the amplifier, the cooling system being configured with an outer layer of polymeric material coated upon an outer surface of the amplifier and capable of withstanding a temperature of up to a several hundred ° C.

20 . The ultra-high power fiber laser system of claim 19 , wherein the cooling system

Assignees

• Gapontsev Valentin
• Samartsev Igor
• Yagodkin Dimitri
• Ipg Photonics Corp

Inventors

• Gapontsev Valentin
• Samartsev Igor
• Yagodkin Dimitri

Classifications

• H01S3/094038

  End pumping · CPC title

• H01S3/0407

  Liquid cooling, e.g. by water · CPC title

• H01S3/094003

  the pumped medium being a fibre · CPC title

• H01S3/06754 Primary

  Fibre amplifiers (H01S3/06708 takes precedence) · CPC title

• H01S3/06729

  Peculiar transverse fibre profile · CPC title