System and method for transverse pumping of laser-sustained plasma

Patent metadata

Field	Value
Publication number	US-9723703-B2
Application number	US-201514675322-A
Country	US
Kind code	B2
Filing date	Mar 31, 2015
Priority date	Apr 1, 2014
Publication date	Aug 1, 2017
Grant date	Aug 1, 2017

Abstract

A laser-sustained plasma light source for transverse plasma pumping includes a pump source configured to generate pumping illumination, one or more illumination optical elements and a gas containment structure configured to contain a volume of gas. The one or more illumination optical elements are configured to sustain a plasma within the volume of gas of the gas containment structure by directing pump illumination along a pump path to one or more focal spots within the volume of gas. The one or more collection optical elements are configured to collect broadband radiation emitted by the plasma along a collection path. Further, the illumination optical elements are configured to define the pump path such that pump illumination impinges the plasma along a direction transverse to a direction of propagation of the emitted broadband light of the collection path such that the pump illumination is substantially decoupled from the emitted broadband radiation.

First claim

What is claimed:

1. A laser-sustained plasma light source comprising:
a pump source configured to generate pumping illumination;
one or more illumination optical elements;
a gas containment structure configured to contain a volume of gas,
wherein the one or more illumination optical elements are configured to sustain a plurality of plasma features along a selected direction within the volume of gas by directing pump illumination along one or more pump paths to a plurality of focal spots arranged along the selected direction within the volume of gas, wherein the plurality of plasma features are sustained simultaneously within the gas containment structure, wherein gas separates two or more of the plasma features;
one or more collection optical elements configured to collect broadband radiation emitted by the plurality of plasma features along a collection path,
wherein the one or more illumination optical elements are configured to define the pump path such that pump illumination impinges the plurality of plasma features along a direction transverse to a primary direction of propagation of the emitted broadband light of the collection path such that the pump illumination is substantially decoupled from the emitted broadband radiation.

2. The light source of claim 1 , wherein the numerical aperture of the pump illumination of the pump illumination path does not overlap with the numerical aperture of the emitted broadband radiation of the collection path.

3. The light source of claim 1 , wherein the one or more illumination optics are configured to sustain the plurality of plasma features, wherein at least some of the plasma features are elongated having a first dimension and a second dimension larger than the first dimension.

4. The light source of claim 3 , wherein the one or more illumination optical elements are configured to direct pump illumination of the pump path along the first dimension of at least some of the elongated plasma features.

5. The light source of claim 3 , wherein the one or more collection optical elements are configured to collect emitted broadband radiation along the second dimension of at least some of the elongated plasma features.

6. The light source of claim 1 , wherein the one or more illumination optical elements are configured to sustain the plurality of plasma features having an elongated shape within the volume of gas by directing pump illumination along one or more pump paths to the plurality of focal spots having an elongated shape within the volume of gas.

7. The light source of claim 6 , wherein the one or more illumination optical elements comprise: a cylindrical lens configured to sustain the plurality of elongated plasma features within the volume of gas by directing pump illumination along one or more pump paths to the plurality of elongated focal spots within the volume of gas.

8. The light source of claim 6 , wherein the one or more illumination optical elements comprise: a cylindrical mirror configured to sustain the plurality of elongated plasma features within the volume of gas by directing pump illumination along one or more pump paths to the plurality of elongated focal spots within the volume of gas.

9. The light source of claim 6 , wherein the one or more illumination optical elements comprise: a plurality of confocal cylindrical mirrors configured to sustain the plurality of elongated plasma features within the volume of gas by directing pump illumination along one or more pump paths to the plurality of elongated focal spots within the volume of gas.

10. The light source of claim 6 , wherein the one or more illumination optical elements comprise: an axicon configured to sustain the plurality of elongated plasma features within the volume of gas by directing pump illumination along one or more pump paths to the plurality of elongated focal spots within the volume of gas.

11. The light source of claim 1 , wherein the one or more illumination optical elements comprise: a plurality of confocal cylindrical mirrors configured to sustain the plurality of plasma features having an elongated shape along a selected direction within the volume of gas by directing pump illumination to the plurality of focal spots arranged along the selected direction within the volume of gas.

12. The light source of claim 11 , wherein the pump source comprise:
a first pump source configured to deliver pump illumination to the plurality of confocal cylindrical mirrors via a first insertion point; and
at least an additional pump source configured to deliver pump illumination to the plurality of confocal cylindrical mirrors via an additional insertion point.

13. The light source of claim 12 , wherein the first pump source and the additional pump source are counter-propagating.

14. The light source of claim 1 , wherein the one or more illumination optical elements comprise: an axicon; and a reflector pipe configured to sustain the plurality of plasma features having an elongated shade within the volume of gas by directing pump illumination along a pump path to the plurality of focal spots having an elongated shape within the volume of gas.

15. The light source of claim 1 , wherein the one or more illumination optical elements comprise: a multi-pass reflector pipe configured to sustain the plurality of plasma features having an elongated shape within the volume of gas by directing pump illumination along a pump path to the plurality of focal spots having an elongated shape within the volume of gas, wherein a first elongated plasma feature is separated from at least a second elongated plasma feature.

16. The light source of claim 15 , wherein the multi-pass reflector pipe includes at least one reflector element being at least partially reflective of the broadband radiation emitted by the plurality of elongated plasma features, wherein the at least one reflect element is configured to direct the broadband radiation emitted by the plurality of elongated plasma features into the plasma in order to pump the plasma via the broadband radiation.

17. The light source of claim 1 , wherein the pump sources comprises: a plurality of optical fiber elements configured to sustain the plurality of plasma features along a selected direction by delivering pump illumination to the plurality of focal spots arranged along the selected direction within the gas, wherein pump illumination from each optical fiber is focused to a different focal spot.

18. The light source of claim 17 , wherein the plurality of plasma features are positioned to form an elongated plasma structure.

19. The light source of claim 1 , wherein the pump source comprises:
a pump source configured to emit pump illumination at a first wavelength and illumination at an additional wavelength different from the first wavelength.

20. The light source of claim 19 , wherein the one or more illumination optical elements comprises:
a dispersive optical element configured to form a first plasma feature by focusing pump illumination of the first wavelength to a first focal spot, wherein the dispersive optical element is further configured to form an additional plasma feature by focusing pump illumination of the additional wavelength to an additional focal spot different from the first focal spot, wherein the first plasma feature and the additional plasma feature are positioned to form an elongated plasma structure.

21. The light source of claim 1 , wherein the pump source comprises:
an adjustable pump source, wherein a wavelength of pump illumin

Assignees

• Kla Tencor Corp

Inventors

• Bezel Ilya
• Shchemelinin Anatoly
• Solarz Richard
• Oh Sebaek
• Derstine Matthew

Classifications

• H01J61/025

  Associated optical elements · CPC title

• H01J65/042 Primary

  by an external electromagnetic field · CPC title

• H05G2/003 Primary

  the plasma being generated from a material in a liquid or gas state · CPC title

• H05G2/008

  involving an energy-carrying beam in the process of plasma generation · CPC title

• H05G2/001

  Production of X-ray radiation generated from plasma · CPC title