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`US008309943B2
`
`(12) United States Patent
`Smith et al.
`
`(10) Patent No.:
`
`(45; Date of Patent:
`
`US 8,309,943 B2
`Nov. 13, 2012
`
`(54)
`
`(75)
`
`LASER—DRIVEN LIGHT SOURCE
`
`Inventors: Donald K. Smith. Boston. MA (US):
`William M. Ilolber. Winchester. MA
`(US); Jeffrey A. Casey, Winchester. MA
`(US)
`
`(73)
`
`Assignee: Energetiq Technology. Inc.. Woburn.
`MA (us)
`
`(“‘)
`
`Notice:
`
`Subject to any disclaimer. t11e term ofthjs
`patent is extended or adjusted under 35
`U.S.(_". 154(1)) by 41 days.
`
`(21)
`
`Appl. No; 137099323
`
`(22)
`
`Filed:
`
`May 3, 2011
`
`(65)
`
`(63)
`
`(51)
`
`(52)
`
`(53)
`
`Prior Publication Data
`
`US 201170204265 Al
`
`Aug. 25. 2011
`
`Related U.S. Application Data
`
`Continuation of application No. 127166.918. tiled on
`.1111. 2. 2008. now Pat. No. 7.989.786. which is El
`continttation-in-part of application No.
`lI)"695,3-48.
`filed o11 Apr. 2. 2007. now Pat. No. 7.786.455. which is
`a cotitinuation-in—parI of application No. 117395.523.
`filed on Mar. 31. 2006. now Pat. No. 7.435.982.
`
`Int. C1.
`1101.! 63/08
`H0511 L94’
`H05B 31/00
`U.S. C1.
`
`(2006.01)
`(2006.01)
`(2006.01)
`250l493.'1:250)'504 R: 25075011;
`25073651315714‘): 315711121: 313)'23l.31
`Field of(.‘lassifieation Search
`25075011,
`250504 R. 365. 493.]; 3157149. 111.21;
`313723131
`
`Sec application tile for complete search liistory.
`
`(56)
`
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`12.-‘"2003 Sate et a].
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`Beck. "Simple 1-’u1se Generator for Pulsing Xenon Arcs with High
`Repetition Rate." Rev. Sci. In.-m'mn.. vol. 45. No. 2. Feb. 1974. pp.
`318-319.
`
`(Cotttiriued)
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`Pr.fmar_i-' E.\'m:::'r:er — Nikita Wells
`(74) .=i:.-‘o-racy. Agem, or Fim: — Proskauer Rose LLP
`
`(57)
`
`ABSTRACT
`
`An apparatus for producing light includes a chamber and an
`ignition source that ionizes a gas within the chamber. The
`apparatus also includes at least one laser that provides energy
`to the ionized gas within the cliamher to produce a high
`briglttness light. The laser can provide a stlbstantially con-
`tinuous amounl of energy to the ionized gas to generate a
`substantially continuous high brightness light.
`
`21 Claims, 17 Drawing Sheets
`
`I
`5
`E
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`
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`
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`
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`1583
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`
`<—1sa
`
`1
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`ASML 1101
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`
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`LI!
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`1510
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`

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`US 8,309,943 B2
`Page 2
`
`US. PATENT DOCUMENTS
`2004.-"D0265 12 Al
`2.-"2004 Otstlbo
`2004.-"0264S 12 Al
`12.-‘"2004 Haftlovc ct al.
`200570167618 Al
`8."2D{}5 1-Ioshino et al.
`201 la"Dl8l I91 Al ‘“
`7f20ll Smith et al.
`
`OH-IF.R PUBI ,lCAl‘lONS
`
`315.-"149
`
`Ca.rlhofl' et al.. “Continuous Optical Discharges at Very High Pres-
`sure.”Plrysim 103C. 198i. pp. 439-447.
`Creiners et ai.. "Evaluation of the Continuous Optical Discharge for
`Spectrochcmical Analysis.” Sfierirocbiiriica Acta. Vol. 40B. No. 4.
`I985. pp. 665-679.
`Iiiedorowicz et a].._ "X-Ray Emission form Laser-Irradiated Gas Puff
`Targets." Apps’. Phys. Len. 62 (22). May 31. 1993. pp. 2778-2780.
`Franzen. "CW Gas Breakdown in Argon Using 10.6» pm I.a.se1‘
`Radiation."AppI.P!rys. Left. vol. 21. No. 2. Jul. l5. 1972. pp. 62-64.
`Generalov ct al.. “Continuous Optical Discharge." ZIJETFPFS. Red.
`11. No. 9. May 5. 1970. pp. 302-304.
`Generalov et al.. "l3.*-:peri1nental lnvestigation of a Continuous Opti-
`cal Discharge." Soviet Plmvics .HITP. vol. 34. No. 4. Apr. I972. pp.
`763-769.
`I-Iecht. “Re£raction“. Optics (l{3‘zi'rd Edmoii). 1998, Chapter 4. pp.
`I00-l0l.
`
`Jeng et .11.. “Theoretical Investigation ofI_aser-Sustained Argon Plas-
`n1as."J. Appi‘. Pig-'5. 60 (7). Oct. 1. 1986, pp. 2272-2279.
`
`Keefer. “Laser-Sustained Plasmas.” Las-er—."ndm.~ed l"t'.:1wiIas and
`AppJ'ic'arions'. published by Marcel Dckker. edited by Radziemski et
`al.. 1989, pp. I69-206.
`Keefer at al.. “Experimental Study of a Stationary Laser-Sustained
`Air Plasma." Joarrmzf qfAppii'ed Physics. vol. 46. No. 3. Mar. i975.
`pp. I080-1083.
`Knzlov et al.. "Radiative Losses by Argon Plasma and the Emissive
`Model of a Continuous Optical i)iscl1a.rge."S-av. Phys. JETP. vol. 39.
`No. 3. Sop. 1974. pp. 463-468.
`Kozlov et al.. "Sustained Optical Discharges in Molecular Gases."
`Soy. Piiys. Tbcii. Phys‘. 49( l l ). Nov. 1979. pp. 1283-1287.
`Moody. “:VIai ntenance ofa Gas Breakdown in Argon Using 10.611 cw
`Radiation.” .."0rrrnar'ojZ41rJpIied P.Fr_vs:'r:.s', vol. 46. N0. 6. Jun. 1975. pp.
`2475-2482.
`Raizer. “Optical Discha.rges.“Sov. Phys. Usp. 23(l 1). Nov. 1980. pp.
`789-806.
`“Super-Quiet Xenon Lamp Super-Quiet Mercury-Xenon l- I6.
`I.a.mp.“ .i'llfl'l'Nafll'(l!SH Prvdim 1’i{foi'mati'0rr. Nov. 2005. pp. 1-16.
`Wilbers et al.. "The Continuum Emission of an Arc Plasma." J.
`Qrram‘. Spectwsc. Radirrt. 7'r'ai:.y"er-. vol. 45. No. 1. 1991. pp. I-10.
`Wilbers et .11., "The VUV Emissivity Ofa Higl1—Pressu.re Cascade
`Argon Arc from 125 to 200 n1n.”.;’. Qztrmt. Suecrmsc. Radiar.
`i'i'aJ:s-
`fer. vol. 45. 1991. pp. 299-308.
`
`“‘ cited by examiner
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`2
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`for ionizing a gas within the chamber. The light source also
`includes at least one laser for providing energy to the ionized
`gas within the chamber to produce a high brightness light.
`In some embodiments. the at least one laser is a plurality of
`lasers directed at a region from which the high brightness
`light originates. In some embodiments, the light source also
`includes at least one optical element for modifying a property
`ofthe laser energy provided to the ionized gas. The optical
`element can be, for example, a lens (e.g.. an aplanatic lens, an
`achromatic lens, a single element lens. and a fresnel lens) or
`mirror (e.g., a coated mirror. a dielectric coated mirror, a
`narrow band mirror. and an ultraviolet transparent ittfmred
`retloeting mirror). In some entbodiments. the optical element
`is one or more fiber optic elements for directing the laser
`energy to the gas.
`The chamber can include an ultraviolet transparent region.
`The chamber or a window in the chamber can include a
`
`material selected from the group consisting of quartz. Supra-
`siltli) quartz (I-Ieraeus Quartz America. I..l..C. Buford. Ga).
`sapphire. Mgl?'2_. diamond, and (Tali? In some embodiments.
`the chamber is a sealed chamber. In some embodintents, the
`chamber is capable of being actively pumped.
`In some
`embodiments,
`the chamber includes a dielectric material
`(e.g.. quartz}. The chamber can be, for example. a glass bulb.
`In some embodiments, the chamber is an ultraviolet transpar-
`ent dielectric chamber.
`
`5
`
`1D
`
`|'\J I.»-
`
`1
`LASER-DRIVEN LIGHT SOURCE
`
`Rl:'iLA'fED APPLICATIONS
`
`This application is a continuation of U .S. Ser. No, I 21166.
`918. filed on Jul. 2, 2008. which is a continuation-in-part of
`U.S. Ser. No. l li'695.348. filed o11Apr. 2. 2007, now U .S. Pat.
`No. 7,786,455. which is a continuation-in-part of U.S. Ser.
`No. lll395.523. filed on Mar. 31. 2006. now US. Pat. No.
`7,435,982, the entire disclosures of which are hereby incor-
`porated by reference herein.
`
`1'-‘II.il .1) O1" TI-II7, INVIi.N'l‘ION
`
`The invention relates to methods and apparants for provid-
`i11g a laser-driven light source.
`
`BACKGROUND OF THE INVENTION
`
`lligh brightness light sources can he used in a variety of
`applications. For example, a high brightness light source can
`be used for inspection, testing or measuring properties asso-
`ciated with semiconductor wafers or materials used in the
`fabrication of wafers (e.g., rcticles and photomasks). The
`electromagnetic energy produced by high brightness light
`sources can. alternatively. be used as a source of illumination
`in a lithography system used in the fabrication of wafers. a
`microscopy system. or a photoresist curing system. The
`parameters (e.g.. wavelength, power level and brightness] of
`the light vary depending upon the application.
`The state of the art in, for example, wafer inspection sys-
`tems involves the use of xenon or mercury arc lamps to
`produce light. The are lamps include an anode and cathode
`that are used to excite xenon or mercury gas located in a
`chamber of the lamp. An electrical discharge is generated
`between the anode and cathode to provide power to the
`excited {e.g.. ionized) gas to sustain the light emitted by the
`ionized gas during operation of the light source. During
`operation. the anode and cathode become very hot due to
`electrical discharge delivered to the ionized gas located
`between the anode and cathode. As a result, the anode andfor
`cathode are prone to wear and may emit particles that can
`contaminate the light source or result in failure of the light
`source. Also. these are lamps do not provide suificient bright-
`ness for some applications, especially in the ultraviolet spec-
`trum. Further. the position of the are can be unstable in these
`lamps.
`Accordingly. a need therefore exists for improved high
`brightness light sources. A need also exists for improved high
`brightness light sources that do 11ot rely on an electrical dis-
`charge to maintain a plasma that generates a high brightness
`light.
`The properties of light produced by many light sources
`[eg.. arc lamps. microwave lamps) are alfected when the light
`passes through a wall of, for example. a chamber that includes
`the location from which the light is emitted.
`Accordingly. a need therefore exists for an improved light
`source whose emitted light is not significantly affected when
`the light passes through a wall of a chamber that includes the
`location from which the light is emitted.
`
`SUMMARY OF TIII}. lNVIiNTlOl*l
`
`The present invention features a light source for generating
`a high brightness light.
`The invention. in one aspect. features a light source having
`a chamber. The light source also includes an ignition source
`
`3t]
`
`40
`
`The gas can he one or more ofa noble gas. Xe. Ar. Ne. Kr.
`He, D1, H3, 02, F2. a metal halide, a halogen. Hg, Cd, Zn. Sn.
`Ga, Fe. Li. Na, an excimer forming gas. air. a vapor, a metal
`oxide, an aerosol, a flowing media, or a recycled media. The
`gas can be produced by a pulsed laser beam that impacts a
`target (e.g.. a solid or liquid) in the chamber. The target can be
`a pool or film of metal. In some embodiments. the target is
`capable of moving. For example. the target may be a liquid
`that is directed to a region from which the high brightness
`light originates.
`In some embodiments. the at least one laser is multiple
`diode lasers coupled into a fiber optic element. In some
`embodiments. the at least one laser includes a pulse or con-
`tinuous wave laser. In some embodiments. the at least one
`laser is an IR laser. a diode laser. a fiber laser. an ytterbium
`laser. a C0: laser. a YAG laser. or a gas discharge laser. In
`some embodiments, the at least one laser emits at least one
`wavelength of electromagnetic energy that
`is
`strongly
`absorbed by the ionized medium.
`The ignition source can be or can include electrodes. an
`ultraviolet ignition source. a capacitive ignition source. an
`inductive ignition source. an R1’ ignition source. a microwave
`ignition source. a flash lamp. a pulsed laser. or a pulsed lamp.
`The ignition source can be a continuous wave (CW) or pulsed
`laser impinging on a solid or liquid target in the chamber. The
`ignition source can be external or internal to the chamber.
`The light source can include at least one optical element for
`modifying a property ofelectromagnetic radiation emitted by
`the ionized gas. The optical element can be. for example, one
`or more mirrors or lenses. In some embodiments. the optical
`element is configured to deliver the electromagnetic radiation
`emitted by the ionized gas to a tool (e.g., a wafer inspection
`tool. a microscope. a metrology tool. a lithography tool. or an
`endoscopic tool ].
`The invention. in another aspect. relates to a method for
`producing light. The method involves ionizing with an igni-
`tion source a gas within a chamber. The method also involves
`providing laser energy to the ionized gas in the chamber to
`produce a high brightness light.
`111 some cmhodilnents, the method also involves directing
`the laser energy through at
`least one optical element for
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`erty of electromagnetic radiation emitted by the ionized
`medium. The optical element can be configured to deliver the
`electromagnetic radiation emitted by the ionized medium to a
`tool [e.g.. a wafer inspection tool, a microscope, a metrology
`tool. a lithography tool. or an endoscopic tool).
`The invention. in another aspect relates to a method for
`producing light. The method involves ionizing with an igni-
`tion source a11 ionizable medium within a chamber. The
`method also involves providing substantially continuous
`laser energy to the ionized medium in the chamber to produce
`a high brightness light.
`In some embodiments. the method also involves directing
`the laser energy through at
`least one optical element for
`modifying a property of the laser energy provided to the
`ionizable medium. The method also can involve actively
`pumping the chamber. In some ernbodinients. the ionizable
`medium is a moving target. The ionizable medium can
`include a solid, liquid or gas. In some embodiments. the
`method also involves directing the high brightness light
`through at least one optical element to modify a property of
`the light. In some embodiments, the method also involves
`delivering the high brightness light emitted by the ionized
`tttedittm to a tool.
`
`modifying a property of the laser energy provided to the
`ionized gas. In some embodiments. the method also involves
`actively pumping the chamber. The ionizable medium can be
`a moving target. In some embodiments. the method also
`involves directing the high brightness light through at least
`one optical element to modify a property ofthe ligu. In some
`embodiments, the method also involves delivering the high
`brightness light emitted by the ionized n1editu11 to a tool {e.g..
`a wafer inspection tool, a microscope. a metrology tool. a
`lithography tool. or an endoscopic tool).
`In another aspect, the invention features a light source. The
`lights source includes a chamber and an ignition source for
`ionizing an ionizable medium within the chamber. The light
`source also includes at least one laser for providing substan-
`tially continuotts energy to the ionized medium within the
`chamber to produce a high brightness light.
`In some embodiments. the at least one laser is a continuous
`wave laser or a high pulse rate laser. In some enibodiments,
`the at least one laser is a high pulse rate laser that provides
`pulses ofcnergy to the ionized rnediurn so the high brightness
`ligt is substantially continuous. In some embodiments, the
`magnitude ofthe high brightness light does not vary by more
`than about 90% during operation. in some embodiments, the
`at least one laser provides energy substantially continuously
`to minimize cooling of the ionized medium when energy is
`not provided to the ionized medium.
`In some embodiments. the light source can include at least
`one optical element (e.g.. a lens or mirror) for modifying a
`property ofthe laser energy provided to the ionized medium.
`"The optical element can be, for example, an aplanatic lens, an
`achnornatic lens, a single element lens, a tresnel lens, a coated
`mirror. a dielectric coated mirror. a narrow band mirror. or an
`ultraviolet transparent infrared reflecting minor. In some
`embodiments. the optical element is one or more fiber optic
`elements for directing the laser energy to the ionizable
`medium.
`In some embodiments. the chamber includes an ultraviolet
`transparent region. In some embodiments, the chamber or a
`window in the chamber includes a quartz material. suprasil
`quartz material. sapphire material. MgF2 material, diamond
`material. or Cal"; material. In some embodiments. the cham-
`ber is a sealed chamber. The chamber can be capable of being
`actively pumped.
`In some embodiments,
`the chamber
`includes a dielectric material (e.g.. quartz). In some embodi-
`ments, the chamber is a glass bulb. In some embodiments, the
`chamber is an ultraviolet transparent dielectric chamber.
`The ionizable medium can be a solid. liquid or gas. The
`ionizable medium can include one or more o fa noble gas. Xe.
`Ar, Ne. Kr. He. D2, H2, 02, F3. a metal halide, a halogen. Hg,
`Cd, Zn, Sn, Ga, Fe, Li, Na. an excimer forming gas, air, a
`vapor. a metal oxide, an aerosol. a flowing media, a recycled
`media. or an evaporating target. in some embodiments, the
`ionizable medium is a target in the chamber and the ignition
`source is a pulsed laser that provides a pulsed laser beam that
`strikes the target. The target can be a pool or film of metal. In
`some embodiments. the target is capable of moving.
`In some embodiments, the at least one laser is multiple
`diode lasers coupled into a fiber optic element. The at least
`one laser can emit at least one wavelength of electromagnetic
`energy that is strongly absorbed by the ionized medium.
`The ignition source can be or can include electrodes. an
`ultraviolet ignition source. a capacitive ignition source. an
`inductive ignition source, an RF ignition source, a microwave
`ignition source, a flash lamp. a pulsed laser, or a pulsed lamp.
`The ignition source can be extemal or internal to the chamber.
`[11 some enibodiments. the light source incltttles at least one
`optical element (eg. a mirror or lens) for modifying a prop-
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`The invention, in another aspect, features a light source
`having a chamber. The light source includes a first ignition
`means for ionizing an ionizable medium within the chamber.
`The light source also includes a means for providing substan-
`tially continuous laser energy to the ionized medium within
`the cha mb er.
`The invention, in another aspect, features a light source
`having a chamber that includes a neflective surface. The light
`source also includes an ignition source for ionizing a gas
`within the chamber. The light source also includes a reflector
`that at least substantially reflects a first set of predefined
`wavelengths of electromagnetic energy directed toward the
`reflector and at least substantially allows a second set of
`predefined wavelengths of electromagnetic energy to pass
`through the reflector. ’]he light source also includes at least
`one laser (e.g.. a continuous-wave fiber laser) external to the
`chamber for providing electromagnetic energy to the ionized
`gas within the chamber to produce a plasma that generates a
`high brightness light. A conti11uous—wave laser emits radia-
`tion continuously or substantially continuously rather than in
`short bursts. as in a pulsed laser.
`In some embodiments. at least one laser directs a first set of
`wavelengths of electromagnetic energy through the reflector
`toward the reflective surface (e.g.. inner surface) ofthe cham-
`ber and the reflective surface directs at least a portion of the
`first set of wavelengths of electromagnetic energy toward the
`plasma. In some embodiments. at least a portion of the high
`brightness light is directed toward the reflective surface ofthe
`chamber, is reflected toward the reflector, and is reflected by
`the reflector toward a tool. In some embodiments, at least one
`laser directs a first set of wavelengths of electromagnetic
`energy toward the reflector. the reflector reflects at least a
`portion of the first wavelengths of electromagnetic energy
`towards the reflective surface ofthe chamber, and the reflec-
`tive surface directs a portion ofthe first set ofwavelengths of
`electromagnetic energy toward the plasma.
`In some embodiments, at least a portion of the high bright-
`ness light is directed toward the reflective surface of the
`chamber, is reflected toward the reflector, and passes through
`the reflector toward an output of the light source. In some
`embodiments. the light source comprises a microscope, ultra-
`violet microscope, wafer inspection system, reticle inspec-
`tion systcni or lithography system spaced relative to the ottt-
`put of the light source to receive the high brightness light. In
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`sortie embodiments, a portion ofthe high brightness light is
`directed toward the reflective surface of the chamber,
`is
`reflected toward the reflector. and electromagnetic energy
`comprising the second set ofpredefined wavelengths ofclcc-
`tromagnetic energy passes through the reflector.
`The chamber ofthe light source can include a window. In
`sortie embodiments, the chamber is a sealed chamber. In some
`embodiments, the reflective surface of the chamber com-
`prises a curved shape, parabolic shape. elliptical shape.
`spherical shape or aspherical shape. In some embodiments.
`the chamber has a reflective inner surface. 111 some embodi-
`
`ments. a coating or film is located on the outside of the
`chamber to produce the reflective surface. In some embodi-
`ments. a coating or film is located on the inside ofthe chamber
`to produce the reflective surface. In some embodiments. the
`reflective surface is a structure or optical element that is
`distinct from the imicr surface of the chamber.
`
`The light source can include an optical element disposed
`along a path the electromagnetic energy from the laser travels.
`In some enibodiments. the optical element is adapted to pro-
`vide electromagnetic energy front the laser to the plasma over
`a large solid angle. In some embodinrents. the reflective sur-
`face of the chamber is adapted to provide electromagnetic
`energy from the laser to the plasma over a large solid angle. In
`some embodiments, the reflective surface of the chamber is
`adapted to collect the high brightness light generated by the
`plasma over a large solid angle. In some embodiments. one or
`more of the reflective surface, reflector and the window
`include {e.g.. are coated or include) a material to filter pre-
`defined wavelengths (e.g., infrared wavelengths of electro-
`magnetic energy] of electromagnetic energy.
`The invention. in another aspect. features a light source that
`includes a chamber that has a reflective surface. The light
`source also includes an ignition source for ionizing a gas
`within the chamber. The light source also includes at least one
`laser external to the chamber for providing electromagnetic
`energy to the ionized gas within the chamber to produce a
`plasma that generates a l1igl1 brightness light. The light source
`also includes a reflector positioned along a path that the
`elcctroniagnetic energy travels from the at least one laser to
`the reflective surface of the chamber.
`In some embodiments. the reflector is adapted to at least
`substantially reflect a first set of predefined wavelengths of
`electromagnetic energy directed toward the reflector and at
`least substantially allow a second set of predefined wave-
`lengths of electromagnetic energy to pass through the reflec-
`for.
`
`The invention. in another aspect. relates to a method for
`producing light. The method involves ionizing with an igni-
`tion source a gas within a chamber that has a reflective sur-
`face. The method also involves providing laser energy to the
`ionized gas in the chamber to produce a plasma that generates
`a high brightness light.
`In some embodiments. the method involves directing the
`laser energy comprising a first set ofwavelengths of electro-
`magnetic energy through a reflector toward the reflective
`surface of the chamber. the reflective surface reilecting at
`least a portion of the first set of wavelengths of electromag-
`netic energy toward the plasma. In some embodiments. the
`method involves directing at least a portion of the high bright-
`ness light toward the reflective surface of the chamber which
`is reflected toward the reflector and is reflected by the reflec-
`tor toward a tool.
`
`In some embodiments. the method involves directing the
`laser energy comprising a first set ofwavelengths of electro-
`magnetic energy toward the reflector. the reflector reflects at
`least a portion of the first wavelengths of electromagnetic
`
`energy toward the reflective surface of the chamber. the
`reflective surface directs a portion of the first set of wave-
`lengths ofelectroma gnetic energy toward the plasma. In some
`ernbodiments. the method involves directing a portion of the
`high brightness light
`toward the reflective surface of the
`chamber which is reflected toward the reflector and, electro-
`magnetic energy comprising the second set of predefined
`wavelengths of electromagnetic energy passes through the
`reflector.
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`The method can involve directing the laser energy through
`an optical element that modifies a property ofthe laser energy
`to direct the laser energy toward the plasma over a large solid
`angle. In some embodiments. the method involves directing
`the laser energy through an optical element that modifies a
`properly of the laser energy to direct the laser energy toward
`the plasma over a solid angle of approximately 0.012 stem-
`dians. In seine embodiments. the method involves directing
`the laser energy through an optical elenrent that modifies a
`property of the laser energy to direct the laser energy toward
`the plasma over a solid angle of approximately 0.048 stern-
`dians. In some embodiments. the method involves directing
`the laser energy through an optical element that modifies a
`property of the laser energy to direct the laser energy toward
`the plasma over a solid angle of greater than about 2:‘: (about
`6.28) steradians. In some embodiments, the reflective surface
`of the chamber is adapted to provide the laser energy to the
`plasma over :1 large solid angle. In some embodiments. the
`refiective surface of the chamber is adapted to collect the high
`brightness light generated by the plasma over a large solid
`angle.
`The invention. in another aspect. relates to a method for
`producing light. The method involves ionizing with an igni-
`tion source a gas within a chamber that has a reflective sur-
`face. The method also involves directing electromagnetic
`energy from a laser toward a reflector that at least substan-
`tially reflects a first set of wavelengths of electromagnetic
`energy toward the ionized gas 111 the chamber to produce a
`plasma that generates a high brightness light.
`In some embodiments. the electromagnetic energy from
`the laser first is reflected by the reflector toward the reflective
`surface of the chamber. In some ernbodintents. the electro-
`magnetic energy directed toward the reflective surface of the
`chamber is reflected toward the plasma. In some embodi-
`ments. a portion ofthe high brightness light is directed toward
`the reflective surface of the chamber, reflected toward the
`reflector and passes through the reflector.
`In some embodiments, the electromagnetic energy from
`the laser first passes through the reflector and travels toward
`the reflective surface of the chamber. In sonre embodiments.
`the electromayetic energy directed toward the reflective sur-
`face of the chamber is reflected toward the plasma. I11 sotne
`embodiments, a portion of the high brightness light is directed
`toward the reflective surface of the chamber, reflected toward
`the reflector and reflected by the reflector.
`The invention. in another aspect, features a light source that
`includes a chamber having a reflective surface. The light
`source also includes a means for ionizing a gas within the
`chamber. The light source also includes a means for at least
`substantially reflecting a first set ofpredeflncd wavelengths of
`electromagnetic energy directed toward the reflector and at
`least substantially allowing a second set of predefined wave-
`lengths ofelectroniagnetic energy to pass tfuough the reflec-
`tor. The light source also includes a means for providing
`electromagnetic energy to the ionized gas within the chamber
`to produce a plasma that generates a high brightness light.
`The invent ion. in arm ther aspect, features a light source that
`includes a sealed chamber. The light source also includes an
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`US 8,309,943 B2
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`ignition source for ionizing a gas within the chamber. The
`light source also includes at least one laser external to the
`sealed chamber for providing electromagnetic energy to the
`ionized gas within the chamber to produce a plasma that
`generates a high brightness light. The light source also
`includes :1 curved reflective surface disposed external to the
`sealed chamber to receive at leas a portion of the l1igl1 bright-
`ness light emitted by the sealed chamber and reflect the high
`brightness light toward an output ofthe light source.
`In some embodiments. the light source includes an optical
`element disposed along a path the electromagnetic energy
`from the laser travels. In some embodiments.
`the sealed
`chamber includes a support element that locates the sealed
`chamber relative to the curved reflective surface. In some
`
`embodiments. the sealed chamber is a quartz bulb. In some
`embodiments,
`the light source includes a second curved
`reflective surface disposed internal or extemal to the sealed
`chamber to receive at least a portion of the laser electro1nag-
`netic energy and focus the electromagnetic energy on the
`plasma that generates the high brightness light.
`The invention. in another aspect, features a limit source that
`includes a sealed chamber and an ignition source for ionizing
`a gas within the chamber. The light source also includes at
`least one laser external to the sealed chamber for providing
`electromagnetic energy. The light source also includes a
`curved reflective surface to receive and reflect at least a por-
`tion of the electromagnetic energy toward the ionized gas
`within the chamber to produce a plasma that generates a high
`brightness light. the curved refiective surface also receives at
`least a portion of the high brightness light emitted by the
`plasma and reflects the high brightness light toward an output
`of the light source.
`the curved reflective surface
`In sotne embodiments,
`focuses the electromagnetic energy on a region in the c