IPR2015-01377
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`UNITED STATES PATENT AND TRADEMARK OFFICE
`_____________
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`BEFORE THE PATENT TRIAL AND APPEAL BOARD
`_____________
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`ASML NETHERLANDS B.V., EXCELITAS TECHNOLOGIES CORP., AND
`QIOPTIQ PHOTONICS GMBH & CO. KG,
`Petitioners
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`v.
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`ENERGETIQ TECHNOLOGY, INC.,
`Patent Owner
`_____________
`
`Case IPR2015-01377
`U.S. Patent No. 7,435,982
`_____________
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`DECLARATION OF DONALD K. SMITH, PH.D.
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`Energetiq Ex. 2016, Page 1, IPR2015-01377
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`UNITED STATES PATENT AND TRADEMARK OFFICE
`_____________
`
`BEFORE THE PATENT TRIAL AND APPEAL BOARD
`_____________
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`ASML NETHERLANDS B.V., EXCELITAS TECHNOLOGIES CORP., AND
`QIOPTIQ PHOTONICS GMBH & CO. KG,
`Petitioners
`
`v.
`
`ENERGETIQ TECHNOLOGY, INC.,
`Patent Owner
`_____________
`
`Case IPR2015-01377
`U.S. Patent No. 7,435,982
`_____________
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`DECLARATION OF DONALD K. SMITH, PH.D.
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`Energetiq Ex. 2016, Page 1, IPR2015-01377
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`I, Donald K. Smith, Ph.D., hereby declare as follows:
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`I.
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`INTRODUCTION
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`1.
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`I am the President of Energetiq Technology, Inc. (“Energetiq”), which
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`has its principal place of business at 7 Constitution Way, Woburn, MA 01801. I
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`have worked at Energetiq in this capacity since 2004.
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`2.
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`I am a named inventor on United States Patent Nos. 8,525,138 (the
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`“’138 patent”), 7,435,982 (the “’982 patent”), 8,309,943 (the “’943 patent”) and
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`7,786,455 (the “’455 patent).
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`3.
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`I submit this declaration in support of Energetiq’s Patent Owner
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`Response in connection with inter partes review proceedings IPR2015-01368,
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`IPR2015-01277, IPR2015-01279, IPR2015-01300, IPR2015-01303, and
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`IPR2015-01377. I have personal knowledge of the matters discussed below
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`unless otherwise noted. If called upon as a witness, I could and would
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`competently testify to the statements made herein.
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`4.
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`I received my Bachelor of Science in Physics from Davidson College
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`in 1975, my M.S. in in electrical engineering from the University of Wisconsin in
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`1976, and my Ph.D. in Electrical Engineering from the University of Wisconsin in
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`1980. I have authored more than ten publications in peer reviewed scientific
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`journals and am an inventor on more than 40 United States Patents and additional
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`related foreign patents in the fields of vacuum technology, instrumentation,
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`turbomolecular pumps, ion trap mass spectrometers, plasma sources for etching
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`and deposition, plasma-based reactive gas sources (such as ozone generators,
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`atomic fluorine generators and atomic oxygen sources), plasma-based light
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`sources, plasma devices and plasma chemical vapor deposition reactors. I have
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`more than 35 years of professional experience in research and development in the
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`areas of plasma physics and power electronics. I have 12 years of experience with
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`inductively driven pulsed plasma light sources for EUV and DUV applications
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`and patents on these devices. I have more than 10 years of experience in the
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`research, design and functionality of high brightness laser-driven light sources
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`such as those at issue in this proceeding. My curriculum vitae is attached hereto
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`as Exhibit 2026.
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`5. During my career spanning over 35 years, I have held many positions
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`relating to plasma physics, including as a Research Scientist at the University of
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`Wisconsin for one year and for 7 years at the MIT Plasma Fusion Center. In
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`1988, I co-founded and served on the board of directors and as Vice President of
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`Advanced Technology for Applied Science and Technology, Inc., ASTEX,
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`developing plasma devices and reactive gas generators for semiconductor
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`processing and chemical vapor deposition of diamond. Many tens of thousands of
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`the products developed by me and by my team at ASTEX have been and continue
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`to be installed in semiconductor fabs worldwide. On the strength of these
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`products, ASTEX became a successful public company and was acquired by MKS
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`Instruments in 2001. I served as Vice-president and Chief Technology Officer at
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`MKS between 2000 and 2004, when my colleagues and I founded Energetiq
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`Technology, Inc.
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`II. MATERIALS REVIEWED
`In preparing this declaration, I reviewed and considered the materials
`6.
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`listed in Appendix A to this declaration. In addition, I reviewed the petitions,
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`institution decisions, and supporting affidavits of Dr. Eden for each inter partes
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`review proceeding, i.e. numbers IPR2015-01368, IPR2015-01277, IPR2015-
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`01279, IPR2015-01300, IPR2015-01303, and IPR2015-01377.
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`III. OVERVIEW OF ENERGETIQ AND ITS PATENTED
`TECHNOLOGY
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`7. Energetiq is a leading developer and manufacturer of ultra-bright
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`broadband light sources that enable the manufacture and analysis of nano-scale
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`structures and products. Energetiq’s light source products are based on
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`technology that generates high brightness light with high reliability, high stability,
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`and long life, all in a compact package. Energetiq’s light sources are used for
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`analytical spectroscopy, microscopy, and sensing in the life-sciences; lithography,
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`metrology, inspection and photoresist development in semiconductor
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`manufacturing; and for a variety of applications where synchrotron radiation and
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`traditional arc-lamps have commonly been used.
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`For at least a decade prior to the invention, semiconductor
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`8.
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`manufacturing equipment used xenon or mercury arc lamps to produce light for
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`use in wafer inspection, metrology and lithography systems. These lamps
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`included an anode and cathode to generate an electrical discharge to provide
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`power to a gas to generate and sustain a plasma which emitted light—they did not
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`use lasers. Yet, arc lamps suffered from a number of shortcomings, including
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`instability of the arc, undesirably short time to failure, and limits on how bright
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`they could get, which severely constrained the accuracy and efficiency of the
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`semiconductor manufacturing equipment that used them. In particular, the
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`spectral brightness of xenon and mercury arc lamps (ordinarily in the range of
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`about 1 to 9 mW/mm2-sr-nm) was limited by the maximum current density. (See
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`M. W. P. Cann, Light Sources in the 0.15-20-μ Spectral Range, Vol. 8 No. 8
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`Applied Optics 1645, 1658, Fig. 9 (1969) (Ex. 2072); (Solarz at 1:34-43 (Ex.
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`2073).) If the current density was too high, it would melt the electrodes.
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`9. Thus, for many years, the necessary improvements in semiconductor
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`manufacturing tools had to come through steady improvements in components
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`other than the light source, such as in the optics for collecting the light and the
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`sensors for detecting and measuring light, rather than from the ability to deliver
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`more light into smaller places. However, over time, the semiconductor industry
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`eventually demanded improvements in the brightness level of light sources
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`beyond that which could be met by traditional arc lamps.
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`10. For instance, in 2005, Energetiq was approached by an industry leader
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`to see whether Energetiq could use a plasma to develop a high brightness light
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`source. The industry required light that was at least many times higher brightness
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`than that of existing arc lamps. Petitioner ASML agrees that “[s]ignificant . . .
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`brightness improvements” are necessary over arc lamps. (U.S. Pub. No. US
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`2013/0329204 A1 at ¶ 0008 (Ex. 2009).) Energetiq’s patented Laser Driven Light
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`Source technology delivers a light source for these applications that provides
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`brightness that is greater than Mercury or Xenon arc lamps.
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`11.
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`In particular, Energetiq’s patented technology provides a light source
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`that does not rely on an electrical discharge to sustain a plasma, but instead uses a
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`laser to sustain a plasma under particular conditions to produce a high brightness
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`light for semiconductor manufacturing applications, as shown below:
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`12. By way of brief non-limiting summary, Energetiq’s patented laser-
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`driven light source technology operates by providing, to a gas disposed within a
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`pressurized chamber, laser energy (e.g., at a wavelength within 10 nm of a strong
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`absorption line of the gas). The laser energy sustains a plasma, which produces a
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`plasma-generated light (broadband output). The light of Energetiq’s laser-driven
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`light source technology offers improved characteristics over light generated by
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`earlier light sources, including, for example, higher brightness, broader
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`wavelength range, and significantly longer operating life. For example, an
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`experiment described in the patent showed a brightness of 8 to 18W/(mm2-sr) over
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`the 200-400 nm wavelength band, which is equivalent to a spectral brightness of
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`40 to 90 mW/(mm2-sr-nm)—i.e., four to ten times the brightness of existing
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`mercury and xenon arc lamps. (See, e.g., ‘138 Patent at Fig. 3.)
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`IV. DEFINITION OF PERSON OF ORDINARY SKILL IN THE ART
`I believe that the level of ordinary skill in the art is a master of science
`13.
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`degree in physics, electrical engineering or an equivalent field, and 4 years of
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`work or research experience in plasmas and a basic understanding of lasers; or a
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`Ph.D. degree in physics, electrical engineering or an equivalent field and 2 years
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`of work or research experience in plasmas and a basic understanding of lasers.
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`14. The main difference between Energetiq’s definition and Petitioners’
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`(adopted in the Institution Decision) is that Petitioners definition requires
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`expertise in lasers—knowledge that the active workers in the field did not have.1
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`Energetiq’s definition is fully supported, taking into account the experience of
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`1 I understand that Petitioners proposed definition is “a Ph.D. in physics, electrical
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`engineering, or an equivalent field, and 2–4 years of work experience with lasers
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`and plasma, or a master’s degree in physics, electrical engineering, or an
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`equivalent field, and 4–5 years of work experience with lasers and plasma.” ‘138
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`Petition at 3; ‘943 Petition at 3.
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`active workers in the field, and further informed by other pertinent factors that
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`determine the level of skill of an ordinary artisan.
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`A. Active Workers In The Field And The Inventor
`15. Energetiq’s R&D staff at the time of the invention typifies the
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`educational level of active workers in the field. At the time of the invention,
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`when they were hired, 4 out of 7 individuals in Energetiq’s R&D staff had a basic
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`understanding of lasers, which is consistent in scope with Energetiq’s proposed
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`definition—the rest had no experience in lasers. None had the lasers expertise
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`Petitioners propose.
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`B. Problems In The Art, Prior Art Solutions, Rapidity with Which
`Innovations are Made, and Sophistication of the Technology
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`16. The problems encountered in the art included the need for a high
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`brightness light sources for applications such as semiconductor manufacturing.
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`(See, e.g., ’138 patent, at 1:38-62.) Prior art solutions used by ordinary artisans
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`consisted of arc lamps which used electrodes to excite gas in a chamber and
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`produce light – they did not use lasers. Energetiq’s invention enabled the sale of
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`the first commercial laser driven light source—a market that did not exist prior to
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`the invention. Innovations had been slow and incremental, consisting of
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`improvements to existing arc lamps. (Id.) Thus, requiring laser expertise—as
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`proposed by Petitioners—is incorrect and unsupported.
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`V. OVERVIEW OF GÄRTNER
`17. Gärtner is a 1985 French patent application that describes an
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`incomplete system which appears to relate to a radiation source for optical
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`devices.
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`18. As far as I can determine, Gärtner discloses technology that was never
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`developed into a commercial product. Indeed, Gärtner is so far removed from
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`mainstream knowledge that it was unknown to me, and had never been cited by
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`the Patent Office, until Petitioners identified it to Energetiq in the heat of this
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`dispute. Since then, the Patent Office has issued two of Energetiq’s patents with
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`Gartner in front of it.
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`19. Gärtner describes using a CO2 laser to try to generate a plasma
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`discharge. It is patentably important that Gärtner uses a CO2 laser, because while
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`Gärtner does not expressly disclose its wavelength, it is well-known that CO2
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`lasers produce energy at a wavelength between 9,400 and 10,600 nm—which far
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`exceeds the wavelength ranges contemplated by Energetiq’s patents (e.g., within
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`10 nanometers of certain strong absorption lines of xenon at 980 nm, 895 nm, 882,
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`nm, or 823 nm).
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`20. Gärtner does not describe or suggest using any other laser, let alone a
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`short wavelength laser, to sustain a plasma. The wavelength is important to the
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`invention – this is not a technology where one would just swap one type of laser
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`for any other type, where wavelength is irrelevant. At the time of the invention,
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`those of ordinary skill would not have expected the results Energetiq obtained by
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`using a short wavelength laser.
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`VI. OPINIONS REGARDING CHALLENGED CLAIMS IN THE ’138
`PATENT
`A. Claim Interpretation of “Light”
`Independent claim 1 recites the term “light.” I understand that the
`21.
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`Board has construed the term to mean “electromagnetic radiation in the ultraviolet
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`(“UV”), extreme UV, vacuum UV, visible, near infrared, middle infrared, or far
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`infrared regions of the spectrum, having wavelengths within the range of 10 nm to
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`1,000 μm.” While this construction is a fair start, it is my opinion that the term
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`“light” should more properly be construed to mean “electromagnetic energy.”
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`However, my opinions regarding the challenged claims do not turn on the
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`meaning of the term “light,” and I am applying the adopted construction where
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`appropriate throughout this declaration. But, while the Board adopted this
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`construction here, in other parallel IPR proceedings, it adopted a different
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`construction with wavelength ranges as proposed by Petitioners. That
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`construction is wrong in my view.
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`B. Claim Interpretation of “Sustain”
`22. The term “sustain” is used in the claims to contrast the behavior of the
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`plasma, from other terms relating to the plasma, such as “generate” or “initiate.”
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`An illustrative use of this term appears in claim 1, which states: “[a] laser
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`configured to provide energy … to sustain a plasma…” (’138 patent, claim 1
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`(‘1368 IPR, Ex. 1001).) The ’138 patent discusses that “the light source 700
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`includes an ignition source…that, for example, generates an electrical discharge
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`in the chamber 728…to ignite the ionizable medium. The laser source 704 then
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`provides laser energy to the ionized medium to sustain the plasma 732 which
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`generates the high brightness light 736.” (Id. at 20:64-21:4 (emphases added)
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`(‘1368 IPR, Ex. 1001).)
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`23. The distinction between “igniting” or “generating” a plasma and
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`“sustaining” a plasma is brought into sharper focus with reference to other
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`embodiments in the ’138 patent, in which laser energy is both “igniting” and
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`“sustaining” the plasma. In those instances, each term, i.e., ‘ignite’ and ‘sustain,’
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`has independent meaning with respect to the effect that the laser is having on the
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`plasma. See id. at 20:58-62 (“The laser beam 724 passes through the chamber
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`728…where the plasma 732 exists (or where it is desirable for the plasma 732 to
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`be generated by the laser 724 and sustained)…[T]he ionizable medium is ignited
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`by the laser beam 724.”). Similarly, claim 1 requires “an ignition source” and a
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`“laser…to sustain a plasma within the chamber…” (Id. at claim 1.)
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`24.
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`I believe that an ordinary artisan would understand that to “sustain a
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`plasma” means to maintain the plasma without interruption. Petitioners’ expert
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`acknowledges he understood the term “sustain” to mean “to maintain the
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`existence of” such that the “plasma would continue to exist.” (Eden Tr. 66:16-19;
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`68:18-21 (Ex. 2006).) This understanding is also reflected in common technical
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`references in the field. (See, e.g., Keefer at 169 (“With the advent of continuous,
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`high-power carbon dioxide lasers, it became possible to sustain a plasma in a
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`steady-state…”) (Ex. 2082).)
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`25. The term “laser sustained plasma” is frequently used in the art to
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`describe a plasma that generates steady-state light output, in contrast to plasma
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`sources that exhibit other modes of operation, such as “pulsed” plasmas existing
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`only transiently, and to which the term sustain would not be not applied. (See id.
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`at 172 (“High-energy pulsed lasers can generate plasma breakdown directly within
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`a gas that results in a transient expanding plasma similar to an explosion.”) (Ex.
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`2082).
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`26. The customary and ordinary meaning of the term is also reflected in
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`and consistent with dictionary definitions. Webster’s Third New International
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`Dictionary (2002) defines “sustain” to mean “to cause to continue (as in existence
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`or a certain state or in force or intensity): to keep up esp. without interruption,
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`diminution, or flagging : maintain.” (Webster’s Third New Int’l Dict. of the
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`English Language, Unabridged, “Sustain,” 2304 (2002) (Ex. 2023); see also, The
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`Merriam-Webster Dictionary 722 (2004) (sustain, “to keep going: prolong”) (Ex.
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`2024); The American Heritage Dictionary of the English Language 1744 (4th ed.
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`2006) (sustain, “To keep in existence; maintain.”) (Ex. 2025).) Thus, I believe
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`that “sustain” should be construed to mean “maintain without interruption.”
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`C. Overview of Beterov
`27. Beterov is a scholarly article that considers the role of atomic
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`resonance in forming plasmas. Beterov shows the manner in which a plasma may
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`be formed in an atomic vapor, such as a sodium metal vapor, by tuning a laser to a
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`resonant excitation frequency for the atoms, and then allowing the resonantly
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`excited atoms to ionize via the process of collisions between excited atoms (a
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`process called “associative ionization”). Beterov discusses multiple lasers using
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`short wavelengths.
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`28. Notably, Beterov’s disclosure is devoid of any discussion that would
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`connect plasmas that are purportedly generated to any application for which a
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`bright broadband light source would be required. Instead, the discussion in
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`Beterov appears to be directed to “realization and application of the optogalvanic
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`effect” and to “study the kinetics of nonequilibrium plasma, to study elementary
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`processes in a plasma and in a gas, [and] to detect radiation having a certain
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`wavelength, etc.” (Beterov at 552 (‘1368 IPR, Ex. 1006).) I believe that a person
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`of ordinary skill in the art, seeking to improve on the brightness of prior art light
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`sources (e.g., arc lamps) would not have turned to Beterov’s academic disclosure
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`directed to disparate applications.
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`D. An Ordinary Artisan Would Not Have Redesigned Gartner with a
`Short Wavelength Laser
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`29. Petitioners fail to recognize that the state of the art expressly taught
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`away from using short wavelength lasers, such as those discussed in Beterov, to
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`sustain a plasma and produce bright light—which is the purpose of the ‘138
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`invention.
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`30.
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`In 2006, when this invention was disclosed, I believe that an ordinary
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`artisan would not have been motivated to replace Gärtner’s CO2 laser with a short
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`wavelength laser such as Beterov’s, because doing so would have been contrary to
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`the conventional understanding in the field of the “inverse bremsstrahlung”
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`absorption mechanism.
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`31.
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`Indeed, Energetiq was the first to discover that the industry’s
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`understanding of laser plasma heating was incomplete. The “inverse
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`bremsstrahlung” absorption mechanism, which governed the traditional
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`understanding of laser-sustained plasma interactions before Energetiq’s invention,
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`is “one of the fundamental interactions in optical physics” that an ordinary artisan
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`at the time of the invention would have been aware of. (Eden Tr. at 97:6-14.)
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`32. According to the “inverse bremsstrahlung” absorption mechanism, it
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`was believed at the time of the invention that the laser wavelength played a
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`significant role in sustaining the plasma. Inverse bremsstrahlung is a process in
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`which free electrons in plasma absorb energy from an incident laser beam during
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`collisions with ions and neutral atoms. (D. Keefer, “Laser Sustained Plasmas,”
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`Chapter 4, in Radziemski et al., Laser-Induced Plasmas and Applications 173
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`(1989) (Ex. 2082) (“Keefer”).) The amount of energy absorbed by the plasma is
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`based on the absorption coefficient, which is given by:
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`𝛼=�𝜋𝜋𝜔�2𝑛𝑆0𝐺𝑘𝑘 �1−𝑒−ℏ𝜔/𝑘𝑘ℏ𝜔/𝑘𝑘 �
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`Eq. (1)
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`wherein ω, frequency, is given by ω=(2πc)/(λ) and c is the speed of light. (Keefer
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`at 173 (Ex. 2082)) Relatedly, the absorption length of the plasma is equal to 1/α.
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`Because energy absorbed by the plasma is proportional to the square of the
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`wavelength (λ2) of the light being absorbed, it was believed that as the wavelength
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`became shorter, the energy absorbed by the plasma would decrease. Less energy
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`absorbed means lower brightness.
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`33. Similarly, because the absorption length of the plasma is
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`approximately proportional to 1/(λ2) of the light being absorbed, it was believed
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`that as the laser wavelength became shorter, the absorption length (and resulting
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`plasma size) would increase. Because brightness is a measure of power radiated
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`by a source per unit surface area, longer (and larger) plasma again means lower
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`brightness.
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`34. For many years, these principles guided the work in the field and, as a
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`result, long wavelength CO2 lasers, as in Gärtner, which have a wavelength
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`λ=10,600 nm, were the preferred source for laser-sustained plasmas – because
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`they had a long wavelength. By the time of the invention, numerous references
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`recognized the inverse bremsstrahlung mechanism, and expressly taught away
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`from using a short wavelength laser.
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`35. Energetiq was the first to recognize that, even though short
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`wavelength lasers were supposed to produce lower absorption and larger plasma
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`according to inverse bremsstrahlung, they instead were able to sustain small,
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`bright plasmas in higher pressure gases. It was only after Energetiq’s invention
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`that researchers, trying to understand this phenomenon, recognized that short
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`wavelength lasers produced significant additional heating due to absorption by
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`bound-bound electrons which could sustain a plasma, even though these lasers
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`produced lower absorption for free electrons under the inverse bremsstrahlung
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`mechanism. That is, after Energetiq made its invention, it was discovered that for
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`short wavelength lasers, the plasma heating due to bound-bound electron
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`absorption took dominance over inverse bremsstrahlung.
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`36. Applying the inverse bremsstrahlung principles, energy absorbed by a
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`plasma is approximately proportional to the square of the wavelength (λ2) of the
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`light being absorbed. Thus, conventional wisdom understood that as the
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`wavelength is made shorter, the energy absorbed by the plasma decreases. Less
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`energy absorbed means lower brightness. By way of example, under the inverse
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`bremsstrahlung Eq. 1 (above), energy absorption is approximately 100 times
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`stronger for a CO2 laser (λ=10,600 nm) than a NIR laser (λ=1,060 nm).
`
`37. That this was conventional wisdom is clear – numerous references
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`recognized this relationship between laser wavelength and energy absorption and
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`expressly discouraged incorporating shorter wavelength lasers, like that of
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`Beterov, to sustain a bright plasma. (See, for example, Cremers at 671 (1985)
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`(Ex. 2081) (cautioning that “unsuccessful attempts were made to generate the
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`[plasma discharge] with up to 60W of 1.06-μm radiation from a multimode cw-
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`Nd:YAG laser. Because laser heating of a plasma via inverse bremsstrahlung
`
`varies as 𝜆2…, the failure to form the COD was probably due to the 100 times
`
`lower absorption of the plasma at 1.06 μm compared to 10.6 μm.”); Cross at 5:40-
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`52 (1988) (Ex. 1021) (cited by Petitioners, that “cw-laser sources [continuous-
`
`wave] having shorter wavelengths …are absorbed less effectively, and would
`
`require substantially greater cw-laser output power levels to sustain the plasma.”
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`Thus, “carbon dioxide lasers [as in Gärtner] have been used since the output
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`therefrom is readily absorbed by plasmas.”); Keefer at 178 (Ex. 2082) (also cited
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`by the Petitioner, that for “LSP [laser-sustained plasma], ℏω≪kT and the
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`absorption is approximately proportional to the square of the laser wavelength.
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`Due to this strong wavelength dependence, all of the reported experimental results
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`for the LSP have been obtained using the 10.6 µm wavelength carbon dioxide
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`laser [as in Gärtner].”)
`
`38. All these references attribute the lack of adequate plasma generation
`
`to an expected lower absorption rate of short wavelength lasers. In fact, this
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`remained the “conventional wisdom” through the date of the invention, despite
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`other advances in laser technology. Energetiq herein supplies evidence to
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`document that it remained the conventional wisdom until the invention – Raizer
`
`(1991, 1997), Toumanov (2003) and Fridman (2004), all published “between 1989
`
`and 2006.”
`
`39.
`
`In 1991 and then, again in 1997, a textbook by Raizer described that
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`“[f]ortunately, the wavelength of the IR radiation of CO2 lasers is large, since the
`
`absorption coefficient of plasma for light falls off steeply with frequency [which is
`
`1/ λ].” (Raizer 1991 at 306 (Ex. 2007)); Raizer 1997 at 306 (Ex. 2011).) Raizer
`
`observed that, at pressure of 1 atm, the maximum value of the absorption
`
`coefficient for a CO2 laser (λ=10.6μm) is 0.85 cm-1. On the other hand, the
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`maximum value of the absorption coefficient for a neodymium laser (λ=1.06μm)
`
`is 6x10-3 cm, which is 140 times less. Thus, Raizer warned that “these figures
`
`show clearly why short-wave radiation is not advantageous for sustaining a
`
`plasma: the transparency of the plasma is too great.” Id.
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`In 2003, a textbook by Toumanov again recognized that “[t]he
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`40.
`
`absorption coefficient of the light radiation in plasma falls abruptly with raising
`
`frequency. Therefore the generation of the optical discharge in the visible light
`
`frequency range would require a power greater than that of CO2 lasers by a factor
`
`of 102-103.” I.N. Toumanov, Plasma and High Frequency Processes for
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`Obtaining and Processing Materials in the Nuclear Fuel Cycle 60 (2003) (Ex.
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`2045).) And, in 2004, and then again in 2011, a textbook by Fridman—which
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`Petitioners’ expert conceded had “universal” “ideas” (Eden Tr. 231:1-8)—taught
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`that “[l]ight absorption coefficient in plasma significantly decreases with growth
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`of electromagnetic wave frequency [frequency is the inverse of wavelength]….”
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`(Fridman 2004 at 619 (Ex. 2022); Fridman et al., Plasma Physics and Engineering
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`639 (2nd ed. 2011) (Ex. 2046.).
`
`41. Thus, the conventional wisdom at the time of the invention was that
`
`the inverse bremsstrahlung absorption mechanism discouraged the use of short
`
`wavelength lasers such as Beterov’s to sustain a high brightness plasma due to the
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`expected lower absorption rate of shorter wavelength lasers.
`
`42. When this invention was made, I believe that an ordinary artisan
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`would not have been motivated to replace Gärtner’s CO2 laser with Beterov’s
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`short wavelength laser because this would have led to a larger plasma, resulting in
`
`lower brightness.
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`Energetiq Ex. 2016, Page 20, IPR2015-01377
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`43. Applying the inverse bremsstrahlung principles, the absorption length
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`of the plasma is approximately proportional to 1/(λ2) of the light being absorbed.
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`Thus, the conventional wisdom was that as the laser wavelength is made shorter,
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`the absorption length (and resulting plasma size) is expected to increase. Because
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`brightness is a measure of power radiated by a source per a unit surface area (and
`
`solid angle), a longer (and larger) plasma also means lower brightness. By way of
`
`example, under the inverse bremsstrahlung Eq. 1 (above), the absorption length is
`
`approximately 100 times longer for a NIR laser (λ=1,060 nm) than a CO2 laser
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`(λ=10,600 nm).
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`44. Here, too, contemporaneous references recognized that a shorter
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`wavelength laser such as those of Beterov would have resulted in a larger plasma
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`and expressly discouraged incorporating shorter wavelength lasers to sustain a
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`high brightness plasma. For example, Keefer (1989) stated that “[d]ue to this
`
`strong wavelength dependence, all of the reported experimental results for the
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`LSP have been obtained using the 10.6 micrometer wavelength carbon dioxide
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`laser [as in Gärtner]. Since the length scale for the plasma is of the order of the
`
`absorption length, the length of the plasma and the power required to sustain it
`
`would be expected to increase dramatically for shorter wavelength lasers.”
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`(Keefer at 178 (Ex. 2082).) Similarly, Raizer (1991, 1997) observed that, at a
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`pressure of one atmosphere, the minimum absorption length of the laser radiation
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`for a CO2 laser (λ=10.6μm) is 1.2 cm while the minimum absorption length for a
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`neodymium laser (λ=1.06μm) is 170 cm. Raizer then concluded that “these
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`figures show clearly why short-wave radiation is not advantageous for sustaining
`
`a plasma: the transparency of the plasma is too great.” (Raizer 1991 at 308 (Ex.
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`2007).); Raizer 1997 at 308 (Ex. 2011).).
`
`45. Thus, well known physics principles—e.g., the inverse
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`bremsstrahlung—as well as both Keefer (1989) and Raizer (1991, 1997),
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`expressly discouraged the use of short wavelength lasers to sustain bright plasma
`
`as it would lead to a larger plasma resulting in lower brightness light.
`
`46. Energetiq discovered that, despite the implications of the widely
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`accepted inverse-bremsstrahlung excitation mechanism, a shorter wavelength laser
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`would penetrate to and excite the electrons and atoms of the plasma, sustain the
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`plasma, and produce a higher brightness light.
`
`47.
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`In fact, Energetiq’s discovery eventually led to the recognition that
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`short wavelength lasers produced significant additional absorption for bound
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`electrons even though they produced lower absorption for free electrons under
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`inverse bremsstrahlung.
`
`48. Energetiq’s invention and contributions to the field of plasma
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`generation have been repeatedly praised by numerous researchers. For example,
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`Zimakov noted that “[i]t was treated for a long time since COD [continuous
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`Energetiq Ex. 2016, Page 22, IPR2015-01377
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`optical discharge] was obtained for the first time with CO2 laser (λ = 9.4-10.6 μm)
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`that near infrared lasers (λ ≈ 1 μm) cannot be used for efficient sustaining of COD
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`because of low absorption coefficients…” (Zimakov 2013 at 5 (Ex. 2029).) Citing
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`to Energetiq’s work, Zimakov recognized that “[t]ill now authors know one or two
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`correspondences that may be treated as containing some scientific information on
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`the practical realization of COD with lasers emitted radiation around 1.07-1.09
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`μm….” (Id. at 2.) Another paper by Zimakov expressly credited Energetiq’s
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`work for its “unexpected” discovery of sustaining plasma using a short
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`wavelength laser. (Zimako
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