US 5600668

I'll check for any litigation or docket activity before summarizing.

Search results for litigation / docket activity

I ran targeted searches for US 5,600,668 in connection with USPTO proceedings and 2026 CAFC dockets. No CAFC 2026 appeal, district-court action, ITC investigation, or PTAB proceeding involving this patent number surfaced. Several hits contained the string "066" (e.g., the '066 Bobo patent in j2 Global v. EasyLink; the '066 patent in the Tinnus balloon cases) but these are different patents and were excluded per your instruction not to substitute similar numbers.

Two caveats on this finding:

• My tools are general web search, not authenticated USPTO PatentCenter / PACER / CAFC docket queries. I cannot guarantee a complete docket sweep.
• US 5,600,668 is recorded as "Expired – Lifetime," anticipated expiration 2015-06-23, so live 2026 enforcement litigation is unlikely as a practical matter.

Bibliographic summary — US 5,600,668 A

Abstract (verbatim): "A slab laser includes cooled, mutually parallel electrodes having a given thickness. The electrodes have flat surfaces facing each other and defining a discharge chamber therebetween for containing a gas to be pumped, and the electrodes have flat surfaces facing away from the discharge chamber. Each of the electrodes has a plurality of sections being spatially separated from one another over at least a portion of the given thickness of the respective electrode. The electrodes are supported in such a way that movements of the flat surfaces facing away from the discharge chamber being caused by thermal expansion are opposed by only a negligible mechanical resistance."

Plain-language overview of the independent claim

Only claim 1 is independent. Every other claim (2–19) depends, directly or indirectly, from claim 1.

Claim 1 (preamble: "In a slab laser, an electrode assembly...") requires all of the following:

1. A carrier — a support structure.
2. Mutually parallel electrodes supported on that carrier, each electrode having a stated thickness.
3. Facing flat surfaces that define and border a discharge chamber between them for holding a gas to be pumped.
4. Back surfaces on the electrodes that face away from the discharge chamber.
5. Each electrode is divided into a plurality of sections that are spatially separated from one another over at least a portion of the electrode thickness — i.e., the electrode is segmented/notched through part of its depth rather than being one solid block.
6. The electrodes are supported on the carrier such that the back surfaces are "freely movable" — i.e., the mounting does not resist thermal-expansion movement at the rear face.

The inventive concept, in plain terms: instead of fighting thermally induced bending of a long, solid slab electrode (hot inner face, cooled outer face → bowing that ruins resonator alignment), the electrode is broken into smaller sections linked by thin "hinge" regions so each section bows only slightly, and the electrode is mounted so its back face can expand/move freely. The specification states that segmenting into three sections reduced sag to roughly 10% of an undivided electrode, enabling roughly 1 m × 20 cm electrodes and ~2 kW output (at ~1.5–2 W/cm²).

Dependent-claim landscape (brief):

• Separation over a majority of thickness (cl. 2); separation by groove-like notches (cl. 3), in the back face (cl. 4), running crosswise to the longitudinal direction (cl. 5), or in the discharge-facing face (cl. 6); notch depth > 4/5 (cl. 8) or > 9/10 (cl. 9) of thickness; rounded groove bottom (cl. 10).
• Two-layer electrodes with one layer made of side-by-side separate segments (cl. 11); a covering plate over the segments (cl. 12).
• Fully separated segments joined by retainers (cl. 13).
• Spacers between the electrodes (cl. 14) and a slidably supported electrode (cl. 15).
• Per-section coolant conduits (cl. 16) joined by elastic coolant-carrying connecting elements (cl. 17).
• RF generator connection at electrode end faces (cl. 18) or long edges (cl. 19).

Literal-text anomalies worth flagging (not corrected):

• Claim 12 recites "The slab laser according to claim 10," yet its subject matter (a plate covering individual segments facing the discharge chamber) corresponds to the two-layer/segment feature of claim 11, not claim 10 (rounded groove bottom). I take the claim text as published.
• The abstract describes back-face motion "opposed by only a negligible mechanical resistance," whereas claim 1 uses the stronger wording "freely movable." These are not identical formulations.

Prior art cited on the face of the patent

DE 8633774U1; EP 0 275 023 A1; EP 0 305 893 A2; US 4,939,738; WO 91/15045 A1; EP 0 486 152 A2; US 5,430,753; US 5,433,881. Non-patent literature: Wang et al., IEEE Journal of Quantum Electronics, QE-20 (1984), March, No. 3, pp. 276–283, "Radio Frequency Pumped Mid-Infrared Waveguide Lasers."

Source: https://patents.google.com/patent/US5600668/en (fetched 2026-09-24). Family members include EP 0 729 657 B1, JP H08-505007 A, WO 1994/015384 A1, DE 9217640U1, and DE 59307134 D1.

Uncertainty note: I have high confidence in the bibliographic data and claims because they come from the full authoritative patent text. I have low-to-moderate confidence that the absence of 2026 litigation is exhaustive, since I could not query official USPTO/CAFC/PACER dockets directly.

I'll search for litigation involving US patent 5600668.

Let me search litigation-specific sources.

No litigation hits yet. Let me try more targeted litigation databases.

Litigation Search: US Patent 5,600,668

Result: No litigation involving US Patent 5,600,668 was found.

After searching patent litigation sources (including the Unified Patents portal case list, PTAB/docket aggregators, and general web searches for the specific number), I found no records of any district court litigation, Federal Circuit appeal, or PTAB post-grant proceeding (IPR/PGR/CBM) involving US 5,600,668. Searches returned only the patent's own bibliographic/prosecution record, citations to it by later patents, and unrelated cases.

What US 5,600,668 is

• Title: "Slab laser"
• Patent number: US 5,600,668 (interpreted literally — I did not substitute any similar number)
• Application: US 08/494,056, filed 1995-06-23 (a continuation of PCT/EP93/03648)
• Priority: 1992-12-23 (DE 9217640U)
• Granted: 1997-02-04
• Original assignee: Siemens AG; later reassigned to Rofin Sinar Laser GmbH (recorded 1998-12-21)
• Inventors: Kai Erichsen, Hermann Hage, Wolfgang Knapp, Berthold Leifermann, Volker Scholz, Norbert Taufenbach
• Status: Expired – Lifetime (anticipated expiration 2015-06-23, i.e., 20 years from the PCT filing date)
• 19 claims directed to a slab waveguide laser with segmented/notched electrodes to reduce thermal bending

(source: https://patents.google.com/patent/US5600668/en)

Basis and scope of this finding

• The Google Patents record lists "Cited By," "Citations," and "Families Citing this family," but contains no litigation section or litigation-flagged entries for this patent.
• The patent family (EP 0729657 B1, JP H08505007 A, WO 1994015384 A1, DE 9217640 U1, DE 59307134 D1) likewise shows no litigation linkage in the material reviewed.
• My litigation-specific searches for the number returned no complaints, docket entries, judgments, or PTAB petitions naming this patent.

Important caveats (I do not want to overstate this)

1. Absence of evidence is not proof of absence. A null result means no case was surfaced in the sources I could reach; it does not affirmatively establish that no suit was ever filed. Some older or obscure actions may not be indexed in the sources searched.
2. This patent's practical posture reduces litigation likelihood. It is a gas (CO₂) slab laser patent that expired in 2015 and was assigned to an operating laser manufacturer (Rofin-Sinar), not to an NPE/PAE. Patents of this type and vintage are rarely asserted in monetization campaigns.
3. Possible confusion risk: Laser/optics patents have many similar numbers. I limited results strictly to 5,600,668 and excluded near-matches.

Recommendation

If you need a definitive answer (e.g., for a freedom-to-operate or validity opinion), verify against:

• PACER (federal district court dockets) — a full-text/party search for the patent number;
• USPTO Patent Trial & Appeal Board (PTAB) portal — search petition filings by patent number (no IPR found here, but confirm directly);
• Unified Patents litigation dashboard (https://portal.unifiedpatents.com/litigation/caselist) and Docket Alarm / Lex Machina / Westlaw Litigation Analytics for party- and patent-level searches.

Summary: Based on the sources available to me, no litigation — no plaintiff, defendant, jurisdiction, case number, filing date, or outcome — is known for US Patent 5,600,668. I recommend a direct PACER/PTAB confirmation before relying on this as conclusive.

I'll verify the structured data against public sources before drafting.

PTAB / AIA Trial Proceedings — US Patent 5,600,668 ("Slab laser")

Analysis date: 2026-09-30. Source of record for the proceedings list: the structured "PTAB proceedings on file" block (USPTO Open Data Portal ingest). Web search used only to cross-check; it surfaced nothing beyond the ODP result.

Proceedings overview

Total AIA trial proceedings on file for US 5,600,668: zero — 0 active, 0 with claims invalidated, 0 with claims sustained, 0 settled, 0 institution denials. This is not a "the patent has survived two IPRs and is hardened" situation; it is a "the Board has never touched this patent" situation. The bottom-line defensive posture is driven by a different fact entirely: US 5,600,668 is listed as Expired – Lifetime, with an anticipated expiration of 2015-06-23 (Google Patents legal-status field), and it is more than a decade past that date today. Any demand letter citing this patent in 2026 should be tested first for expiration and for the § 286 six-year damages lookback — not for IPR estoppel, because there is no IPR estoppel to be had.

Proceedings

None. There is no IPR, PGR, or CBM proceeding to report on US 5,600,668.

Because the format for this section is per-proceeding, and there are no proceedings, I am deliberately not generating placeholder entries. Per your instruction not to invent proceeding numbers, I have not. What I checked and what I found:

• ODP structured block: "The USPTO ODP API returns no AIA trial proceedings for this patent as of the most recent ingest." That is the canonical list, and it is empty.
• Web cross-check (2026-09-30): searches pairing the patent number with PTAB/IPR/PGR/CBM, with the assignees (Rofin-Sinar Laser GmbH, Siemens AG), and with the inventors (Erichsen, Hage, Knapp, Leifermann, Scholz, Taufenbach) returned no petition, institution decision, final written decision, or appeal naming US 5,600,668. The patent appears in the record only as cited prior art — e.g., the UK search report for GB 2 334 616 A cites "US 5600668 A (Ericksen)" as a category-A document against a Rofin-Sinar slab-laser electrode cooling application. That is a citation, not an AIA trial.
• No CAFC appeal involving this patent surfaced, which is consistent with there being no PTAB decision to appeal.
• The cited-by record (21 examiner-cited / 40 third-party citations on Google Patents) is dense, but citation by later patents is not PTAB activity.

Why the absence is plausible (and not just an indexing gap): the AIA trial regime began 2012-09-16, when this patent had roughly one to three years of term left depending on how the expiration is computed (see the caveat below), and the patent was held by Rofin-Sinar Laser GmbH, an operating laser manufacturer (Rofin-Sinar Technologies later became part of Coherent), rather than by a non-practicing assertion entity. Patents of that profile, near end of life and in the hands of a competitor rather than a monetization vehicle, have a low IPR-attraction rate. The empty ODP list and the empty web result set are mutually consistent.

One open item I could not resolve with high confidence: the term arithmetic is ambiguous on the face of the public record. Priority is 1992-12-23 (DE 9217640U), the international application PCT/EP93/03648 was filed 1993-12-21, and the US application 08/494,056 was filed 1995-06-23 as a continuation of that PCT. A straight 20-years-from-earliest-filing calculation from the 1993-12-21 PCT date gives an earlier expiration than Google's listed 2015-06-23 (which corresponds to 20 years from the 1995-06-23 US filing date). Either way the patent is long expired; the exact expiration date is not load-bearing for the defensive conclusion, but if you are relying on the precise date, pull the USPTO Patent Center "Application Data" / term-adjustment tab rather than trusting the Google field.

Strategic summary

Claim status. No claim of US 5,600,668 has been canceled, narrowed, or held unpatentable by the PTAB, because no AIA trial was ever filed. All claims 1–19 stand as issued (subject to two Certificates of Correction, recorded 1997-06-24 and 2009-09-01 — I have not verified what those certificates changed). There are therefore no PTAB-canceled claims and no PTAB-sustained claims; the entire claim set is untested at the Board. The important qualifier is that "untested and intact" is not the same as "enforceable": the patent's legal status is Expired – Lifetime, and it has been expired since the mid-2010s.

Estoppel landscape. There is none to map. 35 U.S.C. § 315(e)(2) estoppel applies only to a petitioner that obtained a final written decision, and no such petitioner exists here. That cuts both ways for a defendant: nothing is foreclosed, but also there is no free prior-art kill shot handed to you by the Board. If you are evaluating invalidity today, you start from scratch on the merits (and, more practically, from the threshold questions of expiration, standing, and the six-year damages window under § 286). If you are evaluating validity — for example, drafting around this patent as prior art against a later Rofin/Coherent electrode-segmentation filing — the operative references are the ones this patent itself cites: EP 0 275 023 A1 / US 4,719,639 (Tulip), EP 0 305 893 A2 / US 4,939,738 (Deutsche Forschung), WO 91/15045 A1 (Rofin-Sinar), and EP 0 486 152 A2 (Coherent, "Gas slab laser"), plus US 5,430,753 and US 5,438,881 (Siemens stripline-laser cases cited on the face of the patent). Those, not PTAB outcomes, are the usable art.

Pattern signals. No petitioner has filed even once against this patent, so there is no repeat-petitioner pattern, no joinder activity, and no defensive-aggregator (Unified Patents or similar) involvement in the chain. The patent owner never pursued a PTAB appeal concerning this patent, for the straightforward reason that the owner never had a PTAB loss to appeal. If you are looking for a proxy for how this family has been litigated at the Board, look at the later Rofin/Coherent stripline-laser patents (the cited-by list includes several Synrad, Coherent, Videojet/LiteLaser, and Trumpf proceedings referencing family members like "CO2 slab laser" and "Stripline laser") — but none of those proceedings is against US 5,600,668, and their outcomes do not bind anything here.

Recommended next steps

• Treat this as a no-PTAB-activity patent and say so plainly. There is no FWD to quote and no E2E proceeding to link. The canonical proceeding list is empty; the E2E/IPR search page (https://ptacts.uspto.gov/ptabs/appl/action/party/search) and the ODP will both confirm zero hits for US 5,600,668.
• If you are a defendant, pivot from PTAB analysis to the expiration timeline. The absence of IPRs means your defense is not "the Board already killed claim 1." Your defense is that the patent is Expired – Lifetime (listed anticipated expiration 2015-06-23), that no asserted conduct after expiration can infringe an expired patent, and that any past-infringement claim is constrained by the § 286 six-year limitation and the patent's actual expiration date. Verify the exact expiration date and the content of the two Certificates of Correction (1997-06-24, 2009-09-01) on Patent Center before responding to any demand.
• If you are assessing the patent as prior art (the more likely live use for a 1992-priority, expired slab-laser patent), note that it is fully available as prior art and pair it with the four primary references it names: US 4,719,639; US 4,939,738; WO 91/15045 A1; and EP 0 486 152 A2.
• No trial-stage milestones to track. There are no institution deadlines, no oral hearings, and no statutory one-year FWD deadlines running, because no trial was instituted.
• On the "absence is a signal" point: here the silence is explained, not suspicious. A 1992-priority patent that expired in the mid-2010s and was owned throughout by an operating laser manufacturer (Rofin-Sinar, later part of Coherent) is exactly the population that never attracts IPRs. Read the empty proceedings list as "no Board litigation ever happened," not as "undiscovered prior art must be out there."

Confidence note: the "zero proceedings" conclusion rests on the ODP structured data plus multiple concordant web searches on 2026-09-30. I could not independently confirm the precise expiration date, the substance of the two Certificates of Correction, or the current ownership chain (Rofin/Coherent), and I have flagged those as unverified rather than asserting them.

I'll research the ownership chain and cross-reference sources before writing the analysis.

I hit the tool-call limit before I could pull the USPTO Assignment Center record directly. Below I flag exactly where that leaves an evidence gap. Everything I do assert is grounded in the authoritative patent text you supplied (Google Patents legal-events table) plus the cross-reference searches that did return.

⚠️ Sourcing note up front: I could not open assignmentcenter.uspto.gov or assignment.uspto.gov in this session, so I could not retrieve the correspondent of record (the recording attorney/agent) for either assignment. The reel/frame data below is taken from the legal-events table in the authoritative patent text. I am not filling the correspondent field with a guess.

Inventors

Employer determination. All six are named as assignors on the recorded assignment of inventors' interest. The PCT parent (PCT/EP93/03648 → WO 94/15384 A1) lists Rofin-Sinar Laser GmbH as applicant, and the two inventors whose cities appear on the face of the patent — Scholz (Lübeck) and Taufenbach (Basthorst) — both sit in the Hamburg commuter belt, i.e. the Rofin-Sinar Hamburg works. Rofin-Sinar was acquired 100% by Siemens AG in 1987 and remained wholly Siemens-owned until the September 1996 IPO. So "employer at filing" is genuinely ambiguous between Siemens AG and Rofin-Sinar Laser GmbH, and the assignment record itself is ambiguous on the same point (see timeline).

Pattern notes (I do not want to overstate these):

• I see no evidence of all inventors departing within 12 months of filing. The signing dates on the assignment span 1995-07-12 to 1996-07-15 (as originally recorded) — a one-year spread that is consistent with inventors signing at different points during national-stage entry, not with a coordinated exit.
• Counter-signal worth noting: Norbert Taufenbach stayed in the same technical field for decades after this filing — he appears as inventor on later Rofin-Sinar filings (e.g. EP 0 712 345 B1, Rofin Sinar Laser GmbH, Hamburg) and later as assignee in his own right on US 6,853,668 / US 7,274,722 / DE 19520401 C1 ("CO2 slab laser", priority 1998-11-13) and, per EP 2 028 733, through Taufenbach GmbH. That is the opposite of the "inventors flee the shell" tell.

Original assignee

On the issued patent: Siemens Aktiengesellschaft (Germany). However, the recorded assignment of the inventors' interest was subsequently corrected — by re-record — to name Rofin-Sinar Laser GmbH as assignee. Treat the "original assignee" as the Siemens/Rofin-Sinar Laser GmbH family, not as two competing entities.

Rofin-Sinar Laser GmbH (Hamburg):

• Line of business: industrial CO₂ laser sources and laser-based material-processing systems. Founded 1975 in Hamburg as SINAR Laser System Verkaufsgesellschaft mbH; became ROFIN-SINAR on acquiring Rofin (UK) in 1978; wholly acquired by Siemens in 1987; spun off via NASDAQ IPO (Rofin-Sinar Technologies Inc., ticker RSTI) in September 1996.
• Did it ship a product embodying the claims? Yes, directly and at scale. Rofin's own secondary-listing document states that "In 1998, Rofin shifted the majority of its CO₂ laser production from the traditional fast-flow technology to the newly developed diffusion-cooled Slab laser technology." The commercial line was the ROFIN DC series — e.g. DC 035 (3.5 kW) and the DC 040 W (4 kW) shown at EMO 2001, and by 2014 the DC family was quoted at powers up to 8,000 W with K ≈ 0.95. That is a textbook operating-company embodiment of a diffusion-cooled slab-laser electrode patent.
• Current status: Rofin-Sinar Technologies Inc. was acquired by Coherent Inc., completed 2016-11-07 (€800M+/$940M). Siemens AG remains a going concern. Most recently (reporting dated Dec 2025/Jan 2026), Bystronic is taking over the Tools for Materials Processing business unit and the Rofin brand from Coherent's North American group.
• Where this leaves US 5,600,668: legally "Expired – Lifetime," anticipated expiration 2015-06-23 — it expired before the Coherent integration mattered commercially.

Assignment timeline

Two recorded assignment events only, both from the same six inventors on the same document; the second is a name correction, not a new transfer.

Event 1

• Executed 1995-07-12 → 1996-07-15 / recorded 1996-10-22 — Reel 008191 / Frame 0630
  • Conveyance: Assignment of assignors' interest ("ASSIGNMENT OF ASSIGNORS' INTEREST")
  • Assignor: Erichsen, Kai; Hage, Hermann; Knapp, Wolfgang; Leifermann, Berthold; Scholz, Volker; Taufenbach, Norbert (all six named inventors)
  • Assignee as recorded: Siemens Aktiengesellschaft, Germany
  • Correspondent of record: ⚠️ not retrieved — could not open the USPTO Assignment Center in this session. No recurrence finding is possible.
  • Context: In-house / internal. The initial inventor→employer assignment captured as the US national-stage case (continuation of PCT/EP 93/03648) was filed.

Event 2

• Executed 1995-07-12 → 1995-08-15 / recorded 1998-12-21 — Reel 009445 / Frame 0368
  • Conveyance: Assignment — expressly recorded as a re-record "to correct assignee's name on a document previously recorded at Reel 8191 Frame 0630."
  • Assignor: same six inventors
  • Assignee: Rofin-Sinar Laser GmbH, Germany
  • Correspondent of record: ⚠️ not retrieved (same gap as above). Note that under the naming-correction rubric, a body correcting a mis-recorded assignee name is exactly the kind of filing where a single repeat correspondent often appears — I simply cannot confirm or deny it here.
  • Context: Correction only, not a transfer. It harmonizes the US record with the rest of the family (the PCT/WO applicant was already Rofin-Sinar Laser GmbH) and lands two years after the Siemens divestiture of Rofin-Sinar (IPO September 1996). It is not a third-party sale.

Non-assignment legal events (not ownership links — listed so the record is complete): 1997-01-27 patent-grant notification (STCF); certificates of correction 1997-06-24 and 2009-09-01 (document corrections, not ownership changes); maintenance-fee payments 2000-07-05, 2004-07-29, 2008-07-22.

No assignment recorded after 1998-12-21. In particular, the 2016 Coherent/Rofin merger does not appear as a recorded US assignment — consistent with title sitting in the German operating entity (Rofin-Sinar Laser GmbH) and passing via a share purchase rather than a recorded instrument. This is why Google Patents still shows Rofin Sinar Laser GmbH as current assignee.

Timeline diagram

timeline
    title Ownership of US 5600668
    1992 : Priority filing DE 9217640U1
    1993 : PCT filed at Rofin-Sinar Laser
    1995 : US application filed
    1996 : Assignment recorded to Siemens AG
    1997 : Patent issued
    1998 : Corrected to Rofin-Sinar Laser GmbH
    2015 : Patent term expires
    2016 : Coherent acquires Rofin

NPE / troll-pattern signals

Verdict

Insufficient data (no records beyond the original inventor-to-employer assignment).

The record consists solely of the initial inventors' assignment (Reel 008191/0630, executed 1995-07-12→1996-07-15, recorded 1996-10-22) and a 1998 name-correction re-record (Reel 009445/0368, recorded 1998-12-21) that changed the assignee from Siemens Aktiengesellschaft to Rofin-Sinar Laser GmbH — all within one corporate family. There is no third-party transfer of any kind.

That said, the affirmative finding is a clean negative: zero NPE signals are present, and the chain terminates at Rofin-Sinar Laser GmbH, an operating industrial-laser manufacturer that demonstrably shipped the claimed technology (the diffusion-cooled CO₂ DC-series slab lasers, up to 8 kW). This patent is not an NPE asset — it is a mid-1990s European industrial-laser patent that expired in 2015 while still owned by its operating originator, and it passed indirectly to Coherent with the 2016 Rofin acquisition without a recorded US assignment.

Two open verification items for whoever has live docket access:

1. Pull the correspondent of record on Reel 008191/0630 and Reel 009445/0368 at the USPTO Assignment Center — the one field I could not reach.
2. Confirm there is no later recorded assignment attached to the German Rofin-Sinar Laser GmbH entity post-2016 (a share-purchase chain would not necessarily be recorded in the US).

Verify at: https://assignmentcenter.uspto.gov/ (search patent number 5600668) — also https://assignment.uspto.gov/patent/index.html

I'll research US 5,600,668 and each of its cited references. Let me run targeted searches.

Let me gather details on the remaining cited references.

Prior-Art Analysis — US 5,600,668 A ("Slab laser")

0. Record confirmation

I searched for the literal number 5600668. The record matches the material already generated (title "Slab laser"; App. US 08/494,056; filed 1995-06-23 as a continuation of PCT/EP93/03648; priority 1992-12-23 from DE 9217640U; granted 1997-02-04; assignee Siemens AG → Rofin Sinar Laser GmbH; 19 claims). Sources: https://patents.google.com/patent/US5600668/en and http://www.everypatent.com/comp/pat5600668.html. (I did not query USPTO PatentCenter directly; this is the Google Patents/everypatent rendering of the USPTO record. I did not substitute any similar number.)

1. Critical date and the § 102 framework

• Critical (priority) date: 1992-12-23 (DE 9217640U1). Pre-AIA § 102/§ 103 applies (application filed before 2013-03-16).
• Publications dated before 1992-12-23 are § 102(a)/(b) art (relative to the DE priority, foreign priority under § 119 is available to antedate them).
• US patents/applications are § 102(e) art as of their US filing date; foreign priority does not give a § 102(e) date. So a cited US patent only counts under § 102(e) if its US filing predates 1992-12-23.
• Logical rule I apply throughout: because every claim 1–19 depends from claim 1, a reference cannot "anticipate" any dependent claim unless it discloses every claim-1 element: (a) a carrier; (b) mutually parallel electrodes on the carrier with a given thickness; (c) facing flat surfaces defining/bordering a discharge chamber; (d) back surfaces facing away; (e) each electrode divided into a plurality of sections spatially separated over at least a portion of the thickness; and (f) mounting such that the back surfaces are freely movable.

Bottom line up front: no single cited reference discloses both distinguishing elements (e) and (f), so on the disclosures available, none of the eight cited references anticipates claim 1 (and therefore none anticipates any claim). They are, however, the correct § 103/§ 102(b) backdrop. The closest are US5430753, US5434881 and EP0486152A2.

2. The eight cited references — table

Date columns are as printed in the Google Patents citation table for US5600668.

3. Per-reference detail

3.1 DE 8633774U1 — "Transversely excited waveguide laser" (Siemens AG)

• Full citation: German utility model (Gebrauchsmuster) DE 8633774U1; priority 1986-12-17; published 1988-06-23; Siemens AG.
• Description: A transversely (RF) excited waveguide/slab gas laser — the basic genre of US5600668's environment. I could not retrieve the full text in this session, so detail is limited (low confidence on specifics).
• § 102 potential: Teaches the preamble/environment (carrier-housed, parallel electrodes forming a waveguide discharge gap). Does not appear to disclose element (e) (electrode sectioned over a portion of its thickness) or (f) (freely movable back faces). Potentially anticipates no claim; § 102(b) background art.

3.2 EP 0275023A1 / US 4,719,639 — "Carbon dioxide slab laser" (John Tulip)

• Full citation: EP 0275023A1; priority 1987-01-08; published 1988-07-20; John Tulip (the patent text itself notes the US counterpart, US 4,719,639).
• Description: Sealed CO₂ slab waveguide laser; a pair of cooled, polished metal electrodes held parallel to form a discharge gap (typically ≤ ~5 mm deep, ~2 mm wide), RF excitation, conduction cooling, dielectric/insulating spacers (7, 8) fixing the gap, electrodes mounted in a U-shaped housing/base (9). The beam is guided between the electrodes in one dimension and free in the other.
• § 102 potential: Strong § 102(b) teaching of elements (a)–(d) and of the spacers that later appear as claim 14. No teaching of sectioned electrodes (e) or of free thermal movement of the back faces (f). Anticipates no claim of US5600668; core § 103 environment art.

3.3 EP 0305893A2 / US 4,939,738 — "High-power strip-guide laser" / "High-power waveguide laser" (DLR / Opower)

• Full citation: EP 0305893A2; priority 1987-08-31; published 1989-03-08; Deutsches Zentrum für Luft- und Raumfahrt e.V. US counterpart US 4,939,738A; issued 1990-07-03; assignee Deutsche Forschungs- und Versuchsanstalt für Luft- und Raumfahrt.
• Description: Slab/strip-guide waveguide laser with a rectangular waveguide section formed in a first aluminum block and a ceramic cover plate clamped by a second (grounded) aluminum block; microwave excitation via a longitudinal slit; positive-branch unstable resonator with confocal mirrors (per the summary of this reference in EP 0486152B1).
• § 102 potential: § 102(b) art for elements (a)–(d). No sectioned electrodes (e); no free-back-face mounting (f). Anticipates no claim.

3.4 US 4,939,738A — see 3.3 (US counterpart)

• Same disclosure as EP 0305893A2; § 102(b) from its 1990-07-03 grant. Anticipates no claim; environment art.

3.5 WO 1991015045A1 — "Gas laser" (Rofin-Sinar Laser GmbH)

• Full citation: WO 1991015045A1; priority 1990-03-21; published 1991-10-03; Rofin-Sinar Laser GmbH.
• Description: Listed simply as "Gas laser." I was not able to retrieve the full text in this session, so I will not characterize its disclosure beyond its title/assignee (gas-laser subject matter; Rofin-Sinar is the later assignee of US5600668). Low confidence on content.
• § 102 potential: § 102(b) art by date. Cannot be mapped to specific claim elements without the text; on its face it does not suggest the sectioned-electrode/free-mount combination. Anticipation not established.

3.6 EP 0486152A2 — "Gas slab laser" / "Slab laser" (Coherent, Inc.)

• Full citation: EP 0486152A2; priority 1990-10-12 (US 59646390 et al.); published 1992-05-20; Coherent, Inc. Source: EPO published data, http://data.epo.org/pise-server/rest/collections/lgpi/EP0486152A2.pdf
• Description (from the abstract): CO₂ slab waveguide laser with spaced-apart electrodes (36, 38) having opposed reflecting surfaces, guiding in one plane only; negative-branch unstable resonator; a support structure (60) maintaining the electrodes spaced apart without confining the discharge; pipes (70, 72) for cooling; and a sliding support (52) for accommodating thermal expansion of the parts; adjustable external mirror assemblies.
• § 102 potential: This is the cited reference that best teaches element (f) — the sliding support that lets the parts accommodate thermal expansion corresponds to US5600668's "back surfaces freely movable" and to claim 15 ("one of said electrodes is slidably supported"). It also teaches the cooling-pipe concept (claim 16 environment). But it does not disclose element (e), sectioning the electrodes over a portion of their thickness. Because (e) is absent, EP 0486152A2 does not anticipate claim 1 or any dependent claim. It is the strongest § 103 combination partner (its sliding support + a sectioned electrode such as in US 5,430,753/US 5,433,881). Note it is § 102(a) art (published 1992-05-20, within one year of the 1992-12-23 critical date).

3.7 US 5,430,753A — "Stripline laser having composite electrodes" (Siemens AG)

• Full citation: US 5,430,753A; priority/filing 1992-08-31; issued 1995-07-04; Siemens Aktiengesellschaft.
• Description (from the patent): RF-excited, diffusion-cooled stripline laser with two metal electrodes fixed to form a discharge gap. Each electrode is a "composite electrode" formed of a carrier (hollow profile of V2A steel, elements 1/12) and a copper electrode plate (2/3); cooling channels (4) are milled into the copper plates, open toward the carrier; ceramic spacers (8, e.g. Al₂O₃) with Invar/Kovar laminae (9, 10) fix the gap; the copper waveguide surfaces (5) are polished/gold-coated; coils equalize the RF voltage distribution.
• § 102 potential: Qualifies as § 102(e) art (US filing 1992-08-31, before the 1992-12-23 critical date). It is the closest cited reference for the carrier/electrode-plate composite structure, the cooling conduits (claim 16), and the spacers between electrodes (claim 14). However, its "composite" electrode is a carrier + a single continuous plate, not a plate divided into "a plurality of spatially separate individual segments" and not "sections spatially separated over at least a portion of the thickness." It also does not disclose free thermal movement of the back faces. Therefore it does not anticipate claim 1 (or claims 11/14/16, which depend from claim 1). It is the leading § 102(e)/§ 103 reference for the structural environment.

3.8 US 5,433,881A — "Diffusion-cooled CO₂ stripline laser having reduced ignition voltage" (Siemens AG)

• Full citation: US 5,433,881A; priority 1992-09-30; issued 1995-07-18; Siemens Aktiengesellschaft.
• Description (from the patent): HF-excited, diffusion-cooled CO₂ stripline laser in which the HF electrode is segmented into at least two electrically separated surface elements with separate HF feed (FIG. 1: HF electrode 2 "segmented into three parts"), to reduce ignition voltage/time; alternatively an auxiliary electrode forms an auxiliary discharge path. Electrode surfaces (5, 6) carry integrated cooling channels (7, 8) on carrier parts (3, 4).
• § 102 potential — important caveat: this is the only cited reference that segments an electrode (its claim 1 requires the HF electrode "segmented into at least two electrically separated surface elements"), which is the feature nearest to US5600668's element (e). But two problems defeat § 102 anticipation: (i) the segmentation is for electrical isolation/ignition, and the reference does not describe sectioning "over at least a portion of the thickness" with hinge-like connections or freely movable back faces (element (f) is absent); and (ii) its prior-art status is doubtful — the granted patent shows [22] Filed: Sep. 23, 1993 (https://patentimages.storage.googleapis.com/ab/d9/05/fa4133a478dba9/US5434881.pdf), i.e. after the 1992-12-23 critical date, and its 1992-09-30 date is a foreign priority that does not establish a § 102(e) date. If the effective US filing is 1993-09-23, US 5,433,881A is not § 102(e) prior art to US5600668 at all (flagging the discrepancy between the Google Patents table's "priority 1992-09-30" and the printed filing date). Either way, no anticipation.

3.9 Non-patent literature — Wang et al. (1984)

• Full citation: Wang et al., "Radio Frequency Pumped Mid-Infrared Waveguide Lasers," IEEE Journal of Quantum Electronics, QE-20 (1984), March, No. 3, pp. 276–283.
• Description: Foundational paper on RF-pumped mid-IR waveguide lasers — establishes RF excitation and waveguide/discharge-gap geometry.
• § 102 potential: § 102(b) art for the general environment. No sectioned electrodes, no free-back-face mounting. Anticipates no claim.

4. Synthesis — most relevant prior art

1. Most relevant overall: US 5,430,753A — § 102(e) art (US filing 1992-08-31) disclosing composite carrier+electrode construction, milled cooling channels, and ceramic spacers. It maps to the environment of claim 1 and to the spacer/cooling features of claims 14/16, but lacks sectioning and free back-face mounting.
2. Most relevant to the "freely movable" limitation: EP 0486152A2 (Coherent) — sliding support (52) accommodating thermal expansion → matches claim 1 element (f) and claim 15.
3. Most relevant to the "sections" limitation: US 5,433,881A — segmented HF electrode (three parts) → superficially matches element (e), but its segmentation is electrical and its § 102(e) status is doubtful given the printed 1993-09-23 US filing date.
4. Environment/§ 102(b) art: DE 8633774U1, EP 0275023A1 (US 4,719,639), EP 0305893A2 (US 4,939,738), WO 1991015045A1, and Wang et al. — all teach cooled parallel-electrode slab/waveguide lasers but none teaches sectioned electrodes.

Anticipation conclusion (literal application): Applying the rule that a dependent claim cannot be anticipated unless its independent claim is, no cited reference anticipates any of claims 1–19 of US 5,600,668. Each reference lacks at least one of element (e) (sections separated over a portion of thickness) or element (f) (freely movable back faces), and no reference discloses both. The cited art is best deployed under § 103 — e.g., US 5,430,753 (composite/cooled electrodes + spacers) or EP 0486152A2 (sliding thermal-expansion support) in view of US 5,433,881A (segmented electrode) for the combination.

5. Confidence and caveats

• High confidence in the citation list, dates, and claim text (from the authoritative patent text and the Google Patents record).
• Moderate confidence on the content of EP 0275023A1/US 4,719,639, EP 0305893A2/US 4,939,738, US 5,430,753 and US 5,433,881 (retrieved from the patent texts/abstracts).
• Low confidence on WO 1991015045A1 and DE 8633774U1, whose full texts I could not retrieve this session; I have not attributed specific claim elements to them beyond their titles.
• Flagged discrepancy (not auto-corrected): US 5,433,881A shows priority 1992-09-30 in the Google Patents citation table but "[22] Filed: Sep. 23, 1993" on its face — this materially affects its § 102(e) status and should be confirmed against the USPTO file.
• This is a prior-art/§ 102 mapping only, not a legal opinion; for an opinion, verify each reference's full text and dates in USPTO PatentCenter/Espacenet.

I'll ground the analysis by pulling details on the key prior-art references cited on the face of the patent.

Let me pull details on the remaining key references.

Obviousness Analysis — US 5,600,668 under 35 U.S.C. § 103

Note on posture: Because the earliest effective date is the DE 9217640U1 priority of 1992-12-23, the pre-AIA § 103 framework governs, but the KSR rationales (predictable variations, known-technique-to-known-device, design incentives) are the operative analytical toolkit. Sources: https://patents.google.com/patent/US5600668/en (claims, spec, citation list).

1. The problem the patent claims to solve

The specification frames the invention entirely as an electro-mechanical solution to a thermal-bending problem (not an optical one):

"[L]arge-area electrodes are needed, which nevertheless cannot be kept adequately parallel to one another because of their non-uniform heating… That causes bending moments, which in turn cause the electrodes to be spaced farther apart at their ends than in the middle… the known lasers cannot attain output power of more than a few hundred watts."

Every element of claim 1 is a conventional slab-laser element except two:

1. Segmentation of each electrode into sections separated over part of the thickness (the "hinge" idea); and
2. Free movability of the back (cooled) face — i.e., a mount that does not restrain thermal expansion.

So the § 103 question is narrow: was it obvious, as of Dec. 1992, to fix thermal bowing in a diffusion-cooled RF slab/stripline laser by (a) sub-dividing the electrode into sections and (b) floating the electrode on its carrier?

2. Element-by-element mapping of claim 1

Result: every limitation of claim 1 has a home in the cited art; nothing in claim 1 requires a structure that was not already known in the slab/stripline-laser field by the priority date.

3. Combination A (primary): slab-laser architecture + floating mount + segmented electrode

References: EP 0 275 023 A1 / EP 0 305 893 A2 / US 4,939,738 (the "slab-laser architecture") + Coherent EP 0 486 152 A2 / US 5,131,003 (the "unconstrained mount") + US 5,433,881 and/or US 5,430,753 (the "segmented / composite electrode").

Why a POSITA would combine — the rationales:

1. Common problem, common art. All references are diffusion-cooled, RF-excited CO₂ waveguide/slab lasers; they address the same design constraint (electrode area = output power, but larger area invites thermal distortion). The patent itself concedes the scaling relationship: "1.5W to 2.0W of power… per square centimeter," and Coherent likewise notes "the output power… scales with the area of the discharge between the electrodes."

2. Coherent supplies the express reason to float the back face. Coherent does not merely permit thermal movement — it states the object: to avoid a mount that would "result in warping and deviation from the desired separation between the electrodes." A POSITA seeking the claim-1 architecture would apply this teaching for its stated purpose.

3. '881 and '753 supply the segmentation teaching within the identical device. '881 subdivides the very electrode (the HF electrode) of the same kind of stripline laser into three parts; '753 expressly contemplates the same electrode plates "fashioned in segments." KSR "use of a known technique to improve a similar device" and "application of a known technique to a known device ready for improvement" apply directly.

4. Predictable mechanical result. Dividing a bending beam into shorter spans to reduce accumulated deflection is routine engineering (expansion joints, articulated/tiled optics). The patent's own language confirms the mechanism is ordinary: the thin transition "act as hinges." Per KSR, "[t]he combination of familiar elements according to known methods is likely to be obvious when it does no more than yield predictable results."

Conclusion for claim 1: Reasonably likely obvious over Combination A. The strongest attack pairs the slab-laser architecture of the Tulip/DLR/Coherent documents with the Coherent floating mount and either Siemens segmentation reference.

4. Combination B (secondary, and arguably stronger on dates): the two Siemens references together

References: US 5,430,753 + US 5,433,881.

Both are Siemens applications in the same development program — '753 refers to "a CO₂ laser… shown in a corresponding application filed simultaneously herewith." Together they disclose:

• Carrier + electrode plate composite structure ('753: hollow-profile carriers 1, 12 + copper electrode parts 2, 3) → claim 1's "carrier" + two-layer electrode of claims 11/12;
• Cooling channels open at the back side ('753) → claim 1's back-face limitation and claim 16 (coolant conduits);
• Electrode segmentation ('881: HF electrode in three parts; '753: "fashioned in segments") → claim 1's "plurality of sections";
• Ceramic spacers fixed to Invar/Kovar laminae "intended to keep [the electrodes] at a constant, temperature-independent spacing" ('753) → claim 14;
• Springs/mechanical decoupling of grounded electrode to the jacket tube ('881 Fig. 2) → support flexibility.

Motivation: both references are aimed at the same article of manufacture (a diffusion-cooled stripline/slab laser electrode pair) and the same problem class (thermal and mechanical stability of large electrodes). Combining two references from the same assignee, filed months apart, describing complementary aspects of one electrode design, is the paradigm of an obvious combination under KSR.

5. Dependent claims 2–19

Net assessment: claims 2–10 and 14–19 look strongly obvious (optimization, obvious placement, or express disclosure). Claims 11–13 are also largely met by '753/'881. The overall claim set is vulnerable.

6. Where the patent retains its best (but still weak) nonobviousness argument

• Secondary considerations. The spec asserts a ~10% residual sag for a three-section electrode versus an undivided electrode. This could be framed as an "unexpected result." But it is a quantitative confirmation of a predictable geometric effect (deflection scales with the unbroken span), and there is no nexus to any claim element that '753/'881 did not already suggest — '753 expressly recites "fashioned in segments." Under KSR, a predictable, explained improvement does not rescue an otherwise obvious combination.
• No commercial-success or copying evidence appears in the record I retrieved; I found no license or litigation history indicating objective indicia (see prior sections — no litigation surfaced).
• The "freely movable" vs. "negligible mechanical resistance" gap. Claim 1 uses the stronger term "freely movable," while the abstract says motion is "opposed by only a negligible mechanical resistance." A challenger would argue these describe the same modest degree of decoupling taught by Coherent. The patent owner would argue "freely movable" is a higher bar. This is a genuine but narrow claim-construction dispute, not a validity shield.

7. Date / statutory-status caveat (important — please verify)

The two closest references, US 5,430,753 (priority 1992-08-31; issued 1995-07-04) and US 5,433,881 (DE priority 1992-09-30; US filed 1993-09-23; issued 1995-07-18), have US filing dates in 1993 — after '668's DE priority of 1992-12-23 but before '668's US filing of 1995-06-23.

• If '668 perfects its DE 9217640U1 priority, these references may not qualify under pre-AIA § 102(e) (the In re Hilmer doctrine limits a US patent's § 102(e) date to its US filing date, not its foreign priority), and they would only be prior art under § 102(a)/(b) if '668's actual invention date postdates their publication.
• The examiner nevertheless cited both on the face of the patent, so at least one was treated as prior art on some basis.

I cannot confirm the statutory basis from the record I retrieved. For a formal opinion, verify each reference's § 102(e) date and the priority chain of '668 against the file wrapper.

By contrast, the following are cleanly prior art (published well before 1992-12-23): EP 0 275 023 A1 (Tulip, 1988), EP 0 305 893 A2 (DLR, 1989), US 4,939,738 (1990-07-03), EP 0 486 152 A2 (Coherent, 1992-05-20), WO 91/15045 A1 (1991), DE 8633774U1 (1988), and the Wang et al. NPL. These are the safest foundations for the obviousness attack, and Combination A is built primarily on them.

8. Confidence and sourcing caveats

• High confidence in the text and claims of US 5,600,668 (full authoritative text supplied) and in the disclosures of US 5,430,753 and US 5,433,881 (full text retrieved: https://patents.google.com/patent/US5430753A/en, https://patents.google.com/patent/US5434881, https://patents.justia.com/patent/[5430753](/patent/5430753), https://patents.justia.com/patent/[5434881](/patent/5434881)).
• Moderate confidence in attributing the floating-mount and flexible-pipe teachings to the Coherent family: the retrieved page (titled "RF excited CO₂ slab waveguide laser") was served at freepatentsonline.com/5131004.html, while the patent's own "similar documents" list attributes "RF excited CO₂ slab waveguide laser" to US 5,131,003A (1992-07-14) — the apparent US counterpart of EP 0 486 152 A2. I did not independently confirm the exact document number of that disclosure.
• Lower confidence in the specific disclosures of the non-Latin/non-US-codeless references — EP 0 275 023 A1, EP 0 305 893 A2, US 4,939,738, WO 91/15045 A1, DE 8633774U1 — which I did not retrieve in full text. The EP 0 305 893 A2 extract I did retrieve (https://patents.google.com/patent/EP0305893A2/en) confirms it is a diffusion-cooled strip-guide ("Bandleiter") laser using an unstable resonator, but I did not verify its electrode-mounting disclosure.
• Not legal advice. This is a technical § 103 sketch; a validity opinion requires the full file wrapper, claim construction, and confirmatory § 102 date analysis.

Bottom line: On the art cited on the face of US 5,600,668, claim 1 is reasonably likely obvious over (i) a slab/stripline-laser reference combined with Coherent's unconstrained electrode mount and either Siemens segmentation reference, or (ii) the two Siemens references ('753 + '881) in combination. Claims 2–19 are individually weak, being either expressly disclosed (claims 11, 14, 16, 17) or routine design optimizations (claims 2, 5, 6, 8, 9, 10). The only meaningful defense is a date/perfection argument against '753 and '881, which the older Tulip/DLR/Coherent/Rofin art in Combination A largely moots.