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                                                                   Exhibit 10.13

                              PURCHASE AGREEMENT
                              ------------------

     THIS PURCHASE AGREEMENT (this "Agreement"), dated as of August 24/th/,
2000, is by and between IPG PHOTONICS CORPORATION, a corporation organized under
the laws of the State of Delaware ("Purchaser"), and DR. VALENTIN P. GAPONTSEV
("Seller"), the owner of 50% of the issued and outstanding common stock of IPG
Laser GmbH, a corporation organized under the laws of the Republic of Germany
(the "Company").

                                   RECITALS
                                   --------

     A.   Purchaser desires to purchase shares of Seller's capital stock or
other equity interests in the Company representing 4% of the total issued and
outstanding shares of or other equity interests in the Company.

     B.   Seller owns shares of capital stock or other equity interests in the
Company representing 50% of the total issued and outstanding shares of or other
equity interests in the Company.

     C.   Seller desires to sell to Purchaser, and Purchaser desires to purchase
from Seller, shares of Seller's capital stock or other equity interests in the
Company representing 4% of the total issued and outstanding shares of the
Company, all on the terms and conditions, and subject to the limitations and
exclusions, set forth herein.

     NOW, THEREFORE, in consideration of the purchase price described below, the
representations, warranties, and mutual agreements contained in this Agreement
and other good and valuable consideration, the receipt and sufficiency of which
are hereby acknowledged, the parties hereto hereby agree as follows:

                                   Section 2

                          ACQUISITION OF LASER SHARES

     2.1  Purchase and Sale.  On the terms and subject to the conditions hereof,
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and in reliance on the representations and warranties of Seller (in the case of
Purchaser) and of Purchaser (in the case of Seller) contained herein, on the
Closing Date, Seller shall sell, transfer, assign, convey and deliver to
Purchaser, and Purchaser shall purchase and accept from Seller, the Laser
Shares, in consideration of the delivery to Seller of the Sale Price.

     2.2  Withholding Taxes.  The Sale Price to be paid on the Closing Date
          -----------------
shall be reduced by any applicable withholding taxes required under applicable
law to be withheld and paid by Purchaser to U.S. or other taxing authorities
with respect to the Sale Price. Such withholding shall be at the applicable
statutory rate unless Seller provides Purchaser with an opinion of counsel (the
"Tax Opinion") that no such withholding is required or that withholding is
required at a lower rate. On the Closing Date, Purchaser shall withhold such
amounts as calculated in the immediately preceding sentence and send
confirmation to Purchaser's
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independent auditors of the amounts of taxes required to be withheld and paid by
Purchaser. Any balance of the amount so withheld shall be remitted promptly to
Seller.

                                   Section 3

                                    CLOSING

     3.1  Closing.  The closing of the transactions contemplated herein (the
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"Closing") will take place at the offices of Schleifenbaum, Adler & Partner GbR,
Hindenburgstrasse 1, 57072 Siegen, Germany (or at such other location as the
parties hereto may agree) on the Closing Date.

                                   Section 4

                             CONDITIONS TO CLOSING

     4.1  Conditions Precedent to the Obligations of Purchaser. The obligations
          ----------------------------------------------------
of Purchaser hereunder are subject to the fulfillment (or waiver by Purchaser)
on or prior to the Closing Date of each of the following conditions precedent:

          (a)  Approvals.  The Company and Seller shall have taken all such
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actions required to be taken by either of them with respect to this Agreement.

          (b)  No Liens.  The Laser Shares shall have been transferred to
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Purchaser free and clear of all Liens.

     4.2  Conditions Precedent to the Obligations of Seller. The obligations of
          -------------------------------------------------
Seller hereunder are subject to the fulfillment (or waiver by Seller) on or
prior to the Closing Date of the following condition precedent:

          (a)  Approvals.  Purchaser shall have taken all such actions required
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to be taken by it with respect to this Agreement.

                                   Section 5

                                   COVENANTS

          Name Change. As soon as reasonably practicable after the Closing Date,
Seller shall change the corporate name of "IPG Laser Components" so that it does
not contain "IPG".

                                   Section 6

                        REPRESENTATIONS AND WARRANTIES

     6.1  Representations and Warranties of Seller. Seller represents and
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warrants to Purchaser as of the date hereof that:

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          (a)  Authorization; No Conflict.  Seller has the power to enter into
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this Agreement and all other agreements contemplated by this Agreement to which
such Seller is a party and to consummate the transactions contemplated hereby
and thereby. The execution, delivery and performance by Seller of this Agreement
and the transactions (and the consummation of the transactions) contemplated
hereby will not: (i) result in the breach of, or constitute a default (with or
without notice or lapse of time, or both) under, any provision or accelerate any
obligation or give rise to the termination of (A) any contract, agreement, debt
instrument, indenture, mortgage agreement or other instrument or arrangement to
which Seller or the Company is a party or (B) any judgment, order or decree by
which Seller or the Company is bound; (ii) result in the imposition of any Lien
on any assets of Seller or the Company; or (iii) violate, conflict with or
constitute a default of any applicable law, statute, ordinance, rule or
regulation.

          (b)  Enforceability. This Agreement has been duly executed and
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delivered by Seller and constitutes the legal, valid and binding obligation of
Seller enforceable against him in accordance with its terms, except as such
enforcement may limited by applicable bankruptcy, insolvency, reorganization or
similar laws affecting enforcement of creditors' rights generally and by general
equitable principles.

          (c)  Title to the Laser Shares. Seller is the lawful record owner and
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beneficial owner of the Laser Shares, which have been duly authorized by all
necessary action and which are validly issued, fully paid and nonassessable.
Seller is, and will be on the Closing Date, the record and beneficial owner and
holder of all of the Laser Shares, and on the Closing Date will convey to
Purchaser good and marketable title to the Laser Shares free and clear of all
Liens.

     6.2  Representations and Warranties of Purchaser.  Purchaser hereby
          -------------------------------------------
represents and warrants as of the date hereof that:

          (a)  Due Organization, etc.  Purchaser is a corporation duly organized
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and validly existing and in good standing under the laws of the State of
Delaware. Purchaser has the requisite corporate power and authority to enter
into and perform its obligations hereunder.

          (b)  Authorization; No Conflict. The execution, delivery and
               --------------------------
performance of this Agreement have been duly authorized by all necessary
corporate action on its part and neither the execution and delivery hereof, nor
the consummation of the transactions contemplated thereby, nor compliance by
Purchaser with any of the terms and provisions thereof requires or will require
any approval or consent, other than such consents and approvals as have been
obtained. The execution, delivery and performance by Purchaser of this Agreement
and the transactions (and the consummation of the transactions) contemplated
hereby will not: (i) result in the breach of, or constitute a default (with or
without notice or lapse of time, or both) under, any provision of (A) any debt
instrument, indenture, mortgage agreement or other instrument or arrangement to
which Purchaser is a party or (B) any judgment, order or decree by which
Purchaser is bound; or (ii) result in the imposition of any Lien on any assets
of Purchaser.

          (c)  Enforceability, etc.  This Agreement has been duly executed and
               --------------------
delivered by Purchaser and (assuming the due authorization, execution and
delivery by each other party

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hereto) constitutes its legal, valid and binding obligation enforceable against
Purchaser in accordance with its terms, except as such enforcement may be
limited by applicable bankruptcy, insolvency, reorganization or similar laws
affecting enforcement of creditors' rights generally and by general equitable
principles.

          (d)  Investment Status.  Purchaser is purchasing the Laser Shares for
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its own account, for investment only and not with a view to, or any present
intention of, effecting a distribution of such securities or any part thereof
except pursuant to a registration or an available exemption under applicable
law. Purchaser acknowledges that the Laser Shares have not been registered under
the Securities Act of 1933, as amended (the "Securities Act") or the securities
laws of any state or other jurisdiction and cannot be disposed of unless they
are subsequently registered under the Securities Act and any applicable state
laws or an exemption from such registration is available.

          (e)  Accredited Investor.  Purchaser is an "accredited investor" as
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such term is defined in Rule 501 promulgated under the Securities Act.

          (f)  Rule 144.  Purchaser understands that the exemption from
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registration afforded by Rule 144 (the provisions of which are known to
Purchaser) promulgated under the Securities Act depends on the satisfaction of
various conditions and that, if applicable, Rule 144 may only afford the basis
for sales under certain circumstances and only in limited amounts.

          (g)  Exemption.  Purchaser hereby acknowledges and agrees that the
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purchase and sale of the Laser Shares is intended to be exempt from registration
under the Securities Act by virtue of Section 4(2) and/or Section 3(b) of the
Securities Act, and, if applicable, in the sole judgment of Seller, the
provisions of Regulation D thereunder, which exemption is dependent upon the
truth, completeness and accuracy of the statements made by Purchaser herein and
in any other documents furnished by Purchaser to Seller.

                                   Section 7

                                INDEMNIFICATION

     7.1  General Indemnification.  Each of the parties hereto shall indemnify
          -----------------------
the other against any claim (including all costs, expenses, fees, damages,
penalties, fines, obligations, and liabilities, and costs of enforcement
(including attorneys' fees) under this Section 7 which shall result from (a) the
incorrectness of any representation or breach of any warranty of such party
contained herein or, (b) the breach by such party of any of his or its covenants
or agreements contained herein. Any amount payable pursuant to this Section 7
shall be paid promptly upon receipt of a written demand therefor from the
indemnified party, accompanied by a written statement describing the basis for
such indemnity.

     7.2  Withholding Tax Indemnification.  If Purchaser fails to withhold
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applicable U.S. withholding taxes on the basis of the Tax Opinion, Seller shall
indemnify Purchaser for any adverse consequences resulting from such failure to
withhold, including, but not limited to, any taxes, interest or penalties.

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                                   Section 8

                                 MISCELLANEOUS

     8.1  Fees and Expenses.  Seller and the Purchaser shall bear their own
          -----------------
respective expenses incurred in connection with this Agreement and consummation
of the transactions described therein.

     8.2  Notices.  Unless otherwise specifically provided herein, all notices,
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consents, directions, approvals, instructions, requests, waivers, acceptances,
and other communications required or permitted by the terms hereof to be given
to any Person shall be given in writing by nationally recognized courier service
or by hand delivery, or by facsimile communication followed by such courier
service delivery, and any such notice shall become effective one business day
after delivery to a nationally recognized overnight courier service or if by
facsimile communication or by hand delivery, when received, and shall be
directed to the address as follows; provided that from time to time either party
                                    -------- ----
may designate a new address for purposes of notice hereunder by notice to the
other party:

                          If to Purchaser:

                                   IPG Photonics Corporation
                                   P.O. Box 519
                                   660 Main Street
                                   Sturbridge, MA 01566
                                   Telephone No.: (508) 347-6800
                                   Telecopy No.: (508) 347-6838

                          with a copy to:

                                   Winston & Strawn
                                   200 Park Avenue
                                   New York, New York 10166
                                   Attention: John W. Kaufmann
                                   Telephone No.: (212) 294-4754
                                   Telecopy No.: (212) 294-4700

                          If to Seller:

                                   Dr. Valentin P. Gapontsev

                                   c/o IPG Laser GmbH

                                   Siemensstrasse 7

                                   D-57299 Burbach

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                                   Telephone No.: (2736) 4420-0

                                   Telecopy No.: (2736) 4420-25

     8.3  Entire Agreement; Amendments.  This Agreement contains the entire
          ----------------------------
agreement of the parties with respect to the subject matter hereof, and
supersedes all prior agreements and understandings between the parties, whether
written or oral. This Agreement may not be amended except by written instrument
signed by all of the parties thereto.

     8.4  Successors and Assigns/Third Party Beneficiary.  This Agreement shall
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be binding upon and inure to the benefit of each of the parties hereto and their
respective heirs, personal representatives, successors and assigns. The
Investors listed on Exhibit A to the Stock Purchase Agreement. Relating to the
purchase of Series B Convertible Participating Preferred Stock, par value $0001
per share, of Purchaser shall be third-party beneficiaries of this Agreement.

     8.5  Governing Law/Jurisdiction.  This Agreement shall be construed and
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enforced in accordance with and governed by the laws of the State of New York
(without giving effect to principles of conflicts of law). All actions and
proceedings arising out of or relative to this Agreement shall be heard and
determined a Massachusetts state or federal court sitting in the City of Boston.
The parties hereby irrevocably submit to the exclusive jurisdiction of any
Massachusetts state or federal court sitting in the City of Boston in any action
or proceeding arising out of or relating to this Agreement, and hereby
irrevocably agree that all claims in respect of such action or proceeding may be
heard and determined in such Massachusetts state or federal court. The parties
hereby irrevocably waive, to the fullest extent they may effectively do so, the
defense of an inconvenient forum to the maintenance of such action or
proceeding. The parties agree that a final judgment in any such action or
proceeding shall be conclusive and may be enforced in other jurisdictions by
suit on the judgment or in any other manner provided by law. TO THE EXTENT NOT
PROHIBITED BY APPLICABLE LAW THAT CANNOT BE WAIVED, EACH PARTY HEREBY WAIVES,
AND COVENANTS THAT IT WILL NOT ASSERT (WHETHER AS PLAINTIFF, DEFENDANT OR
OTHERWISE), ANY RIGHT TO TRIAL BY JURY IN ANY FORUM IN RESPECT OF ANY ISSUE,
CLAIM, DEMAND, ACTION OR CAUSE OF ACTION ARISING OUT OF OR BASED UPON THIS
AGREEMENT OR THE SUBJECT MATTER HEREOF, WHETHER NOW EXISTING OR HEREAFTER
ARISING AND WHETHER SOUNDING IN TORT OR CONTRACT OR OTHERWISE.

     8.6  Counterparts.  This Agreement may be executed in separate
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counterparts, each of which when so executed and delivered shall be an original
for all purposes, but all such counterparts shall constitute but one and the
same instrument.

     8.7  Severability.  Any provision of this Agreement that is prohibited or
          ------------
unenforceable in any jurisdiction shall, as to such jurisdiction, be ineffective
to the extent of such prohibition or unenforceability without invalidating the
remaining provisions hereof, and any such prohibition or unenforceability in any
jurisdiction shall not invalidate or render unenforceable such provision in any
other jurisdiction.

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     8.8  Headings.  The section and article headings contained herein are for
          --------
convenience only and shall not be construed as part of this Agreement.

     8.9  Further Assurances.  Each of the parties hereto agrees that it shall
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do, execute, acknowledge and deliver all such further actions, conveyances,
assignments, transfers, documents and other assurances necessary to effectuate
the purpose and carry out the terms and intent of this Agreement.

     8.10 Tax Consequences.  Purchaser shall have no liability for the tax
          ----------------
consequences to Seller and Seller shall have no liability for the tax
consequences to Purchaser as a result of the transactions contemplated hereby.

     8.11 Survival.  The representations, warranties, indemnities and covenants
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contained in this Agreement shall survive indefinitely.

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     IN WITNESS WHEREOF, the parties hereto have each caused this Purchase
Agreement to be duly executed as of the day and year first written above.

     PURCHASER:                           IPG PHOTONICS CORPORATION

                                          By: /s/ Verghese Mammen
                                              ---------------------------------
                                          Name:  VERGHESE MAMMEN
                                          Title: Treasurer


     SELLER:                              /s/ Dr. Valentin P. Gapontsev
                                          ------------------------------------
                                          DR. VALENTIN P. GAPONTSEV

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