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                                                                    EXHIBIT 10.1

                    MASTER REAFFIRMATION AND AMENDMENT NO. 4
                                TO LOAN DOCUMENTS

     THIS MASTER REAFFIRMATION AND AMENDMENT NO. 4 TO LOAN DOCUMENTS (this
"Agreement") is made as of the 18th day of December, 2003, by and among ZYGO
CORPORATION, a Delaware corporation with its principal place of business located
at Laurel Brook Road, Middlefield, Connecticut 06455 ("Zygo"), ZTO PROPERTY
HOLDINGS, LLC, a Delaware limited liability company with its principal place of
business located at 20 Walkup Drive, Westborough, Massachusetts 01581 ("ZTO"),
ZYGO TERAOPTIX, INC., a Delaware corporation with its principal place of
business located at 100 Kuniholm Drive, Holliston, Massachusetts 01746
("TeraOptix" and together with Zygo and ZTO, the "Obligors"), and FLEET NATIONAL
BANK, a national bank with a place of business at 777 Main Street, Hartford,
Connecticut 06115 ("Lender"). Unless otherwise defined herein, capitalized terms
used herein shall have the meanings ascribed to them in the Credit Agreement
described below.

                              W I T N E S S E T H:

     WHEREAS, Obligors and Lender are parties to that certain Amended and
Restated Credit Agreement dated as of May 14, 2001 (as amended, modified,
restated or otherwise supplemented from time to time, including, but not limited
to, that certain Master Reaffirmation and Amendment to Loan Documents dated as
of November 22, 2001 and that certain Master Reaffirmation and Amendment No. 2
to Loan Documents dated as of June 26, 2002, the "Credit Agreement"), pursuant
to which, among other things, Lender has extended to Zygo a commercial revolving
loan/letter of credit facility in the original principal amount of up to
$3,000,000 (the "Revolving Credit Facility"); and

     WHEREAS, ZTO and TeraOptix have each, among other things, unconditionally
guaranteed payment and performance of the Obligations of Zygo under the
Revolving Credit Facility, whether now existing or hereafter arising, pursuant
and subject to the terms and conditions set forth in their respective Guaranty
Agreements; and

     WHEREAS, Obligors have each requested Lender, and Lender has agreed, to
extend the Maturity Dates of the Revolving Loan Commitment and L/C Commitment
from November 20, 2003 to November 18, 2004; and

     WHEREAS, Lender is willing to extend the accommodations requested by
Obligors subject to and in reliance upon the representations, warranties,
acknowledgments, covenants and agreements of Obligors contained herein.

     NOW, THEREFORE, in consideration of the premises set forth herein (which
are incorporated herein as though fully set forth below, by this reference
thereto) and for other good and valuable consideration, the receipt and
sufficiency of which are hereby acknowledged, each of the undersigned agrees as
follows:

1. Amendments to Credit Agreement and other Loan Documents.

     a. Each reference in the Loan Documents to the Credit Agreement shall mean
the Credit Agreement as modified by this Agreement.

     b. Section 1.1 of the Credit Agreement, entitled "Defined Terms", is hereby
amended by deleting the definition of "Maturity Date" in its entirety and
inserting the following in lieu thereof:

          "Maturity Date" means (a) with respect to the Revolving Loan
     Commitment, November 18, 2004, and any subsequent date to which such
     Maturity Date may be extended by Lender in writing in its sole and absolute
     discretion, (b) with respect to the L/C Commitment, November 18, 2004, and
     (c) with respect to the Converted Construction Loan, May 14, 2007.




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2. Reaffirmation. Each of Obligors, as maker, debtor, grantor, pledgor,
assignor, obligor, or in other similar capacity in which it incurs obligations
to Lender or grants liens or security interests in its properties under any of
the Loan Documents, hereby ratifies and reaffirms all of its Obligations,
contingent or otherwise, under each of the Loan Documents to which it is a party
and, to the extent it granted liens on or security interests in any of its
properties pursuant to any Loan Document as security for the Obligations under
or with respect to the Credit Agreement and the other Loan Documents, hereby
ratifies and reaffirms such grant of liens and security interests and confirms
and agrees that such liens and security interests hereafter secure all of the
Obligations, including without limitation, the Obligations arising under the
Revolving Credit Facility, as hereby amended, in each case as if each reference
in such Loan Document to the obligations secured thereby are construed to
hereafter mean and refer to such Obligations under the Credit Agreement and
other Loan Documents, as hereby amended. Each of Obligors acknowledges that each
of the Loan Documents to which it is a party remains in full force and effect,
continues to apply to the Obligations, including, but not limited to, the
Obligations arising under the Revolving Credit Facility as hereby amended, and
is hereby ratified and confirmed. The execution of this Agreement shall not
operate as a novation, waiver of any right, power or remedy of Lender nor
constitute a waiver of any provision of any of the Loan Documents, except as
expressly set forth herein and shall be limited to the particular instance
expressly set forth. Each of Obligors confirms and agrees that the Loan
Documents and each and every covenant, condition, obligation, representation
(except those representations which relate only to a specific date, which are
confirmed as of such date only), warranty and provisions set forth therein are,
and shall continue to be, in full force and effect and are hereby confirmed,
reaffirmed and ratified in all respects.

3. No Default or Event of Default, No Defenses. Each of Obligors hereby
represents and warrants to, and covenants with Lender that, as of the date
hereof, (a) no Default or Event of Default has occurred and is continuing, (b)
it has no defense, offset or counterclaim of any kind or nature whatsoever
against Lender with respect to the Revolving Credit Facility, the Obligations,
or any of the Loan Documents to which it is a party, or any action previously
taken or not taken by Lender with respect thereto or with respect to any
security interest, encumbrance, lien or collateral in connection therewith to
secure the Obligations, and (c) that Lender has fully performed all obligations
to Obligors which it may have had or has on and as of the date hereof.

4. Fee. Simultaneously herewith, in consideration of the Lender's extension of
the Maturity Dates of the Revolving Loan Commitment and L/C Commitment
Termination Date, Zygo shall pay to Lender on the date hereof a non-refundable
commitment fee in the amount of $7,500.

5. Successors and Assigns. This Agreement shall be binding upon each of Obligors
and their respective successors and assigns, and shall inure to the benefit of
Lender and its successors and assigns. The successors and assigns of such
entities shall include, without limitation, their respective receivers,
trustees, or debtors-in-possession.

6. Further Assurances. Each of Obligors hereby agrees from time to time, as and
when requested by Lender, to execute and deliver or cause to be executed and
delivered all such documents, instruments and agreements and to take or cause to
be taken such further or other action as Lender may reasonably deem necessary or
desirable in order to carry out the intent and purposes of this Agreement and
the Loan Documents.

7. Authorization. Each of Obligors is duly authorized to execute and deliver
this Agreement and to perform its obligations under the Credit Agreement and the
other Loan Documents to which it is a party, each as amended hereby.

8. No Conflicts. The execution and delivery of this Agreement, and the
performance by each of Obligors of their respective obligations hereunder and
under any Loan Documents to which any of them may be a party, each as amended
hereby to the extent applicable, do not and will not conflict with any provision
of law or of the charter or by-laws of any of them or of any agreement binding
upon any of them.

9. Severability. Wherever possible, each provision of this Agreement shall be
interpreted in such manner as to be effective and valid under applicable law,
but if any provision of this Agreement shall be prohibited by or invalid under
such law, such provision shall be ineffective to the extent of such prohibition
or invalidity without invalidating the remainder of such provision or the
remaining provisions of this Agreement.


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10. Merger. This Agreement represents the final agreement of Obligors and Lender
with respect to the matters contained herein and may not be contradicted by
evidence of prior or contemporaneous agreements, or prior or subsequent oral
agreements.

11. Execution in Counterparts. This Agreement may be executed in any number of
counterparts and by different parties hereto in separate counterparts, each of
which when so executed shall be deemed to be an original and all of which taken
together shall constitute one and the same agreement.

12. Section Headings. The section headings herein are for convenience of
reference only, and shall not affect in any way the interpretation of any of the
provisions hereof.

13. Governing Law. This Agreement shall be governed by the internal substantive
laws of the State of Connecticut (without regard to its conflicts of law
provisions).

                       THE NEXT PAGE IS THE SIGNATURE PAGE


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     IN WITNESS WHEREOF, this Agreement has been duly executed by the
undersigned as of the day and year first set forth above.

WITNESSES (AS TO OBLIGORS):


/s/ Joyce Goldberg
-----------------------------           ZYGO CORPORATION


/s/ Michael M. Vehlies                  By: /s/ Richard Dressler
-----------------------------               ------------------------------------
                                                Richard M. Dressler
                                                Its Treasurer


                                        ZTO PROPERTY HOLDINGS, LLC


                                        By: /s/ Richard M. Dressler
                                            ------------------------------------
                                                Richard M. Dressler
                                                Its Treasurer


                                        ZYGO TERAOPTIX, INC.


                                        By: /s/ Richard M. Dressler
                                            ------------------------------------
                                                Richard M. Dressler
                                                Its Treasurer


WITNESSES (AS TO LENDER):


/s/ Veronica Leonard
-----------------------------           FLEET NATIONAL BANK


/s/ Matthew Latham                      By: /s/ Matthew E. Hummel
-----------------------------               ------------------------------------
                                            Matthew E. Hummel
                                            Its Senior Vice President


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