Exhibit 4.1

                                ZYGO CORPORATION
                          EMPLOYEE STOCK PURCHASE PLAN

     1. Purpose. The purpose of the Zygo Corporation Employee Stock Purchase
Plan is to provide Eligible Employees of the Company and its Subsidiaries with a
means to acquire shares of Common Stock through payroll deductions. The Plan is
intended to qualify as an "employee stock purchase plan" under Section 423 of
the Code and shall be interpreted and construed accordingly.

     2. Definitions. For purposes of the Plan, the following terms have the
following meanings:

          (a) "ACCOUNT" shall mean the bookkeeping account established in the
     name of each Participant to reflect the payroll deductions made on behalf
     of the Participant.

          (b) "BOARD" shall mean the Board of Directors of the Company.

          (c) "CODE" shall mean the Internal Revenue Code of 1986, as amended.

          (d) "COMMITTEE" shall mean the committee appointed to administer the
     Plan in accordance with Section 4 or, if no such committee is duly
     constituted or appointed, the Board.

          (e) "COMMON STOCK" shall mean the Company's common stock, par value
     $0.10

          (f) "COMPANY" shall mean Zygo Corporation, a Delaware corporation, and
     any successor thereto.

          (g) "COMPENSATION" shall mean the base compensation paid by the
     Company or a Subsidiary to a Participant which is required to be reported
     as wages on the Participant's Form W2, including such additional amounts
     which are not includible in gross income by reason of Sections 125,
     402(e)(3) or 402(h)(1)(B) of the Code, and excluding any bonuses, overtime
     pay, severance, sick leave, expense and relocation allowances, gains from
     the exercise of stock options and other irregular payments (except
     commissions).

          (h) "EMPLOYEE" shall mean any person on the active employment payroll
     of the Company or any of its Subsidiaries. Any person classified by the
     Company or any of its Subsidiaries at the time services are provided as an
     independent contractor or consultant shall not be eligible to participate
     in the Plan during the period which he or she is so classified even if
     later retroactively reclassified as an Employee during all or any part of
     such period pursuant to applicable law or otherwise.

          (i) "ELIGIBLE EMPLOYEE" shall mean, with respect to an Offering
     Period, any Employee on the Enrollment Date who satisfies each of the
     following criteria:


               (1) the Employee does not immediately after the grant, directly
          or indirectly, own stock (as defined by the Code) and/or hold
          outstanding options to purchase stock possessing five percent (5%) or
          more of the total combined voting power or value of all classes of
          stock of the Company or a "parent corporation" or Subsidiary of the
          Company;


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               (2) the Employee's customary employment is for twenty (20) hours
          or more per week or such lesser number of hours established by the
          Committee on a uniform and nondiscriminatory basis; and

               (3) the Employee customarily works a minimum of five (5) months
          per year, or such lesser number of months established by the Committee
          on a uniform and nondiscriminatory basis.

          If the Committee permits any Eligible Employee of a Subsidiary to
          participate in the Plan during an Offering Period, then all Eligible
          Employees of that Subsidiary shall also be permitted to participate in
          the Plan during such Offering Period.

          (j) "ENROLLMENT DATE" shall mean the first day of an Offering Period.

          (k) "EXERCISE DATE" shall mean the last day of an Offering Period.

          (l) "FAIR MARKET VALUE" for purposes of the Plan, unless otherwise
     required by the Code, shall mean, as of any date, the closing sale price
     per share of Common Stock as published by the principal national securities
     exchange on which the Common Stock is traded on such date or, if there is
     no sale of Common Stock on such date, the average of the bid and asked
     prices on such exchange at the close of trading on such date, or if shares
     of the Common Stock are not listed on a national securities exchange on
     such date, the last reported trading price or, if none, the average of the
     bid and asked prices in the over-the-counter market at the close of trading
     on such date. If there is no such reported price for the Common Stock for
     the date in question due to the applicable stock market not being open for
     trading, then such price on the last preceding date for which such price
     exists shall be determinative of Fair Market Value.

          (m) "OFFERING PERIOD" shall mean the six (6) month period commencing
     on January 1, 2001 or such later date as established by the Committee, and
     each successive six (6) month period thereafter. To the extent permitted
     under Section 423 of the Code, the Committee shall have the power to change
     the duration of future Offering Periods and the commencement dates thereof.

          (n) "PARTICIPANT" shall mean any Eligible Employee for whom an Account
     is maintained under the Plan.

          (o) "PURCHASE PRICE" shall mean, subject to adjustment pursuant to
     Section 10 hereof, eighty-five percent (85%) of the lesser of the Fair
     Market Value of a share of Common Stock on (i) the Enrollment Date or (ii)
     the Exercise Date.

          (p) "PLAN" shall mean this Zygo Corporation Employee Stock Purchase
     Plan, as amended from time to time.

          (q) "SUBSIDIARY" shall mean any "subsidiary corporation" of the
     Company (within the meaning of Section 424(f) of the Code) that is
     designated by the Committee as an eligible Subsidiary under the Plan from
     time to time.

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     3. Available Shares. Subject to adjustment as provided in Section 10, the
maximum number of shares of Common Stock that may be sold under the Plan shall
not exceed 500,000 shares. Such shares may be either authorized and unissued or
held by the Company in its treasury. The Committee may cause the Company to
purchase previously issued and outstanding shares of Common Stock in order to
enable the Company to satisfy its obligations hereunder. Subject to adjustment
pursuant to Section 10 or as otherwise determined by the Committee prior to the
commencement of any Offering Period, the maximum number of shares of Common
Stock a Participant may purchase during any Offering Period shall not exceed 500
shares.

     4. Administration. The Plan shall be administered by the Company's
Compensation and Stock Option Committee or such other committee appointed by the
Board from time to time. Subject to the provisions of the Plan, the Committee,
acting in its sole and absolute discretion, shall have full power and authority
to interpret the provisions of the Plan, to change the time covered by an
Offering Period, to supervise the administration of the Plan, and to take such
other action as may be necessary or desirable in order to carry out the
provisions of the Plan. A majority of the members of the Committee shall
constitute a quorum. The Committee may act by the vote of a majority of its
members present at a meeting at which there is a quorum or by written consent.
The decision of the Committee, including questions of construction,
interpretation and administration, shall be final, binding and conclusive on all
persons. The Company shall indemnify and hold harmless each member of the
Committee and any employee or director of the Company or of a Subsidiary who
provides assistance or performs services in connection with the administration
or interpretation of the Plan against any loss, cost, liability (including any
sum paid in settlement of a claim with the approval of the Board), damage and
expense (including legal and other expenses incident thereto) arising out of or
incurred in connection with the Plan, unless and except to the extent
attributable to such person's fraud or wilful misconduct.

     5. Eligibility and Enrollment. An Eligible Employee shall become a
Participant on the first Enrollment Date occurring on or after his or her
satisfaction of the Plan's eligibility requirements and completion of a Plan
enrollment form authorizing payroll deductions. Such enrollment form must be
filed with the Company prior to the applicable Offering Period and during the
enrollment period established by the Company. Payroll deductions for a
Participant shall commence with the first payroll and shall end with the last
payroll in the Offering Period to which such authorization is applicable, unless
sooner terminated by the Participant in accordance with the provisions hereof.
Notwithstanding any provisions of the Plan to the contrary, to the extent
required by applicable law, no Participant may be granted the right to purchase
Common Stock under the Plan if and to the extent that the Participant's right to
purchase stock under all employee stock purchase plans (within the meaning of
Section 423 of the Code) of the Company or a Subsidiary would accrue at a rate
which exceeds $25,000 in Fair Market Value (determined at the time of grant) in
accordance with the Code for each calendar year in which such right is
outstanding.

     6. Payroll Deduction. At the time a Participant enrolls in the Plan, he or
she must elect the amount to be deducted from each paycheck during the Offering
Period(s) covered by the election, provided that (i) unless otherwise determined
by the Committee with respect to future Offering Periods, no more than ten
percent (10%) of a Participant's Compensation may be withheld under the Plan on
any pay date, and (ii) the Committee, acting in its discretion and in a uniform
and nondiscriminatory manner, may establish a minimum required amount or
percentage of

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Compensation which must be withheld during an Offering Period. All payroll
deductions made for a Participant shall be credited to the Participant's
Account. Interest shall not accrue on any amounts credited to a Participant's
Account. The rate of a Participant's contribution, once established, shall
remain in effect for all subsequent Offering Periods unless changed by the
Participant in writing at such time and in such manner as the Committee may
prescribe.

     7. Purchase of Shares. On each Exercise Date, the amount credited to a
Participant's Account shall be used to purchase a whole number of shares of
Common Stock, the number of which will be determined by dividing the amount
credited to the Participant's Account by the Purchase Price per share. Any
amount remaining in the Participant's Account shall be credited to the
Participant's Account as of the beginning of the next Offering Period. If the
total number of shares of Common Stock to be purchased as of an Exercise Date,
when aggregated with shares of Common Stock previously purchased under the Plan,
exceeds the number of shares then authorized under the Plan, a pro-rata
allocation of the available shares shall be made among the Participants based
upon the amounts in their respective Accounts as of the Exercise Date.

     8. Discontinuance or Withdrawal; Withholding Changes.

          (a) Discontinuance or Withdrawal. At any time during an Offering
     Period, a Participant may notify the Company that he or she wishes to
     discontinue contributions under the Plan. This notice shall be in writing
     and shall become effective as soon as practicable following its receipt by
     the Company. A Participant may elect to withdraw all, but not less than
     all, of the amount of his or her Account at any time during an Offering
     Period, except on the Exercise Date with respect to that Offering Period.
     If a withdrawal is made during an Offering Period, no further contributions
     shall be permitted during that Offering Period by the withdrawing
     Participant.

          (b) Withholding Changes. At any time during an Offering Period, a
     Participant may increase or decrease the rate of his or her payroll
     deductions by completing or filing with the Company a new enrollment form
     authorizing a change in payroll deduction rate. The Committee may, in its
     discretion, limit the number of payroll deduction rate changes during any
     Offering Period. The change in rate shall be effective as soon as
     practicable following the Company's receipt of the new enrollment form.

          (c) Termination of Employment. Any Participant whose employment with
     the Company and its Subsidiaries is terminated for any reason before an
     Exercise Date shall thereupon cease being a Participant. The total amount
     credited to the Participant's Account during the Offering Period shall be
     returned to the Participant or, in the case of a deceased Participant, to
     the Participant's beneficiary, as soon as practicable after the
     Participant's termination of employment.

     9. Rights as a Stockholder. No shares of Common Stock shall be issued under
the Plan until full payment therefor has been made. A Participant shall have no
rights as a stockholder with respect to any shares until the date a stock
certificate (or its equivalent) for such shares is issued to him or her. Except
as otherwise specifically provided herein, no adjustments shall be made for
dividends or distributions of other rights for which the record date is prior to
the date such stock certificate (or its equivalent) is issued.

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     10. Capital Changes; Reorganization; Sale.

          (a) Adjustments Upon Changes in Capitalization. The aggregate number
     and class of shares of Common Stock which may be sold under the Plan and
     purchased by a Participant, as well as the number and class of shares of
     Common Stock and the price per share covered by each right outstanding
     under the Plan which has not yet been exercised, shall be adjusted
     proportionately or as otherwise appropriate to reflect any increase or
     decrease in the number of issued shares of Common Stock resulting from a
     split-up or consolidation of shares or any like capital adjustment, or the
     payment of a stock dividend, and/or to reflect a change in the character or
     class of shares covered by the Plan arising from a readjustment or
     recapitalization.

          (b) Cash, Stock or Other Property for Stock. Except as otherwise
     provided in this Section, in the event of an Exchange Transaction (as
     defined below), each Participant shall be permitted to purchase Common
     Stock with the balance of his or her Account immediately prior to such
     Exchange Transaction, and any amount credited to a Participant's Account
     which is not used to purchase Common Stock before the Exchange Transaction
     shall be distributed to the Participant. Notwithstanding the preceding
     sentence, (i) if, as part of the Exchange Transaction, the stockholders of
     the Company receive capital stock of another corporation ("Exchange Stock")
     in exchange for their shares of Common Stock (whether or not such Exchange
     Stock is the sole consideration), and if the Board, in its sole discretion,
     so directs, then the rights of all Participants to purchase shares of
     Common Stock shall be converted into rights to purchase shares of Exchange
     Stock on an economically equivalent basis; and (ii) the Board, acting in
     its discretion, may suspend operation of the Plan as of any date that
     occurs after a contract is made which, if consummated, would result in an
     Exchange Transaction and before the Exchange Transaction is consummated.

          (c) Definition of Exchange Transaction. For purposes hereof, the term
     "Exchange Transaction" shall mean a merger (other than a merger of the
     Company in which the holders of Common Stock immediately prior to the
     merger have the same proportionate ownership of Common Stock in the
     surviving corporation immediately after the merger), consolidation,
     acquisition of property or stock, separation, reorganization (other than a
     mere reincorporation or the creation of a holding company), liquidation of
     the Company or any other similar transaction or event so designated by the
     Board in its sole discretion, as a result of which the stockholders of the
     Company receive cash, stock or other property in exchange for or in
     connection with their shares of Common Stock.

          (d) Determination of Committee to be Final. All adjustments under this
     Section 10 shall be made by the Committee, and its determination as to what
     adjustments shall be made, and the extent thereof, shall be final, binding
     and conclusive.

     11. Amendment and Termination. The Board may amend or terminate the Plan at
any time; provided, however, that, except as otherwise provided in Section 10
hereof, any amendment which increases the aggregate number of shares of Common
Stock which may be issued under the Plan, modifies the corporations or class of
corporations whose employees are offered options under the Plan or otherwise
requires stockholder approval under applicable law shall be subject to the
approval of the Company's stockholders.

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     12. Transferability. The rights of a Participant to purchase Common Stock
under the Plan are not assignable or transferable and may only be exercised
during the Participant's lifetime by the Participant. A Participant may file a
written designation of a beneficiary who is to receive the amount credited to
the Participant's Account in the event of the Participant's death during an
offering period. A Participant's beneficiary designation may be changed by the
Participant at any time by written notice. In the event of the death of a
Participant and in the absence of a validly designated beneficiary who is living
at the time of the Participant's death, the Participant's estate shall be deemed
to be his or her designated beneficiary.

     13. No Rights Conferred. Nothing contained in the Plan shall be deemed to
give any individual any right to be retained in the employ of the Company and
its Subsidiaries or to interfere with the right of the Company and its
Subsidiaries to discharge him or her at any time.

     14. Use of Funds. All payroll deductions received or held by the Company
under the Plan may be used by the Company for any corporate purpose, and the
Company shall not be obligated to segregate such payroll deductions.

     15. Legal Requirements. The Committee may impose such other conditions with
respect to the purchase of Common Stock hereunder, including, without
limitation, any conditions relating to the application of federal or state
securities laws and/or any exchange or listing requirements as it may deem
necessary or advisable.

     16. Governing Law. The Plan shall be governed by the laws of the State of
Delaware, without regard to its principles of conflicts of law.

     17. Decisions and Determinations. Any decision or determination made by the
Board pursuant to the provisions hereof and, except to the extent rights or
powers under the Plan are reserved specifically to the discretion of the Board,
all decisions and determinations of the Committee are final, binding and
conclusive.

     18. Effective Date. The Plan shall become effective as of the date of its
adoption by the Board, subject to approval by the Company's stockholders within
twelve (12) months thereafter.

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