<PAGE>

                                                                   Exhibit 10.15

                              SECOND AMENDMENT TO
                      364-DAY REVOLVING CREDIT AGREEMENT

        SECOND AMENDMENT TO 364-DAY REVOLVING CREDIT AGREEMENT, dated as of
March 5, 2001, among NEWPORT CORPORATION (herein referred to as the "Borrower")
and ABN AMRO BANK N.V. (herein referred to as the "Bank").

                             W I T N E S S E T H:

        WHEREAS, the Borrower and the Bank are parties to that certain 364-Day
Revolving Credit Agreement, as amended, dated as of October 29, 1999 (the
"Credit Agreement"); and

        WHEREAS, the Borrower has requested that the Credit Agreement be amended
in certain respects; and

        WHEREAS, the Borrower has requested, among other things, that the Bank
reduce the Commitment and extend the Termination Date; and

        WHEREAS, the Bank is willing to so amend the Credit Agreement, subject
to the terms and conditions hereinafter set forth;

        NOW, THEREFORE, the parties hereto, in consideration of their mutual
covenants and agreements hereinafter set forth and intending to be legally bound
thereby, covenant and agree as follows:

        1.   General. All terms used herein which are not otherwise specifically
defined herein shall have the same meaning herein as defined in the Credit
Agreement as further amended hereby.

        2.   Revolving Credit. Section 1.1 of the Credit Agreement shall be
hereby amended by deleting the amount "$20,000,000" in line 8 thereof and
substituting in its place the amount of "$10,000,000" therefor.

        3.   Revolving Credit Loans. Section 1.2 of the Credit Agreement shall
be amended by deleting the amount "$20,000,000" in line 6 thereof and
substituting in its place the amount of "$10,000,000" therefor.

        4.   Definitions. Section 4.1 of the Credit Agreement shall be and is
hereby amended as follows:

                    (a)  The definition of "EBITDA" shall be amended
               and restated in its entirety as follows:

               "EBITDA" means, with reference to any period, Net
               Income for such period plus all amounts deducted in
               arriving at such Net Income amount in respect of (a)
               Interest Expense for such period,
<PAGE>

               plus (b) federal, state and local income taxes for such
               period, plus (c) all amounts properly charged for
               depreciation of fixed assets and amortization of
               intangible assets during such period on the books of
               the Borrower and its Subsidiaries; provided, however,
               that notwithstanding anything in this definition to the
               contrary: (a) any gains on sales or other dispositions
               of assets of the Company and its Subsidiaries outside
               the ordinary course of their business shall be given no
               effect in determining EBITDA; and (b) interest income
               as determined according to GAAP shall be given no
               effect in determining EBITDA.

                    (b)  The definition of "Termination Date" shall be
               amended and restated in its entirety as follows:

               "Termination Date" means March 4, 2002, or such earlier
               date on which the Commitment is terminated in whole
               pursuant to Section 3.3, 8.2 or 8.3.

                    (c)  A new definition of "Total Funded Debt" shall be
               inserted in the appropriate alphabetical order as follows:

               "Total Funded Debt" means, at any time the same is to
               be determined, the aggregate of all Indebtedness for
               Borrowed Money of the Borrower and its Subsidiaries at
               such time, plus all Indebtedness for Borrowed Money of
               any other Person which is directly or indirectly
               guaranteed by the Borrower or any of its Subsidiaries
               or which the Borrower or any of its Subsidiaries has
               agreed (contingently or otherwise) to purchase or
               otherwise acquire or in respect of which the Borrower
               or any of its Subsidiaries has otherwise assured a
               creditor against loss, plus obligations of the Borrower
               and its Subsidiaries as less under capital leases (in
               accordance with GAAP).

                    (d)  The definition "Total Liabilities" shall be
               deleted in its entirety.

        5.   Leverage Ratio. Section 7.8 of the Credit Agreement shall be
amended and restated in its entirety as follows:

                    Section 7.8.  Leverage Ratio. The Company will at
               all times maintain a ratio of Total Funded Debt to
               EBITDA (the "Leverage Ratio") of not more than 2.0 to
               1.00.

        6.   Tangible Net Worth. Section 7.9 of the Credit Agreement shall be
amended and restated in its entirety as follows:

                                      -2-
<PAGE>

                    Section 7.9.  Tangible Net Worth. The Company will
               at all times maintain Tangible Net Worth at not less
               than the sum of $324,929,000 plus, on a cumulative
               basis, 75% of positive Net Income for each fiscal
               quarter end subsequent to the fiscal quarter ended
               December 31, 2000 plus, at the time of offering, 75% of
               Equity Offerings issued after the date of this
               Agreement.

        7.   Capital Expenditures. Section 7.12 of the Credit Agreement shall be
amended and restated in its entirety as follows:

                    Section 7.12. Capital Expenditures. The Company
               will not, nor will it permit any Subsidiary to, expend
               or become obligated for capital expenditures (as
               determined in accordance with GAAP) in an aggregate
               amount in excess of $29,000,000 during any fiscal year
               of the Company.

        8.   Acquisitions. Subsection (g) of Section 7.15 of the Credit
Agreement shall be amended and restated in its entirety as follows:

                    (g)  Acquisitions by the Company of substantially
               all of the assets of corporations or Acquisitions of
               Wholly-Owned Domestic Restricted Subsidiaries from and
               after the date hereof so long as (i) the aggregate
               amount of cash consideration payable in connection with
               such Acquisitions does not exceed $12,000,000, (ii) the
               aggregate amount of stock consideration payable in
               connection with such Acquisitions does not exceed
               $18,000,000, (iii) the Acquisition of a Domestic
               Restricted Subsidiary shall have been approved by the
               board of directors of such Person prior to such
               Acquisition, (iv) such acquired Domestic Restricted
               Subsidiary shall have complied with the provisions of
               Section 7.23 hereof and (v) prior to such Acquisition,
               Company shall deliver a written certificate in form
               acceptable to the Bank signed by the President or chief
               financial officer of the Company to the effect that to
               the best of such officer's knowledge and belief no
               Default or Event of Default has occurred or is
               continuing as a result of such Acquisition on a pro
               forma basis;

        9.   Revolving Note. The Note executed by the Company in favor of Bank
in the form attached as Exhibit A to the Credit Agreement shall be amended and
restated in its entirety by the note executed by the Company in favor of the
Bank of even date herewith in the form of Exhibit A attached hereto. The Bank
shall mark such prior Note as "Cancelled" and return the same to the Company
found in Exhibit A to the Credit Agreement shall be amended and restated in its
entirety by replacing such with Exhibit A attached hereto.

                                      -3-
<PAGE>

       10.   Compliance Certificate. The Compliance Certificate found in Exhibit
B to the Credit Agreement shall be amended and restated in its entirety by
replacing such with Exhibit B attached hereto.

       11.   Representations. In order to induce the Bank to execute and deliver
this Amendment, the Borrower hereby represents to the Bank that as of the date
hereof the representations and warranties set forth in Section 5 of the Credit
Agreement are and shall be and remain true and correct (except that the
representations contained in Section 5.5 shall be deemed to refer to the most
recent financial statements of the Borrower delivered to the Bank) and the
Borrower is in compliance with the terms and conditions of the Credit Agreement
and no Default or Event of Default has occurred and is continuing under the
Credit Agreement or shall result after giving effect to this Amendment.

       12.   Effectiveness. This Amendment shall become effective (i) when it
shall be executed by the Borrower and the Bank, (ii) the Borrower shall have
executed and delivered a new Note to the Bank as identified in Exhibit A hereto,
(iii) the Bank has received certified copies of the resolutions of the Board of
Directors of the Borrower approving the increase and extension described herein,
(iv) the Bank shall have received copies (executed or certified, as may be
appropriate) of all legal documents or proceedings taken in connection with the
execution and delivery of this Amendment to the extent the Bank or its counsel
may reasonably request. This Amendment may be executed in separate counterparts,
all of which taken together shall constitute one and the same instrument. This
agreement shall be construed and determined in accordance with the laws of the
State of California. Except as herein specifically amended, the Credit Agreement
shall be and remain in full force and effect and wherever reference is made in
any note, document, letter or other communication to the Credit Agreement, such
reference shall, without more, be deemed to refer to the Credit Agreement as
amended hereby.

                 [REMAINDER OF PAGE INTENTIONALLY LEFT BLANK]

                                      -4-
<PAGE>

        IN WITNESS WHEREOF, the parties hereto, by their officers thereunto duly
authorized, have executed and delivered this Agreement as of the date first
above written.

                                               NEWPORT CORPORATION, as Borrower

                                               By
                                                  Title:

                                               ABN AMRO BANK N.V., as Bank



                                               By
                                                  Title:



                                               By
                                                  Title:

                                      -5-
<PAGE>

                                   EXHIBIT A

                              NEWPORT CORPORATION

                             REVOLVING CREDIT NOTE

$10,000,000                                                        March 5, 2001

        On the Termination Date, for value received, the undersigned, Newport
Corporation, a Nevada corporation (the "Company"), hereby promises to pay to the
order of ABN AMRO BANK N.V. (the "Bank") at its office at 300 South Grand
Avenue, Los Angeles, California, the principal sum of (i) TEN MILLION and no/100
DOLLARS ($10,000,000), or (ii) such lesser amount as may at the time of the
maturity hereof, whether by acceleration or otherwise, be the aggregate unpaid
principal amount of all Loans owing from the Company to the Bank under the
Revolving Credit provided for in the Credit Agreement hereinafter mentioned.

        This Note evidences Loans made and to be made to the Company by the Bank
under the Revolving Credit provided for under that certain 364-Day Revolving
Credit Agreement, as amended, dated as of October 29, 1999 between the Company
and the Bank (said Credit Agreement, as the same may be amended, modified or
restated from time to time, being referred to herein as the "Credit Agreement"),
and the Company hereby promises to pay interest at the office described above on
such Loans evidenced hereby at the rates and at the times and in the manner
specified therefor in the Credit Agreement.

        Each Loan made under the Revolving Credit against this Note, any
repayment of principal hereon, the status of each such Loan from time to time as
part of the Domestic Rate Portion or a LIBOR Portion and, in the case of any
Fixed Rate Portion, the interest rate and Interest Period applicable thereto
shall be endorsed by the holder hereof on a schedule to this Note or recorded on
the books and records of the holder hereof (provided that such entries shall be
endorsed on a schedule to this Note prior to any negotiation hereof). The
Company agrees that in any action or proceeding instituted to collect or enforce
collection of this Note, the entries endorsed on a schedule to this Note or
recorded on the books and records of the holder hereof shall be prima facie
evidence of the unpaid principal balance of this Note, the status of each Loan
from time to time as part of the Domestic Rate Portion or a LIBOR Portion and,
in the case of any Fixed Rate Portion, the interest rate and Interest Period
applicable thereto.

        This Note is issued by the Company under the terms and provisions of the
Credit Agreement and this Note and the holder hereof are entitled to all of the
benefits and security provided for thereby or referred to therein, to which
reference is hereby made for a statement thereof. This Note may be declared to
be, or be and become, due prior to its expressed maturity, voluntary prepayments
may be made hereon, and certain prepayments are required to be made hereon, all
in the events, on the terms and with the effects provided in the Credit
Agreement. All capitalized terms used herein without definition shall have the
same meanings herein as such terms are defined in the Credit Agreement.
<PAGE>

        The Company hereby promises to pay all costs and expenses (including
attorneys' fees) suffered or incurred by the holder hereof in collecting this
Note or enforcing any rights in any collateral therefor. The Company hereby
waives presentment for payment and demand. This Note shall be construed in
accordance with, and governed by, the internal laws of the State of California
without regard to principles of conflicts of laws.

                                          NEWPORT CORPORATION

                                          By:_________________________________
                                          Name:_______________________________
                                          Its:________________________________

                                      -2-
<PAGE>

                                   EXHIBIT B

                            COMPLIANCE CERTIFICATE


     This Compliance Certificate is furnished to ABN AMRO Bank N.V. (the "Bank")
pursuant to that certain 364-Day Revolving Credit Agreement, as amended, dated
as of October 29, 1999, by and between Newport Corporation (the "Company") and
the Bank (the "Credit Agreement"). Unless otherwise defined herein, the terms
used in this Compliance Certificate have the meanings ascribed thereto in the
Credit Agreement.

     THE UNDERSIGNED HEREBY CERTIFIES THAT:

          1.  I am the duly elected _____________________________________ of the
     Company;

          2.   I have reviewed the terms of the Credit Agreement and I have
     made, or have caused to be made under my supervision, a detailed review of
     the transactions and conditions of the Company and its Subsidiaries during
     the accounting period covered by the attached financial statements;

          3.   The examinations described in paragraph 2 did not disclose, and I
     have no knowledge of, the existence of any condition or the occurrence of
     any event which constitutes a Default or Event of Default during or at the
     end of the accounting period covered by the attached financial statements
     or as of the date of this Certificate, except as set forth below;

          4.   The financial statements required by Section 7.5 of the Credit
     Agreement and being furnished to you concurrently with this certificate
     are, to the best of my knowledge, true, correct and complete as of the
     dates and for the periods covered thereby; and

          5.   The Attachment hereto sets forth financial data and computations
     evidencing the Company's compliance with certain covenants of the Credit
     Agreement, all of which data and computations are, to the best of my
     knowledge, true, complete and correct and have been made in accordance with
     the relevant Sections of the Credit Agreement.

     Described below are the exceptions, if any, to paragraph 3 by listing, in
detail, the nature of the condition or event, the period during which it has
existing and the action which the Company has taken, is taking, or proposes to
take with respect to each such condition or event:

________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
<PAGE>

        The foregoing certifications, together with the computations set forth
in the Attachment hereto and the financial statements delivered with this
Certificate in support hereof, are made and delivered this _____ day of
____________, 20__.

                                               NEWPORT CORPORATION

                                               By

                                                 Its:_________________________

                                      -2-
<PAGE>

                     Attachment to Compliance Certificate
                              Newport Corporation

                 Compliance Calculations for Credit Agreement
                         Dated as of October 29, 1999
                     Calculations as of ____________, 20__

================================================================================


A.   Quick Ratio (Section 7.7)
     -------------------------

     1.   Current assets                                           $___________
                                                                       A1

     2.   Inventory                                                $___________
                                                                       A2

     3.   Line A1 minus Line A2                                    $___________
                                                                       A3

     4.   Current liabilities (excluding Loans)                    $___________
                                                                       A4

     5.   Ratio of Line A3 to Line A4                              ______:  1.0

     6.   Line A5 ratio must not be less than                          1.0: 1.0

          Company in compliance?                                       yes/no

B.   Tangible Net Worth (Section 7.9)
     --------------------------------
     1.   Total shareholder's equity                               $___________
                                                                       B1

     2.   Sum of:

          (i)  intangibles         $__________

          (ii) write-up of assets  $__________                     $___________
                                                                       B2

     3.   Line B1 minus Line B2                                        $=======
          (Tangible Net Worth)                                         B3

     4.   Line B3 must be greater than or equal to                 $___________

          Company in compliance?                                       yes/no
<PAGE>

C.   Leverage Ratio (Section 7.8)
     ----------------------------

     1.   Total Funded Debt                                        $___________
                                                                      C1

     2.   Net Income for past 4 quarters                           $___________
                                                                      C2

     3.   Interest Expense for past 4 quarters                     $___________
                                                                      C3

     4.   Federal, state and local income                          $___________
          taxes for past 4 quarters                                   C4

     5.   Depreciation and amortization for                        $___________
          past 4 quarters                                             C5

     6.   Interest income for past 4 quarters                      $___________
                                                                      C6

     7.   Extraordinary gains.                                     $___________
                                                                      C7

     8.   Sum of Lines C2, C3, C4 and C5 less sum of Lines C6         $========
          and C7 (EBITDA)                                             C8

     9.   Ratio of Line C1 to Line C8                              ______:  1.0

     10.  Line C9 ratio must not be greater than                      2.0: 1.0

          Company in compliance?                                      yes/no

D.   Interest Coverage Ratio (Section 7.11)
     --------------------------------------


     1.   EBITDA (Line C8 above)                                      $========
                                                                      D1


     2.   Interest expense (Line C3 above)                            $========
                                                                      D2


     3.   Ratio of Line D1 to Line D2                              ______:  1.0


     4.   Line D3 ratio must not be less than                         3.5: 1.0

          Company in compliance?                                      yes/no
<PAGE>

E.   Net Income (Section 7.10)
     -------------------------

     1.   Net Income for past quarter                             $___________
                                                                      E1

     2.   Net Income for fiscal quarter preceding                 $___________
          Line E1 quarter                                             E2

     3.   10% of Tangible Net Worth (Line B3 above)               $___________
                                                                      E3

     4.   Line E1 amount must not exceed Line E3

     5.   Line E2 amount must exceed $0

          Company in compliance                                       yes/no

F.   Capital Expenditures (Section 7.12)
     -----------------------------------

     1.   Capital expenditures fiscal year to date                $___________
                                                                      F1

     2.   Line F1 amount must not exceed $29,000,000

          Company in compliance?                                      yes/no