Document:

<PAGE>

                                                                   EXHIBIT 10.13
                           SECOND AMENDMENT TO LEASE

This Second Amendment to Lease ("Second Amendment") is dated as of April, 2000,
and is entered into by and between The Esplanade on Redhill LLC, a California
limited liability company ("Landlord") and Irvine Sensors Corporation, a
Delaware corporation ("Tenant").

                                   RECITALS

A.   Landlord's predecessor's predecessor, Carlsberg Realty, Inc., as Landlord,
and Tenant as Tenant, are parties to that certain Lease dated May 1, 1996
("Lease"), of that certain premises containing approximately 2,894 rentable
square feet in Building 5, Suites 201-210 of the Project defined in the Lease
which is commonly known as The Esplanade.

B.   Landlord's predecessor, Esplanade Property, Ltd., a California limited
partnership, which was the successor Landlord to Carlsberg Realty, Inc., entered
into that certain Amendment No. 1 to Lease dated July 17, 1998 ("First
Amendment").

C.   The Esplanade on Redhill LLC, as successor Landlord to Esplanade Property,
Ltd. and Tenant, desire to amend the Lease as amended by the First Amendment
(hereinafter sometimes collectively referred to as the "Lease") in the following
particulars. Capitalized terms not otherwise defined herein shall have the
meanings given them in the Lease.

                                  AGREEMENTS

NOW THEREFORE, for valuable consideration, the receipt and sufficiency of which
are hereby acknowledge, Landlord and Tenant agree as follows:

1.   Tenant's Acknowledgment of Occupancy, No Default. Tenant acknowledges that
     ------------------------------------------------
it is presently occupying and has fully accepted the Premises in its "as is"
condition as of the date hereof To the best of Tenant's knowledge, neither
Tenant nor Landlord are in default under the Lease nor has any event occurred
which, with the passage of time or the giving of notice, or both, would
constitute a default or breach of the Lease by Tenant or Landlord.

2.   Confirmation of the Term. Landlord and Tenant confirm that the Term of the
     ------------------------
Lease extends to and expires on September 30, 2001.

3.   Cancellation of Tenant's Right to Terminate in the First Amendment. The
     ------------------------------------------------------------------
Tenant's right to terminate the Lease set forth in Section 4 of the First
Amendment is hereby canceled, and Section 4 of the First Amendment is hereby
deleted and eliminated in its entirety.

4.   Tenant's New Right to Cancel the Lease. Concurrently with the execution of
     --------------------------------------
this Second Amendment, Tenant is executing that certain Lease of even date of
premises in Building 4 of the Project consisting of 8,560 square feet of office
space and 1,450 square feet of warehouse space ("Building 4 Lease"). Provided
that Tenant is not then in default of its obligations under the Building 4 Lease
or this Lease, Tenant shall have the right upon at least two (2) calendar months
written notice to Landlord to terminate this Lease on the last calendar day of a
month subject to all the applicable
<PAGE>

provisions of this Lease regarding termination and Tenant's obligations with
respect thereto, including, without limitation, the provisions of Section 30,
Surrender of Premises, and Section 31, Holding Over, of the Lease.

5.   Addresses of Landlord and Tenant. The addresses of Landlord and Tenant for
     --------------------------------
the payment of rent and notices and all other purposes under the Lease are as
follows:

Landlord

     THE ESPLANADE ON REDHILL LLC
     c/o California Industrial Properties LLC
     2402 Michelson Drive, Suite 270
     Irvine, CA 92612-1323
     Phone: 949/474-7030
     Fax: 949/474-2101

 Tenant

     IRVIN SENSORS CORPORATION
     3001 Red Hill Avenue
     Building 3, Suite 102
     Costa Mesa, CA 92626
     Phone:
     Fax:

6.   Reaffirmation of Lease as Amended. The Lease, as amended by the First
     ---------------------------------
Amendment and this Second Amendment, remains in full force and effect and is
hereby reaffirmed.

                           [Signature Page to Follow]

                                       2
<PAGE>

IN WITNESS WHEREOF, the parties hereto have executed this Second Amendment as of
the date first above written.

                                      LANDLORD

                                      THE ESPLANADE ON REDHILL LLC,
                                      a California limited liability company

                                      By: __________________________________
                                          Authorized Signatory

                                      TENANT

                                      IRVINE SENSORS CORPORATION,
                                      a Delaware corporation

                                      By: /s/ [ILLEGIBLE]
                                          ----------------------------------

                                       3
<PAGE>

                           AMENDMENT NO. 1 TO LEASE
                           ------------------------

     AMENDMENT NO. 1 TO LEASE, dated as of July 17, 1998 between ESPLANADE
PROPERTY, LTD., a California limited partnership ("Landlord") and IRVINE SENSORS
CORPORATION, a Delaware corporation ("Tenant").

     Pursuant to that certain Lease dated May 1, 1996, by and between Landlord's
predecessor and Tenant (the "Lease"), Tenant has leased certain premises
consisting of approximately 2,894 rentable square feet, lamed at 3001 Redhill
Avenue, Building 5, Suites 201, 203, 204, 205, 206, 207, 208, and 210, Costa
Mesa, California 92626 (the "Premises").

     Landlord and Tenant desire to modify the Lease as provided herein.

     NOW, THEREFORE, for good and valuable consideration, the receipt of which
is hereby acknowledged, the parties hereby agree as follows:

     1.   Tenant acknowledges that it is presently occupying and has fully
accepted the Premises in "AS IS" condition.

     2.   The term of the Lease, as provided in Section 3, shall be extended for
a period of thirty-six (36) months, commencing August 1, 1998, and ending
September 30, 200l.

     3.   Effective August 1, 1998, the monthly Base Rent for the extended term
shall be $3,097 per month for Months 1 - 12, $3,154 per month for Months 13 -
24, and $3,212 per month thereafter.

     4a.  Tenant may terminate the Lease any time after the end of the twenty-
fourth (24th) month of the extended term hereof, but only if Tenant notifies
Landlord in writing by certified mail of its election to do so at least 180 days
prior to the effective date of such termination and pays to Landlord a
termination fee equal to aa amount equal to three (3) month's base rent.

     4b.  For every four (4) month period after the twenty-fourth (24th) month
of the term Tenant remains in the Premises, the termination penalty shall be
reduced by one (1) month.

          For example: (4a) To terminate the lease at the end of the twenty-
fourth (24th) month, the notification to Landlord shall be due on or before
January 31, 200O and (4b) If Tenant remains in the Premises &or twenty-eight
(28) months the termination fee shall be two (2) months base rent, etc.

     5.   As promptly as practicable, Landlord, at its cost, shall provide new
building standard vinyl flooring in the copy rooms of the Premises.

     6.   Landlord's obligation to extend the Lease under this Amendment is
expressly contingent upon Terra&s performance of all of its obligations under
the Lease, including the obligation to pay the monthly base rent. If Tenant at
any time fails to perform any of the obligations under the Lease, Landlord may
exercise all of its remedies under the Lease in accordance with the terms
thereof.

     7.   Except as amended herein, all the provisions of the Lease shall remain
 unchanged and in full force and effect.

     IN WITNESS WHEREOF, the parties have executed this Amendment No. 1 to
 Lease as of this date first above written.

 "Landlord"                                     "Tenant"

ESPLANADE PROPERTY, LTD.,                       IRVINE SENSORS CORPORATION,
a California limited partnership                a Delaware corporation

By: IMC ASSET MANAGEMENT COMPANY,
    a California corporation,
    its general partner

    By:  /s/ William W. Geary, Jr.              By:  /s/ John Stuart
         ---------------------------                 -------------------------
         William W. Geary, Jr.                       John Stuart

    Its: President                              Its: Chief Financial Officer<PAGE>

                                                                   Exhibit 10.50

                                STAMPS.COM INC.
                       3420 Ocean Park Blvd., Suite 1040
                        Santa Monica, California 90405

December 20, 2000

Mr. John M. Payne
660 Thalia Street
Laguna Beach, California 92651

Dear John:
     The following confirms our mutual agreement to the terms of your separation
from Stamps.com Inc. (the "Company"):

     1.  The Company agrees to accept your resignation from the offices of
Chairman and Chief Executive Officer at the Company and as an employee of the
Company. These resignations shall be effective October 11, 2000. In addition,
you agree to resign from the Company's board of directors and from your roles as
Chairman and a member of the board of directors of EncrypTix, Inc. Your
resignation from the EncrypTix board shall be effective November 6, 2000 and
your resignation from the Stamps.com board shall be effective upon execution of
this letter by you.

     2.  Upon receipt of this letter signed and dated by you, the Company agrees
to:
         (a)  Pay your monthly salary of $25,000 for a period of nine months
              from October 11, 2000 until July 11, 2001. Amounts paid under this
              paragraph shall be less any and all appropriate withholding taxes.
         (b)  Continue payment of your Company medical, dental and vision
              benefits for a period of nine months from October 11, 2000 until
              July 11, 2001.
         (c)  Pay you for any accrued and unused vacation and reimburse you for
              any unpaid reasonable business expenses incurred by you as of
              October 11, 2000.
<PAGE>

          (d)  Allow your restricted shares to continue to vest at a rate of
               31,250 shares per month until June 30, 2001; provided, however,
               the terms of the consulting services agreement attached hereto as
               Exhibit A shall remain in effect during such time and you shall
               ---------
               not have breached any covenant, representation or warranty of
               this agreement. On June 30, 2001 (or such earlier termination
               date of your consulting agreement), the Company shall repurchase
               any unvested shares from you in accordance with the repurchase
               provisions of that certain agreement between you and the Company
               dated February 17, 1999 (the "Vesting Agreement"). Due to your
               resignation as an employee of the Company, you acknowledge that
               the change in control provisions of the Vesting Agreement are no
               longer applicable. In connection with and as a condition to this
               Section 2(d), you agree to execute the consulting agreement in
               the form attached hereto as Exhibit A.
                                           ---------

     3.   You acknowledge that by payment of the amounts set forth above, you
will receive all money and other benefits due you as a result of your employment
with and discontinuation of your executive role with the Company.

     4.   You fully release and discharge the Company, all affiliated
corporations, past and present officers, directors, employees, agents and
representatives, and each of them of and from, without limitation, any and all
rights, claims, liabilities, losses or expenses of any kind whether arising out
of, from, or related to your employment relationship with the Company, your
resignation thereof, or arising out of any other matter between you and the
Company, and specifically including any claim of age discrimination under the
Age Discrimination in Employment Act, as amended, and the California Fair
Employment & Housing Act. The Company agrees to release and discharge you from,
without limitation, any and all rights, claims, liabilities, losses or expenses
of any kind whether arising out of, from, or related to your employment
relationship with the Company, your resignation thereof, or arising out of any
other

                                       2
<PAGE>

matter between you and the Company. This agreement does not alter the extent to
which you are entitled to indemnification pursuant to the Company's Certificate
of Incorporation and Bylaws, the Company's insurance policies, Section 2802 of
the California Labor Code and any other provision of Delaware or California law.

     5.   Each party understands and agrees that the claims released hereby are
intended to and do include any and all claims of every nature and kind
whatsoever, known or unknown, suspected or unsuspected, which each party has or
may have against the other and each party hereby waives any and all rights it
may have or may have under Section 1542 of the California Civil Code. Section
1542 provides as follows:

               A general release does not extend to claims which the creditor
               does not know or suspect to exist in his favor at the time of
               executing the release, which if known by him must have materially
               affected his settlement with the debtor.

     6.   The Company agrees not to directly or indirectly disparage you in any
manner. You agree not to directly or indirectly disparage the Company, its
officers or employees in any manner, or directly or indirectly solicit or
attempt to solicit is employees or customers. In addition, you agree that you
are bound by the terms of a Confidential Information and Inventions Assignment
Agreement ("CIIAA"), a copy of which is attached hereto as Exhibit B and which
                                                           ---------
you agree to execute concurrent with the execution of this letter. Nothing
contained in this paragraph shall prohibit you from complying with any subpoena,
court order, deposition notice, or other legal process.

     7.   You acknowledge that you have been advised to consult with an attorney
before signing this agreement, and that you have voluntarily and knowingly
executed this agreement and voluntarily and knowingly waived the statutory
provisions described in Sections 8 and 9 below after having had the opportunity
to consult with an attorney.

                                       3
<PAGE>

     8.   You further acknowledge that you may consider the terms of this
agreement for 21 days before signing it, and that you have been so advised. You
agree to waive this right.

     9.   For a period of seven days following your execution of this agreement,
you may revoke the agreement, and the agreement shall not become effective or
enforceable until the revocation period has expired. You agree to waive this
right.

     10.  The Company agrees to repay any balances due under your margin account
with Salomon Smith Barney, which balance was $6,523,690.36 on November 30, 2000
and has been paid in full by the Company on such date. As a result, you are
currently indebted to the Company for such amount, less any amounts required to
be repaid by you under Section 11 of this Agreement. Upon execution of this
letter, you will immediately execute a promissory note and security agreement in
the forms attached hereto as Exhibits C and D. The promissory note requires,
                             ----------------
among other terms, the repayment of any principal and interest amounts owing by
you to the Company on or before June 30, 2001, subject to the acceleration
provisions of such note. The security agreement requires a pledge of cash assets
and securities, including any shares of the Company's common stock and shares of
EncrypTix, Inc. owned by you.

     11.  Within 30 days of execution of this letter, you agree to pay to the
Company the amount of $25,000 by wire transfer in immediately available funds,
which amount represents loan proceeds from your Salomon Smith Barney margin loan
which were held by you in a checking, money market, brokerage or securities
account on or before October 11, 2000. You represent and warrant that the amount
set forth in the preceding sentence, which amount has been verified through the
delivery of financial statements and account statements from you to the Company,
is the entire amount of loan proceeds held by you as of October 11, 2000. The
Company agrees to keep such financial statements and account statements
confidential and only Bruce Coleman and Michael Zuercher shall be entitled to
receive and view such statements; provided, however, that Messrs. Coleman and
Zuercher shall be allowed to summarize your financial position to the Executive
Committee or Compensation Committee of the Board, if necessary.

                                       4
<PAGE>

     12.  With respect to the foregoing, you agree to cooperate fully and
execute such documents, including, but not limited to, any security release or
stock powers, required to facilitate the transfer of any shares or other
security to the Company and to perfect any security interest in favor of the
Company in accordance with the terms of the security agreement attached hereto
as Exhibit D.
   ---------

     13.  With the exception of Exhibit A through D hereto (each of which shall
be executed concurrently with this letter), this letter constitutes the entire
agreement between you and the Company concerning the terms of your employment
severance and the compensation related thereto. No amendments to this agreement
will be valid unless written and signed by you and an officer of the Company.

     I believe this letter fully describes our agreement, and if you are in
accord, please sign and date below. We wish you the best in your future
endeavors.

                                        Sincerely yours,

                                        _______________________________
                                        Kenneth T. McBride
                                        Chief Financial Officer

     I agree to and accept the
     terms of this letter.

     ____________________________           ___________________________
     John M. Payne                           Date

                                       5
<PAGE>

                                   EXHIBIT A

                             CONSULTING AGREEMENT

                                       6
<PAGE>

                                   EXHIBIT B

          CONFIDENTIAL INFORMATION AND INVENTION ASSIGNMENT AGREEMENT

                                       7
<PAGE>

                                   EXHIBIT C

                      NOTE SECURED BY SECURITY AGREEMENT

                                       8
<PAGE>

                                   EXHIBIT D

                              SECURITY AGREEMENT

                                       9

Source: [{"source": "alea-institute/alea-institute/kl3m-data-edgar-agreements/train-00019-of-00352.parquet"}, [{"source": "alea-institute/alea-institute/kl3m-data-edgar-agreements/train-00019-of-00352.parquet"}]]