EXIBIT 10.15

                  UNSECURED DEMAND CONVERTIBLE PROMISSORY NOTE

Principal Amount:     $100,000.00                 September 27, 1995
Interest Rate:        10%                         Northvale, New Jersey

     FOR VALUE RECEIVED, INRAD, INC., a New Jersey corporation (the "Obligor" or
the  "Company")  promises  to pay,  in  lawful  monies of the  United  States of
America, to the order of Clarex Limited (the "Holder"),  ON DEMAND the principal
sum of One Hundred Thousand Dollars  ($100,000.00),  together with interest,  at
any such place as the Holder may designate.

     1.  Interest.  Interest  will accrue on the unpaid  principal  balance from
today's  date at the rate of ten  percent  (10%)  per  annum and will be due and
payable quarter-annually on the 27th day of December, March, June and September,
or on such  earlier date as the Holder  shall  demand  payment of the  principal
amount. Interest on the Note will be paid in the form of additional Common Stock
in whole shares at the conversion price of $1.00.

     2. Conversion  Right.  The Holder of this Note shall have the right, at his
option, at any time during the period commencing on the date hereof, on at least
30 days advance  written  notice to the Company,  to convert all or part of this
Note into shares of Common  Stock by applying the  principal  amount of the Note
plus all accrued and unpaid interest thereon, to the purchase of Common Stock at
the conversion price of $1.00.

The conversion price shall be subject to adjustment  according to the same terms
as provided for in Section 11.5 of the Subordinated Convertible Note dated April
9, 1995, between INRAD, Inc. and Clarex Limited.

     3.  Subordination to Senior  Indebtedness.  Anything in this Note or in the
Agreement to the contrary notwithstanding, payment of the principal and interest
on this Note is hereby expressly subordinated and subject in right of payment to
the extent and in the manner  hereinafter set forth to the prior payment in full
of all Senior  Indebtedness.  For purposes of this Note,  "Senior  Indebtedness"
shall mean the Company's  indebtedness pursuant to (a) any credit agreement with
Chemical  Bank now  existing or as modified  or  restructured  from time to time
hereafter or any credit  agreement with any other bank or financial  institution
hereafter entered into by the Company, (b) any capital leases now outstanding or
hereafter  incurred  in which  the  Company  is the  lessee  or (c) any  secured
indebtedness  of the  Company  now  outstanding  or  hereafter  incurred.  It is
understood that payment of the principal and interest on this Note is pari passu
with payment of a note dated  December 15, 1993 in the principal sum of $566,049
in favor of Warren Ruderman.

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     4. Collection  Costs and Expenses.  The Obligor agrees to pay all costs and
expenses,  including  reasonable  attorneys'  fees,  incurred  by the  Holder in
effecting  collection  of all  amounts  due under this Note.  All such costs and
expenses shall be added to the principal amount due under this Note.

     5. No Waiver by  Lender.  Any delay or  failure by the Holder in taking any
action or  exercising  any remedy  shall not  prevent  the Holder  from doing so
later,  and shall not act as a waiver of any of the  Holder's  rights under this
Note.

     6. Borrower's Waivers. The Obligor waives presentment for payment,  demand,
notice of non-payment,  protest,  notice of protest,  notice of dishonor and any
other notices or demands in connection with the delivery,  acceptance,  payment,
performance or enforcement of this Note. In any action or proceeding  brought by
the Holder to collect any amount due under this Note or otherwise arising out of
or in connection with this Note, the Obligor waives trial by jury.

     7.  Governing  Law. This Note is made and delivered in accordance  with New
Jersey law.


                                                  INRAD, INC.


                                             By:    /s/  Warren Ruderman
                                                  ---------------------------
                                                  Warren Ruderman, President

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