<PAGE>

                                                                   EXHIBIT 10.28

                                 PROMISSORY NOTE

<TABLE>
<CAPTION>

<S>                                              <C>
Borrower: Semiconductor Laser International      Lender: BSB Bank & Trust Company
          Corporation                                    P.O. Box 1056 (56-68 Exchange Street)
          15 Link Drive                                  Binghamton, NY 13902
          Binghamton, NY 13904-3218
Principal Amount: $1,000,000                     Initial Rate: 12.000%                   Date of Note: May 16, 2000

</TABLE>


PROMISE TO PAY. To repay Borrower's loan, Semiconductor Laser International
Corporation ("Borrower") promises to pay to BSB Bank & Trust Company ("Lender"),
or order, in lawful money of the United States of America, the principal amount
of One Million & 00/100 Dollars ($1,000,000.00) or so much as may be
outstanding, together with interest on the unpaid outstanding principal balance
of each advance. Interest shall be calculated from the date of each advance
until repayment of each advance.

PAYMENT: Borrower will pay this loan in one payment of all outstanding principal
plus all accrued unpaid interest on March 31, 2001. In addition, Borrower will
pay regular monthly payments of all accrued unpaid interest due as of each
payment date, beginning June 1, 2000, with all subsequent interest payments to
be due on the same day of each month after that. Unless otherwise agreed or
required by applicable law, payments will be applied first to accrued unpaid
interest, then to principal, and any remaining amount to any unpaid collection
costs and late charges. The annual interest rate for this Note is computed on a
365/360 basis; that is, by applying the ratio of the annual interest rate over a
year of 360 days, multiplied by the outstanding principal balance, multiplied by
the actual number of days the principal balance is outstanding. Borrower will
pay Lender at Lender's address shown above or at such other place as Lender may
designate in writing.

VARIABLE INTEREST RATE. The interest rate on this Note is subject to change from
time to time based on changes in an index which is Lender's Prime Rate (the
"Index"). This is the rate Lender charges, or would charge, on 90-day unsecured
loans to the most creditworthy corporate customers. This rate may or may not be
the lowest rate available from Lender at any given time. Lender will tell
Borrower the current Index rate upon Borrower's request. The interest rate
change will not occur more often than each day. Borrower understands that Lender
may make loans based on other rates as well. The Index currently is 9.500% per
annum. The interest rate to be applied to the unpaid principal balance of this
Note will be at a rate of 2.500 percentage points over the Index, resulting in
an initial rate of 12.000% per annum.

PREPAYMENT. Borrower may pay without penalty all or a portion of the amount owed
earlier than it is due. Early payments will not, unless agreed to by Lender in
writing, relieve Borrower of Borrower's obligation to continue to make payments
of accrued unpaid interest. Rather, early payments will reduce the principal
balance due. Borrower agrees not to send Lender payments marked "paid in full",
"without recourse", or similar language. If Borrower sends such a payment,



<PAGE>

Lender may accept it without losing any of Lender's rights under this Note, and
Borrower will remain obligated to pay any further amount owed to Lender. All
written communications concerning disputed amounts, including any check or other
payment instrument that indicates that the payment constitutes "payment in full"
of the amount owed or that is tendered with other conditions or limitations or
as full satisfaction of a disputed amount must be mailed or delivered to: BSB
BANK & TRUST COMPANY, P.O. Box 1056 (58-68 Exchange Street), Binghamton, NY
13902.

LATE CHARGE: If a payment is 10 days or more late Borrower will be charged
4.000% of the unpaid portion of the regularly scheduled payment or $10.00,
whichever is greater. No Late Charge will be payable in the event of a Default
rate of interest is being charged.

INTEREST AFTER DEFAULT. Upon default, including failure to pay upon final
maturity, Lender, at its option, may, if permitted under applicable law,
increase the variable interest rate on this Note to 3.500 percentage points over
the Index. The interest rate will not exceed the maximum rate permitted by
applicable law.

DEFAULT. Each of the following shall constitute an event of default ("Event of
Default") under this Note:

     PAYMENT DEFAULT. Borrower fails to make any payment when due under this
     Note.

     OTHER DEFAULTS. Borrower fails to comply with or to perform any other term,
     obligation, covenant or condition contained in this Note or in any of the
     related documents or to comply with or to perform any term, obligation,
     covenant or condition contained in any other agreement between Lender and
     Borrower.

     FALSE STATEMENTS. Any warranty, representation or statement made or
     furnished to Lender by Borrower or on Borrower's behalf under this Note or
     the related documents is false or misleading in any material respect,
     either now or at the time made or furnished or becomes false or misleading
     at any time thereafter.

     DEATH OR INSOLVENCY. The death of Borrower or the dissolution or
     termination of Borrower's existence as a going business, the insolvency of
     Borrower, the appointment of a receiver for any part of Borrower's
     property, any assignment for the benefit of creditors, any type of creditor
     workout, or the commencement of any proceeding under any bankruptcy or
     insolvency laws by or against Borrower.

     CREDITOR OR FORFEITURE PROCEEDINGS. Commencement of foreclosure or
     forfeiture proceedings, whether by judicial proceeding, self-help,
     repossession or any other method, by any creditor of Borrower or by any
     governmental agency against any *Material* collateral securing the loan.
     This includes a garnishment of any of Borrower's accounts, including
     deposit accounts, with Lender. However, this Event of Default shall not
     apply if there is a good faith dispute by Borrower as to the validity or
     reasonableness of the claim which is the basis of the credits or forfeiture
     proceeding and if Borrower gives Lender written notice of the creditor or
     forfeiture proceeding and deposits with Lender monies or a surety bond for
     the creditor or forfeiture proceeding, in an amount


<PAGE>

     determined by Lender, in its sole discretion, as being an adequate reserve
     or bond for the dispute, being an adequate reserve or bond for the dispute.

     EVENTS AFFECTING GUARANTOR. Any of the preceding events occurs with respect
     to any guarantor, endorser, surety, or accommodation party of any of the
     indebtedness or any guarantor, endorser, surety, or accommodation party
     dies or becomes incompetent, or revokes or disputes the validity of, or
     liability under, any guaranty of the indebtedness.

     ADVERSE CHANGE. A material adverse change occurs in Borrower's financial
     condition, or Lender believes the prospect of payment or performance of
     this Note is impaired.

     CURE PROVISIONS. If any default, other than a default in payment, is
     curable and if Borrower has not been given a notice of a breach of the same
     provision of this Note withing the preceding twelve (12) months, it may be
     cured (and no event of default will have occurred) if Borrower, after
     receiving written notice from Lender demanding cure of such default: (1)
     cures the default within thirty (30) days; or (2) if the cure requires more
     than thirty (30) days, immediately initiates steps which Lender deems in
     Lender's sole discretion to be sufficient to cure the default and
     thereafter continues and completes all reasonable and necessary steps
     sufficient to produce compliance as soon as reasonably practical.

LENDER'S RIGHTS. Upon default, Lender may declare the entire unpaid principal
balance on this Note and all accrued unpaid interest immediately due, and then
Borrower will pay that amount.

ATTORNEY'S FEES; EXPENSES. Borrower agrees to pay all costs and expenses Lender
incurs to collect the loan. This includes, subject to any limits under
applicable law, Lender's reasonable attorneys' fees and Lender's legal expenses
whether or not there is a lawsuit, including reasonable attorneys' fees and
expenses for bankruptcy proceedings (including efforts to modify or vacate any
automatic stay or injunction), and appeals. If not prohibited by applicable law,
Borrower also will pay any court costs, in addition to all other sums provided
by law.

JURY WAIVER. Lender and Borrower hereby waive the right to any jury trial in any
action, proceeding, or counterclaim brought by either Lender or Borrower against
the other.

GOVERNING LAW. This Note will by governed by, construed and enforced in
accordance with federal law and the laws of the State of New York. This Note has
been accepted by Lender in the State of New York.

RIGHT OF SETOFF. In addition to Lender's right of setoff arising by operation of
law, Borrower grants to Lender a contractual security interest in all Borrower's
accounts with Lender (whether checking, savings, or some other account and
whether evidenced by a certificate of deposit). This includes all accounts
Borrower holds jointly with someone else and all accounts Borrower may open in
the future. However, this does not include any IRA or Keogh accounts, or any
trust accounts for which the grant of a security interest would by prohibited by
law. Borrower


<PAGE>

authorizes Lender, to the extent permitted by applicable law, to charge or
setoff all sums owing on the Indebtedness against any and all such accounts.

COLLATERAL. Borrower acknowledges this Note is secured by a second Mortgage from
Semiconductor Laser International Corporation to Lender dated January 31, 2000.
All Accounts, Inventory, Equipment and General Intangibles, now owned or
acquired later. All proceeds of collateral. If there is any inconsistency
between the terms and conditions of this Note and the terms and conditions of
the collateral documents, the terms and conditions of this Note shall prevail.

LINE OF CREDIT. This note evidences a revolving line of credit. Advances under
this Note, as well as directions for payment from Borrower's accounts, may be
requested orally or in writing by Borrower or by an authorized person. Lender
may, but need not, require that all oral requests by confirmed in writing.
Borrower agrees to by liable for all sums either: (A) advanced in accordance
with the instructions of an authorized person or (B) credited to any of
Borrower's accounts with Lender. The unpaid principal balance owing on this Note
at any time may be evidenced by endorsements on this Note or by Lender's
internal records, including daily computer print-outs. Lender will have no
obligation to advance funds under this Note if (A) Borrower or any guarantor is
in default under the terms of this Note or any agreement that Borrower or any
guarantor has with Lender, including any agreement made in connection with the
signing of this Note; (B) Borrower or any guarantor ceases doing business or is
insolvent; (C) any guarantor seeks, claims or otherwise attempts to limit,
modify or revoke such guarantor's guarantee of this Note or any other loan with
Lender; or (D) Borrower has applied funds provided pursuant to this Note for
purposes other than those authorized by Lender. YEAR 2000. Borrower warrants and
represents that all software utilized in the conduct of Borrower's business will
have appropriate capabilities and compatibility for operation to handle calendar
dates falling on or after January 1, 2000, and all information pertaining to
such calendar dates, in the same manner and with the same functionality as the
software does respecting calendar dates falling on or before December 31, 1999.
Further, Borrower warrants and represents that the data-related user interface
functions, data-fields, and data-related program instructions and functions of
the software include the indication of the century.

BORROWING BASE. Availability of funds under this line of credit shall be
reviewed monthly, based on company prepared financial statements, and shall be
limited to the lesser of $1,000,000.00, or an amount representing the sum of
$300,000.00, plus 35% of eligible accounts receivable 90 days or less from
invoice date, plus 30% of inventories, with a maximum inventory value
eligibility of $250,000.00. Weekly reporting of accounts receivable agings are
required.

PRIOR NOTE.  A mortgage and note dated January 31, 2000.

GENERAL PROVISIONS. Lender may delay or forgo enforcing any of its rights or
remedies under this Note without losing them. Borrower and any other person who
signs, guarantees or endorses this Note, to the extent allowed by law, waive
presentment, demand for payment, and notice of dishonor. Upon any change in the
terms of this Note, and unless otherwise expressly stated in writing, no party
who signs this Note, whether as maker, guarantor, accommodation maker or
endorser, shall be released from liability. All such parties agree that Lender
may renew or extend (repeatedly and for any length of time) this loan or release
any party or guarantor or


<PAGE>

collateral; or impair, fail to realize upon or perfect Lender's security
interest in the collateral; and take any other action deemed necessary by Lender
without the consent of or notice to anyone. All such parties also agree that
Lender may modify this loan without the consent of or notice to anyone other
than the party with whom the modification is made. The obligations under this
Note are joint and several.

PRIOR TO SIGNING THIS NOTE, BORROWER READ AND UNDERSTOOD ALL THE PROVISIONS OF
THIS NOTE, INCLUDING THE VARIABLE INTEREST RATE PROVISIONS. BORROWER AGREES TO
THE TERMS OF THE NOTE.

BORROWER ACKNOWLEDGES RECEIPT OF A COMPLETED COPY OF THIS PROMISSORY NOTE.



BORROWER:

--------------------------------------------------
Semiconductor Laser International Corporation