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                                                                    Exhibit 4.15
                                          
                               STOCK PURCHASE WARRANT
                                          
                           To Subscribe For and Purchase
                                  Common Stock of
                                          
                                PHOTRAN CORPORATION
                                          
                                  February 9, 1998
                                          
     THIS CERTIFIES THAT, for good and valuable consideration received, Steven
King, or his registered assigns, is entitled to subscribe for and purchase from
Photran Corporation (the "Company"), a Minnesota corporation, 100,000 fully paid
and nonassessable shares of the Common Stock, no par value, of the Company (the
"Common Stock"), or such greater or lesser number of such shares as may be
determined by the anti-dilution provisions of this Warrant, at a Warrant
exercise price of $4.25 per share, or such greater or lesser Warrant exercise
price as may be determined by the anti-dilution provisions of this Warrant.

     This Warrant has been issued to Steve King by the Company pursuant to the
Loan Agreement of even date, by and between the Company and Steven King (the
"Agreement"), and is subject to the terms and conditions thereof.

     This Warrant may be exercised in whole or in part at any time or from time
to time commencing twelve (12) months following the date of issuance of this
Warrant and on or before 5:00 p.m., Minneapolis, Minnesota time, on September
10, 2007.

     This Warrant is subject to the following provisions, terms and conditions.

     1.   EXERCISE.  The rights represented by this Warrant may be exercised by
the holders hereof, in whole or in part, by written notice of exercise delivered
to the Company and by the surrender of this Warrant (properly endorsed if
required) at the principal office of the Company and upon payment to it by check
of the purchase price for such shares.

     2.   ISSUANCE OF COMMON STOCK.  The Company agrees that the shares of
Common Stock purchased hereby shall be and are deemed to be issued to the
holders hereof as the record owner of such shares as of the close of business on
the date on which this Warrant shall have been surrendered and payment made for
such shares as aforesaid.  Certificates for the shares of Common Stock so
purchased shall be promptly delivered to the holders hereof and in no event
later than 10 days after the rights represented by this Warrant shall have been
so exercised, and, unless this Warrant has expired, a new Warrant representing
the number of shares of Common Stock, if any, with respect to which this Warrant
shall not then have been exercised shall also be delivered to the holders hereof
within such time.

THIS WARRANT IS SUBJECT TO THE RESTRICTION ON TRANSFER SET FORTH AT 
THE BOTTOM OF THE LAST PAGE HEREOF.

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     3.   COVENANTS OF COMPANY.  The Company covenants and agrees that all
shares of Common Stock which may be issued upon the exercise of the rights
represented by this Warrant will, upon issuance, be duly authorized and issued,
fully paid and nonassessable, and free from all taxes, liens and charges with
respect to the issue thereof.  The Company further covenants and agrees that
during the period within which the rights represented by this Warrant may be
exercised, the Company will at all times have authorized, and reserved for the
purpose of issue or transfer upon exercise of the subscription rights evidenced
by this Warrant, a sufficient number of shares of its Common Stock to provide
for the exercise of the rights represented by this Warrant.

     4.   ANTI-DILUTION ADJUSTMENTS.    The provisions of this Warrant are
subject to adjustment as provided in this Section 4.

     (a)  The Warrant Exercise Price shall be adjusted from time to time such
     that in case the Company shall hereafter:

          (i)   pay any dividends on any class of stock of the Company payable 
          in Common Stock or securities convertible into Common Stock;

          (ii)  subdivide its then outstanding shares of Common Stock into a
          greater number of shares; or

          (iii) combine outstanding shares of Common Stock, by
          reclassification or otherwise;

     then, in any such event, the Warrant Exercise Price in effect immediately
     prior to such event shall (until adjusted again pursuant hereto) be
     adjusted immediately after such event to a price (calculated to the nearest
     full cent) determined by dividing (a) the number of shares of Common Stock
     outstanding immediately prior to such event, multiplied by the then
     existing Warrant Exercise Price, by (b) the total number of shares of
     Common Stock outstanding immediately after such event (including the
     maximum number of shares of Common Stock issuable in respect of any
     securities convertible into Common Stock), and the resulting quotient shall
     be the adjusted Warrant Exercise Price per share.  An adjustment made
     pursuant to this Subsection shall become effective immediately after the
     record date in the case of a dividend or distribution and shall become
     effective immediately after the effective date in the case of a
     subdivision, combination or reclassification.  If, as a result of an
     adjustment made pursuant to this Subsection, the Holder of any Warrant
     thereafter surrendered for exercise shall become entitled to receive shares
     of two or more classes of capital stock or shares of Common Stock and other
     capital stock of the Company, the Board of Directors (whose determination
     shall be conclusive) shall determine the allocation of the adjusted Warrant
     Exercise Price between or among shares of such classes of capital stock or
     shares of Common Stock and other capital stock.  All calculations under
     this Subsection shall be made to the nearest cent or to the nearest 1/100
     of a share, as the case may be.  In the event that at any time as a result
     of an adjustment made pursuant to this Subsection, the holders of any
     Warrant 

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     thereafter surrendered for exercise shall become entitled to
     receive any shares of the Company other than shares of Common Stock,
     thereafter the Warrant Exercise Price of such other shares so receivable
     upon exercise of any Warrant shall be subject to adjustment from time to
     time in a manner and on terms as nearly equivalent as practicable to the
     provisions with respect to Common Stock contained in this Section 4.

     (b)  Upon each adjustment of the Warrant Exercise Price pursuant to Section
     4(a) above, the Holders of each Warrant shall thereafter (until another
     such adjustment) be entitled to purchase at the adjusted Warrant Exercise
     Price the number of shares, calculated to the nearest full share, obtained
     by multiplying the number of shares specified in such Warrant (as adjusted
     as a result of all adjustments in the Warrant Exercise Price in effect
     prior to such adjustment) by the Warrant Exercise Price in effect prior to
     such adjustment and dividing the product so obtained by the adjusted
     Warrant Exercise Price.

     (c)  In case of any consolidation or merger to which the Company is a party
     other than a merger or consolidation in which the Company is the continuing
     corporation, or in case of any sale or conveyance to another corporation of
     the property of the Company as an entirety or substantially as an entirety,
     or in the case of any statutory exchange of securities with another
     corporation (including any exchange effected in connection with a merger of
     a third corporation into the Company), there shall be no adjustment under
     Subsection (a) of this Section above but the Holders of each Warrant then
     outstanding shall have the right thereafter to convert such Warrant into
     the kind and amount of shares of stock and other securities and property
     which he would have owned or have been entitled to receive immediately
     after such consolidation, merger, statutory exchange, sale, or conveyance
     had such Warrant been converted immediately prior to the effective date of
     such consolidation, merger, statutory exchange, sale, or conveyance and in
     any such case, if necessary, appropriate adjustment shall be made in the
     application of the provisions set forth in this Section with respect to the
     rights and interests thereafter of any Holders of the Warrant, to the end
     that the provisions set forth in this Section shall thereafter
     correspondingly be made applicable, as nearly as may reasonably be, in
     relation to any shares of stock and other securities and property
     thereafter deliverable on the exercise of the Warrant.  The provisions of
     this Subsection shall similarly apply to successive consolidations,
     mergers, statutory exchanges, sales or conveyances.

     (d)  Upon any adjustment of the Warrant Exercise Price, then and in each
     such case, the Company shall give written notice thereof, by first class
     mail, postage prepaid, addressed to the Holders as shown on the books of
     the Company, which notice shall state the Warrant Exercise Price resulting
     from such adjustment and the increase or decrease, if any, in the number of
     shares of Common Stock purchasable at such price upon the exercise of this
     Warrant, setting forth in reasonable detail the method of calculation and
     the facts upon which such calculation is based.

     5.   COMMON STOCK, WARRANT SHARES.  As used herein, the term "Common Stock"
shall mean and include the Company's currently authorized shares of Common Stock
and shall also 

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include any capital stock of any class of the Company hereafter authorized 
which shall not be limited to fixed sum or percentage of par value in respect 
of the rights of the holders thereof to participate in dividends or in the 
distribution of assets upon the voluntary or involuntary liquidation, 
dissolution or winding up of the Company; provided that the shares 
purchasable pursuant to this Warrant shall include shares designated as 
Company Stock of the Company on the date of original issue of this Warrant 
or, in the case of any reorganization, reclassification, consolidation or 
merger provided for in paragraph 4(g) above, the stock, securities or assets 
provided for in such paragraph.  As used herein, the term "Warrant Shares" 
shall mean the shares which may be acquired upon the exercise of this Warrant.

     6.   NO VOTING RIGHTS.  This Warrant shall not entitle the holders hereof
to any voting rights or other rights as a shareholder of the Company.

     7.   SECURITIES LAWS RESTRICTIONS.  The holders of this Warrant by
acceptance hereof, acknowledges that this Warrant and the shares of Common Stock
which may be issued pursuant hereto have not been registered under the
Securities Act of 1933, as amended (the "Securities Act"), or any applicable
state securities laws.  Any exercise by the holders shall constitute a
representation by the holders that the shares of Common Stock issuable upon
exercise hereof are being acquired for the holders' own account and not with the
view to, or for resale in connection with, any distribution or public offering
thereof in violation of the Securities Act or applicable state securities laws. 
The holders of this Warrant, by acceptance hereof, further represents that it is
fully informed as to the applicable limitations upon any distribution or resale
of the shares of Common Stock purchased pursuant hereto under the Securities Act
and applicable state securities laws and agrees not to distribute or resell any
such shares of Common Stock if such distribution or resale would constitute a
violation of the Securities Act or applicable state securities law.

     The holders of this Warrant, by acceptance hereof, agrees to give written
notice to the Company before transferring this Warrant or transferring any
Common Stock issuable or issued upon the exercise hereof of such holder's
intentions as to such proposed transfer and the circumstances thereof.  Promptly
upon receiving such notice, the Company shall present copies thereof to counsel
to the company and to special counsel to the original holders of this Warrant. 
If in the opinion of each such counsel the proposed transfer of this Warrant or
disposition of shares may be effected without registration or qualification
(under the Securities Act or applicable state securities laws) of this Warrant
or the shares of Common Stock issuable or issued upon the exercise hereof, the
company, as promptly as practicable, shall notify such holders of such opinion,
whereupon such holders shall be entitled to transfer this Warrant or to dispose
of shares of Common Stock received upon the exercise of this Warrant, all in
accordance with the terms of the notice delivered by such holders to the
company, provided that an appropriate legend respecting the aforesaid
restrictions on transfer and disposition may be endorsed on this Warrant or the
certificates for such shares.  The Company hereby indemnifies such holders, in
transferring this Warrant or in disposing of shares received upon the exercise
of this Warrant in reliance upon such notification by the Company, against all
liability which such holders may incur through failure of this Warrant or such
shares of Common Stock to be registered or qualified provided such transfer or
disposition is in accordance with the proposed transfer or disposition.

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     8.   REGISTRATION RIGHTS.

     (a)  If at any time after February 9, 1999 and prior to February 9, 2000,
     the Company proposes to register under the 1933 Act (except by a Form S-4
     or Form S-8 Registration Statement or any successor forms thereto) or
     qualify for a public distribution under Section 3(b) of the 1933 Act, any
     of its securities, it will give written notice to all holders of this
     Warrant, and any Warrant Shares of its intention to do so and, on the
     written request of any such holders given within twenty (20) days after
     receipt of any such notice (which request shall specify the interest in
     this Warrant or the Warrant Shares intended to be sold or disposed of by
     such holders and describe the nature of any proposed sale or other
     disposition thereof), the Company will use its best efforts to cause all
     such Warrant Shares,  the holders of which shall have requested the
     registration or qualification thereof, to be included in such registration
     statement proposed to be filed by the Company; provided, however, that if a
     greater number of Warrant Shares is offered for participation in the
     proposed offering than in the reasonable opinion of the managing
     underwriter of the proposed offering can be accommodated without adversely
     affecting the proposed offering, then the amount of Warrant Shares proposed
     to be offered by such Holders for registration, as well as the number of
     securities of any other selling shareholders participating in the
     registration, shall be proportionately reduced to a number deemed
     satisfactory by the managing underwriter.

     (b)  Further, on a one-time basis during the four-year period commencing
     February 9, 1999, upon request by the holders or holders of a majority in
     interest of this Warrant, and of any Warrant Shares, the Company will
     promptly take all necessary steps to register or qualify, under the 1933
     Act and the securities laws of such states as the holders may reasonably
     request, such number of Warrant Shares issued and to be issued upon
     conversion of the Warrants requested by such holders in their request to
     the Company.  The Company shall keep effective and maintain any
     registration, qualification, notification, or approval specified in this
     Paragraph (b) for such period as may be reasonably necessary for such
     holders or holders of such Warrant Shares to dispose thereof and from time
     to time shall amend or supplement the prospectus used in connection
     therewith to the extent necessary in order to comply with applicable law.

     (c)  With respect to each inclusion of securities in a registration
     statement pursuant to this Section 8, the Company shall bear the following
     fees, costs, and expenses:  all registration, filing and NASD fees,
     printing expenses, fees and disbursements of counsel and accountants for
     the Company, fees and disbursements of counsel for the underwriter or
     underwriters of such securities (if the Company is required to bear such
     fees and disbursements), all internal expenses, the premiums and other
     costs of policies of insurance against liability arising out of the public
     offering, and legal fees and disbursements and other expenses of complying
     with state securities laws of any jurisdictions in which the securities to
     be offered are to be registered or qualified.  Fees and disbursements of
     special counsel and accountants for the selling holders, underwriting
     discounts and commissions, and transfer taxes for selling holders and any

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     other expenses relating to the sale of securities by the selling holders
     not expressly included above shall be borne by the selling holders.

     (d)  The Company hereby indemnifies each of the holders of this Warrant and
     of any Warrant Shares, against all losses, claims, damages, and liabilities
     caused by (1) any untrue statement or alleged untrue statement of a
     material fact contained in any Registration Statement or Prospectus (and as
     amended or supplemented if the Company shall have furnished any amendments
     thereof or supplements thereto), any Preliminary Prospectus or any state
     securities law filings; (2) any omission or alleged omission to state
     therein a material fact required to be stated therein or necessary to make
     the statements therein not misleading except insofar as such losses,
     claims, damages, or liabilities are caused by any untrue statement or
     omission contained in information furnished in writing to the Company by
     such holders expressly for use therein; and each such holders by its
     acceptance hereof severally agrees that it will indemnify and hold harmless
     the Company, each of its officers who signs such Registration Statement,
     and each person, if any, who controls the Company, within the meaning of
     Section 15 of the 1933 Act, with respect to losses, claims, damages, or
     liabilities which are caused by any untrue statement or alleged untrue
     statement, omission or alleged omission contained in information furnished
     in writing to the Company by such holders expressly for use therein.

     9.   MISCELLANEOUS.

          (a)  Subject to the provisions of paragraph 8 hereof, this Warrant and
     all rights hereunder are transferable, in whole or in part, at the
     principal office of the Company by the holders hereof in person or by duly
     authorized attorney, upon surrender of this Warrant properly endorsed. 
     Each holders of this Warrant, by taking or holding the same, consents and
     agrees that the bearer of this Warrant, when endorsed, may be treated by
     the Company and all other persons dealing with this Warrant as the absolute
     owner hereof for any purpose and as the person entitled to exercise the
     rights represented by this Warrant, or to the transfer hereof on the books
     of the Company, any notice to the contrary notwithstanding; but until such
     transfer on such books, the Company may treat the registered holder hereof
     as the owner for all purposes.

          (b)  This Warrant is exchangeable, upon the surrender hereof by the
     holders hereof at the principal office of the Company, for new Warrants of
     like tenor representing in the aggregate the right to subscribe for and
     purchase the number of shares of Common Stock which may be subscribed for
     and purchased hereunder, each of such new Warrants to represent the right
     to subscribe for and purchase such number of shares as shall be designated
     by said holders hereof at the time of such surrender.

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     IN WITNESS WHEREOF, the Company has caused this Warrant to be signed by its
duly authorized officer and to be dated as of the date set forth above.

                         PHOTRAN CORPORATION


                         By  /s/ Paul T. Fink
                           --------------------------------
                         Its President
                           --------------------------------



                              RESTRICTION OF TRANSFER

     The securities evidenced hereby have not been registered under the 
Securities Act of 1933 and may not be sold, transferred, assigned, offered, 
pledge or otherwise distributed for value unless there is an effective 
registration statement under such Act covering such securities or the Company 
receives an opinion of counsel satisfactory to the Company stating that such 
sale, transfer, assignment, pledge or distribution is exempt from the 
registration and prospectus delivery requirements of such Act.





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