FORM 4 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP OF SECURITIES Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940

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1. Name and Address of Reporting Person * CALDWELL DONALD R   2. Issuer Name and Ticker or Trading Symbol Rubicon Technology, Inc. [RBCN] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) __X__ Director __X__ 10% Owner _____ Officer (give title below) _____ Other (specify below) (Last) (First) (Middle) C/O RUBICON TECHNOLOGY INC., 9931 FRANKLIN AVENUE 3. Date of Earliest Transaction (Month/Day/Year) 06/06/2008 (Street) FRANKLIN PARK, IL 60131 4. If Amendment, Date Original Filed(Month/Day/Year) 6. Individual or Joint/Group Filing(Check Applicable Line) _X_ Form filed by One Reporting Person ___ Form filed by More than One Reporting Person (City) (State) (Zip) Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned

1.Title of Security (Instr. 3) 2. Transaction Date (Month/Day/Year) 2A. Deemed Execution Date, if any (Month/Day/Year) 3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4) Code V Amount (A) or (D) Price Common Stock               7,341 (1) D   Common Stock 06/06/2008   S   65,650 (2) (3) D $ 22.77 5,886,423 (2) (4) I See footnote (2)

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
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Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned
(e.g., puts, calls, warrants, options, convertible securities)

1. Title of Derivative Security (Instr. 3)

2. Conversion or Exercise Price of Derivative Security

3. Transaction Date (Month/Day/Year)

3A. Deemed Execution Date, if any (Month/Day/Year)

4. Transaction Code (Instr. 8)

5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4, and 5)

6. Date Exercisable and Expiration Date (Month/Day/Year)

7. Title and Amount of Underlying Securities (Instr. 3 and 4)

8. Price of Derivative Security (Instr. 5)

9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4)

10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4)

11. Nature of Indirect Beneficial Ownership (Instr. 4)

Code

V

(A)

(D)

Date Exercisable

Expiration Date

Title

Amount or Number of Shares

Reporting Owners

Reporting Owner Name / Address	Relationships
	Director	10% Owner	Officer	Other
CALDWELL DONALD R C/O RUBICON TECHNOLOGY INC. 9931 FRANKLIN AVENUE FRANKLIN PARK, IL 60131	X	X

Signatures

/s/ Scott Glickson, attorney-in-fact		06/10/2008
**Signature of Reporting Person		Date

Explanation of Responses:

*	If the form is filed by more than one reporting person, see Instruction 4(b)(v).
**	Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
(1)	Includes 241 shares of restricted stock pursuant to grants that vest ratably over three years.
(2)	Consists of shares held by Cross Atlantic Technology Fund, L.P., Cross Atlantic Technology Fund, II, L.P., and/or The Co-Investment 2000 Fund, L.P. The Reporting Person is the owner and director of Cross Atlantic Capital Partners, Inc., which is the general partner of XATF Management, L.P., which is the general partner of Cross Atlantic Technology Fund, L.P. The Reporting Person is a director, shareholder and officer of Cross Atlantic Capital Partners II, Inc., which is the general partner of XATF Management II, L.P., which is the general partner of Cross Atlantic Technology Fund II, L.P. The Reporting Person is a shareholder, director and officer of Co-Invest Capital Partners, Inc., which is the general partner of Co-Invest Management, L.P., which is the general partner of The Co-Investment 2000 Fund, L.P. The Reporting Person disclaims beneficial ownership of the shares held by the Funds except to the extent of his pecuniary interest therein.
(3)	As part of the issuer's secondary offering overallotment option, Cross Atlantic Technology Fund, L.P. sold 7,796 shares of its common stock, Cross Atlantic Technology Fund II, L.P. sold 27,219 shares of its common stock and The Co-Investment 2000 Fund, L.P. sold 30,635 shares of its common stock.
(4)	After the sale of shares in the issuer's secondary offering overallotment option, Cross Atlantic Technology Fund, L.P. holds 727,693 shares of common stock, Cross Atlantic Technology Fund II, L.P. holds 2,438,732 shares of common stock and The Co-Investment 2000 Fund, L.P. holds 2,719,998 shares of common stock.

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