Statement of Changes in Beneficial Ownership (4)

FORM 4 [ X ] 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	OMB APPROVAL OMB Number: 3235-0287 Estimated average burden hours per response... 0.5
	Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934 or Section 30(h) of the Investment Company Act of 1940

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 _____ 10% Owner _____ Officer (give title below) _____ Other (specify below)
(Last) (First) (Middle) 150 RADNOR CHESTER RD, SUITE A225	3. Date of Earliest Transaction (MM/DD/YYYY) 11/16/2017
(Street) RADNOR, PA 19087 (City) (State) (Zip)	4. If Amendment, Date Original Filed (MM/DD/YYYY)	6. Individual or Joint/Group Filing (Check Applicable Line) _ X _ Form filed by One Reporting Person ___ Form filed by More than One Reporting Person

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1.Title of Security (Instr. 3)	2. Trans. Date	2A. Deemed Execution Date, if any	3. Trans. 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)
1.Title of Security (Instr. 3)	2. Trans. Date	2A. Deemed Execution Date, if any	Code	V	Amount	(A) or (D)	Price		6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	7. Nature of Indirect Beneficial Ownership (Instr. 4)
Common Stock								13900	D ⁽¹⁾
Common Stock	11/16/2017		S		221784 ⁽²⁾	D	$8.00	0	I	See Note ⁽²⁾

*Table II - Derivative Securities Beneficially Owned ( e.g.* , puts, calls, warrants, options, convertible securities)**
1. Title of Derivate Security (Instr. 3)	2. Conversion or Exercise Price of Derivative Security	3. Trans. Date	3A. Deemed Execution Date, if any	4. Trans. 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		7. Title and Amount of Securities Underlying Derivative Security (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)
1. Title of Derivate Security (Instr. 3)	2. Conversion or Exercise Price of Derivative Security	3. Trans. Date	3A. Deemed Execution Date, if any	Code	V	(A)	(D)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares	8. Price of Derivative Security (Instr. 5)			11. Nature of Indirect Beneficial Ownership (Instr. 4)

Explanation of Responses:
(1)	Includes 13,190 shares held for the benefit of the Funds (as defined below), which are entitled to receive the net economic benefit of the shares as a credit against the management fees owed by the Funds to Cross Atlantic Capital Partners, Inc. The Reporting Person disclaims beneficial ownership of the shares except to the extent of his pecuniary interest therein.
(2)	Consists of 104,769 shares sold by Cross Atlantic Technology Fund II, L.P. and 117,015 shares sold by The Co-Investment 2000 Fund, L.P. (collectively with Cross Atlantic Technology Fund II, L.P, the "Funds"). The Reporting Person is the owner and director of Cross Atlantic Capital Partners, Inc., which is the investment manager for each of the Funds. 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.

Remarks:
The Reporting Person disclaims beneficial ownership of the shares held by the Funds except to the extent of the Reporting Person's own pecuniary interest therein.
The Reporting Person resigned as a director of the Issuer on November 16, 2017.

Reporting Owners
Reporting Owner Name / Address	Relationships
Reporting Owner Name / Address	Director	10% Owner	Officer	Other
CALDWELL DONALD R 150 RADNOR CHESTER RD, SUITE A225 RADNOR, PA 19087	X

Signatures
/s/ Mardel A. Graffy, Attorney-in-Fact		11/20/2017
^** Signature of Reporting Person		Date

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
*	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).
Note:	File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.
Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB control number.