X0306 4 2016-01-01 0 0001410172 Rubicon Technology, Inc. RBCN 0001211700 CALDWELL DONALD R C/O RUBICON TECHNOLOGY, INC. 900 EAST GREEN ST., UNIT A BENSENVILLE IL 60106 1 0 0 0 Common Stock 2016-01-01 4 A 0 69517 0.00 A 105050 D Common Stock 2217851 I See footnote. Consists of restricted stock pursuant to grants that vest according to the following schedule: 17,379 shares vest on March 31, 2016, 17,379 shares vest on June 30, 2016, 17,379 shares vest on September 30, 2016 and 17,380 shares vest on December 31, 2016. Includes 69,517 shares of restricted stock pursuant to grants that vest as indicated in footnote 1. Under the terms of the applicable partnership agreements of the Funds (as defined below), the Reporting Person is deemed to hold the newly acquired shares plus an additional 28,433 shares (for a total of 97,950 shares), for the benefit of the Funds, 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. Consists of shares held by Cross Atlantic Technology Fund, II, L.P. and/or The Co-Investment 2000 Fund, 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. Cross Atlantic Technology Fund II, L.P. holds 1,047,698 shares of common stock and The Co-Investment 2000 Fund, L.P. holds 1,170,153 shares of common stock. /s/ Scott Glickson, attorney-in-fact for Donald R. Caldwell 2016-01-05