X0304 4 2011-12-02 0001111928 IPG PHOTONICS CORP IPGP 0001130421 GAPONTSEV VALENTIN P C/O IPG PHOTONICS CORPORATION 50 OLD WEBSTER ROAD OXFORD MA 01540 1 1 1 0 CEO & Chairman of the Board 0001508155 Valentin Gapontsev Trust I C/O IPG PHOTONICS CORPORATION 50 OLD WEBSTER ROAD OXFORD MA 01540 0 0 1 0 0001378544 Shcherbakov Eugene A C/O IPG PHOTONICS CORPORATION 50 OLD WEBSTER ROAD OXFORD MA 01540 1 1 1 0 Managing Director of IPG Laser 0001130423 IP FIBRE DEVICES LTD C/O IPG PHOTONICS CORPORATION 50 OLD WEBSTER ROAD OXFORD MA 01540 0 0 1 0 0001508148 PLATONOV NIKOLAI C/O IPG PHOTONICS CORPORATION 50 OLD WEBSTER ROAD OXFORD MA 01540 0 0 1 0 Common Stock 2011-12-02 4 S 0 1607 41.44 D 1901324 D Common Stock 2011-12-02 4 S 0 4875 41.44 D 7499127 I Through IP Fibre Devices (UK) Ltd. Common Stock 2011-12-05 4 S 0 20514 41.29 D 1880810 D Common Stock 2011-12-05 4 S 0 62265 41.29 D 7436862 I Through IP Fibre Devices (UK) Ltd. Common Stock 2011-12-06 4 S 0 27879 39.95 D 1852931 D Common Stock 2011-12-06 4 S 0 82860 39.95 D 7354002 I Through IP Fibre Devices (UK) Ltd. The reported transaction involved sales transactions from $41.25 to $41.74 per share. The Reporting Person undertakes to provide upon request by the SEC staff, the Issuer or a security holder of the Issuer information regarding the number of shares sold at each separate price. The reported transaction involved sales transactions from $41.25 to $41.73 per share. The Reporting Person undertakes to provide upon request by the SEC staff, the Issuer or a security holder of the Issuer information regarding the number of shares sold at each separate price. The reported transaction involved sales transactions from $40.68 to $41.72 per share. The Reporting Person undertakes to provide upon request by the SEC staff, the Issuer or a security holder of the Issuer information regarding the number of shares sold at each separate price. The reported transaction involved sales transactions from $40.68 to $41.72 per share. The Reporting Person undertakes to provide upon request by the SEC staff, the Issuer or a security holder of the Issuer information regarding the number of shares sold at each separate price. These shares are owned directly by IP Fibre Devices (UK) Ltd. (IPFD), and indirectly by (i) Valentin P. Gapontsev, the managing director and a 5% shareholder of IPFD, (ii) the Valentin Gapontsev Trust I, a 48% shareholder of IPFD (Gapontsev Trust I), (iii) Nikolai Platonov, a trustee of Gapontsev Trust I and an 8% shareholder of IPFD, and (iv) Eugene Scherbakov, a trustee of Gapontsev Trust I and an 8% shareholder of IPFD. On May 20, 2011, Eugene Scherbakov was appointed as a trustee of Gapontsev Trust I. Drs. Gapontsev, Platonov and Scherbakov and Gapontsev Trust I each disclaim ownership of the securities directly owned by IPFD except to the extent of his or its pecuniary interest therein, and the inclusion of these shares in this report shall not be deemed an admission of beneficial ownership of the reported securities for purposes of Section 16 of the Securities Exchange Act of 1034, as amended, or for any other purpose. Angelo P. Lopresti, Attorney-in-fact for Valentin Gapontsev 2011-12-06 By: Angelo P. Lopresti, Attorney-in-fact for IP Fibre Devices (UK) Ltd. 2011-12-06 By: Angelo P. Lopresti, Attorney-in-fact for Valentin Gapontsev Trust I 2011-12-06 By: Angelo P. Lopresti, Attorney-in-fact for N. Platonov 2011-12-06 By: Angelo P. Lopresti, Attorney-in-fact for E. Scherbakov 2011-12-06