**EXHIBIT 31.1**

 

**Rule 13a-14(a)/15d-14(a) Certification of the Chief Executive Officer**

 

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| I,      Günther Braun, certify that: |
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| 1.                                        | I have reviewed this Amendment No. 1 to Annual Report on Form 10-K of Rofin-Sinar Technologies Inc.                                                                                                                                                                                                                                                                                                                |
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| 2.                                        | Based on my knowledge, this report does not contain any untrue statement of a material fact or omit to state a material fact necessary to make the statements made, in light of the circumstances under which such statements were made, not misleading with respect to the period covered by this report.                                                                                                         |
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| 3.                                        | Based on my knowledge, the financial statements, and other financial information included in this Annual Report, fairly present in all material respects the financial condition, results of operations and cash flows of the registrant as of, and for, the periods presented in this Annual Report.                                                                                                              |
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| 4.                                        | The                registrant’s other certifying officer(s) and I are responsible                for establishing and maintaining disclosure controls and procedures                (as defined in Exchange Act Rules 13a-15(e) and 15d-15(e)) and                internal control over financial reporting (as defined in Exchange            Act Rules 13a-15(f) and 15d-15(f) for the registrant and have: |
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|                                           | a)                                                                                                                                                                                                                                                                                                                                                                                                                 | designed such disclosure controls and procedures, or caused such disclosure controls and procedures to be designed under our supervision, to ensure that material information relating to the registrant, including its consolidated subsidiaries, is made known to us by others within those entities, particularly during the period in which this report is being prepared;                                                        |
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|                                           | b)                                                                                                                                                                                                                                                                                                                                                                                                                 | designed such internal control over financial reporting, or caused such internal control over financial reporting to be designed under our supervision, to provide reasonable assurance regarding the reliability of financial reporting and the preparation of financial statements for external purposes in accordance with Generally Accepted Accounting Principles;                                                               |
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|                                           | c)                                                                                                                                                                                                                                                                                                                                                                                                                 | evaluated                the effectiveness of the registrant’s disclosure controls                and procedures and presented in this report our conclusions about                the effectiveness of the disclosure controls and procedures,                as of the end of the period covered by this report, based on            such evaluation; and                                                                      |
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|                                           | d)                                                                                                                                                                                                                                                                                                                                                                                                                 | disclosed                in this report any change in the registrant’s internal control over financial reporting that occurred during the registrant’s most recent fiscal quarter (the registrant’s fourth fiscal quarter in the case of an annual report) that has materially affected, or is reasonably likely to materially affect, the registrant’s            internal control over financial reporting; and |
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| 5.                                        | The                registrant’s other certifying officer and I have disclosed, based on our most recent evaluation of internal control over financial reporting, to the registrant’s auditors and the audit committee of registrant’s            board of directors (or persons performing the equivalent functions):                                                                               |
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|                                           | a)                                                                                                                                                                                                                                                                                                                                                                                                                 | all                significant deficiencies and material weaknesses in the design                or operation of internal control over financial reporting which                are reasonably likely to adversely affect the registrant’s                ability to record, process, summarize and report financial information;            and                                                                                 |
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|                                           | b)                                                                                                                                                                                                                                                                                                                                                                                                                 | any                fraud, whether or not material, that involves management or other                employees who have a significant role in the registrant’s            internal control over financial reporting.                                                                                                                                                                                                              |

 

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| Date:      December      23, 2010 | /s/      Günther Braun |        |
|                                                            | Günther      Braun     |        |
|                                                            | Chief Executive Officer     |        |

 

 

 

 

 

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