EXHIBIT 31.1

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

I, Günther Braun, Chief Executive Officer of Rofin-Sinar Technologies, Inc., certify that:

|1. | I have reviewed this Annual Report on Form 10-K of Rofin-Sinar Technologies Inc.                                                                                                                                                                                                                                                      
|-- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
|  
|2. | Based on my knowledge, this Annual 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.                     
|  
|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.                                 
|  
|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:
|  
|   | a)                                                                                                                                                                                                                                                                                                                                    
|  
|   | b)                                                                                                                                                                                                                                                                                                                                    
|  
|   | c)                                                                                                                                                                                                                                                                                                                                    
|  
|   | d)                                                                                                                                                                                                                                                                                                                                    
|  
|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):                                           
|  
|   | a)                                                                                                                                                                                                                                                                                                                                    
|  
|   | b)                                                                                                                                                                                                                                                                                                                                    
|  

|Date: November 29, 2007 |                         | 
|----------------------- | ----------------------- | 
|                        | /s/ Günther Braun       | 
|                        | Günther Braun           | 
|                        | Chief Executive Officer | 

---