EXHIBIT 31.1



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



I, Thomas Merk, certify that:



| | 1. | I
have reviewed this Annual Report on Form 10-K of ROFIN-SINAR Technologies Inc.
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| | 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.
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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: January 28, 2016



| | /s/ Thomas Merk        
| | -----------------------
| | Thomas Merk            
| | Chief Executive Officer