Towards the control of the modal energy transfer in transverse mode instabilities

Christoph Stihler; Cesar Jauregui; Andreas Tünnermann; Jens Limpert

doi:10.1117/12.2289889

26 February 2018 Towards the control of the modal energy transfer in transverse mode instabilities

Christoph Stihler, Cesar Jauregui, Andreas Tünnermann, Jens Limpert

Proceedings Volume 10512, Fiber Lasers XV: Technology and Systems; 1051204 (2018) https://doi.org/10.1117/12.2289889
Event: SPIE LASE, 2018, San Francisco, California, United States

Abstract

Thermally-induced refractive index gratings (RIG) in high-power fiber laser systems lead to transverse mode instabilities (TMI) above a certain average power threshold. The effect of TMI is currently the main limitation for the further average power scaling of fiber lasers and amplifiers with nearly diffraction-limited beam quality. In this work we experimentally investigate, for the first time, the growth of the RIG strength by introducing a phase-shift between the RIG and the modal interference pattern in a fiber amplifier. The experiments reveal that the RIG is strong enough to couple energy between different transverse modes even at powers significantly below the TMI threshold, provided that the introduced phase-shift is high enough. This indicates that, as the strength of the RIG further increases with increasing average output power, the RIG becomes more and more sensitive to even small noise-induced phase-shifts, which ultimately trigger TMI. Furthermore, it is shown that a beam cleaning also occurs when a positive phase-shift is introduced, even above the TMI threshold. This finding will pave the way for the development of a new class of mitigation strategies for TMI, which key feature is the control of the introduced phase-shift.

Citation Download Citation

Christoph Stihler, Cesar Jauregui, Andreas Tünnermann, and Jens Limpert "Towards the control of the modal energy transfer in transverse mode instabilities", Proc. SPIE 10512, Fiber Lasers XV: Technology and Systems, 1051204 (26 February 2018); https://doi.org/10.1117/12.2289889

ACCESS THE FULL ARTICLE

INSTITUTIONAL
Select your institution to access the SPIE Digital Library.

SELECT YOUR INSTITUTION

PERSONAL
Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.

PERSONAL SIGN IN

No SPIE Account? Create one

PURCHASE THIS CONTENT

SUBSCRIBE TO DIGITAL LIBRARY

50 downloads per 1-year subscription

Members: $195

Non-members: $335 ADD TO CART

25 downloads per 1 - year subscription

Members: $145

Non-members: $250 ADD TO CART

PURCHASE SINGLE ARTICLE

Includes PDF, HTML & Video, when available