Real-time modal decomposition of fiber laser beams using a spatial mode multiplexer

Yiming Tu; Cesar Jauregui; Sobhy E. Kholaif; Jens Limpert

doi:10.1117/12.2609322

4 March 2022 Real-time modal decomposition of fiber laser beams using a spatial mode multiplexer

Yiming Tu, Cesar Jauregui, Sobhy E. Kholaif, Jens Limpert

Proceedings Volume 11981, Fiber Lasers XIX: Technology and Systems; 1198111 (2022) https://doi.org/10.1117/12.2609322
Event: SPIE LASE, 2022, San Francisco, California, United States

Abstract

Modal decomposition (MD) techniques are a way to characterize the modal amplitudes and phases of eigenmodes in optical fibers. Some applications such as, e.g., diagnosing/analyzing transverse mode instabilities or monitoring a laser beam during operation, require a high-speed modal decomposition. However, the proposed modal decomposition techniques up to now are seldom able to implement a real-time MD due to their complex post-processing (e.g., most of the numerical computing-based MD). In this work a high-speed, real-time modal decomposition of fiber laser beams is presented. It employs a spatial mode multiplexer (MUX), which is a multipass cavity with multiple single-mode fiber (SMF) inputs and a single few-mode fiber (FMF) output, operated in reverse. Thus, if the output of a fiber laser system is imaged on the end facet of the FMF, then the MUX is used as a demultiplexer and, thus, the modal amplitude information can be obtained by reading out the different SMF input ports. We have carried out several experiments with the MUX and it has been proven that this method is accurate and extremely fast. In fact, it is even able to decompose the beam during a Q-switched pulse emission and produce real-time results.

Conference Presentation

Citation Download Citation

Yiming Tu, Cesar Jauregui, Sobhy E. Kholaif, and Jens Limpert "Real-time modal decomposition of fiber laser beams using a spatial mode multiplexer", Proc. SPIE 11981, Fiber Lasers XIX: Technology and Systems, 1198111 (4 March 2022); https://doi.org/10.1117/12.2609322

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