Novel high-speed camera analysis of transverse mode instabilities in rod fiber amplifiers

Abstract

Document VersionPublisher's PDF, also known as Version of record Link back to DTU Orbit Citation (APA): Christensen, S. L., Johansen, M. M., Michieletto, M., Triches, M., Hout, L., Maack, M. D., & Laegsgaard, J. (2020). Novel high-speed camera analysis of transverse mode instabilities in rod fiber amplifiers. "Novel high-speed camera analysis of transverse mode instabilities in rod fiber amplifiers," Proc. ABSTRACTIn this work a novel accurate method of measuring beam fluctuations is presented and applied to analyze transverse mode instabilities (TMI). The new measurement, ST-measurement, uses Fourier analysis on data from a high-speed camera to achieve raw spatial information about beam fluctuations. TMI in a 65 µm modefield-diameter aeroGain-ROD-PM85 fiber is investigated using both the ST-and standard photo detector measurement. A comparison of the two measurements shows the quantitative and qualitative superiority of the new ST-measurement due to the spatial information. Numerical simulations are carried out to support the interpretation of the data.

Study of seeding mechanisms of TMI with spatially and temporally resolved imaging

“…The ST method fully describes fluctuations of a beam by separating fluctuations in frequency as mentioned in the introduction. 9,10 The fundamental data required for this method is a movie of the beam intensity fluctuations which is Fourier transformed in time. The Fourier transform results in a complex data structure depending on transverse space and frequency, defined as…”

“…In this work we study the effect of inherent pump noise on the resulting TMI fluctuations using the ST method. 9,10 The ST method allows for detailed analysis of beam fluctuations by utilizing the periodic nature of fluctuations and applications on TMI have already been fruitful.…”

“…[3][4][5][6][7] In order to further understand TMI, detailed experimental characterizations of the phenomenon are needed. 8 In our recent work, 9,10 we proposed and applied the spatially and temporally resolved imaging (ST) technique which is also the basis of this work. The ST method makes use of the periodicity of TMI fluctuations and can fully describe different beam dynamics.…”

Experimental investigations of seeding mechanisms of TMI in rod fiber amplifier using spatially and temporally resolved imaging

“…In this section, application of spatially and temporally resolved imaging [18] is outlined. The ST method is applied on both numerical and experimental data.…”

“…We have recently developed a more quantitative and qualitative method called spatially and temporally resolved imaging [18], ST in short. This method accurately captures fluctuations using the transverse spatial dimension.…”