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

Christensen, Simon L.; Johansen, Mette Marie; Michieletto, Mattia; Triches, Marco; Maack, Martin D.; Lægsgaard, Jesper

doi:10.1364/oe.400520

Cited by 10 publications

(6 citation statements)

References 26 publications

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“…2 while each higher harmonics has an added lobe in both the intensity and phase. The spatial distribution of the peak at 450 Hz was discussed in our previous work 10 and is due to transfer of power between LP 01 and LP 11 -modes. The structure of the fluctuations at 675 Hz was however not discussed.…”

Section: Seeding Of Tmi With a Kinematic Mirror Mountmentioning

confidence: 75%

“…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…”

Section: Spatially and Temporally Resolved Imagingmentioning

confidence: 99%

“…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.…”

Section: Tmi In the Presence Of Pump Intensity Noisementioning

confidence: 99%

“…[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.…”

Section: Introductionmentioning

confidence: 99%

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

Christensen

Johansen

Michieletto

et al. 2021

Fiber Lasers XVIII: Technology and Systems

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In this work we investigate transverse mode instability (TMI) in the presence of pump intensity noise and a controlled perturbation of the input coupling for a rod-type fiber amplifier using spatially and temporally resolved imaging (ST). We show that inherent pump intensity noise from the power supply can define significant peaks in the resulting TMI spectrum. ST measurements in the transition region of TMI also indicates that the simple picture of TMI being seeded by the combination of a static initial fraction of LP11 and pump or signal intensity noise is not valid for our measurements. Furthermore, we present seeding of TMI by perturbing the input coupling dynamically which allows measurements of the TMI gain as a function of frequency and signal power.

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Section: Seeding Of Tmi With a Kinematic Mirror Mountmentioning

confidence: 75%

Section: Spatially and Temporally Resolved Imagingmentioning

confidence: 99%

Section: Tmi In the Presence Of Pump Intensity Noisementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

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

Christensen

Johansen

Michieletto

et al. 2021

Fiber Lasers XVIII: Technology and Systems

Self Cite

View full text Add to dashboard Cite

show abstract

“…A popular alternative to the 2PDs method is the use of a high-speed camera (HSC). The HSC is more robust than the 2PDs method against other system dynamics and it offers a vastly increased amount of information of the TMI dynamics [7,16]. Unfortunately, HSCs are expensive devices, and this will prevent them from becoming ubiquitous for the characterization of TMI.…”

Section: Introductionmentioning

confidence: 99%

Characterization of Transverse Mode Instability with a 4-Quadrant Photodiode

Kholaif¹,

Jáuregui²,

Tu³

et al. 2023

Preprint

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Transverse mode instability (TMI) represents the main limitation for the power scaling of fiber laser systems with a diffraction-limited beam quality. In this context, it has become increasingly important to find a cheap and reliable way to monitor and characterize TMI and distinguish this effect from other dynamic perturbations. In this work, with the help of a position-sensitive detector, a novel method is developed to characterize the TMI dynamics even in the presence of power fluctuations. The position information of the fluctuating beam is recorded in the X- and Y-axis of the detector, which are used to track the temporal evolution of the center of gravity of the beam. The trajectories described by the beam within a specific time window contain rich information about TMI, which can be used to gain further insight into this phenomenon.

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Pump RIN reduction of the TMI threshold powers in Yb-doped kW class fiber amplifiers

Mermelstein

2022

Appl. Opt.

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A 3D spatially resolved coupled mode and perturbation analysis for the transverse mode instability threshold powers in Yb-doped fiber amplifiers is extended to include threshold power reduction induced by the pump laser relative intensity noise (RIN). A static intensity grating combines with the fluctuating pump intensity to generate an inversion standing wave. The forward component of the standing wave contributes to the nonlinear coupling between the fundamental mode and the higher-order mode (HOM), thereby reducing the threshold power. It is estimated that a pump RIN level < Privacy Policy and Terms of Service apply.

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