Analytical model of thermal effect and optical path difference in end-pumped Yb:YAG thin disk laser

Zhu, Guangping; Zhu, Xiao; Wang, Mu; Feng, Yufan; Zhu, Congshan

doi:10.1364/ao.53.006756

Cited by 20 publications

(7 citation statements)

References 13 publications

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“…We find a reduction of the overall disk thermal lens by ~33% when operating in vacuum or 1 bar of He as compared to 1 bar of air or 1 bar of nitrogen (N 2 ), with the disk temperature being independent of the gas environment. In a newly developed numerical simulation, we modeled our experimental results with a gas lens induced by the heated gas in front of the thin disk, which adds to the disk-material thermal effects analyzed in Ref [24]. This gas lens is non-existent for vacuum environments and roughly a factor of five smaller for He as compared to air and N 2 .…”

Section: Introductionmentioning

confidence: 99%

Gas-lens effect in kW-class thin-disk lasers

et al. 2018

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We unveil a gas-lens effect in kW-class thin-disk lasers, which accounts in our experiments for 33% of the overall disk thermal lensing. By operating the laser in vacuum, the gas lens vanishes. This leads to a lower overall thermal lensing and hence to a significantly extended power range of optimal beam quality. In our high-power continuous-wave (cw) thin-disk laser, we obtain single-transverse-mode operation, i.e. M < 1.1, in a helium or vacuum environment over an output-power range from 300 W to 800 W, which is 70% broader than in an air environment. In order to predict the magnitude of the gas-lens effect in different thin-disk laser systems and gain a deeper understanding of the effect of the heated gas in front of the disk, we develop a new numerical model. It takes into account the heat transfer between the thin disk and the surrounding gas and calculates the lensing effect of the heated gas. Using this model, we accurately reproduce our experimental results and additionally predict, for the first time by means of a theoretical tool, the existence of the known gas-wedge effect due to gas convection. The gas-lens and gas-wedge effects are relevant to all high-power thin-disk systems, both oscillators and amplifiers, operating in cw as well as pulsed mode. Specifically, canceling the gas-lens effect becomes crucial for kW power scaling of thin-disk oscillators because of the larger mode area on the disk and the resulting higher sensitivity to the disk thermal lens.

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Section: Introductionmentioning

confidence: 99%

Gas-lens effect in kW-class thin-disk lasers

et al. 2018

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“…Heat removal from the disk is efficient because of the large cooled surface to active volume ratio. Since the heat flux occurs along the laser axis, the thermally induced lens effects are minimized resulting in small phase-front distortions also for beams of large diameter [4,5,6,7]. This cooling scheme allows thus for power and energy scaling [8,9,10,11,12,13] simply by increasing the diameter of laser and pump spots, eventually limited by amplified spontaneous emission effects [4,14,15,16].…”

Section: Introductionmentioning

confidence: 99%

Thin-disk laser pump schemes for large number of passes and moderate pump source quality

Schuhmann¹,

Hänsch

Kirch³

et al. 2015

Appl. Opt.

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Novel thin-disk laser pump layouts are proposed yielding an increased number of passes for a given pump module size and pump source quality. These novel layouts result from a general scheme which bases on merging two simpler pump optics arrangements. Some peculiar examples can be realized by adapting standard commercially available pump optics simply by introducing an additional mirror-pair. More pump passes yield better efficiency, opening the way for usage of active materials with low absorption. In a standard multi-pass pump design, scaling of the number of beam passes brings about an increase of the overall size of the optical arrangement or an increase of the pump source quality requirements. Such increases are minimized in our scheme, making them eligible for industrial applications.

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“…lasers therefore it is essential to consider the stability properties of the resonator for variations of the disk thermal lens [7,12,13]. These are usually represented in form of so called "stability plots" [14] where the eigen-mode size at an optical element in the resonator is plotted for variations of the disk dioptric power V .…”

Section: Motivationmentioning

confidence: 99%

“…However, power (energy) scaling calls for an increase of the beam waist resulting in an increased sensitivity to the residual thermal lens effects which eventually limits the achievable scaling [6,7,8,9,10,11]. When designing high power (energy) lasers therefore it is essential to consider the stability properties of the resonator for variations of the disk thermal lens [7,12,13]. These are usually represented in form of so called "stability plots" [14] where the eigen-mode size at an optical element in the resonator is plotted for variations of the disk dioptric power V .…”

Section: Motivationmentioning

confidence: 99%

Thin-disk laser scaling limit due to thermal lens induced misalignment instability

Schuhmann¹,

Kirch²,

Nez

et al. 2016

Appl. Opt.

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We present a fundamental obstacle in power scaling of thin-disk lasers related to self-driven growth of misalignment due to thermal lens effects. This self-driven growth arises from the changes of the optical phase difference at the disk caused by the excursion of the laser eigen-mode from the optical axis. We found a criterion based on a simplified model of this phenomenon, which can be applied to design laser resonators insensitive to this effect. Moreover, we propose several resonator architectures that are not affected by this effect.

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Analytical model of thermal effect and optical path difference in end-pumped Yb:YAG thin disk laser

Cited by 20 publications

References 13 publications

Gas-lens effect in kW-class thin-disk lasers

Gas-lens effect in kW-class thin-disk lasers

Thin-disk laser pump schemes for large number of passes and moderate pump source quality

Thin-disk laser scaling limit due to thermal lens induced misalignment instability

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