kW level narrow linewidth Yb fiber amplifiers for beam combining

Khitrov, V. V.; Farley, Kevin; Leveille, Ryan; Galipeau, Joshua; Majid, Imtiaz; Christensen, S.; Samson, Bryce; Tankala, K.

doi:10.1117/12.862648

Cited by 34 publications

(21 citation statements)

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“…Standard phase modulation techniques include driving the electro-optic modulator with a sine wave or white noise source (WNS) that allow power scaling of fiber amplifiers well beyond the single-frequency SBS threshold. 8,9 The work presented here is focused on the SBS threshold enhancement of a high power monolithic Yb-doped fiber amplifier seeded with a single-frequency laser which is phase modulated by a pseudo-random bit sequence (PRBS) generator. Our numerical simulations show that this phase modulation scheme provides significant improvement in the SBS threshold if the appropriate bit pattern is selected.…”

Section: Introductionmentioning

confidence: 99%

Pseudo-random binary sequency phase modulation in high power Yb-doped fiber amplifiers

Robin

Dajani

Zernigue³

et al. 2013

Fiber Lasers X: Technology, Systems, and Applications

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We present experimental and theoretical studies on the stimulated Brillouin scattering (SBS) threshold in fiber amplifiers seeded with a spectrally broadened single-frequency laser source. An electro-optic phase modulator is driven with various pseudo-random binary sequence (PRBS) patterns to highlight the unique characteristics of this linewidth broadening technique and its facility in SBS mitigation. Theoretical predictions show a variation in SBS suppression based on PRBS pattern and modulation frequency. These predictions are experimentally investigated in a kilowatt level monolithic fiber amplifier operating with near diffraction-limited beam quality. We also show Rayleigh scattering and other sources of back reflected light in phase modulated signals can seed the SBS process and significantly reduce the nonlinear threshold.

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Section: Introductionmentioning

confidence: 99%

Pseudo-random binary sequency phase modulation in high power Yb-doped fiber amplifiers

Robin

Dajani

Zernigue³

et al. 2013

Fiber Lasers X: Technology, Systems, and Applications

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“…그러나, SBC 방식은 CBC 방식 에 비해서 상대적으로 구현이 용이하고, 각 채널빔의 파장 혹은 주파수 선폭을 충분히 좁게 하고, 결합되는 채널 수를 적절히 제한할 경우, 이상적인 CBC 방식에 근접한 결합 효 율 및 빔 품질을 구현할 수 있다 [49,50] . 따라서, 이를 위한 다 양한 방식의 고출력 협대역 광원 시스템에 대한 많은 연구개 발 노력들이 이어지고 있고 [17] , 수 GHz 선폭을 가지면서도 kW급 출력을 갖는 MOPA 기반 협대역 광원이 빔 결합 시스 템의 주요 단위 레이저 구성 요소로 적용되고 있다 [59,61] . 최 근 결합 효율의 최적화를 통해 77%에 달하는 휘도 효율 (결 합 빔의 휘도/채널빔의 휘도의 합)이 보고된 바 있으며 [56] , 출 력 관점에서는 SBC 기술을 통해 30 kW에 이르는 출력의 연 속광 발진 사례가 보고된 바 있다 [62] .…”

Section: 다중 빔 결합 기술의 현황unclassified

“…한편 후자의 경우, 시드 광의 선폭이 일반적인 실 리카 소재 광섬유의 브릴루앙 이득 대역(약 60 MHz)보다 [30] 현저히 좁으므로, 만약 kW의 출력 수준으로 증폭된다고 가 정한다면, 필연적으로 전술한 바 있는 SBS 현상을 심각하게 야기하게 되는데, 이를 해결하기 위해서는 시드 신호의 선폭 을 일정 수준으로 증대시킬 필요가 있다. 통상적으로 브릴루 앙 이득의 대역폭인 수십 MHz 수준보다 충분히 크고, 최종 결합 빔 품질의 저하가 심각하지 않은 GHz 수준에서 시드 광의 선폭을 결정한다 [59] . 시드 광의 선폭 증대는 [59,64,65] .…”

Section: 분광형 다중 빔 결합 기술unclassified

“…통상적으로 브릴루 앙 이득의 대역폭인 수십 MHz 수준보다 충분히 크고, 최종 결합 빔 품질의 저하가 심각하지 않은 GHz 수준에서 시드 광의 선폭을 결정한다 [59] . 시드 광의 선폭 증대는 [59,64,65] . 전자는 일반적인 백색 노이즈 광원(White Noise Source)을 인가하는 방식으로, 구현이 가장 용이하다 는 장점을 가지지만 [59,64] , 시드 신호의 선폭을 임의로 조정하 기 어려운 단점이 있다.…”

Section: 분광형 다중 빔 결합 기술unclassified

“…시드 광의 선폭 증대는 [59,64,65] . 전자는 일반적인 백색 노이즈 광원(White Noise Source)을 인가하는 방식으로, 구현이 가장 용이하다 는 장점을 가지지만 [59,64] , 시드 신호의 선폭을 임의로 조정하 기 어려운 단점이 있다. 반면에 후자는 모조 랜덤 이진수 시 퀀스에 따른 디지털 신호를 인가하는 방식으로, 확장된 시드 신호의 스펙트럼이 안정적이고 경우에 따라 실시간으로 조정 가능하다는 장점을 가지는 반면 전자에 비해 상대적으로 구현 이 복잡하고, SBS 억제 효과가 다소 감소되는 단점을 갖는다 [65] .…”

Section: 분광형 다중 빔 결합 기술unclassified

See 2 more Smart Citations

Current Status and Prospects of High-Power Fiber Laser Technology (Invited Paper)

Kwon¹,

Park²,

Lee³

et al. 2016

Korean Journal of Optics and Photonics

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Over the past two decades, fiber-based lasers have made remarkable progress, now having reached power levels exceeding kilowatts and drawing a huge amount of attention from academy and industry as a replacement technology for bulk lasers. In this paper we review the significant factors that have led to the progress of fiber lasers, such as gain-fiber regimes based on ytterbium-doped silica, optical pumping schemes through the combination of laser diodes and double-clad fiber geometries, and tandem schemes for minimizing quantum defects. Furthermore, we discuss various power-limitation issues that are expected to incur with respect to the ultimate power scaling of fiber lasers, such as efficiency degradation, thermal hazard, and system-instability growth in fiber lasers, and various relevant methods to alleviate the aforementioned issues. This discussion includes fiber nonlinear effects, fiber damage, and modal-instability issues, which become more significant as the power level is scaled up. In addition, we also review beam-combining techniques, which are currently receiving a lot of attention as an alternative solution to the power-scaling limitation of high-power fiber lasers. In particular, we focus more on the discussion of the schematics of a spectral beam-combining system and their individual requirements. Finally, we discuss prospects for the future development of fiber laser technologies, for them to leap forward from where they are now, and to continue to advance in terms of their power scalability.

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Engineering of Coherently Combined, High‐Power Laser Systems

Goodno

Rothenberg

2013

Coherent Laser Beam Combining

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In recent years, much effort has been expended toward scaling electric lasers to CW power levels on the order of 100 kW or greater [1]. The key challenge in such scaling is maintaining near-diffraction-limited (DL) beam quality (BQ) to enable tight focusing onto a distant target. Despite the maturation of scalable, diode-pumped laser amplifier technologies such as zigzag slabs [2] or fibers [3], thermal effects or optical nonlinearities currently limit near-DL output from single lasers to an order of magnitude lower power, around 10 kW.Actively phase-locked coherent beam combination (CBC) of N laser amplifiers seeded by a common master oscillator (MO) represents an engineerable approach toward scaling laser brightness B (loosely defined here as B $ power/BQ 2 ) beyond the limits of the underlying single-element laser technology. Ideally, the combined output behaves as if it were a single beam, and B is thereby increased by a factor of N over an unphased array or by a factor of N 2 over any individual laser [4].A compelling architectural advantage of CBC systems in comparison to singleaperture lasers of comparable power is the graceful degradation in response to failure of any gain element. This feature can be elucidated from the scaling of B $ N 2 , so the relative rate of change in brightness as individual lasers fail is 1/B(dB/dN) ¼ 2/N. Hence, for large arrays, the drop in brightness is gradual. For example, failure of 1 out of N ¼ 100 lasers would still allow a CBC system to continue operating at 98% of its original brightness.Active CBC with servo-based phase locking can be straightforwardly engineered for very high channel counts and for very high-power laser gain elements. Recently, Northrop Grumman Aerospace Systems adopted an actively phaselocked approach to combine seven 15 kW Nd:YAG slab amplifier chains to demonstrate the world's first 100 kW electric laser with record-setting brightness [5]. As of this writing, work is underway to extend this technology to achieve similar power levels in a CBC array of fiber lasers with improved BQ and efficiency as well as reduced size and weight [6,7].

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kW level narrow linewidth Yb fiber amplifiers for beam combining

Cited by 34 publications

References 0 publications

Pseudo-random binary sequency phase modulation in high power Yb-doped fiber amplifiers

Pseudo-random binary sequency phase modulation in high power Yb-doped fiber amplifiers

Current Status and Prospects of High-Power Fiber Laser Technology (Invited Paper)

Engineering of Coherently Combined, High‐Power Laser Systems

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