Fabrication of kW-level chirped and tilted fiber Bragg gratings and filtering of stimulated Raman scattering in high-power CW oscillators

Jiao, Kerong; Shen, Hua; Guan, Zhiwen; Yang, Feiyan; Zhu, Rihong

doi:10.1017/hpl.2019.18

Cited by 39 publications

(32 citation statements)

References 23 publications

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“…Chirped fiber Bragg gratings (CFBGs) are an alternative, but in many fabrication systems it was difficult to obtain such structures with high reflectance and low FWHM values until recently. Nowadays there are new techniques and possibilities to achieve CFBGs with high reflectance and low FWHM values [ 27 , 28 , 29 ]. Hence, their use in interrogation systems is problematic.…”

Section: Analysis Of the Obtained Results And Discussionmentioning

confidence: 99%

Numerical and Experimental Analysis of Matched Filter Interrogation of FBG Sensors with Large Side Lobes

Skorupski

Cięszczyk

Panas

et al. 2020

Sensors

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This article presents the effect of fiber Bragg gratings side lobes on interrogation systems consisting of sensor and matched filters. The conducted research shows that high-value side lobe structures applied as sensors and/or filters are characterized by some interesting properties. The paper presents both numerical analysis and experimental verification of the fiber Bragg gratings (FBG) interrogation systems with matched filters for gratings containing high side lobes. Numerical modeling of Bragg structures was performed for two different cases: uniform and inverse apodization. Modification of apodization can change the side lobe reflectance level even above levels found in uniform structures. This is a case not described in the literature, especially in terms of possible applications. Transfer characteristics, i.e., the relationship between power intensity as a function of wavelength shift, were determined. A collection of gratings with spectra corresponding to those analyzed in numerical experiments were fabricated. Next, the transfer characteristics of the interrogation systems containing real FBG were determined. The properties of the proposed systems are described. It has been shown that a significant level of sidebands, which is often the subject of many drawbacks in filtering or telecommunications systems, can be an advantage. It has been demonstrated that a high level of side lobes can be used to increase the measurement range of the FBG sensor interrogation systems. It has been determined numerically and confirmed experimentally that from the point of view of the design of sensor interrogation systems, it is beneficial to combine specific pairs of gratings: one with a spectrum characterized by a low side lobe level and a second one in which the spectrum has very high side lobes.

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Section: Analysis Of the Obtained Results And Discussionmentioning

confidence: 99%

Numerical and Experimental Analysis of Matched Filter Interrogation of FBG Sensors with Large Side Lobes

Skorupski

Cięszczyk

Panas

et al. 2020

Sensors

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“…Figure 4c shows the temperature image recorded by a thermal camera when laser power was 1935 W. It can be seen that the temperature distribution along the CTFBG is relatively uniform, and the maximum value is about 52 • C with a thermal slope of~0.015 • C/W. The thermal image indicated there are no defects along the CTFBG, and the heat should be mainly caused by the inscription technology, as well as residual hydrogen and -OH-related chemical bonds [22].…”

Section: Fabrication Of High-power Ctfbgsmentioning

confidence: 99%

“…The typical index modulation depth was 10 −3 , and the spectral shape indicated that its uniformity over the grating length of 35 mm was fine. After inscription, the grating needs further post-processing to release the thermal stress and remove the residual hydrogen, which will cause a large amount of heat while operating [22]. After step annealing and packaging, this CTFBG can operate at 2 kW power level.…”

Section: Fabrication Of High-power Ctfbgsmentioning

confidence: 99%

“…In comparison, CTFBGs possess better stability and have been intensively studied in the past few years [16][17][18][19][20]. Although good SRS suppression have been obtained in many high-power fiber laser systems, in most cases CTFBGs were inserted between the seed and the amplification-stage in master oscillator power-amplifier (MOPA) systems [21,22], which is mainly limited by the power handling capacity. For the commonly used ultraviolet (UV) inscription technology, the residual hydrogen, thermal stress, and other defects will cause a large amount of heat in CTFBGs when working at a high-power level [22].…”

Section: Introductionmentioning

confidence: 99%

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Fabrication of 2 kW-Level Chirped and Tilted Fiber Bragg Gratings and Mitigating Stimulated Raman Scattering in Long-Distance Delivery of High-Power Fiber Laser

et al. 2021

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Chirped and tilted fiber Bragg gratings (CTFBGs) have attracted a lot of attention in stimulated Raman scattering (SRS) suppression of high-power fiber lasers. However, the laser power handling capacity seriously limits their applications. In this paper, by optimizing the inscription parameters and post-processing strategy, we fabricate a large-mode-area double-cladding CTFBG with a thermal slope of ~0.015 °C/W due to the low insertion loss of about 0.15 dB, which make it possible for direct kilowatt-level application. A 2 kW-level fiber laser oscillator is employed to test the CTFBG, and a series of experiments have been carried out to compare the effect of SRS mitigation in high-power fiber laser long-distance delivery. In addition, the influence of CTFBGs on laser beam quality is studied for the first time. Experimental results indicated that the CTFBG could effectively mitigate SRS and has no obvious influence on laser beam quality. This work opens a new opportunity for further power scaling and the delivery of high-power fiber lasers over longer distances.

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“…Then, they used cascading multiple CTFBGs to suppress SRS in a 5-kW fiber laser [18][19][20] . In 2019, we enabled CTFBG to work well at over 1-kW laser power and applied it to suppress SRS in a kilowattlevel continuous-wave (CW) fiber laser whose SRS was suppressed by 99.5% [21] . Similarly, LPFGs can suppress SRS by coupling the Raman scattered light from forwardpropagating core modes to forward-propagating cladding modes.…”

Section: Introductionmentioning

confidence: 99%

Utilizing phase-shifted long-period fiber grating to suppress spectral broadening of a high-power fiber MOPA laser system

Bian

Jiao

et al. 2021

High Pow Laser Sci Eng

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Suppressing nonlinear effects in high-power fiber lasers based on fiber gratings has become a hotspot. At present, research is mainly focused on suppressing stimulated Raman scattering in a high-power fiber laser. However, the suppression of spectral broadening, caused by self-phase modulation or four-wave mixing, is still a challenging attribute to the close distance between the broadened laser and signal laser. If using a traditional fiber grating with only one stopband to suppress the spectral broadening, the signal power will be stripped simultaneously. Confronting this challenge, we propose a novel method based on phase-shifted long-period fiber grating (PS-LPFG) to suppress spectral broadening in a high-power fiber master oscillator power amplifier (MOPA) laser system in this paper. A PS-LPFG is designed and fabricated on 10/130 passive fiber utilizing a point-by-point scanning technique. The resonant wavelength of the fabricated PS-LPFG is 1080 nm, the full width at half maximum of the passband is 5.48 nm, and stopband extinction exceeds 90%. To evaluate the performance of the PS-LPFG, the grating is inserted into the seed of a kilowatt-level continuous-wave MOPA system. Experiment results show that the 30 dB linewidth of the output spectrum is narrowed by approximately 37.97%, providing an effective and flexible way for optimizing the output linewidth of high-power fiber MOPA laser systems.

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Fabrication of kW-level chirped and tilted fiber Bragg gratings and filtering of stimulated Raman scattering in high-power CW oscillators

Cited by 39 publications

References 23 publications

Numerical and Experimental Analysis of Matched Filter Interrogation of FBG Sensors with Large Side Lobes

Numerical and Experimental Analysis of Matched Filter Interrogation of FBG Sensors with Large Side Lobes

Fabrication of 2 kW-Level Chirped and Tilted Fiber Bragg Gratings and Mitigating Stimulated Raman Scattering in Long-Distance Delivery of High-Power Fiber Laser

Utilizing phase-shifted long-period fiber grating to suppress spectral broadening of a high-power fiber MOPA laser system

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