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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Different Lasing Regimes of Parity-Time Symmetric Fiber Ring Laser
摘要： The concept of parity-time (PT) symmetry in optics attracts great deal of attention. Recently, a parity-time symmetry-breaking laser consisted of two coupled microrings has been experimentally demonstrated [1, 2]. A single-mode operation in an initially multimode system was achieved through stronger mode discrimination close to a PT-symmetry breaking transition. Further on, a single transverse mode operation in a system of coupled microring lasers was demonstrated near the exceptional point [3]. A possible route to a PT symmetry-based mode-locking has been theoretically discussed in paper [4]. This work develops a recently proposed concept of PT-symmetric fiber laser [5]. The laser layout [5] comprises two fiber loops of the same length cross-coupled via a set of two fiber 50:50 couplers with incorporated adjustable phase shifts ((cid:77)1, (cid:77)2) between them. Changing phase shift difference one can control coupling ratio between two fiber loops and get either PT-symmetric or PT-broken lasing regime [5]. Using exhaustive numerical modeling based on generalized nonlinear Schr?dinger equation we investigated into spectral and spatio-temporal dynamics [6] of this PT-symmetric fiber Raman laser. In particular we demonstrate that such laser is capable to operate in a variety of lasing regimes, including turbulent [7] (stochastic quasi-stationary), laminar (coherent quasi-stationary) lasing, as well as generation of a single pulse or multiple pulses per cavity round-trip, see Fig. 1. We analyze PT-symmetry of laser radiation in each regime and show how the laser can switch between these lasing regimes by means of adjustment of pump power and phase shift between fiber loops. In particular, when (cid:77)1 ≈ (cid:77)2 the gain and loss fiber loops are almost uncoupled, the radiation is almost completely concentrated in the gain loop, so that the laser operates in PT-broken turbulent regime irrespective to pump power. In the opposite limiting case (cid:77)1 - (cid:77)2 ≈ (cid:83), two fiber loops are fully coupled. Once the pump power is above the threshold and (cid:77)1 - (cid:77)2 ≈ (cid:83), the laser always operates in PT-symmetric regime thus having equal powers in the middle of gain and loss segments. The laser produces highly coherent narrow-bandwidth radiation (laminar regime [7]) near the lasing threshold and stochastic (turbulent) radiation with broad optical spectrum and low coherence well above the threshold. We show that at intermediate phase shift 0 < (cid:77)1 - (cid:77)2 < (cid:83) where PT-transition takes place, the laser may operate in pulsed regimes with “partial” (local) symmetry, i.e. temporal areas of PT-symmetric and PT-broken radiation interleave. The laser pulses correspond to areas of PT-broken regime with power concentrated mainly inside gain loop, whereas between adjacent pulses there’s a PT-symmetric laminar background with equal extremely low-level powers at the middle of gain and loss loops.
关键词： laminar,turbulent,parity-time symmetry,fiber laser,PT-broken,PT-symmetric,pulsed,lasing regimes
更新于2025-09-12 10:27:22
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All-Fiber Erbium-doped Q-Switched Laser with Recycled Graphite Oxide
摘要： This work demonstrates a passively Q-Switched fiber laser employing graphite oxide as a saturable absorber, generating tunable microsecond pulses with kHz repetition rates, pulse energies of up to 15.54 nJ and the pulse-to-pulse timing jitter of 46.14 fs. The graphite oxide samples were obtained by recycling the graphite present in Li-ion batteries utilized in cell phone devices through a chemical separation and subsequent oxidation process. Sample characterization employing X-ray diffraction, solid-state nuclear magnetic resonance and Raman spectroscopy showed that the produced graphite oxide exhibited a homogeneously oxidized structure. These results indicate that applications in the physics of pulsed lasers can benefit from the recycling of lithium batteries, directing the process of discarding spent batteries.
关键词： Recycled Graphite Oxide,Lithium Batteries,Erbium-Doped Fiber Laser,Saturable Absorber,Q-Switched
更新于2025-09-12 10:27:22
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Wavelength-switchable fiber laser based on Mach-Zehnder filter with LP11 mode output
摘要： We experimentally demonstrated a method of generating continuously wavelength-switchable LP11 mode in an all-fiber laser. A Mach–Zehnder filter is constructed to provide a comb spectrum. A fused mode selective coupler (MSC) is used to obtain mode conversion and LP11 mode can be output successfully. The experiment result shows that, the proposed fiber laser can operate at single-, dual-, triple- and quadruple-wavelength with LP11 modes output by adjusting the polarization controllers (PCs). The wavelength ranges are adjustable, when the output of the proposed fiber laser are single-, dual-, and triple-wavelength. Besides, the interval of dual wavelengths is also adjustable to some extent. Due to the superior characteristics of the Mach–Zehnder filter and the MSC, the proposed wavelength-switchable fiber laser has the merits of good stability, high signal-to-noise ratio (SNR, higher than 36 dB) and high mode purity (high to 95%).
关键词： wavelength-switchable,fiber laser,mode purity
更新于2025-09-12 10:27:22
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Peak-power-clamping in an all-polarization-maintaining Q-switched mode-locking fiber laser
摘要： We report the peak-power-clamping (PPC) effect in a polarization-maintaining (PM) Q-switched mode locking fiber laser. The laser cavity with a compact and stable all-PM fiber configuration can clearly demonstrate three different output states including normal Q-switching, PPC Q-switching, and PPC Q-switched mode-locking (QML) with the increasing pump power. To the best of our knowledge, it is the first time that PPC effect is successfully obtained and analyzed from the Q-switching to QML. This research extends the theory of PPC in pulsed lasers and reveals the potential to achieve ultra-high pulse energy.
关键词： peak-power-clamping,polarization-maintaining,Q-switched mode locking,fiber laser
更新于2025-09-12 10:27:22
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - 4.37 GHz L-Band Passively Harmonic Mode-Locked Fiber Laser Based on Nonlinear Polarization Rotation
摘要： L-band passively harmonic mode-locked (PHML) fiber lasers are important because various practical applications, such as high-speed optical sampling, dense wavelength division multiplexed (DWDM) systems and material processing, etc. Therefore, L-band PHML fiber lasers have been widely concerned in recent years. In 2012, J. Du et al experimentally achieved L-band PHML pulses by utilizing graphene as a saturable absorber (SA) [1]. Under a certain pumping power, 2nd to 4th harmonic orders can be tuned by adjusting polarization controllers (PCs). In 2014, Y. Meng et al obtained 5.88 GHz L-band PHML pulses with 19 dB super-mode suppression ratio (SMSR) in an Er-Yb co-doped double-clad fiber laser using a graphene SA [2]. In 2018, Q. Huang et al built up a 550 MHz L-band PHML fiber laser based on carbon nanotubes film for the first time [3]. It is worth noting that all of these results are focused on the generation of L-band PHML by utilizing a physical SA. However, the fabrication of physical SA can be complicated with high cost and its thermal damage threshold is not enough to support high pump power which have great impact on the repetition rate of harmonic pulses. Meanwhile, nonlinear polarization rotation as an effective SA have many advantages including high thermal damage threshold, low fabrication cost, high modulation depth and compactness. Therefore, it is desirable to build an L-band PHML fiber laser based on NPR.
关键词： fiber laser,nonlinear polarization rotation,passively harmonic mode-locked,L-band
更新于2025-09-12 10:27:22
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Hydrophilic to ultrahydrophobic transition of Al 7075 by affordable ns fiber laser and vacuum processing
摘要： A lot of research efforts have been invested in the fabrication of superhydrophobic surfaces in recent years due to many protentional applications in science and industry including anti-icing, self-cleaning and anti-corrosive surfaces. Laser as a non-polluting, precise and flexible tool can be applied to replicate surface microstructures of extremely water repellent lotus leave surface. In this study, a common nanosecond laser source is used to fabricate a super/ultrahydrophobic surfaces with different microstructure designs, contact angles above 170° and sliding angles below 5°. The freshly processed surface is hydrophilic and becomes hydrophobic and superhydrophobic in a certain time period, which could be dramatically reduced by storing samples in high vacuum. The transformation in wetting properties are analysed with respect to surface geometry and surface chemistry.
关键词： Surface functionalization,fiber laser,vacuum processing,ultrahydrophobicity
更新于2025-09-12 10:27:22
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Ultrafine frequency linearly tunable single-frequency fiber laser based on intracavity active tuning
摘要： An ultrafine frequency linearly tunable single-frequency fiber laser based on the intracavity active tuning is demonstrated. Single-frequency operation can be achieved by an ultrashort cavity and ultranarrow polarization-maintaining fiber Bragg grating. A sub-nanometer-accuracy piezoelectric ceramic actuator with closed-loop mode has been employed to realize the cavity-length active tuning scheme, which can achieve a linear tuning range of >1 GHz with a 3.2 -MHz/nm tuning resolution. The periodic tuning repeatability and repeat accuracy show that the scheme can realize linear frequency tuning with great tuning repeatability and high tuning precision.
关键词： Ultrafine,Linearly Tunable,Fiber Laser
更新于2025-09-12 10:27:22
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Samarium (III) oxide thin film as a saturable absorber for the passively Q-switched Tm-doped fiber laser
摘要： We have demonstrated a passive Q-switched Thulium-doped fiber laser (TDFL using samarium oxide (Sm2O3) nanomaterial as saturable absorber (SA). The Sm2O3 based SA was fabricated by simply mixing the Sm2O3 powder solution with polyvinyl alcohol (PVA) solution. The homogeneously mixed solution was spread and dry to form a thin film. A piece of 1 mm x 1 mm of the SA thin film is sandwiched between two fiber ferrules and incorporated into a TDFL ring cavity for pulses generation. By controlling the loss and gain in the cavity, stable Q-switching operation was generated. The repetition rate was tunable from 17.62 kHz to 29.20 kHz by varying the pump power from 619 mW to 784 mW. The smallest pulse width of 3.54 μs and the highest pulse energy of 0.20 uJ were obtained at the highest pump power.
关键词： Fiber laser,saturable absorber,Q-switched
更新于2025-09-12 10:27:22
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[IEEE 2019 21st International Conference on Transparent Optical Networks (ICTON) - Angers, France (2019.7.9-2019.7.13)] 2019 21st International Conference on Transparent Optical Networks (ICTON) - Assessment of the Combined Effect of Laser Phase Noise and Intercore Crosstalk on the Outage Probability of DD OOK Systems
摘要： We study the influence of the combined effect of laser phase noise and intercore crosstalk on the outage probability of direct-detection 10 Gbit/s on-off keying optical communication systems. We show that the laser phase noise can affect significantly the outage probability, for lasers with linewidths in the MHz range, for low and high skew-bit rate products. We also show that the laser phase noise effect on the received eye-pattern is qualitatively similar to the one found for high skew-bit rate product in the absence of laser phase noise.
关键词： intercore crosstalk,on-off keying,multicore fiber,laser phase noise,outage probability
更新于2025-09-12 10:27:22
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High-Power Large-Energy Raman Soliton Generations Within a Mode-Locked Yb-Doped Fiber Laser Based on High-Damage-Threshold CVD-MoS2 as Modulator
摘要： In our work, based on a high-damage-threshold MoS2 saturable absorber (SA), high-power intra-cavity Raman solitons within a passively mode-locked Yb-doped fiber laser were demonstrated successfully for the first time. The damage threshold of the MoS2 SA was as high as ~0.48 J/cm2. By adjusting the polarization states, stable single- or dual-pulse Raman soliton operations were obtained. The maximum average output power for single-pulse and dual-pulse Raman soliton operations was 80.11 and 89.33 mW, respectively. Our experiment results show significant enhancement in comparison with previous works, which provides fundamental guidance for future designs of high-power, large-energy, intra-cavity Raman soliton generations based on two-dimensional materials as SAs.
关键词： mode-locked Raman fiber laser,high-damage 2D MoS2 materials,ultra-fast optical modulation
更新于2025-09-12 10:27:22