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Self-wavelength-sweeping in a bi-directional thulium-doped fiber ring laser
摘要： We report for the first time the self-wavelength-sweeping phenomenon of a bi-directional thulium-doped fiber ring laser. The laser wavelength can spontaneously sweep in both lasing directions at a rate up to 0.2 nm s?1 over 15 nm sweeping range in the 1.95 μm wavelength region. The sweeping rate can be controlled by simply changing the state of polarization of the laser cavity. The laser can be tuned to generate a periodical wavelength-swept output with microsecond pulses in the time domain. The sweep rate can also be tuned to zero to give a static lasing wavelength.
关键词： self-wavelength-sweeping,thulium-doped fiber ring laser,polarization control,bi-directional
更新于2025-11-28 14:23:57
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Femtosecond Pulse Laser Near-Field Ablation of Ag Nanorods
摘要： Ag nanorods (Ag NRs) with a mean aspect ratio of 3.9 were prepared through a wet-chemical method, and the absorption spectra for various aspect ratios were obtained. The morphology transformation of Ag NRs irradiated with a femtosecond pulse laser was investigated through transmission electron microscopy (TEM). The near-field ablation was dependent on the laser polarization and wavelength. Laser-induced high electric field intensity was observed at the ends, middle, and junctions of the Ag NRs under various ablation conditions. Through simulation, the evolution mechanism was analyzed in detail. The effect of laser polarization angle on plasmonic junction welding was also investigated. By controlling the electronic field distribution, several nanostructures were obtained: bone-shaped NRs, T-shaped NRs, dimers, trimers, curved NRs, and nanodots. This study suggests a potentially useful approach for the reshaping, cutting, and welding of nanostructures.
关键词： femtosecond pulse laser,polarization,Ag nanorods,near-field ablation
更新于2025-11-14 17:04:02
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High-power long-wave infrared laser based on polarization beam coupling technique
摘要： We demonstrated a high-power long-wave infrared laser based on a polarization beam coupling technique. An average output power at 8.3 μm of 7.0 W was achieved at a maximum available pump power of 107.6 W, corresponding to an optical-to-optical conversion of 6.5%. The coupling ef?ciency of the polarization coupling system was calculated to be approximately 97.2%. With idler single resonance operation, a good beam quality factor of ～1.8 combined with an output wavelength of 8.3 μm was obtained at the maximum output power.
关键词： optical parametric ampli?er,long-wave infrared laser,polarization coupling,optical parametric oscillator
更新于2025-09-23 15:21:01
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Influence of the polarization of the laser beam in femtosecond laser-induced breakdown spectroscopy
摘要： Laser-induced breakdown spectroscopy (LIBS) is an important technique which is widely used to analyze element composition. In order to improve the sensitivity of LIBS, researchers have been dedicated to enhance the spectral intensity of LIBS by proposing a number of methods. In addition, we find that laser polarization has great influence on the emission intensity of femtosecond LIBS. By comparing the emission intensity of femtosecond LIBS in the circular and linear polarizations, the spectral intensity in the case of circular polarization is stronger than that in the case of linear polarization. Moreover, this phenomenon is more obvious as laser energy increases. The polarization plays an important role in LIBS signal intensity. Based on the observation, the enhanced mechanism of the laser polarization on the spectral intensity is discussed in this paper, which will be helpful to spectral analysis and component analysis.
关键词： femtosecond laser,LIBS,spectral enhancement,laser polarization
更新于2025-09-23 15:19:57
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Spectral responsivity calibration of a polarization remote sensor based on a supercontinuum laser and monochromator
摘要： Relative spectral responsivity is a basic parameter for detecting and evaluating the in-band response non-consistency of the channel polarization remote sensor (CPRS) in laboratory calibration. In this paper, a spectrally resolved calibration facility was assembled for the calibration of relative spectral responsivity by using novel supercontinuum laser and monochromator (SLM). Taking three polarization channels of 490 nm, 670 nm and 910 nm as examples, the relative spectral responsivity of the CPRS was obtained from two calibration sources, respectively – the SLM and the monochromatic light from SLM steered into integrating sphere. Before measuring the relative spectral responsivity of the CPRS, the degree of linear polarization (DOLP) and the polarization orientation angle of two calibration sources were acquired by the spectral polarization analyser (SPOLA). The test result indicates that the output light of the latter calibration source has less the DOLP and smaller range of variation in the polarization orientation angle. In the experiment of measuring the relative spectral responsivity, while using monochromator as calibration source, the in-band response non-consistency of the three channels were 0.91%, 4.25% and 1.06%, respectively. Correspondingly, while using monochromatic light steered into integrating sphere, there were 0.15%, 0.47% and 0.57%, respectively. It can be concluded that SLM equipped integrating sphere sharply decreased the impact from the polarization characteristic of the source and could be e?ectively applied in the relative spectral responsivity calibration of CPRS.
关键词： spectral responsivity,integrating sphere,monochromator,supercontinuum laser,polarization remote sensor
更新于2025-09-19 17:13:59
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Evolving Crystal Morphology of Potassium Chloride Controlled by Optical Trapping
摘要： Dynamic morphology evolution of potassium chloride (KCl) crystal was demonstrated by surface optical trapping with a focused continuous-wave near-infrared laser. Optical trapping at an air/solution interface triggered the crystallization, and then the dynamic change in crystal morphology was observed in real time. We observed three different crystal morphologies of needle, rectangle, and cubic at the early stage of crystallization. As the laser power increases, the probability of generation of a cubic crystal increases, especially upon the irradiation with linear polarization. We also found laser-polarization-dependent morphology evolution by the continuous irradiation to the generated crystals. Upon linearly-polarized laser irradiation, the stepwise morphology evolutions from needle, rectangle, and eventually to cubic, which is an equilibrium shape of KCl crystal. While, circularly-polarized laser irradiation only induced morphology evolution from needle to rectangle, without morphology change into cubic, because the rectangle crystal was dissolved while crystal rotating. It was made possible to observe such a unique morphological evolution due to the spatiotemporal controllability of our crystallization method. The dynamics and mechanism of these intriguing phenomena are discussed from the perspective of a dense cluster domain formed by optical trapping before nucleation.
关键词： laser polarization,potassium chloride,crystal morphology,optical trapping,surface crystallization
更新于2025-09-19 17:13:59
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Optical Property of Polarization-Maintaining Fiber Taper for Tunable Multi-Wavelength Fiber Laser Generation
摘要： We investigate optical property of polarization-maintaining ?ber taper (PMFT) for tunable multi-wavelength laser generation in a ?ber ring cavity. A panda-type polarization ?ber is fused and tapered into a ?ber taper with a diameter of about 2.5 μm. Optical and thermal properties of the PMFT are investigated theoretically and experimentally. As combined with a polarization dependent isolator, tunable multi-wavelength ?ber laser operation is achieved by controlling of polarization-dependent loss in the ?ber ring cavity. The laser wavelength number can be switched from 1 to 4. The 3 dB bandwidths of laser spectra are less than 0.05 nm for all wavelength numbers, with a maximum OSNR of about 54 dB. For single-wavelength laser operation near 1561.66 nm, the measured wavelength and power ?uctuations are < 0.02 nm and 0.4 dB, respectively.
关键词： polarization-dependent loss.,tunable,multi-wavelength,?ber laser,Polarization maintaining ?ber taper
更新于2025-09-16 10:30:52
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All polarization-maintaining passively mode-locked Yb-doped fiber laser: pulse compression using an anomalous polarization-maintaining photonic crystal fiber
摘要： We report the generation of short pulses at 1 μm using an all-polarization-maintaining (PM) fiber configuration. The pulses are provided by an all normal-dispersion Fabry-Perot Yb-doped cavity and are compressed with an anomalous polarization-maintaining photonic crystal fiber (PM PCF). Opposed to standard configurations; here the filtering action is solely performed by the finite bandwidth of the gain medium. The laser generates 8 ps width sech2 profile pulses at 1046.8 nm with a -10 dB bandwidth of 5.9 nm. After compression using the PM PCF, pulses with an FWHM of 3 ps were obtained, limited by the actual value of the available anomalous dispersion. We also report the changes in the output light pulses when both the net-normal dispersion of the cavity and the medium gain length were varied. We found that the lack of a specific filter within the cavity does not deteriorate the performance as compared with previous works.
关键词： dissipative solitons,photonic crystal fibers,fiber laser,polarization maintaining
更新于2025-09-16 10:30:52
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Effect of laser polarization on the electron dynamics and photon emission in near-critical-density plasmas
摘要： When the laser intensity approaches 1022 W=cm2, the recoil force from high-energy photons radiated by relativistic electrons becomes important and may be comparable with the ponderomotive force of the laser pulse. As a result, the electron dynamics is modified greatly. By using particle-in-cell simulations, we show that the polarization of laser pulse has significant influence on the electron behaviors and accompanying radiation in near-critical-density plasmas. Due to the RR force and the pinching effect of self-generated magnetic field, it turns out that much more electrons are trapped in the center of a circularly-polarized (CP) laser pulse than that of a linearly-polarized (LP) laser pulse. Meanwhile, the (cid:13)(cid:0)photon emission is characterized by a two-peak structure in the LP case, while it is dominated in the forward direction in the CP case where electrons keep moving forward along the laser propagating direction. These may serve as a potential signature for radiation trapping effect in forthcoming experiments to be carried out on petawatt (PW) laser facilities.
关键词： laser polarization,photon emission,electron dynamics,radiation reaction force,near-critical-density plasmas,particle-in-cell simulations
更新于2025-09-12 10:27:22