查看更多>>摘要：We experimentally demonstrate tunable dual-comb soliton rains in a polarization multiplexing fiber laser based on a single-walled carbon nanotube.The repetition frequency difference of dual-comb pulses is about 39 Hz,with a maximum extinction ratio of 29 dB.With suitable polarization states,one of the dual-comb pulses switches into soliton rain sequence with chirped isolating soliton trains.The signal-to-noise ratio reaches 61 dB,which is 11 dB higher than that of the normal dual-comb pulses.The intervals between chirped isolating solitons are distributed progressively,and the number of iso-lating solitons can be flexibly tuned from 2 to 11 by adjusting polarization state or pump power.Our work will provide support for further understanding of interaction dynamics of solitons and give a new route to the application of precision measurement.
查看更多>>摘要：The coexistence of a noise-like pulse[NLP]and a dark pulse was experimentally demonstrated in a net-anomalous dispersion Er/Yb co-doped fiber[EYDF]laser,for the first time,to our knowledge.The cavity was mode-locked by nonlinear polarization rotation[NPR]technique.Meanwhile,a Sagnac loop with a section of polarization-maintaining fiber[PMF]was used as a comb filter to enable multiwavelength pulse operation.When the PMF length was 0.3 m,an asymmetric two-peak spectrum with central wavelengths of 1565.3 and 1594.2 nm was obtained by adjusting polarization controllers[PCs].It is a composite state of NLP and dark pulse due to the cross-phase modulation between the two different wavelength compo-nents along orthogonal polarization axes.The two pulses are synchronized with a repetition rate of 7.53 MHz.By adjusting the PC in the Sagnac loop,the spectral ranges of NLPs and dark pulses can be tuned from 1560 to 1577.8 nm and from 1581.8 to 1605.4 nm,respectively.In addition,the pulse characteristics were investigated by incorporating the PMF with different lengths,where the coexistence patterns can be generated when the PMF lengths were 0.2 and 0.3 m.A longer PMF can lead to a narrowband comb filtering,which causes a larger loss and is not favorable for stable operation of the coexistence regime.This fiber laser demonstrates an interesting operation regime and has significant potential for numerous practical applications.
查看更多>>摘要：In this research,we report the latest progress in the suppression of nanosecond prepulses from regenerative amplifier and multipass amplifiers in the SULF-1PW laser.The prepulse generated from the Pockels cell[PC]in a regenerative amplifier is delay-shifted by enlarging the distance between the PC and the nearby cavity mirror,and then removed by the extra pulse pickers outside the regenerative amplifier.The prepulses arising from multipass amplifiers are also further suppressed by adopting a novel amplifier configuration and properly rotating the Ti:sapphire crystals.After the optimizations,the temporal contrast on a nanosecond time scale is promoted to be better than a contrast level of 10-9.This research can provide beneficial guidance for the suppression of nanosecond prepulses in the high-peak-power femtosecond laser systems.
查看更多>>摘要：In this paper,a spectral beam combining[SBC]structure of multi-single emitters laser diode based on a polarization full feedback[PFF]external cavity is proposed and demonstrated.The maximum combining efficiency is 75.6％,which leads to an output power of 38.48 W,a degree of polarization[DOP]of 99.42％,and electro-optical conversion efficiency of 35.63％under continuous wave operation at a current of 8 A.Compared to the conventional SBC,the output power,the combining effi-ciency,the electro-optical conversion efficiency,and the DOP of the PFF-SBC structure present improvements of 5.73 W,11.26 percentage points,5.3 percentage points,and 7.26 percentage points,respectively.The results show that this SBC method can achieve a high efficiency and linearly polarized laser output of SBC,thereby making the subsequent polarization beam-combining efficiency approach the limit.
查看更多>>摘要：To the best of our knowledge,this is the first time that a mid-infrared Er3+:CaF2-SrF2 laser has achieved continuous-wave mode-locked operation by a semiconductor saturable absorber mirror.The laser emits a maximum output power of 93 mW at 2.73 μm with a repetition rate of approximately 69 MHz and demonstrates a high signal-to-noise ratio of around 71 dB.In addition,a MgF2 birefringent plate was utilized to enable wavelength tuning of the Er3+:CaF2-SrF2 laser,resulting in operation at approximately 2.73 μm,2.75 μm,2.79 μm,and 2.81 μm.These results demonstrate that Er3+:CaF2-SrF2 is a promising alternative for the generation of efficient diode-pumped mode-locked lasers around 2.8 μm.
查看更多>>摘要：Multi-focus parallel scanning can effectively increase laser fabrication throughput.However,the conventional approach of using a spatial light modulator[SLM]to generate multi-foci and scan this fixed number of foci with galvanometer scanners can only achieve a periodic scanning trajectory due to the low switching speed of the SLM.Here we demonstrate a multi-focus non-periodic scanning method for femtosecond lasers by using,instead,a fast-switching digital micromirror device[DMD]to generate a dynamic number of foci.The number of effective foci is quickly switched by introducing aberration to the undesired focus.In this way,the intensity allocated to each focus will not be affected by the number of foci,and a uniformity of 98％with different numbers of foci is achieved without adjusting the total laser energy.Finally,we validate the effectiveness of this scanning method by demonstrating corneal flap fabrication of porcine cornea in vitro.
查看更多>>摘要：We report the generation of quasi-cw vacuum ultraviolet[VUV]light at 160 nm with a repetition rate of 82 MHz by two second-harmonic generations and one sum frequency mixing.The VUV laser light is produced as a fifth-harmonic gener-ation of a mode-locked ps Ti:sapphire laser system by successive stages with nonlinear crystals of LBO and KBBF.A stable generation of laser light at 200 nm for more than 6 h is the most important step for obtaining the generation of light at a wavelength of 160 nm.
查看更多>>摘要：A novel backside-illuminated double-cliff-layer uni-traveling-carrier[DCL-UTC]photodiode with both high responsivity and ultra-broad bandwidth is designed and demonstrated.A thick absorption layer is adopted for high responsivity,and a depletion region with double cliff layers is proposed to alleviate the space charge effect and maintain overshoot electron velocity under large photocurrents.In addition,inductive coplanar waveguide electrodes are employed to enhance the frequency response performance.The 6-pm-diameter photodiode exhibits a high responsivity of 0.51 A/W and a large 3-dB bandwidth of 102 GHz.A high RF output power of 2.7 dBm is recorded at 100 GHz.
查看更多>>摘要：We report the generation of polarization-entangled photon pairs in the 1550 nm band by pumping an uneven nonlinear interferometer loop with two orthogonally polarized counterpropagating pump pulses.The uneven nonlinear interferom-eter,providing a more ideal interference pattern due to the elimination of secondary maxima,consists of four pieces of dispersion-shifted fibers sandwiched with three pieces of standard single-mode fibers,and the lengths of the nonlinear fibers follow the binomial distribution.The mode number of the photon pairs deduced from the measured joint spectrum is～1.03.The collection efficiency of the photon pairs is found to be～94％[after background noise correction].The directly measured visibility of two-photon interference of the polarization-entangled photon pairs is～92％,while no interference is observed in the direct detection of either the signal or idler photons.
查看更多>>摘要：Smart beams play a vital role in modern intelligent vehicles and have recently attracted significant attention.A spatial light modulator with high optical efficiency,low cost,and compact size is crucial for designing smart beams.Here,we mix cholesteric liquid crystals with dichroic black dye and a monomer.After UV polymerization,the sample exhibits a low driving voltage of 26 V,a high transmittance of over 70％,and an On-off ratio over 280,thanks to the joint contribution of both the absorption and the scattering effect.A smart beam device is demonstrated by electrically addressing the dye-doped and polymer-stabilized cholesteric liquid crystal with pixelated electrodes.Light patterns with arbitrary designs are projected dynamically.The switching time reaches several tens of milliseconds.This strategy brings new designs to intelligent vehicles and may also inspire applications in public information displays,advertising,and even AR/VR displays.
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