查看更多>>摘要：A whispering gallery mode resonator[WGMR]filter can narrow laser linewidth while significantly changing the output power characteristics of fiber laser system.It is found that traditional laser output power model is invalid.We report a correction model of a narrow linewidth fiber laser filtered with a WGMR to analyze its power.We believe that the loss of the laser system and the threshold gain increase caused by the WGMR filter lead to the predominate amplified sponta-neous emission during the original laser period.According to that,we assume the correction coefficient is an exponential decay related to the Er-doped fiber length in the large loss situation,and we verify it experimentally.As a result,the correction model is valid for WGMR-filtered fiber laser.
查看更多>>摘要：A high-power CW Yb∶YAG slab laser amplifier with no adaptive optics correction has been experimentally established.At room temperature,the amplifier emits a power of 22 kW with an average beam quality[β]of less than 3 in 0.5 min.To our knowledge,this is the brightest slab laser without closed-loop adaptive optics demonstrated to date.In addition,an extracted power of 17 kW with an optical extraction efficiency of 33％,corresponding to a residual optical path difference of less than 0.5 pm,is achieved with the single Yb∶YAG slab gain module.The slab gain module has the potential to be scalable to higher powers while maintaining good beam quality.This makes a high-power solid-state laser system simpler and more robust.
查看更多>>摘要：A passively switchable erbium-doped fiber laser based on alcohol as the saturable absorber[SA]has been demonstrated.The SA is prepared by filling the gap between two optical patch cords with alcohol to form a sandwich structure.The modulation depth of the alcohol-SA is measured to be 6.4％.By appropriately adjusting the pump power and the polarization state in the cavity,three kinds of mode-locked pulse patterns can be achieved and switched,including bright pulse,bright/dark soliton pair,and dark pulse.These different soliton emissions all operate at the fundamental frequency state,with a repetition rate of 20.05 MHz and a central wavelength of～1563 nm.To the best of our knowledge,this is the first dem-onstration of a switchable soliton fiber laser using alcohol as the SA.The experimental results further indicate that organic liquid-like alcohol has great potential for constructing ultrafast lasers.
查看更多>>摘要：We report a high-stability ultrafast ultraviolet[UV]laser source at 352 nm by exploring an all-fiber,all-polarization-maintaining[all-PM],Yb-doped femtosecond fiber laser at 1060 nm.The output power,pulse width,and optical spectrum width of the fiber laser are 6 W,244 fs,and 17.5 nm,respectively.The UV ultrashort pulses at a repetition rate of 28.9 MHz are generated by leveraging single-pass second-harmonic generation in a 1.3-mm-long BiB306[BIBO]and sum frequency gen-eration in a 5.1-mm-long BIBO.The maximum UV output power is 596 mW.The root mean square error of the output power of UV pulses is 0.54％.This laser,with promising stability,is expected to be a nice source for frontier applications in the UV wavelength window.
查看更多>>摘要：We demonstrate the generation of a unique regime of multiple solitons in a Tm-doped ultrafast fiber laser at～1938.72 nm.The temporal pulse-to-pulse separation among the multiple solitons,10 in a single-pulse bunch,increases from 0.89 ns to 1.85 ns per round trip.In addition,with the increasing pump power,the number of bunched solitons increases from 3 up to 24 linearly,while the average time separation in the soliton bunch varies irregularly between～0.80 and～1.52 ns.These results contribute to a more profound comprehension of nonlinear pulse dynamics in ultrafast fiber lasers.
查看更多>>摘要：Topological nodal-line semimetals attract growing research attention in the photonic and optoelectronic fields due to their unique topological energy-level bands and fascinating nonlinear optical responses.Here,to the best of our knowledge,we first report the saturable absorption property of topological nodal-line semimetal HfGeTe and the related pulse modulation in passively Q-switched visible lasers.Few-layer HfGeTe demonstrates outstanding saturable absorption properties in the visible-light band,yielding the saturation intensities of 7.88,12.66,and 6.64 μJ/cm2 at 515,640,and 720 nm,respectively.Based on an as-prepared few-layer HfGeTe optical switch and a Pr:LiYF4 gain medium,Q-switched visible lasers are also successfully achieved at 522,640,and 720 nm.The minimum pulse widths of the green,red,and deep-red pulsed lasers are 150,125.5,and 420 ns,respectively.Especially for the green and red pulsed laser,the obtained pulse width is smaller than those of the low-dimensional layered materials.Our work sheds light on the application potential of topological nodal-line semimetals in the generation of visible pulsed lasers.
查看更多>>摘要：Wide-field linear structured illumination microscopy[LSIM]extends resolution beyond the diffraction limit by moving unre-solvable high-frequency information into the passband of the microscopy in the form of moiré fringes.However,due to the diffraction limit,the spatial frequency of the structured illumination pattern cannot be larger than the microscopy cutoff frequency,which results in a twofold resolution improvement over wide-field microscopes.This Letter presents a novel approach in point-scanning LSIM,aimed at achieving higher-resolution improvement by combining stimulated emission depletion[STED]with point-scanning structured illumination microscopy[psSIM][STED-psSIM].The according structured illumination pattern whose frequency exceeds the microscopy cutoff frequency is produced by scanning the focus of the sinusoidally modulated excitation beam of STED microscopy.The experimental results showed a 1.58-fold resolution improvement over conventional STED microscopy with the same depletion laser power.
查看更多>>摘要：We present a novel noncontact ultrasound[US]and photoacoustic imaging[PAI]system,overcoming the limitations of traditional coupling media.Using a long coherent length laser,we employ a homodyne free-space Mach-Zehnder setup with zero-crossing triggering,achieving a noise equivalent pressure of 703 Pa at 5 MHz and a-6 dB bandwidth of 1 to 8.54 MHz.We address the phase uncertainty inherent in the homodyne method.Scanning the noncontact US probe enables photoacoustic computed tomography[PACT].Phantom studies demonstrate imaging performance and system stability,underscoring the potential of our system for noncontact US sensing and PAl.
查看更多>>摘要：We investigated the Talbot effect in an anti-parity-time[PT]symmetric synthetic photonic lattice composed of two coupled fiber loops.We calculated the band structures and found that with an increase in the gain-loss parameter,the band tran-sitions from a real spectrum to a complex spectrum.We study the influence of phase in the Hermitian operator on the Talbot effect,and the Talbot effect disappears when the period of the input field is N＞8.Further study shows that the variation of Talbot distance can also be modulated by non-Hermitian coefficients of gain and loss.This work may find significant appli-cations in pulse repetition-rate multiplication,temporal invisibility,and tunable intensity amplifiers.
查看更多>>摘要：The design of nonlinear photonic Vogel's spiral based on quasi-crystal theory was demonstrated.Two main parameters of Vogel's spiral were arranged to obtain multi-reciprocal circles.Typical structure was fabricated by the near-infrared femto-second laser poling technique,forming a nonlinear photonic structure,and multiple ring-like nonlinear Raman-Nath second-harmonic generation processes were realized and analyzed in detail.The structure for the cascaded third-harmonic generation process was predicted.The results could help deepen the understanding of Vogel's spiral and quasi-crystal and pave the way for the combination of quasi-crystal theory with more aperiodic structures.
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