查看更多>>摘要：High-power ultrafast laser amplification based on a non-polarization maintaining fiber chirped pulse amplifier is demon-strated.The active polarization control technology based on the root-mean-square propagation[RMS-prop]algorithm is employed to guarantee a linearly polarized output from the system.A maximum output power of 402.3 W at a repetition rate of 80 MHz is realized with a polarization extinction ratio[PER]of＞11.4 dB.In addition,the reliable operation of the system is verified by examining the stability and noise properties of the amplified laser.The M2 factor of the laser beam at the highest output power is measured to be less than 1.15,indicating a diffraction-limited beam quality.Finally,the amplified laser pulse is temporally compressed t0 755 fs with a highest average power of 273.8 W.This is the first time,to the best of our knowl-edge,that the active polarization control technology was introduced into the high-power ultrafast fiber amplifier.
查看更多>>摘要：A low-numerical-aperture[NA]concept enables large-mode-area fiber with better single-mode operation ability,which is beneficial for transverse mode instability and nonlinear effects suppression.In this contribution,we reported a high-power fiber amplifier based on a piece of self-developed large-mode-area low-NA fiber with a core NA of 0.049 and a core/inner cladding diameter of 25/400 μm.The influence of the pump wavelength and fiber length on the power scaling potential of the fiber amplifier is systematically investigated.As a result,an output of 4.80 kW and a beam quality factor of～1.33 were finally obtained,which is the highest output power ever reported in a fiber amplifier exploiting the low-NA fiber.The results reveal that low-NA fibers have superiority in power scaling and beam quality maintenance at high power levels.
查看更多>>摘要：We demonstrate a stable narrow linewidth single-frequency erbium-doped fiber laser[EDFL]operating at 1.6 μm.A Fabry-Perot fiber Bragg grating and two cascaded subrings are incorporated in the main ring cavity to achieve single-frequency operation.The experimentally measured optical signal-to-noise ratio is greater than 73 dB.Furthermore,the linewidth of the EDFL is measured to be about 480 Hz by the self-built short-delayed self-heterodyne interferometry device.The laser shows superior stability,with no mode-hopping during the 60-min observation period.The proposed EDFL provides a new experimental idea for realizing a single-frequency fiber laser in the L-band.
查看更多>>摘要：To ensure the frequency accuracy of a heterodyne laser source in the ambient temperature range of-20℃ t0 40℃,a dual-longitudinal-mode thermally stabilized He-Ne laser based on non-equilibrium power locking was designed.The ambient adaptive preheating temperature setting scheme ensured the laser could operate normally in the range of-20℃ to 40℃.The non-equilibrium power-locked frequency stabilization scheme compensated for the frequency drift caused by different stabilization temperatures.The experimental results indicated that the frequency accuracy of the laser designed in this study could reach 5.2 × 10-9 in the range of-20℃ to 40℃.
查看更多>>摘要：Fluorescence lifetime imaging can reveal the high-resolution structure of various biophysical and chemical parameters in a microenvironment quantitatively.However,the depth of imaging is generally limited to hundreds of micrometers due to aberration and light scattering in biological tissues.This paper introduces an iterative multi-photon adaptive compensation technique[IMPACT]into a two-photon fluorescence lifetime microscopy system to successfully overcome aberrations and multiple scattering problems in deep tissues.It shows that 400 correction modes can be achieved within 5 min,which was mainly limited by the frame rate of a spatial light modulator.This system was used for high-resolution imaging of mice brain tissue and live zebrafish,further verifying its superior performance in imaging quality and photon accumulation speed.
查看更多>>摘要：Fast and stable phase control is essential for many applications in optics.Here,we propose an all-fiber all-optical phase modulation scheme based on a Fabry-Perot interferometer[FPI]and an Er/Yb co-doped fiber[EYDF].By using the EYDF as an F-P cavity via rational design,a phase shift with a modulation sensitivity of 0.0312π/mW is introduced to the modulator.The phase shifts in the EYDF consist of a thermal phase shift and a nonlinear phase shift with a ratio of 19:1,and the cor-responding temporal responses of the modulation are 204 ms and 2.5 ms,respectively.In addition,the compact FPI is encapsulated to provide excellent stability for the modulator.
查看更多>>摘要：Three-dimensional[3D]nonlinear photonic crystals have received intensive interest as an ideal platform to study nonlinear wave interactions and explore their applications.Periodic fork-shaped gratings are extremely important in this context because they are capable of generating second-harmonic vortex beams from a fundamental Gaussian wave,which has versatile applications in optical trapping and materials engineering.However,previous studies mainly focused on the nor-mal incidence of the fundamental Gaussian beam,resulting in symmetric emissions of the second-harmonic vortices.Here we present an experimental study on second-harmonic vortex generation in periodic fork-shaped gratings at oblique inci-dence,in comparison with the case of normal incidence.More quasi-phase-matching resonant wavelengths have been observed at oblique incidence,and the second-harmonic emissions become asymmetric against the incident beam.These results agree well with theoretic explanations.The oblique incidence of the fundamental wave is also used for the generation of second-harmonic Bessel beams with uniform azimuthal intensity distributions.Our study is important for a deeper understanding of nonlinear interactions in a 3D periodic medium.It also paves the way toward achieving high-quality structured beams at new frequencies,which is important for manipulation of the orbital angular momentum of light.
查看更多>>摘要：High-precision angle measurement of pulsars is critical for realizing pulsar navigation.Compared to visible light and radio waves,the wavelength of X-rays is incredibly short,which provides the possibility of achieving better spatial resolution.However,due to the lack of applicable X-ray apparatus,extracting the angle information of pulsars through conventional X-ray methods is challenging.Here,we propose an approach of pulsar angle measurement based on spatially modulated X-ray intensity correlation[SMXIC],in which the angle information is obtained by measuring the spatial intensity correlation between two radiation fields.The theoretical model for this method has been established,and a proof-of-concept experi-ment was carried out.The SMXIC measurement of observing angles has been demonstrated,and the experimental results are consistent with the theoretical values.The potential of this method in future applications is discussed,and theoretically,the angular measurement at the level of micro-arcsecond can be expected.The sphere of pulsar navigation may benefit from our fresh insights.
查看更多>>摘要：Active metasurfaces have recently attracted more attention since they can make the light manipulation be versatile and real-time.Metasurfaces-based holography possesses the advantages of high spatial resolution and enormous information capacity for applications in optical displays and encryption.In this work,a tunable polarization multiplexing holographic metasurface controlled by an external magnetic field is proposed.The elaborately designed nanoantennas are arranged on the magneto-optical intermediate layer,which is placed on the metallic reflecting layer.Since the non-diagonal elements of the dielectric tensor of the magneto-optical material become non-zero values once the external magnetic field is applied,the differential absorption for the left and right circularly polarized light can be generated.Meanwhile,the amplitude and phase can be flexibly modulated by changing the sizes of the nanoantennas.Based on this,the dynamic multichannel holo-graphic display of metasurface in the linear and circular polarization channels is realized via magnetic control,and it can provide enhanced security for optical information storage.This work paves the way for the realization of magnetically controllable phase modulation,which is promising in dynamic wavefront control and optical information encryption.
查看更多>>摘要：This paper experimentally demonstrates a distributed photonics-based W-band integrated sensing and communication[ISAC]system,in which radar sensing can aid the communication links in alignment and data rate estimation.As a proof-of-concept,the ISAC system locates the users,guides the alignment,and sets a communication link with the esti-mated highest data rate.A peak net data rate of 68.6 Gbit/s and a target sensing with a less-than-1-cm error and a sub-2-cm resolution have been tested over a 10-km fiber and a 1.15-m free space transmission in the photonics-based W-band ISAC system.The achievable net data rates of the users at different locations estimated by sensing are experimentally verified.
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