查看更多>>摘要：Diffraction intensities of the 3D ptychographic iterative engine[3PIE]were written as a set of linear equations of the self-correlations of Fourier components of all sample slices,and an effective computing method was developed to solve these linear equations for the transmission functions of all sample slices analytically.With both theoretical analysis and numeri-cal simulations,this study revealed the underlying physics and mathematics of 3PIE and demonstrated for the first time,to our knowledge,that 3PIE can generate mathematically unique reconstruction even with noisy data.
查看更多>>摘要：A multi-functional full-space metasurface based on frequency and polarization multiplexing is proposed.The metasurface unit consists of metallic patterns printed on the two faces of a single-layered dielectric substrate.The unit cell can control electromagnetic wavefronts to achieve a broadband transmission with amplitudes greater than 0.4 from 4.4 t0 10.4 GHz.Meanwhile,at 11.7 GHz and 15.4 GHz,four high-efficiency reflection channels with a reflection amplitude greater than 0.8 are also realized.When illuminated by linearly polarized waves,five different functions can be realized at five different frequen-cies,which are demonstrated by theoretical calculations,full-wave simulations,and experimental measurements.
查看更多>>摘要：Recently,Mach-Zehnder modulators based on thin-film lithium niobate have attracted broad interest for their potential for high modulation bandwidth,low insertion loss,high extinction ratio,and high modulation efficiency.The periodic capac-itively loaded traveling-wave electrode is optimally adopted for ultimate high-performances in this type of modulator.However,such an electrode structure on a silicon substrate still suffers from the velocity mismatch and substrate leakage loss for microwave signals.Here,we introduce a thin-film lithium niobate modulator structure using this periodic capac-itively loaded electrode on a silicon substrate.Backside holes in the silicon substrate are prepared to solve robustly the above difficulties.The fabricated device exhibits an insertion loss of 0.9 dB,a halfwave-voltage-length product of 2.18 V·cm,and an ultra-wide bandwidth well exceeding 67 GHz for a 10-mm-long device.Data transmissions with rates up to 112 Gb/s are demonstrated.The proposed structure and fabrication strategy are compatible for other types of monolithic and heterogeneous integrated thin-film lithium niobate modulators on a silicon substrate.
查看更多>>摘要：For joint modulation format identification[MFI]and optical signal-to-noise ratio[OSNR]monitoring,a simple and intelligent optical communication performance monitoring method is proposed,and the feasibility is demonstrated by digital coherent optical communication experiments.The experiment results show that for all modulation formats,including 28 GBaud polarization division multiplexing[PDM]QPSK/8-QAM/16-QAM/64-QAM,100％MFI accuracies are achieved even at OSNR values lower than the corresponding theoretical 20％forward error correction limit,as well as the high accuracies for OSNR monitoring.Furthermore,the proposed scheme has a reasonable monitoring level when chromatic dispersion and fiber nonlinear effects are varied.
查看更多>>摘要：A method of preparing panda-shaped photonic crystal fibers[PCFs]based on secondary drawing technology is proposed in this paper.The secondary drawing can not only reduce fiber diameter but also reduce core size by adding a glass sleeve.Silver-filled and non-silver-filled panda PCFs are prepared.The two ends of silver-filled panda PCF are connected with a broadband light source and a spectrometer,respectively,and the surface plasmon resonance phenomenon is detected.The secondary drawing technology provides a meaningful reference for the preparation of PCF in the future,and the prepared silver-filled panda PCF can be prepared into an optical fiber filter.
查看更多>>摘要：We propose a trellis-compressed maximum likelihood sequence estimation[TC-MLSE]-assisted sliding-block decision feed-back equalizer[DFE]to suppress the error propagation resulting from the DFE in high-speed systems.We use an out-of-range detector to detect the end of burst errors from the DFE and activate the optional TC-MLSE to correct burst errors.We conduct experiments to transmit a 201-Gbit/s PAM-8 signal.The results show that the proposed method achieves a bit error rate of 3.65 x 10-3,which is close to that of MLSE.The optional MLSE is only activated when needed and processes 11.4％of the total symbols.Moreover,the proposed method compresses the maximum length of burst errors from 19 t0 5.
查看更多>>摘要：The alkali-atom density measurement method based on light absorption is highly suitable for a spin-exchange relaxation-free[SERF]atomic magnetometer because of its high-precision measurement and complete nonmagnetic interference.In this study,the optical rotation angle detection system based on polarization balance detection is utilized to realize the alkali-atom density real-time measurement without affecting magnetic field measurement.We discovered that there exists an optimal frequency detuning of the probe light,which offers the highest sensitivity in alkali-atom density measurement and the lowest susceptibility to temperature fluctuations in terms of the scale factor.In contrast to conventional light absorption measurements based on pump light,this method demonstrated a threefold improvement in alkali-atom density measurement sensitivity while remaining immune to ambient magnetic fields and incident light intensity fluctuations.Furthermore,we utilized this method to achieve closed-loop temperature control with an accuracy of 0.04℃.
查看更多>>摘要：Effective methods are urgently required to optimize Raman spectroscopy technology to ameliorate its low detection sen-sitivity.Here,we superposed two near-concentric cavities to develop a dual near-concentric cavities group[DNCCG]to assess its effect on gas Raman signal intensity,signal-to-noise ratio[SNR],and limit of detection[LOD].The results showed that DNCCG generally had higher C02 Raman signal intensity than the sum of two near-concentric cavities.Meanwhile,the noise intensity of DNCCG was not enhanced by the superposition of near-concentric cavities.Accordingly,DNCCG increased the SNR.The LOD for C02 was 24.6 parts per million.DNCCG could be an effective method to improve the detection capability of trace gases and broaden the dynamic detection range,which might aid the future development of innovative technology for multicomponent gas detection.
查看更多>>摘要：The optical frequency comb based on microresonators[microcombs]is an integrated coherent light source and has the potential to promise a high-precision frequency standard;self-reference and a long-term stable microcomb are the keys to this realization.Here,we demonstrated a 0.7-octave spectrum Kerr comb via dispersion engineering in a thin-film lithium niobate microresonator,and the single-soliton state can be accessed passively with long-term stability over 3 h.With such a robust broadband coherent comb source using thin-film lithium niobate,a fully stabilized microcomb can be expected for massive practical applications.
查看更多>>摘要：An unstable resonator with seven large aperture ceramic disks and intra-cavity adaptive correction is presented.The composite ceramic disks with absorption rings were adopted to suppress amplified spontaneous emission.An intra-cavity aberration non-conjugate correction based on round-trip wavefront and relaxation iteration was applied in the resonator.After tilt and defocus were corrected in turn,an average output power of 4.5 kW was obtained.The corresponding beam quality factor β was 19.5.After tilt,defocus,and high order aberrations were corrected,the average output power was increased to 5.4 kW,and the beam quality factor β was improved to 6.8.
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