查看更多>>摘要：Studying Rydberg microwave frequency comb(MFC)spectroscopy helps increase the working bandwidth of the Rydberg receiver.This Letter demonstrates off-resonant Rydberg MFC spectroscopy in a meta-waveguide-coupled Rydberg atomic system.An off-resonant MFC field couples with the Rydberg atoms through a meta-waveguide.The system can receive the microwave field in the working band from 0.5 GHz to 13.5 GHz,and the MFC spectroscopy covers a span of 36 MHz at three different arbitrarily-chosen frequencies of 2 GHz,3 GHz,and 5.8 GHz.The MFC spectrum that covers a wide range of 125 MHz is also verified.This work is significant for tunable wide-band instant microwave signal detection in the Rydberg atomic system,which is useful in microwave frequency metrology,communication,and radar.
查看更多>>摘要：Accurate control of magnetic fields is crucial for cold-atom experiments,often necessitating custom-designed control systems due to limitations in commercially available power supplies.Here,we demonstrate precise and flexible control of a static magnetic field by employing a field-programmable gate array and a feedback loop.This setup enables us to maintain exceptionally stable current with a fractional stability of 1 ppm within 30 s.The error signal of the feedback loop exhibited a noise level of 10-5 A·Hz-1/2 for control bandwidths below 10 kHz.Utilizing this precise magnetic field control system,we investigate the second-order Zeeman shift in the context of cold-atom coherent population-trapping(CPT)clocks.Our analysis reveals the second-order Zeeman coefficient to be 574.21 Hz/G2,with an uncertainty of 1.36 Hz/G2.Consequently,the magnetic field stabilization system we developed allows us to achieve a second-order Zeeman shift below 10-14,surpassing the long-term stability of current cold-atom CPT clocks.
查看更多>>摘要：In this Letter,an autofocusing method in optical scanning holography(OSH)system is proposed.By introducing Lissajous scanning into multiple signal classification(MUSIC)method in time-reversal(TR)OSH,the axial locations of the targets can be retrieved with better resolution and the peak prominence increases from 0.21 to 0.34.The feasibility of this method is confirmed by simulation as well as experiment.
查看更多>>摘要：The hologram,which is formed by phases coupled through cascade devices for secret information sharing,still carries a cracking risk.We propose a liquid crystal planar doublet as the information carrier,and new holograms generated by the new coupled phases when the relative displacements of the different liquid crystal layers change.The designed geometrical phases are generated by an optimized iterative restoration algorithm,and each holographic image formed by these phases is readable.This scheme achieves an increase in the capacity of the stored secret information and provides more misdirection,which is expected to have potential value in optical steganography and storage.
查看更多>>摘要：We demonstrated an optical fiber frequency comb stabilized to an acetylene-filled photonic microcell.The short-term insta-bility of the comb at 1 s gate time was 1.66 × 10-12 for a 4.2-h measurement in a laboratory environment with air conditioning.This is the best short-term stability reported for a compact fiber comb stabilized to an acetylene-filled photonic microcell at telecom wavelengths.It is particularly significant in the development of compact fiber combs with target instability of 10-13.Such a device has the potential to serve as an alternative to GPS in areas lacking signal coverage,including remote locations,regions with adverse weather conditions,and military intelligence areas.
查看更多>>摘要：In this work,we proposed and experimentally demonstrated a novel probabilistic shaping(PS)64-ary quadrature amplitude modulation(QAM)orthogonal frequency division multiplexing(OFDM)with low-density parity-check(LDPC)-coded modulation in a W-band radio-over-fiber(RoF)system using envelope detection.The proposed PS scheme has the advantages of no com-plex multiplication and division operations and low hardware implementation complexity.In our experiments,the two-stage bit weight distribution matching-based PS-64QAM OFDM signals with a rate of 28.13 Gb/s transmission over 4 m wireless+45-km standard single-mode fiber transmission can be achieved.The system performance is investigated under one LDPC code rate(3/4)and two PS parameter values(k=3 and 9).The experimental results show that the receiver power sensitivity and the system fiber nonlinear effect tolerance can be significantly improved compared with uniformly distributed OFDM signals.
查看更多>>摘要：In this Letter,we innovatively present general analytical expressions for arbitrary n-step phase-shifting Fourier single-pixel imaging(FSI).We also design experiments capable of implementing arbitrary n-step phase-shifting FSI and compare the experimental results,including the image quality,for 3-to 6-step phase-shifting cases without loss of generality.These results suggest that,compared to the 4-step method,these FSI approaches with a larger number of steps exhibit enhanced robustness against noise while ensuring no increase in data-acquisition time.These approaches provide us with more strategies to perform FSI for different steps,which could offer guidance in balancing the tradeoff between the image quality and the number of steps encountered in the application of FSI.
查看更多>>摘要：In this study,an innovative technique is introduced to significantly enhance the sensitivity of electronic speckle pattern interferometry(ESPI)for the dynamic assessment of specular(mirrorlike)object deformations.By utilizing a common-path illumination strategy,wherein illumination and observation beams are precisely aligned,this method effectively doubles the optical path difference,leading to a twofold increase in measurement sensitivity.In addition,this method mitigates the effects of speckle noise on the measurement of minor deformations,expanding the applications of ESPI.Theoretical and experimental evaluations corroborate the efficacy of this approach.
查看更多>>摘要：The metabolic process of chiral drugs plays a significant role in clinics and in research on drugs.Here,we experimentally demonstrate by all-optical means that the chiral molecules can be quickly discriminated and monitored with the ultrahigh-order modes excited in a metal cladding optofluidic chip,achieving over 5 times sensitivity with a low-dosage sample.We show that the varying concentration of the chiral drugs can be monitored both in cell and animal experiments,presenting a significant difference between chiral enantiomers at the optimal function time and the effect of the reaction.To our knowl-edge,this approach provides a new way to achieve important chiral discrimination for the pharmacokinetics and the phar-macodynamics and may present opportunities in indicating the health status of humans.
查看更多>>摘要：The optical frequency comb has attracted considerable interest due to its diverse applications in optical atomic clocks,ultra-low-noise microwave generation,dual-comb spectroscopy,and optical communications.The merits of large frequency spacing,high integration,and low power consumption have shown that microresonator-based Kerr optical frequency combs will become mainstream in the future.Two methods of pump frequency tuning and self-injection locking were used to obtain Kerr combs in the same silicon nitride microresonators with free spectral ranges of 50 GHz and 100 GHz.Single-soliton combs are realized with both methods.Simplicity,pump power,spectrum bandwidth,conversion efficiency,and linewidth are compared and analyzed.Our results show that the advantages of pump frequency tuning are a wider spectrum and higher soliton power while the advantages of self-injection locking are simplicity,compactness,low cost,significant linewidth narrowing,and high conversion efficiency.
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