Non-iterative complex wave-field reconstructionbased on Kramers–Kronig relations

A non-iterative and non-interferometric computational imaging method to reconstruct a complex wave field called synthetic aperture imaging based on Kramers–Kronig relations(KKSAI)is reported.By collecting images through a modified microscope system with pupil modulation capability,we show that the phase and amplitude profile of the sample at pupil limited resolution can be extracted from as few as two intensity images by using Kramers–Kronig(KK)relations.It is established that as long as each subaperture’s edge crosses the pupil center,the collected raw images are mathematically analogous to off-axis holograms.This in turn allows us to adapt a recently reported KK-relations-based phase recovery framework in off-axis holography for use in KKSAI.KKSAI is non-iterative,free of parameter tuning,and applicable to a wider range of samples.Simulation and experiment results have proved that it has much lower computational burden and achieves the best reconstruction quality when compared with two existing phase imaging methods.

Program-controlled single soliton microcomb source

Soliton microcombs(SMCs)are spontaneously formed in a coherently pumped high-quality microresonator,which provides a new tool for use as an on-chip frequency comb for applications of high-precision metrology and spectroscopy.However,generation of SMCs seriously relies on advanced experimental techniques from professional scientists.Here,we experimentally demonstrate a program-controlled single SMC source where the intracavity thermal effect is timely balanced using an auxiliary laser during single SMC generation.The microcomb power is adopted as the criteria for microcomb states discrimination and a forward and backward thermal tuning technique is employed for the deterministic single SMC generation.Further,based on a closed-loop control system,the repetition rate stability of the SMC source improved more than 20 times and the pump frequency can be continuously tuned by simply changing the operation temperature.The reliability of the SMC source is verified by consecutive 200 generation trials and maintaining over 10 h.We believe the proposed SMC source will have significant promising influences in future SMC-based application development.

Terabit FSO communication based on a soliton microcomb

Free-space optical(FSO)communication technology is a promising approach to establish a secure wireless link,which has the advantages of excellent directionality,large bandwidth,multiple services,low mass and less power requirements,and easy and fast deployments.Increasing the communication capacity is the perennial goal in both scientific and engineer communities.In this paper,we experimentally demonstrate a Tbit/s parallel FSO communication system using a soliton microcomb as a multiple wavelength laser source.Two communication terminals are installed in two buildings with a straight-line distance of~1 km.102 comb lines are modulated by10 Gbit/s differential phase-shift keying signals and demodulated using a delay-line interferometer.When the transmitted optical power is amplified to 19.8 dBm,42 optical channels have optical signal-to-noise ratios higher than 27 dB and bit error rates less than 1×10^(-9).Our experiment shows the feasibility of a wavelength-division multiplexing FSO communication system which suits the ultra-high-speed wireless transmission application scenarios in future satellite-based communications,disaster recovery,defense,last mile problems in networks and remote sensing,and so on.