Measurement of optical coherence structures of random optical fields using generalized Arago spot experiment

The optical coherence structures of random optical fields can determine beam propagation behavior,light–matter interactions,etc.Their performance makes a light beam robust against turbulence,scattering,and distortion.Recently,we proposed optical coherence encryption and robust far-field optical imaging techniques.All related applications place a high demand on precision in the experimental measurements of complex optical coherence structures,including their real and imaginary parts.Past studies on these measurements have mainly adopted theoretical mathematical approximations,limited to Gaussian statistic involving speckle statistic(time-consuming),or used complicated and delicate optical systems in the laboratory.In this study,we provide:a robust,convenient,and fast protocol to measure the optical coherence structures of random optical fields via generalized Arago(or Poisson)spot experiments with rigorous mathematical solutions.Our proposal only requires to capture the intensity thrice,and is applicable to any optical coherence structures,regardless of their type or optical statistics.The theoretical and experimental results demonstrated that the real and imaginary parts of the structures could be simultaneously recovered with high precision.We believe that such a protocol can be widely employed in phase measurement,optical imaging,and image transfer.

Laser polarization-variable autofluorescence of the network of optically anisotropic biological tissues:Diagnostics and differentiation of early stages of cancer of cervia uteri

This research presents the results of investigation of laser_polarization fluorescence ofbiological layers(histological sections,cy tological smears)in the task of diagnostics and differ-en tiation of early stages of cancer:Dysplasia-cervical microinvasive carcinoma of cervic uteri.The analytical conditions of polarization-optimal probing of biological layers were determinedbasing on the model of linear birefringence and dichroism of birefringent(fibrllar,porphyrin)networks.The technique of polarization-variable laser autofluorescence was developed andexperimentally tested.The objective criteria(statistical moments)of differentiation of histo-logical sections autofluorescent images of endometrium biopsy and cytological smears of itmucous coat were defined.The operational characteristics(sensitivity,speifity,accuracy)ofthis technique were determined concerning the positions of probative medicine,and clinical efficiency.

CLASSIFYING OPTICAL PROPERTIES OF SURFACE-AND BULK-SCATTERING BIOLOGICAL LAYERS WITH POLARIZATION SINGULAR STATES

The results of singular approach usage in the tasks of description and classification of appearance of optical anisotropy of different types of phase-inhomogeneous biological layers(surface-scattering,optically thin and optically thick)have been presented.The characteristic values of the fourth Stokes vector parameter(S_(4)=0-linear polarization-(L-state);S_(4)=±1-circular polarization-(C-state))have been chosen as the main analytical tool descni bing polarization-singular states.The value of S.has been deternined by the value of phase shift betwoen the ort hogonal components of amplitude in the point of biological layer laser image and therefore is azimuthally stable.Hence,statistic moments of the first to the fourth orders characterizing the distribution of the amount of characteristic values S4=0;S_(4)=±1 have been used for definition and di ferentiation of optical properties of diferent types of biological layers-surface scattering,optically thin and optically thick human skin.

Evolution of a Thermo Vacuum State in a Single-Mode Amplitude Dissipative Channel

We investigate how an initial thermo vacuum state, in the context of thermo field dynamics, evolves in a single-mode amplitude dissipative channel, and find that in this process the thermo squeezing effect decreases while the fictitious-mode vacuum becomes chaotic.

Photon statistics of pulse-pumped four-wave mixing in fiber with weak signal injection

We study the photon statistics of pulse-pumped four-wave mixing in fibers with weak coherent signal injection by measuring the intensity correlation functions of individual signal and idler fields. The experimental results show that the intensity correlation function of individual signal（idler） field g_（s（i））^（2） decreases with the intensity of signal injection. After applying narrow band filter in signal（idler） band, the value of g_（s（i））^（2） decreases from 1.9 ± 0.02（1.9 ± 0.02） to 1.03 ± 0.02（1.05 ± 0.02） when the intensity of signal injection varies from 0 to 120 photons/pulse. The results indicate that the photon statistics changes from Bose–Einstein distribution to Poisson distribution. We calculate the intensity correlation functions by using the multi-mode theory of four-wave mixing in fibers. The theoretical curves well fit the experimental results.Our investigation will be useful for mitigating the crosstalk between quantum and classical channels in a dense wavelength division multiplexing network.

Ground State of Fermions in a 1D Trap with δ Function Interaction

The ground state of fermions in a 1D trap with δ function interaction is studied mathematically with group theory ideas.

Coherence entropy during propagation through complex media

The deformation,flicker,and drift of a light field owing to complex media such as a turbulent atmosphere have limited its practical applications.Thus,research on invariants in randomly fluctuated light fields has garnered considerable attention in recent years.Coherence is a statistical property of light,while its full and quantitative characterization is challenging.Herein,we successfully realize the orthogonal modal decomposition of partially coherent beams and introduce the application of coherence entropy as a global coherence characteristic of such randomly fluctuated light fields.It is demonstrated that coherence entropy remains consistent during propagation in a unitary system by unraveling complex channels.As representative examples,we study the robustness of coherence entropy for partially coherent beams as they propagate through deformed optical systems and turbulent media.Coherence entropy is anticipated to serve as a key metric for evaluating the propagation of partially coherent beams in complex channels.This study paves the way for a broader application scope of a customized low-coherence light field through nonideal optical systems and complex media.

Optical resonance with subwavelength spectral coherence switch in open-end cavity

The physical properties of light fields at the subwavelength scale have emerged as extensively pursued objectives in nano-optics,photonics,and plasmonics.Here,we report that in the paraxial regime,the spectral density and the spectral axial coherence(z-coherence)structures in a submicron range can be generated by employing a light beam with a suitably chosen spatial coherence state in a counter-propagating configuration,in an open-end cavity.It is established that while the spectral density forms an optical standing wave,the z-coherence state depends on the symmetry of the selected point pair and in particular,the phenomenon termed as periodical coherence switch is found.Our findings shed new light on the discussion of the role of spatial coherence in the photonic cavities,possibly inspiring further studies in the field of enhanced light-nanomaterials interactions by optical cavity.This provides a versatile framework for tailoring coherence in subwavelength space with promising applications in metrology and imaging.

Generation of partially coherent vortex bottle beams

Intensity distribution of the partially coherent Bessel vortex beams focused by an aperture lens is investigated. It is found that the intensity distribution in the neighborhood of the geometrical focus is not only dependent on the topological charge and the radial frequency of the incident partially coherent Bessel vortex beam, but also on its coherence length. Based on this, the desired partially coherent vortex bottle beams can be obtained by choosing appropriate values of parameters. Because such bottle beams possess characteristics of low coherence and vortex, it may be used in microscopic particles guiding, trapping, and inducing rotation.

Generalized high-order twisted partially coherent beams and their propagation characteristics

Twist phase is a nontrivial statistical phase that only exists in partially coherent fields,which makes the beam carry orbital angular momentum(OAM).In this paper,we introduce a new kind of partially coherent beams carrying high-order twist phase,named generalized high-order twisted partially coherent beams(GHTPCBs).The propagation dynamics such as the spectral density and OAM flux density propagating in free space are investigated numerically with the help of mode superposition and fast Fourier transform(FFT)algorithm.Our results show that the GHTPCBs are capable of self-focusing,and the beam spot during propagation exhibits teardrop-like or the diamond-like shape in some certain cases.Moreover,the influences of the twist order and the twist factor on the OAM flux density during propagation are also illustrated in detail.Finally,we experimentally synthesize the GHTPCBs with controllable twist phase by means of pseudo-mode superposition and measure their spectral density during propagation.The experimental results agree well with the theoretical predictions.Our studies may find applications in nonlinear optics and particle trapping.

Holographic 3D imaging through random media: methodologies and challenges

Imaging through random media continues to be a challenging problem of crucial importance in a wide range of fields of science and technology,ranging from telescopic imaging through atmospheric turbulence in astronomy to microscopic imaging through scattering tissues in biology.To meet the scope of this anniversary issue in holography,this review places a special focus on holographic techniques and their unique functionality,which play a pivotal role in imaging through random media.This review comprises two parts.The first part is intended to be a mini tutorial in which we first identify the true nature of the problems encountered in imaging through random media.We then explain through a methodological analysis how unique functions of holography can be exploited to provide practical solutions to problems.The second part introduces specific examples of experimental implementations for different principles of holographic techniques,along with their performance results,which were taken from some of our recent work.