Time-reversed optical focusing through scattering mediaby dligital fullphase and amplitude recovery usinga single phase-only SLM

Focusing light though scattering media beyond the ballistic regime is a challenging task in biomedical optical imaging.This challenge can be overcome by wavefront shaping technique,in which a time reversed(TR)wavefront of scattered light is generated to suppress the scattering.In previous TR optical focusing experiments,a phase only spatial light modulator(SLM)has.been typically used to control the wavefront of incident light.Unfortunately,although the phase information is reconstructed by the phase-only SLM,the amplitude information is lost,resulting in decreased peak to-background ratio(PBR)of optical focusing in the TR wavefront recon-struction.A new method of TR optical focusing through scattering media is proposed here,which numerically reonstructs the full phase and amplitude of a simulated scattered light field by using a single phase only SLM.Simulation results and the proposed optical setup show that the time-reversal of a fully developed speckle field can be digially implemented with both phase and ampltude recovery,affording a way to improve the performance of light focusing through scattering media.

Simple and universal method in designs of high-efficiency diffractive optical elements for spectrum separation and beam concentration

Diffractive optical elements（DOEs） with spectrum separation and beam concentration（SSBC） functions have important applications in solar cell systems. With the SSBC DOEs, the sunlight radiation is divided into several wave bands so as to be effectively absorbed by photovoltaic materials with different band gaps. A new method is proposed for designing high-efficiency SSBC DOEs, which is physically simple, numerically fast, and universally applicable. The SSBC DOEs are designed by the new design method, and their performances are analyzed by the Fresnel diffraction integral method.The new design method takes two advantages over the previous design method. Firstly, the optical focusing efficiency is heightened by up to 10%. Secondly, focal positions of all the designed wavelengths can be designated arbitrarily and independently. It is believed that the designed SSBC DOEs should have practical applications to solar cell systems.

Refocusing and locating effect of fluorescence scattering field

Optical imaging deep inside scattering medium has always been one of the challenges in the field of bioimaging,which significantly drawbacks the employment of con-focal microscopy system.Although a variety of feedback techniques,such as acoustic or nonlinear fluorescence-based schemes have realized the refocusing of the coherent light,the problems of non-invasively refocusing and locating of linearly-excited fluorescent beads inside the scattering medium have not been thoroughly explored.In this paper,we linearly excited the fluorescent beads inside a scattering medium by using our homemade optical con-focal system,collected the fluorescence scattering light as the optimized target,and established a theoretical model of target contrast enhancement,which is consistent with the experimental data.By improving both the cost function and variation rate within the genetic algorithm,we could refocus the fluorescence scattering field while improving the contrast enhancement factor to 12.8 dB.Then,the positions of the fluorescent beads are reconstructed by subpixel accuracy centroid localization algorithm,and the corresponding error is no more than 4.2μm with several fluorescent beads within the field of view.Finally,the main factors such as the number of fluorescent beads,the thickness of the scattering medium,the modulating parameter,the experimental noise and the system long-term stability are analyzed and discussed in detail.This study proves the feasibility of reconstructing fluorescent labeled cells inside biological tissues,which provides certain reference value for deep imaging of biological tissues.

The Study Internal Structure of the Annual Layers in Lake Sediments Using Synchrotron Radiation with X-ray Focusing Optics

1 Introduction Annually laminated(varve)sedimentary deposits are considered as one of the most important archives,since they offer precise temporal information(years)in combination with high time resolutions.Bottom sediments of the lakes contain detailed geochemical information on

Focusing of Intense Laser via Parabolic Plasma Concave Surface

Since laser intensity plays an important role in laser plasma interactions,a method of increasing laser intensity- focusing of an intense laser via a parabolic plasma concave surface- is proposed and investigated by three-dimensional particle-in-cell simulations.The geometric focusing via a parabolic concave surface and the temporal compression of high harmonics increased the peak intensity of the laser pulse by about two orders of magnitude.Compared with the improvement via laser optics approaches,this scheme is much more economic and appropriate for most femtosecond laser facilities.

Active wavefront shaping for controlling and improving multimode fi ber sensor

Wavefront shaping(WFS)techniques have been used as a powerful tool to control light propagation in complex media,including multimode fibers.In this paper,we propose a new application of WFS for multimode fber-based sensors.The use of a single multimode fiber alone,without any special fabrication,as a sensor based on the light intensity variations is not an easy task.The twist effect on multimode fiber is used as an example herein.Experimental results show that light intensity through the multimode fiber shows no direct relationship with the twist angle,but the correlation coefficient(CC)of speckle patterns does.Moreover,if WFS is applied to transform the spatially seemingly random light pattern at the exit of the multimode fiber into an optical focus.The focal pattern correlation and intensity both can serve to gauge the twist angle,with doubled measurement range and allowance of using a fast point detector to provide the feedback.With further development,WFS may find potentials to facilitate the development of multimode fber-based sensors in a variety of scenarios.

Three-dimensional multiple optical cages formed by focusing double-ring shaped radially and azimuthally polarized beams

We propose and simulate a method for generating a three-dimensional （3D） optical cage in the vicinity of focus by focusing a double-ring shaped radially and azimuthally polarized beam. Our study shows that the combination of an inner ring with an azimuthally polarized field and an outer ring with a radially polarized field and a phase factor can produce an optical cage with a dark region enclosed by higher intensity. The shape of the cage can be tailored by appropriately adjusting the parameters of double-mode beams. Furthermore, multiple 3D optical cages can be realized by applying the shift theorem of the Fourier transform and macro-pixel sampling algorithm to a double-ring shaped radially and azimuthally polarized beam.

Design of a linear-rotary ultrasonic motor for optical focusing inspired by the bionic motion principles of the earthworms

Multi-motor configuration of multi-DOF(degree of freedom)optical system is a major source of redundant structure,putting a limitation on the simple and miniaturized design.Thus,a novel two-DOF ultrasonic motor(USM)is proposed to provide a feasible method of application in the lens autofocus of the optical system.The proposed USM operates by one longitudinal mode and two orthogonal bending modes,which is inspired by the bionic motion principle of the earthworms.The frequency degeneration among the three working modes is per-formed,and the working principle of the USM is verified via the FEM simulation.A prototype of the two-DOF USM is fabricated,and its mechanical output characteristics are tested.The experimental results indicate that the prototype achieves the maximum rotary and linear speeds of 3319.6 rpm and 57.6 mm/s,respectively.Furthermore,we demonstrate the result of a simple focusing experiment using the prototype and obtain a series of clear pictures,which verifies the feasibility of application in the optical focusing system.

Electro-optically tunable self-focusing and self-defocusing in KTP crystals by a cascaded second-order process

We report the transformation of a linear electro-optically tunable non-phase-matched second-order nonlinear process into a cascaded second-order nonlinear process in a bulk KTP crystal to generate the effect of electrooptically tunable Kerr-type nonlinearity. By applying an electric field on the x–y plane, parallel to the z-axis of the crystal, phase mismatch is created, which introduces a nonlinear phase shift between the launched and reconverted fundamental waves from the generated second harmonic wave. Due to the nonuniform radial intensity distribution of a Gaussian beam, a curvature will be introduced into the fundamental wavefront, which focuses or defocuses the incident beam while propagating through the crystal.

Redistributing the energy flow of tightly focused ellipticity-variant vector optical fields

The redistribution of the energy flow of tightly focused ellipticity-variant vector optical fields is presented.We theoretically design and experimentally generate this kind of ellipticity-variant vector optical field, and further explore the redistribution of the energy flow in the focal plane by designing different phase masks including fanlike phase masks and vortex phase masks on them. The flexibly controlled transverse energy flow rings of the tightly focused ellipticity-variant vector optical fields with and without phase masks can be used to transport multiple absorptive particles along certain paths, which may be widely applied in optical trapping and manipulation.

Optical forces exerted on a graphene-coated dielectric particle by a focused Gaussian beam

In this paper, we derive the analytical expression for the multipole expansion coefficients of scattering and interior fields of a graphene-coated dielectric particle under the illumination of an arbitrary optical beam. By using this arbitrary beam theory, we systematically investigate the optical forces exerted on the graphene-coated particle by a focused Gaussian beam. Via tuning the chemical potential of the graphene, the optical force spectra could be modulated accordingly at resonant excitation. The hybridized whispering gallery mode of the electromagnetic field inside the graphene-coated polystyrene particle is more intensively localized than the pure polystyrene particle, which leads to a weakened morphology-dependent resonance in the optical forces. These investigations could open new perspectives for dynamic engineering of optical manipulations in optical tweezers applications.

Switchable optical nonlinear properties of W_(18)O_(49) nanowires by Ag nanoparticles supported

During the past decades,nonlinear optical（NLO）materials have attracted special interest because of their potential applications in photonic devices,such as optical switching,frequency conversion and electro-optic modulators.Among the finding ways to obtain excellent NLO materials with both large NLO response and short response time,

Clinical outcomes with a new design in multifocal intraocular lens:a pilot study

Purpose:To evaluate the clinical and visual outcomes,quality of near vision and the influence of photic phenomena in patients bilaterally implanted with a new Precizon Presbyopic multifocal intraocular lens(IOL).Methods:In this prospective consecutive case series,20 eyes of 10 patients were included(mean age 63.80±12.55 years).Uncorrected and corrected visual acuity(far,intermediate and near),subjective refraction,binocular defocus curve,contrast sensitivity(CSV-1000)and quality of vision and satisfaction questionnaires were measured.The follow-up was 12 months after surgery.Results:At 12 months after surgery,uncorrected distance visual acuity(UDVA)improved with surgery(p=0.001)with a value of 0.08±0.08 logMAR.Uncorrected near visual acuity(UNVA)was 0.22±0.12 logMAR and distance corrected near visual acuity(DCNVA)was 0.16±0.13 logMAR.Intermediate distance visual acuity(UIVA)was 0.22±0.10 logMAR.Contrast sensitivity outcomes were similar to normal population in photopic conditions and slightly reduced in mesopic conditions of lighting.Defocus curve showed that this multifocal IOL was able to provide a visual acuity(VA)equal or better to 0.16 logMAR between defocus levels of+1.00 to−2.50 D.Good patient satisfaction was obtained in quality of vision and satisfaction questionnaires outcomes.Conclusions:The Precizon Presbyopic NVA IOL(OPHTEC BV)provides good visual outcomes.This multifocal IOL provides a high percentage of spectacle independence due to good VA at far,intermediate and near distances and satisfactory contrast sensitivity.High patient satisfaction was observed in quality of vision and satisfaction questionnaires with a low percentage of patients manifesting photic phenomena.

Forewords Focus Issue of Nano Optics in Chinese Optics Letters (COL)

Rapid progress of nanoscience and nanotechnology has made significant impact on many academic disciplines and technical fields recently. In particular,

Forewords Focus Issue of Biophotonics in Chinese Optics Letters(COL)

Photonics Technology has made a significant impact on a wide range of medical and biomedical applications.These days,it is not uncommon to find several op- tical equipments in operating rooms and medical research laboratories.This wide