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Lymphatic vessels are structurally similar to blood vessels, and the lymphatic fluid flowing within the lymphatic vessels is distributed throughout the body and plays a vital role in the human immune system. Visualization of the lymphatic vessels is clinically important in the diagnosis of tumor cell metastasis and related immune system diseases, but lymph is difficult to image due to its near-transparent nature and low flow rate. In this paper, we present a lymphography method based on time-autocorrelated optical coherence tomography. By using the minimum value difference of the autocorrelation function of the time-varying interference intensity between the lymph and the surrounding tissues, the non-invasive and high-sensitivity imaging of lymph vessels can be achieved. The method proposed in this paper has potential significance for the research and treatment of immune system diseases.

Regulating the catalytic pathways of single-atom sites in single atom catalysts (SACs) is an exciting debate at the moment, which has redirected the research towards understanding and modifying the single-atom catalytic sites through various strategies including altering the coordination environment of single atom for desirable outcomes as well as increasing their number. One useful aspect concerning the tunability of the catalytic pathways of SACs, which has been overlooked, is the oxidation state dynamics of the single atoms. In this study, iron single-atoms (FeSA) with variable oxidation states, dependent on the precursors, are harnessed inside a nitrogen-rich functionalized carbon quantum dots (CQDs) matrix via a facile one-step and low-temperature synthesis process. Dynamic electronic properties are imparted to the FeSAs by the simpler carbon dots matrix of CQDs in order to achieve the desired catalytic pathways of reactive oxygen species (ROS) generation in different environments, which are explored experimentally and theoretically for an in-depth understanding of the redox chemistry that drives the alternative catalytic pathways in FeSA@CQDs. These alternative and oxidation state-dependent catalytic pathways are employed for specific as well as cascade-like activities simulating natural enzymes as well as biomarkers for the detection of cancerous cells.

The state-of-the-art semiconductor industry is built on the successful production of silicon ingot with extreme purity as high as 99.999999999%, or the so-called “eleven nines”. The coming high-end applications of graphene in electronics and optoelectronics will inevitably need defect-free pure graphene as well. Due to its two-dimensional (2D) characteristics, graphene restricts all the defects on its surface and has the opportunity to eliminate all kinds of defects, i.e., line defects at grain boundaries and point or dot defects in grains, and produce intrinsically pure graphene. In the past decade, epitaxy growth has been adopted to grow graphene by seamlessly stitching of aligned grains and the line defects at grain boundaries were eliminated finally. However, as for the equally common dot and point defects in graphene grain, there are rare ways to detect or reduce them with high throughput and efficiency. Here, we report a methodology to realize the production of ultrapure graphene grown on copper by eliminating both the dot and point defects in graphene grains. The dot defects, proved to be caused by the silica particles shedding from quartz tube during the high-temperature growth, were excluded by a designed heat-resisting box to prevent the deposition of particles on the copper surface. The point defects were optically visualized by a mild-oxidation-assisted method and further reduced by etching-regrowth process to an ultralow level of less than 1/1,000 µm2. Our work points out an avenue for the production of intrinsically pure graphene and thus lays the foundation for the large-scale graphene applications at the integrated-circuit level.

Confined nanospaces provide a new platform to promote catalytic reactions. However, the mechanism of catalytic enhancement in the nanospace still requires insightful exploration due to the lack of direct visualization. Here, we report

The low-energy layer edge states (LESs) from quasi 2D hybrid perovskite single crystals have shown great potential because of their nontrivial photoelectrical properties. However, the underlying formation mechanism of the LESs still remains controversial. Also, the presence or creation of the LESs is of high randomness due to the lack of proper techniques to manually generate these LESs. Herein, using a single crystals platform of quasi-2D (BA)

To achieve non-invasive and high effective resolution microvascular imaging in vivo, photothermal modulation speckle optical coherence tomography (PMS-OCT) imaging technology is proposed in this Letter to enhance the speckle signal of the bloodstream for improving the imaging contrast and image quality in the deeper depth of Fourier domain optical coherence tomography (FD-OCT). The results of simulation experiments proved that this photothermal effect could disturb and enhance the speckle signals, because the photothermal effect could modulate the sample volume to expand and change the refractive index of tissues, leading to the change in the phase of interference light. Therefore, the speckle signal of the bloodstream will also change. With this technology we obtain a clear cerebral vascular nondestructive image of a chicken embryo at a certain imaging depth. This technology expands the application fields of optical coherence tomography (OCT) especially in more complex biological structures and tissues, such as the brain, and provides a new way, to the best of our knowledge, for the application of OCT in brain science.

Carbon dots (CDs) are considered as promising candidates with superior biocompatibilities for multimodel cancer theranostics. However, incorporation of exogenous components, such as targeting molecules and chemo/photo therapeutic drugs, is often required to improve the therapeutic efficacy. Herein, an "all-in-one" CDs that exhibit intrinsic bioactivities for bioimaging, potent tumor therapy, and postoperative management is proposed. The multifunctional CDs derived from gallic acid and tyrosine (GT-CDs) consist of a graphitized carbon core and N, O-rich functional groups, which endow them with a high near-infrared (NIR) photothermal conversion efficiency of 33.9% and tumor-specific cytotoxicity, respectively. A new imaging modality, photothermal optical coherence tomography, is introduced using GT-CDs as the contrast agent, offering the micrometer-scale resolution 3D tissue morphology of tumor. For cancer therapy, GT-CDs initiate the intracellular generation of reactive oxygen species in tumor cells but not normal cells, further induce the mitochondrial collapse and subsequent tumor cellular apoptosis. Combined with NIR photothermal treatment, synergistic antitumor therapy is achieved in vitro and in vivo. GT-CDs also promote the healing process of bacteria-contaminated skin wound, demonstrating their potential to prevent postoperative infection. The integrated theranostic strategy based on versatile GT-CDs supplies an alternative easy-to-handle pattern for disease management.

To realize multimodal hemodynamic imaging, pulse photothermal optical coherence tomography (P-PTOCT) is proposed in this Letter to solve the separation problem of photothermal phase and Doppler phase, which is difficult to solve in traditional PTOCT. This technique can obtain blood flow distribution, light absorption distribution, and concentration images simultaneously. Based on the difference between pulse photothermal phase and Doppler phase, we propose an even number differential demodulation algorithm that can separate the photothermal phase and Doppler phase from the same scanning data set. The separated photothermal phase can characterize the trend of drug concentration, which provides the possibility for quantitative measurement of plasma concentration. The combination of photothermal phase and Doppler phase is helpful for potential clinical research on hemodynamics of cerebral ischemia and provides a technical reference for the rapid acquisition of perfusion volume and plasma concentration at one time.

Nanoparticle-sensitized photoporation for intracellular delivery of external compounds usually relies on the use of spherical gold nanoparticles as sensitizing nanoparticles. As they need stimulation with visible laser light, they are less suited for transfection of cells in thick biological tissues. In this work, we have explored black phosphorus quantum dots (BPQDs) as alternative sensitizing nanoparticles for photoporation with a broad and uniform absorption spectrum from the visible to the near infra-red (NIR) range. We demonstrate that BPQD sensitized photoporation allows efficient intracellular delivery of both siRNA (>80%) and mRNA (>40%) in adherent cells as well as in suspension cells. Cell viability remained high (>80%) irrespective of whether irradiation was performed with visible (532 nm) or near infrared (800 nm) pulsed laser light. Finally, as a proof of concept, we used BPQD sensitized photoporation to deliver macromolecules in cells with thick phantom tissue in the optical path. NIR laser irradiation resulted in only 1.3x reduction in delivery efficiency as compared to photoporation without the phantom gel, while with visible laser light the delivery efficiency was reduced 2x.

Deionization using electrochemical redox reactions has potentially been the latest desalination technique with high salt removal capacity and lower energy cost due to high capacity of electrode materials and electrochemical energy release. Herein, we presented a metal-free continuous electrodialysis desalination technology, which could directly desalt feed water at high concentrations to drinking water level during continuous treatment with unlimited salt removal capacity. The device consists of a recirculating 4-hydroxy-2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO) stream between the flowing positive and negative electrodes in series and the salt feed stream. During the charging process, the flowing TEMPO was oxidized at the positive reservoir, where the anion in the feed was captured through the anion exchange membrane, whereas the TEMPO recovery at the negative reservoir drove the cation removal in the feed through the cation exchange membrane by its reduction. Due to the redox reaction of TEMPO between the cyclical flow electrode streams, it acts as a “catalyst”, and the salt ions in the middle feed are continuously extracted. Our experiments demonstrate that feed water with a 5860 ppm salt concentration can be directly desalted to 136 ppm, a drinking water level, in a single batch treatment during the continuous charging process (salt removal of up to 97.7%). Furthermore, a three-membrane device was demonstrated to stop the salt concentration increase in the TEMPO electrode reservoirs; thus, fully continuous cycling of the TEMPO catalyst was realized without any salt change in the electrode reservoirs. Our research will provide a route for metal-free continuous desalination based on the molecular redox mediator of the electrode material and can be applied directly in open air environment and room temperature.

A new, to the best of our knowledge, method for Stokes vector imaging is proposed to achieve imaging and dynamic monitoring of a non-labeled cytomembrane. In this work, a polarization state vector is described by a Stokes vector and expressed in chrominance space. A physical quantity called polarization chromaticity value (PCV) corresponding to a Stokes vector is used as the imaging parameter to perform Stokes vector imaging. By using the PCV imaging technique, the Stokes vector can be expressed in three-dimensional real space rather than in a Poincare sphere. Furthermore, a four-way Stokes parameter confocal microscopy system is designed to measure four Stokes parameters simultaneously and obtain micro-imaging. Label-free living onion cell membranes and their plasmolysis process are selected as the representative micro-anisotropy experimental analysis. It is proved that PCV imaging can perform visualization of cytomembranes, and further, microscopic orientation is demonstrated. The prospect of universal measurement of anisotropy details for analysis and diagnosis is provided.

Motion correction is an important issue in ophthalmic optical coherence tomography (OCT), and can improve the ability of data sets to reflect the physiological structures of tissues and make visualization and subsequent analysis easier. In this study, we present a novel method to correct the cross-sectional motion artifacts in retinal OCT volumes. Motion along the x-direction (fast-scan direction) is corrected through the normalized cross-correlation algorithm, while axial motion compensation is performed using the polynomial fitting method on the inner segment/outer segment (IS/OS) layer segmented by the shortest path faster algorithm (SPFA). The results of volunteers with central serous chorioretinopathy demonstrate that the proposed method effectively corrects motion artifacts in OCT volumes and may have potential application value in the evaluation of ophthalmic diseases such as diabetic retinopathy, glaucoma and age-related macular degeneration.

The growth of wafer-scale single-crystal two-dimensional transition metal dichalcogenides (TMDs) on insulating substrates is critically important for a variety of high-end applications

In this letter, the topological charge of non-integer vortices determined by three arbitrary spiral spectra is theoretically demonstrated for the first time. Based on the conclusion, a novel method to measure non-integer vortices is presented. This method is applicable not only to arbitrary non-integer vortex but also to arbitrary integer vortex.

The lateral imaging characteristic of an acoustic lens is similar to the well-known object-image relationship of an optical lens. In this paper, axial signal analysis is carried on and reconstruction methods for a sample's axial photoacoustic (PA) image are researched based on the acoustic-lens PA imaging system. The integral and envelope methods are both proposed to reconstruct a sample's axial PA image, which has only been achieved approximately by the PA signals' peak values obtained by a peak-holding circuit in previous reports. And the envelope method is proposed for the first time. Hilbert transform was used to obtain the envelope of the sample's PA signals and axial PA images. Simulation results show that the integral method is appropriate for low frequency samples, and that the envelope reconstruction method can provide low frequency information of the PA images of samples. So for a sample, it would be best to combine the two methods together.

An integrated dual-channel sensing method utilizing polarized dissimilation is investigated with an appropriately designed plasmonic metasurface. By assembling two different kinds of nano-gold antennas to constitute a periodic array, the phase of diffraction fields contains both spin-dependent geometric phase and resonance-dependent dynamic phase components. Accurate control over the superposition of orthogonal spin components utilizing strong photonic spin-orbit interaction of metasurface leads to dissimilar response of different diffraction orders. The simulation shows that the linear polarization of ±1 diffraction orders rotate in the reverse direction (±19°) with the refractive index variation (1.3-1.5). The sensing method exhibits an extremely high signal-to-noise ratio and stability.

In a single quantum dot (QD) system connected with ferromagnetic electrodes, the electron transport properties, assisted by the thermal and Fock state optical fields, are theoretically studied by the Keldysh nonequilibrium Green&rsquo, s function approach. The results show that the evolution properties of the density of state and tunneling current assisted by the Fock state optical field, are quite different from those of the thermal state. The photon sideband shift decreases monotonously with the increase in the electron&ndash, photon coupling strength for the case of the thermal state, while the shift is oscillatory for the case of the Fock state. Negative differential conductance (NDC) appears obviously in a QD system contacted with parallel (P) and antiparallel (AP) magnetization alignment of the ferromagnetic electrode leads, assisted by the Fock state optical field in a wide range of electron&ndash, photon interaction parameters. Evident NDC usually only arises in an AP configuration QD system assisted by the thermal state optical field. The results have the potential to introduce a new way to actively manipulate and control the single-electron tunneling transport on a QD system by the quantum states of the optical field.

In this paper, using the particle-number-resolved master equation, the properties of full counting statistics (FCS) are investigated for a single quantum dot (QD) system interacting with optical fields in the thermal state, Fock state, coherent state, and coherent state with random phase. In these diverse quantum states of optical fields, average tunneling currents have different step shoulder heights at a lower bias voltage with the same light intensity, and a staircase-shaped current can be induced unexpectedly in vacuum state optical field. The characteristics of the Fano factor and skewness in the coherent state differ from those in all of the other cases. For avalanche-like transport at a lower bias voltage, the mechanism is a dynamical channel blockade in a moderate electron&ndash, photon interaction regime. There is a pronounced negative differential conductance that results from tuning the phase of the coherent state optical field in a symmetric QD system.

Solution-processed organo-lead halide perovskites have emerged as promising optical gain media for tunable coherent light sources. The lasing performance is generally determined by the as-synthesized crystal quality. Noble metal nanostructures have been widely utilized to enhance optical responses due to their unique property of localized surface plasmon resonance. Herein, we report a simple method to enhance the near-infrared amplified spontaneous emission (ASE) performance of MAPbI3 polycrystalline films by solution-processing a PMMA spacer layer and an Au NR-doped PMMA top layer on perovskite thin films. As a result, the ASE threshold of the triple-layer perovskite film was significantly reduced by around 36% and the ASE intensity increased by 13.9-fold, compared to the pristine film. The underlying mechanism was attributed to the combined effects of surface passivation by PMMA and plasmon resonance enhancement of Au NRs. The passivation effect results in suppressing the nonradiative recombination and prolonging excited state decay, which have been investigated by transient absorption and pump–probe measurements. The plasmon effect is systematically studied through distance-dependent and spectra-dependent plasmon enhanced emission. The perovskite films with PMMA and Au NR coating showed great stability for 180 min under intense pulse laser continuous irradiation. The improved ASE performance still remained after leaving the film under the atmosphere for more than one month. We have successfully demonstrated a highly stable and sustained ASE output from MAPbI3 films under pulse laser excitation. This study provides a general approach for exploring plasmonic nanostructures in combination with polymers in the development and application of low-cost solution-processed semiconductor lasers.

Photoacoustic microscopy is dominantly sensitive to the endogenous optical absorption, while a fluorescence optical microscopy can detect the fluorescence emission to obtain the image of a sample. To some extent, the physical processes of the 2 methods are opposite, one is absorption and another is emission, but both can be used to image cells. In this article, a simultaneous dual-mode imaging system of photoacoustic microscopy and fluorescence optical microscopy is set up to image tobacco cells. Furthermore, gold nanoparticles, which have a large absorption coefficient and enough fluorescence emission with wavelength of 512 nm, are used to label certain drugs and added to the tobacco cells. Then based on the simultaneous dual-mode microscopy imaging system, the photoacoustic microscopy and fluorescence optical microscopy images of gold nanoparticle-labeled tobacco cells are obtained. The final purpose of this experimental research is to detect if the labeled drugs can enter the cells by the positions of the gold nanoparticles. This will help the experts to deliver organic pesticide more accurately and effectively. The experimental results show that by gold nanoparticle labeling technology, the imaging quality of photoacoustic microscopy and fluorescence optical microscopy can be improved, which indicates that the drugs probably enter the tobacco cells successfully.

We developed a cross-correlation photothermal optical coherence tomography (CC-PTOCT) system for photothermal imaging with high lateral and axial resolution. The CC-PTOCT system consists of a phase-sensitive OCT system, a modulated pumping laser, and a digital cross-correlator. The pumping laser was used to induce the photothermal effect in the sample, causing a slight phase modulation of the OCT signals. A spatial phase differentiation method was employed to reduce phase accumulation. The noise brought by the phase differentiation method and the strong background noise were suppressed efficiently by the cross-correlator, which was utilized to extract the photothermal signals from the modulated signals. Combining the cross-correlation technique with spatial phase differentiation can improve both lateral and axial resolution of the PTOCT imaging system. Clear photothermal images of blood capillaries of a mouse ear in vivo were successfully obtained with high lateral and axial resolution. The experimental results demonstrated that this system can enhance the effective transverse resolution, effective depth resolution, and contrast of the PTOCT image effectively, aiding the ongoing development of the accurate 3D functional imaging.

Temperature increase in tumour tissue during photothermal therapy (PTT) is a significant factor in determining the outcomes of the treatment. Therefore, controlling and optimising temperature distribution in target tissue is crucial for PTT. In this study, we developed a unique ex vivo device to study the temperature distribution during PTT to be used as a guide for the desired photothermal effects for cancer treatment.Bovine liver tissue buried inside agarose gel served as a phantom tumour surrounded by normal tissue. A thermostatic incubator was used to simulate tissue environment in live animals. The temperature distributions were measured by thermocouples with needle probes at different locations inside the target tissue, during laser irradiation using an 805-nm laser.The results obtained using the ex vivo device were verified by comparing the tissue temperature directly measured in animal tumours irradiated under the same conditions. With this model, the spatial distribution of temperature in target tissue can be monitored in real time. A two-dimensional temperature distribution in target tissue allows us to establish the correlations among laser parameters, temperature distribution and tumour size. In addition, the optimal temperature range for tumour destruction and immunological stimulation was determined using metastatic rat mammary tumour model.The device and method developed in this study can provide guidance for choosing the appropriate treatment parameters for optimal photothermal effects, particularly when combined with immunotherapy, for cancer treatment.

Based on the Collins diffraction integral formula, an analytical expression of a general four-petal Gaussian vortex beam passing through a paraxial ABCD optical system is derived by means of the mathematical technique. As a numerical example, the normalized intensity distribution of a four-petal Gaussian vortex beam propagating in free space is graphically demonstrated. The influences of beam order and topological charge on the normalized intensity distribution are discussed in detail. This research is useful to the optical trapping, optical communications, and beam splitting techniques, etc.

The far-field analytical expressions for the electromagnetic fields of amplitude of vector-vortex beams having a Bessel–Gauss (BG) distribution propagating in free space are obtained based on the vector angular spectrum and the method of stationary phase. The far-field energy flux distributions and the beam quality by the power in the bucket (PIB) in the paraxial and nonparaxial regimes are investigated. The PIB of the vector-vortex BG beams depend on the ratio of the waist width to wavelength and the polarization order. The analyses show that vector-vortex BG beams with low polarization order have better energy focusability in the farfield.

Soluble microneedles (MNs) have recently become an efficient and minimally invasive tool in transdermal drug delivery because of their excellent biocompatibility and rapid dissolution. However, direct monitoring of structural and functional changes of MNs in vivo to estimate the efficiency of insulin delivery is difficult. We monitored the dissolution of MNs to obtain structural imaging of MNs’ changes by using optical coherence tomography (OCT). We also observed the effect of MNs on microvascular conditions with laser speckle contrast imaging (LSCI) and measured the blood perfusion of skin to obtain functional imaging of MNs. We determined the performance of two soluble MN arrays made from polyvinyl alcohol (PVA) and polyvinyl alcohol/polyvinylpyrolidone (PVA/PVP) by calculating the cross-sectional areas of the microchannels in mouse skin as a function of time. Moreover, the change in blood glucose before and after using MNs loaded with insulin was evaluated as an auxiliary means to demonstrate the ability of the soluble MNs to deliver insulin. Results showed that the structural imaging of these MNs could be observed in vivo via OCT in real time and the functional imaging of MNs could be showed using LSCI. OCT and LSCI are potential tools in monitoring MNs structural and functional changes.

We designed, fabricated, and tested a rapid and noncontact photoacoustic tomography (PAT) imaging system using a low-coherence interferometer with high-speed phase modulation technique. Such a rapid and noncontact probing system can greatly decrease the time of imaging. The proposed PAT imaging system is experimentally verified by capturing images of a simulated tissue sample and the blood vessels within the ear flap of a mouse (pinna) in vivo. The axial and lateral resolutions of the system are evaluated at 45 and ∼15 μm, respectively. The imaging depth of the system is 1 mm in a special phantom. Our results show that the proposed system opens a promising way to realize noncontact, real-time PAT.

We present implementation of quantum cryptography with polarization code by wave-guide type phase modulator. At four different low input voltages of the phase modulator, coder encodes pulses into four different polarization states, 45°, 135° linearly polarized or right, left circle polarized, while the decoder serves as the complementary polarizers.

A novel photoacoustic (PA) tomographic method, which is based on a time-resolved technique and an acoustic lens imaging system, is presented in this paper. A YAG laser operating at 532 nm with a 7 ns pulse width and 10 mJ optical pulse is employed as the excitation source to irradiate the tissue. PA signals generated from the tissue are imaged onto a multi-element linear array transducer with an acoustic lens. A 64 electronic switch is efficiently used for changing the parallel PA signals into a series. The proposed method directly provides PA images without any complex reconstruction algorithms. With the time-resolved technique, tomographic imaging can be achieved successfully. The results show that the images agree well with the original samples.

A ratio of diameter method based on dynamic light scattering was proposed to measure the size of nanoparticles. In the measurement process, parameters, such as the surrounding temperature T, the viscous coefficient η, and the refractive index n0 of the solvent and the scattering angle θ and the wavelength of the light λ0 in vacuum, are not needed. The only requirement is to provide a particle sample with a known diameter as a reference. After the intensity autocorrelation function values and baseline values are measured, the ratio of diameters from two kinds of particles can be calculated and the size of the sample particles can be deduced. The data analysis process is simple, convenient, and effective. When this method is applied to a polydisperse sample, the intensity-weighted mean diameter can be obtained.

A photoacoustic tomography imaging system using a low-coherence interferometer with rapid detection of phase modulation was designed, fabricated, and tested for biologic imaging. A noncontact probing technique was applied to improve the practicability of the system. The technique is experimentally verified by the image of a simulated tissue sample and the blood vessels within a mouse ear flap (pinna) in vivo. The system’s axial and lateral resolutions are evaluated at 45 and ~15 μm, respectively. The system’s imaging depth is 1mm in a special phantom. The results show that the system has the feasibility to be used as a photoacoustic tomography imaging method, and it may provide a kind of possibility of noncontact real-time PAT.

A wavelet transformation method is introduced to remove the large fluorescence background from polarized Raman spectra of stained tooth enamel. This method exploits the wavelet multiresolution decomposition where the experimental Raman spectrum is decomposed into signals with different frequency components, and where the lowest frequency background and highest frequency noise are removed. This method is optimized using a simulated collection of parallel-polarized and cross-polarized Raman spectra of the enamel and then applied to a set of experimental data. The results show that the wavelet transform technique can extract the pure spectra from background and noise, with the depolarization ratio used to discriminate between early dental caries and sound enamel preserved. Copyright © 2010 Crown in the right of Canada. Published by John Wiley & Sons, Ltd.

We report on a sub-cellular resolution photoacoustic microscopy (PAM) system that employs microcavity synchronous parallel acquisition technique for detecting the weak photoacoustic (PA) signal excited by a modulated continuous wave (CW) laser source. The gas microcavity transducer is developed based on the fact that the bulk modulus of the gas is far less than the solid and the change of the air-gas pressure is inversely proportional to the gas volume, making it extremely sensitive to the tiny PA pressure wave. Besides, considering PA wave expends in various directions, detecting PA signals from different position and adding them together can increase the detecting sensitivity and the signal to noise ratio(SNR), then we employs two microphone to acquire PA wave synchronously and parallelly. We show that the developed PAM system is capable of label-free imaging and differentiating of the hemoglobin distribution within single red blood cells under normal and anemia conditions.

We present a high-speed polarization-coding method, which makes use of phase modulation, for use in a quantum key distribution (QKD) system. This technique has been introduced into a QKD system for the first time. A completely quantum mechanical method is employed to describe quantum information processing here. Experiments on a balanced element for polarization coding by phase modulation are described in detail. The experimental results demonstrate that this technique can encode or decode polarization at high speed (with feasibility in the GHz range) and low voltage (a few volts) successfully.

The transportation and focusing in turbid media by means of Monte Carlo method is presented; by changing the numerical aperture (NA) of lens, the distributions of the intensity of focal spots were obtained. It shows: the NA is larger, the radius of focal spot is larger; all that answers the result of the experiments. Whereas in theory of scalar diffraction: the focal spot is getting smaller when the NA of lens increases. In the process of Monte Carlo simulation, every steps of photons motion are pursued and the scattering and absorption are taken into account; but we have no way to consider the scalar diffraction in it with the limit of the method itself. In fact, the scalar diffraction plays a role in light propagation otherwise it couldn't focus in turbid media. The figure of the NA versus focal spot is plotted using two methods with Monte Carlo simulation and with the scalar diffraction theory. With two methods, we suppose there is a balance position, which we can choose the lens of appropriate NA and get the optimal focal spot.

In this article, the focal properties of cylindrically polarized beams through a high numerical aperture parabolic mirror are numerically investigated. The vector field distributions within the focal region for cylindrically polarized beams are calculated by using the Richards-Wolf vectorial diffraction theory. It shows that the three-dimensional intensity distributions in the vicinity of the focus is dependent on the polarization rotation angle, topological charge and numerical aperture value. Additionally, some interesting focal volume structures, such as adjustably confined flat-topped focus, doughnut focal hole can be obtained by controlling polarization rotator angle. The tightly focused cylindrically polarized beams by a high numerical aperture parabolic mirror have possible applications in particle acceleration, optical trapping and manipulating, single molecule imaging and high resolution imaging microscopy, et al.

The theory of photoacoustic tomography (PAT) imaging using a 4f acoustic lens imaging system has been investigated, and the theoretical results show that a 4f acoustic lens has the ability of imaging and guarantees axial and lateral unit magnification of image. A system, a 4f acoustic lens imaging system combining with time-resolved technique, is developed to acquire PAT images. The 4f acoustic lens is able to image initial photoacoustic (PA) pressure distribution, which exactly resembles the absorption distribution, onto an imaging plane. Combining with time-resolved technique, the linear transducer array is adopted to acquire the PA pressure distribution to reconstruct the PAT images. Experimental results demonstrate that the system is able to obtain PAT images and the images contrast sharply with their backgrounds.

This study aims to develop a simultaneous photoacoustic tomography imaging technique in multilayer media. With an acoustic lens which has the ability of parallel imaging instead of other PA image reconstruction methods on the basis of complex algorithms, obtaining a two-dimensional (2D) PA image in real-time is available. Combining the advantages of the acoustic lens which has long focal depth and the fast data acquisition system, the new system is particularly excellent that it can acquire the complete PA signals from all the object planes. With the time-resolved technique, the PA signals from different object planes can be distinguished. As a result, the multilayer PAT images can be reconstructed simultaneously without any complicated reconstruction algorithms. According to the experimental results, the reconstructed multilayer images agree well with the original samples.

We present implementation of phase modulated polarization coding by polarizing sagnac interferometers. At four different low input voltages of the phase modulator, coder encodes pulse into four different polarization states, 45°, 135° linearly polarized or right, left circle polarized, while the decoder serves as the complementary polarizers. The mean visibility of the system is tested at 94.31%.

A new method of photoacoustic (PA) imaging based on an acoustic lens and the peak-hold technology is presented in this article. A fast PA imaging system, which consists of an acoustic lens, a 64-element linear transducer array, and a peak detection-and-hold circuit, is developed to obtain the two dimensional (2D) PA images of the experimental samples. By utilizing an acoustic lens, the PA signals generated from the sample are directly imaged on the imaging plane and collected by the 64-element linear transducer array which changes the PA signals into the corresponding electronic signals. Then the electronic signals are converted into a one dimensional image using the peak detection-and-hold circuit. After vertical scanning with a step motor on the imaging plane, the 2D PA image of the sample is achieved successfully. The results show that the images reconstructed in this experiment agree well with the original samples. Compared to other methods, this PA imaging system can acquire the PA images more rapidly without any complex algorithms, and it may provide a more convenient method for future in vivo noninvasive imaging of tissues and clinic diagnosis.

Optoacoustic tomography can be applied into medical imaging, which can detect the light absorption distribution of target hidden inside scattering media. When a short laser pulse illuminates the optical turbid media, such as biological tissue, the media will generate ultrasound pulses, which is linearly proportional to the optical absorption of the media. The acoustic pressure distribution can be imaged with an acoustic lens. Similar to an optically imaging system, the optoacoustic signals from a plane in tissue require the same delay time to reach a detecting plane. While the optoacoustic signals from different planes in media require different delay time to reach an image plane. A BOXCAR was used to go on with the same delay-time, and a 64-element linear transducer array was one-dimensional scanned on an imaging plane, and thus the acoustic pressure distribution was acquired. The signals were recorded and reconstructed by a computer. By scanning the sampling gate of BOXCAR, the optoacoustic images of different planes in media could be obtained. The experimental result indicates that the system is able to obtain optoacoustic tomography images of targets hidden optical turbid media, and the reconstructed images agree well with the original samples. The results show that the lateral resolution is about 5mm and the axial resolution is about 1.5mm.

We describe a new method for evaluating the viscoelastical characterization of biological tissue by photoacoustic technique in this paper. The amplitude attenuation curse of the tissue photoacoustic signals (the stress waves) induced by Q-YAG laser provides necessary data for us to work out the decay time of the stress waves. According to the theory of viscoelasticity, the decay time is equal to the tissue viscosity-elasticity ratio. The result we get from measuring gelatin shows the viscosity-elasticity ratio of Kelvin-Voigt model tissue obtained by photoacoustic measurement almostly equals that by conventional rheometer. The agreement is almost 97%. Furthermore, we firstly apply the method to measure the tissue viscosity-elasiicity ratio of Maxwell model. From the theorical analysis and the experimental result, we can conclude that the method can be applied to any model tissue, because it is only related with its acoustic impedance, having nothing to do with tissue state. In short, photoacoustic measurement is real-time, noninvasive and highly sensitive and repetitive. Based on the virtues mentioned above, it can be widely applied to biology and medicine.

Total suspended particles (TSP) are one of the main atmospheric pollutants. The ingredients are very complex, mainly including black carbon (C),organic compound, inorganic compound and biologic component, which will do great harm to human's health. During environmental monitoring, the airborne suspended particle always is an index for evaluating the quality of atmosphere. In this article, possible mixture of TSP is proposed to determine its ingredients and content by photoacoustic spectroscopy. The normalized photoacoustic (PA) signal of the sulfur powder, mixtures of sulfur and black carbon in different proportions are obtained respectively. Simulation with linear equation says that the PA signal has a certain relationship with the content of sample. The normalized PA spectroscopy of various materials is acquired via examining the sample of the powder of cupric sulfate mixed with nitro compound (2, 5 -methoxybenzoic-4nitro-dehyde), Portland cement, residual particles of automobile exhaust pipe, ash of power plant's stocks. The experimental results have important reference value to the practical analysis of TSP, it also provides new possible methodology to the environmental monitoring.

The tight focusing of femtosecond radially polarized vortex laser pulse by a high numerical aperture objective is investigated in this paper. Based on Richards-Wolf vectorial diffraction theory, the electric field and the group velocity of the radially polarized vortex femtosecond laser pulse are studied in great detail. It finds that the femtosecond radially polarized vortex laser pulse can travel at various group velocities near the focus, that is, slower or faster than light velocity in vacuum, depending on the numerical aperture of the focusing objective system. Moreover, the effect of spherical aberration of objective, topological charge and time duration of the radially polarized vortex laser pulse on the group velocity distribution near the focus is discussed.

Photoacoustic microscopy (PAM), whose image quality largely depends on the optical absorption of samples, provides endogenous information for structural and functional imaging. However, PAM technology in general can not provide edge enhancement imaging for absorbing objects. Therefore, PAM and differential microscopy are integrated for the first time in a single technique to obtain an edge enhancement image. The resolution test target RTA-07 and red blood cells are used as samples to achieve the desired spatial differential photoacoustic imaging. The feasible biomedical application of edge enhancement from the improved differential PAM was demonstrated.

Photoacoustic (PA) signals carry much information related to the physical parameters of a sample, such as its optical, thermal, acoustic, and elastic properties. These physical parameters synchronously make their own contributions to PA signals. It is difficult to distinguish the contributions of different physical parameters to the mixed PA signals. To separate these parameters and to extract the featured information, we report herein a means of dissecting the transient PA signal using time-frequency analysis in a forward detection model. The simulated and experimental results indicate that the features of different physical parameters related to the sample can be qualitatively extracted from the mixed PA signals.

Acoustic lens is applied in the research of photoacoustic imaging. The aberration is always inevitable due to the existence of the acoustic lens, and it influences the resolution of the imaging system severely. However, the imaging system based on an acoustic lens also provides a new method for observing the aberration of a system and testing the quality of the acoustic lens. In this paper, a method of observing the aberration of photoacoustic imaging system is reported, and the causes of aberrations are discussed based on the theory of lens aberration. All these would be helpful to correct the aberration and improve the resolving power of acoustic lens.