Application Of Optical Tomography Research Articles

Focus shaping by tightly focusing locally linear polarized vortex beams with Pancharatnam–Berry tailored

Based on vector diffraction theory, we demonstrated that the three-dimensional spatial separation of the two foci can be achieved by modulating the polarization distribution of the input vector light field. The Pancharatnam–Berry tailored vector light field combined with a vortex phase can realize both foci possess vortices of arbitrary topological charges. The simulation results show that the tightly focused vector vortex beam can generate two vortices with independent topological charges, and the spatial distance between the two vortex foci can be adjusted. Moreover, the focal field distribution with optical cage or flat-topped profile can be easily obtained by appropriately choosing the polarized structure and vortex phase of the input beams. We generate a perfect optical cage that is almost surrounded by uniform light intensity. The flat-topped focus can be formed by focusing of a single vortex, as well as the superposition focusing of the two vortices. These engineered focus profiles may find potential applications in optical imaging, laser micromachining, particle trapping and manipulations.

Self-rotating beam in the free space propagation.

We introduce a class of self-rotating beams whose intensity profile tends to self-rotate and self-bend in the free space propagation. The feature of the self-rotating beams is acceleration in the three-dimensional (3D) space. The acceleration dynamics of the self-rotating beams is controllable. Furthermore, multiple self-rotating beams can be generated by a combined diffractive optical element (DOE) simultaneously. Such a beam can be viewed as evolution of a vortex beam by changing the exponential constant of phase. We have generated this beam successfully in the experiment and observed the expected phenomenon, which is basically consistent with the result of the numerical simulation. Our results may provide new insight into the self-rotating beam and extend potential applications in optical imaging.

Frontispiece: 19F MRI Probes for Multimodal Imaging

This review focuses on multimodal imaging encompassing 19F MRI (magnetic resonance imaging) as one of the modalities. Structure of the probes and example applications in optical fluorescence imaging (OFI), 1H MRI, chemical exchange saturation transfer (CEST), MRI, ultrasonography (USG), X-ray computed tomography (CT), single-photon emission tomography (SPECT), positron emission tomography (PET), and photoacoustic imaging (PAI) as well as other less popular techniques were discussed. For more information, see the Review by D. Janasik and T. Krawczyk on page 4–35.

Near-infrared active superparamagnetic iron oxide nanoparticles for magnetomotive optical coherence tomography imaging and magnetic hyperthermia therapeutic applications

A green chemistry-based approach to nanoparticle synthesis is an eco-friendly, simple, and cost-effective way to fabricate nanoparticles. This study aims at the biomedical applications of green synthesized near-infrared (NIR) active superparamagnetic iron oxide nanoparticles (SPIONs). The SPIONs obtained by the green synthesis route are non-toxic and their surface is free from any chemical impurity. The MTT [3-(4, 5-Dimethylthiazol-2-yl)-2, 5-Diphenyltetrazolium Bromide] assay was accomplished on human cervical cancer (HeLa) cells and shows that the SPIONs are biocompatible and thus safe for cells even at higher concentrations up to 500 μg/ml. The synthesized SPIONs display an absorbance in the tissue transparent NIR wavelength region. The SPIONs exhibit a superparamagnetic behavior with high saturation magnetization of 66 emu/g. Owing to their excellent optical and magnetic properties, the potential of these green synthesized SPIONs as an exogenous contrast agent in deep-tissue magnetomotive optical coherence tomography (MM-OCT) imaging was evaluated ex-vivo using chicken breast tissue. A significant enhancement in the contrast and the penetration depth was observed with time. The heating response of green synthesized SPIONs was evaluated under the application of an external magnetic field. The results suggest that these SPIONs could be used as theranostic agents for deep tissue biomedical imaging and therapeutic applications.

Photoactivatable Fluorescent Tags for Dual-Modality Positron Emission Tomography Optical Imaging.

Fluorescent protein conjugates are vital tools in a wide range of scientific disciplines from basic biochemical research to applications in clinical pathology and intraoperative surgery. We report the synthesis and characterization of photoactivatable fluorophores (PhotoTags) based on the functionalization of coumarin, fluorescein, BODIPY, rhodamine B, and cyanine dyes with a photochemically active aryl azide group. Photochemical labeling experiments using human serum albumin produced fluorescent proteins in high yields under irradiation with ultraviolet light for <15 min. We also synthesized DFO-RhodB-PEG3-ArN3─a photoactivatable compound that can be radiolabeled with 89Zr for applications in optical imaging and positron emission tomography. One-pot 89Zr-radiolabeling and light-induced protein conjugation produced [89Zr]ZrDFO-RhodB-PEG3-azepin-trastuzumab. Proof-of-concept studies in vitro and in vivo confirmed that [89Zr]ZrDFO-RhodB-PEG3-azepin-trastuzumab is a potential dual-modality agent for detecting human epidermal growth factor receptor 2 (HER2/neu) expression. Overall, the PhotoTag technology represents a rapid, synthetically versatile, and user-friendly approach for generating novel protein conjugates.

Structural, morphological, and optical properties of carbon nanoparticles unsheathed from date palm fronds.

Several studies have reported the synthesis of carbon nanoparticles (CNPs) by various methods. In this study, an easy one-step process to unsheathe CNPs from date palm fronds through a top-down ball milling method has been reported. The CNPs were characterized using various spectroscopic and microscopic methods to determine their structural and morphological features, optical properties, crystallinity, physicochemical properties, and particle stability. Transmission electron microscopy (TEM) revealed that the obtained CNPs' size ranged from 4 to 22 nm in a crystalline form. Scanning electron microscopy (SEM) confirmed their spherical shape, while the maximum photoluminescence (PL) intensity was recorded at 464 nm when excited at 375 nm. The unsheathed CNPs produced a good quantum yield (QY) of 3.24%. Furthermore, the CNPs exhibited high Raman ratios of ID/IG and I2D/IG with values of 0.59 and 0.04, respectively, verifying their multilayer crystalline graphitic nature. These Raman ratios also agree with the X-ray diffractometry (XRD) results. The CNPs' sp2 and sp3 carbon bonds were confirmed by X-ray photoelectron spectroscopy (XPS), with oxygen on the surface forming carboxyl and carbonyl groups with no other observable impurities. Furthermore, the extracted CNPs showed excellent PL properties for up- and down-conversion. These properties are exemplary for low-cost biomass with potential applications in biomedicine. Therefore, the extracted CNPs reported in this study have potential applications in optical imaging.

High Speed Structured Light Devices and Their Applications in Optical Imaging and Measurement

High Speed Structured Light Devices and Their Applications in Optical Imaging and Measurement

In Vivo Assessment of Protein-Protein Interactions Using BRET Assay.

Proteins play an important part in almost all life activities and across all organisms. Proteins occasionally act on their own but rather fulfill most of their biological tasks by cooperating with other proteins or ligand molecules. The bioluminescence resonance energy transfer (BRET) assay serves to measure dynamic events such as protein-protein or protein-ligand interactions in vitro or in-vivo. With several inherent attributes such as rapid and fairly sensitive ratio-metric measurements, assessment of interactions irrespective of protein location within the cellular compartment, cost-effectiveness consenting to high-throughput screening compatibility, makes BRET a popular genetic reporter-based assay system for protein-protein interaction (PPI) studies. Based on the Förster principle, BRET allows to judge if the proximity has been achieved between the interacting partners. In recent years, the BRET application has emerged as a significantly versatile assay format by using multiple detection devices such as a plate reader or in-vivo optical imaging platform, or even a bioluminescence microscope has expanded its scope for advancing PPI studies. Beyond the scope of quantitative measurement of PPIs, molecular optical imaging applications based on BRET assay have expanded the scope for screening pharmacological compounds by unifying live cell and in-vivo animal-/plant-based experiments using the same platform technology. In this chapter, we have given intricate methodological details for performing in-vitro and in-vivo BRET experiments, primarily by using donor/acceptor reporter protein combinations.

Controlling asymmetric transmission phase in planar chiral metasurfaces

AbstractMetasurfaces with ultrathin artificial structures have attracted much attention because of their unprecedented capability in light manipulations. The recent development of metasurfaces with controllable responses opens up new opportunities in various applications. Moreover, metasurfaces composed of twisted chiral structures can generate asymmetric responses for opposite incidence, leading to more degrees of freedom in wave detections and controls. However, most past studies had focused on the amplitude responses, not to mention using bi-directional phase responses, in the characterization and light manipulation of chiral metasurfaces. Here, we report a birefringent interference approach to achieve a controllable asymmetric bi-directional transmission phase from planar chiral metasurface by tuning the orientation of the metasurface with respect to the optical axis of an add-on birefringent substrate. To demonstrate our approach, we fabricate planar Au sawtooth nanoarray metasurface and measure the asymmetric transmission phase of the metasurface placed on a birefringent sapphire crystal slab. The Au sawtooth metasurface-sapphire system exhibits large oscillatory behavior for the asymmetric transmission phase with the tuning parameter. We confirm our experimental results by Jones matrix calculations using data obtained from full-wave simulations for the metasurface. Our approach in the characterization and light manipulation of metasurfaces with controllable responses is simple and nondestructive, enabling new functionalities and potential applications in optical communication, imaging, and remote sensing.

Orbital angular momentum and beyond in free-space optical communications

AbstractOrbital angular momentum (OAM), which describes tailoring the spatial physical dimension of light waves into a helical phase structure, has given rise to many applications in optical manipulation, microscopy, imaging, metrology, sensing, quantum science, and optical communications. Light beams carrying OAM feature two distinct characteristics, i.e., inherent orthogonality and unbounded states in principle, which are suitable for capacity scaling of optical communications. In this paper, we give an overview of OAM and beyond in free-space optical communications. The fundamentals of OAM, concept of optical communications using OAM, OAM modulation (OAM modulation based on spatial light modulator, high-speed OAM modulation, spatial array modulation), OAM multiplexing (spectrally efficient, high capacity, long distance), OAM multicasting (adaptive multicasting,N-dimensional multicasting), OAM communications in turbulence (adaptive optics, digital signal processing, auto-alignment system), structured light communications beyond OAM (Bessel beams, Airy beams, vector beams), diverse and robust communications using OAM and beyond (multiple scenes, turbulence-resilient communications, intelligent communications) are comprehensively reviewed. The prospects and challenges of optical communications using OAM and beyond are also discussed at the end. In the future, there will be more opportunities in exploiting extensive advanced applications from OAM beams to more general structured light.

Optical Properties and Applications of Crystalline Materials

Optical Properties and Applications of Crystalline Materials

Experimental investigation on the laser backscattering characteristics of complicated targets

For active optical imaging applications where targets are irradiated by a laser beam, the backscattering characteristic influences the image quality. An outfield experimental investigation of kilometer scale was conducted in this study. Unmanned aerial vehicles with complex shapes and various surface materials were used as targets. Backscattered signals were obtained, while the targets were located at different attitudes and distances. Furthermore, the relationship between the amplitude of the backscattered signal and the target distance was deduced and summarized at close and far distances. The experimental results can be helpful in detecting complicated targets with laser illumination.

Dynamics of a chirped Airy pulse in a dispersive medium with higher-order nonlinearity

Chirp can control the dynamics of the Airy pulse, making it an essential factor in pulse manipulation. Finite energy chirped Airy pulses (FECAPs) have potential applications in underwater optical communication and imaging. Hence, it is critical to study the propagation of FECAPs. We present a numerical investigation of the propagation dynamics of a FECAP in a dispersive and highly nonlinear medium. The nonlinearity under study includes self-phase modulation (SPM), self-steepening (SS), as well as intra-pulse Raman scattering (IRS) terms. We have observed soliton shedding, and the chirp parameter is demonstrated to have a considerable impact on the pulse dynamics. In particular, the emergent soliton does not propagate in a straight path; instead, depending on the sign of the chirp parameter, it delays or advances in time. Furthermore, it has been established that the chirp can be employed as an alternate control parameter for spectral manipulation. The results of our study may have implications in supercontinuum generation and for producing tunable sources.

Biomedical Applications of Translational Optical Imaging: From Molecules to Humans.

Light is a powerful investigational tool in biomedicine, at all levels of structural organization. Its multitude of features (intensity, wavelength, polarization, interference, coherence, timing, non-linear absorption, and even interactions with itself) able to create contrast, and thus images that detail the makeup and functioning of the living state can and should be combined for maximum effect, especially if one seeks simultaneously high spatiotemporal resolution and discrimination ability within a living organism. The resulting high relevance should be directed towards a better understanding, detection of abnormalities, and ultimately cogent, precise, and effective intervention. The new optical methods and their combinations needed to address modern surgery in the operating room of the future, and major diseases such as cancer and neurodegeneration are reviewed here, with emphasis on our own work and highlighting selected applications focusing on quantitation, early detection, treatment assessment, and clinical relevance, and more generally matching the quality of the optical detection approach to the complexity of the disease. This should provide guidance for future advanced theranostics, emphasizing a tighter coupling—spatially and temporally—between detection, diagnosis, and treatment, in the hope that technologic sophistication such as that of a Mars rover can be translationally deployed in the clinic, for saving and improving lives.

All‐Fiber Optical Waveform Converter Based on Deformed Catenary Nanostructure

Optical Waveform Converter In article number 2100042, Hongchang Deng, Houquan Liu, and co-workers have designed an all-fiber waveform converter by integrating one-dimensional long helical fiber grating and two-dimensional deformed catenary nanostructure. Through wavelength and circular polarization modulation, the device has a unique ability in optical focusing, divergence and rotation, which can make the generated light beam break through the diffraction limit. It has potential applications in optical manipulation and imaging.

Modeling and optimization of galvanometric point-scanning temporal dynamics.

Galvanometers are ubiquitous in point-scanning applications in optical imaging, display, ranging, manufacturing, and therapeutic technologies. However, galvanometer performance is constrained by finite response times related to mirror size and material properties. We present a model-driven approach for optimizing galvanometer response characteristics by tuning the parameters of the closed-loop galvanometer controller and demonstrate settling time reduction by over 50%. As an imaging proof-of-concept, we implement scan waveforms that take advantage of the optimized galvanometer frequency response to increase linear field-of-view, signal-to-noise ratio, contrast-to-noise ratio, and speed. The hardware methods presented may be directly implemented on galvanometer controllers without the need for specialized equipment and used in conjunction with customized scan waveforms to further optimize scanning performance.

Size-invariant twisted optical modes for the efficient generation of higher-dimensional quantum states

Optical vortex beams are profiled as helical wavefronts with a phase singularity carrying an orbital angular momentum (OAM) associated with their spatial distribution. The transverse intensity distribution of a conventional optical vortex has a strong dependence on the carried topological charge. However, perfect optical vortex (POV) beams have their transverse intensity distribution independent of their charge. Such “size-invariant” POV beams have found exciting applications in optical manipulation, imaging, and communication. In this paper, we investigate the use of POV modes in the efficient generation of high-dimensional quantum states of light. We generate heralded single photons carrying OAM using spontaneous parametric downconversion (SPDC) of POV beams. We show that the heralding efficiency of the SPDC single photons generated with a POV pump is greater than that with normal optical vortex beams. The dimensionality of the two-photon OAM states is increased with POV modes in the pump and projective measurements using Bessel–Gaussian vortex modes that give POV, instead of Laguerre–Gaussian modes.

Improving luminescence behavior and glass stability of tellurium‐doped germanate glasses by modifying network topology

AbstractBroadband near‐infrared (NIR) luminescent materials are of great interest for their potential application in optical communication, remote sensing, imaging, and homeland security. Tellurium (Te) doped glasses were recently recognized as such a promising candidate due to their broadband NIR emission (700–1700 nm). However, the achievement of Te‐doped glasses with high luminescence efficiency and glass stability (GS) remains a daunting challenge. Here, the luminescence behavior and GS of Te‐doped germanate glasses are manipulated by tailoring the glass network topology. Te NIR luminescence is enhanced by tailoring topological cages in germanate glass network structure through varying glass network modifiers. Meanwhile, the GS of potassium germanate glass is significantly enhanced due to increased network connectivity caused by the co‐introduction of alkaline earth oxides. Finally, NIR luminescence intensity of the glass was further enhanced by optimizing the doping concentration of TeO2. The findings here could contribute to designing Te‐activated glasses with improved performance for application in optical amplifiers and tunable fiber lasers.

Computational Inverse Problems for Partial Differential Equations

Inverse problems in partial differential equations (PDEs) consist in reconstructing some part of a PDE such as a coefficient, a boundary condition, an initial condition, the shape of a domain, or a singularity from partial knowledge of solutions to the PDE. This has numerous applications in nondestructive testing, medical imaging, seismology, and optical imaging. Whereas classically mostly boundary or far field data of solutions to deterministic PDEs were considered, more recently also statistical properties of solutions to random PDEs have been studied. The study of numerical reconstruction methods of inverse problems in PDEs is at the interface of numerical analysis, PDE theory, functional analysis, statistics, optimization, and differential geometry. This workshop has mainly addressed five related topics of current interest: model reduction, control-based techniques in inverse problems, imaging with correlation data of waves, fractional diffusion, and model-based approaches using machine learning.

Fabrication of optical vortex array by fixing standing wave mediated periodic defects in nematic liquid crystals via photopolymerization

ABSTRACT Optical vortex beams have attracted significant research interest owing to their potential for application in optical communication and imaging. In this study, we demonstrated devices with electrically switchable topological defects as well as those with permanent topological defects using reactive mesogen (RM) and vertically aligned LC cells. A defect array was created via standing wave-mediated periodic LC orientation control by applying pulse train waves. At a low RM concentration (0.6 wt%), polymerisation induced a pretilt angle, and the periodic LC alignment was memorised with a topological defect array. Thus, the memorised defect structure reappeared upon applying a direct current field or standard square electric fields. In contrast, at a high RM concentration (3 wt.%), a permanent defect array device was realised. Thus, depending on the RM concentration, various types of defect arrays were selectively created. The devices developed in this study can be used for various potential applications, such as in digital data transfer and imaging systems.