Application Of Optical Tomography Research Articles

Intravascular Polarimetry: Clinical Translation and Future Applications of Catheter-Based Polarization Sensitive Optical Frequency Domain Imaging.

Optical coherence tomography (OCT) and optical frequency domain imaging (OFDI) visualize the coronary artery wall and plaque morphology in great detail. The advent of these high-resolution intracoronary imaging modalities has propelled our understanding of coronary atherosclerosis and provided enhanced guidance for percutaneous coronary intervention. Yet, the lack of contrast between distinct tissue types and plaque compositions impedes further elucidation of the complex mechanisms that contribute to acute coronary syndrome (ACS) and hinders the prospective identification of plaques susceptible to rupture. Intravascular polarimetry with polarization-sensitive OFDI measures polarization properties of the coronary arterial wall using conventional intravascular imaging catheters. The quantitative polarization metrics display notable image contrast between several relevant coronary plaque microstructures that are difficult to identify with conventional OCT and OFDI. Tissues rich in collagen and smooth muscle cells exhibit birefringence, while lipid and macrophages cause depolarization. In this review, we describe the basic principles of intravascular polarimetry, discuss the interpretation of the polarization signatures, and outline promising avenues for future research and clinical implications.

Recent Advances in Crosslinked Nanogel for Multimodal Imaging and Cancer Therapy.

Nanomaterials have been widely applied in the field of cancer imaging and therapy. However, conventional nanoparticles including micelles and liposomes may suffer the issue of dissociation in the circulation. In contrast, crosslinked nanogels the structures of which are covalently crosslinked have better physiological stability than micelles and liposomes, making them more suitable for cancer theranostics. In this review, we summarize recent advances in crosslinked nanogels for cancer imaging and therapy. The applications of nanogels in drug and gene delivery as well as development of novel cancer therapeutic methods are first introduced, followed by the introduction of applications in optical and multimodal imaging, and imaging-guided cancer therapy. The conclusion and future direction in this field are discussed at the end of this review.

Bioinspired Underwater Superoleophobic Microlens Array With Remarkable Oil-Repellent and Self-Cleaning Ability.

Underwater superoleophobic microlens array (MLA) has been emerging as a crucial device for its wide applications in ocean optical imaging and sensing, endoscopic surgery, microfluidics and optofluidics, and other biomedical applications. Fabrication of microlens arrays integrated with excellent optical performance as well as underwater superoleophobicity remains a great challenge. In this paper, we report an underwater super oil-repellent MLA on a transparent optical glass substrate via femtosecond laser-induced phase and structural modification and chemical isotropic etching. The fabricated sample simultaneously possesses microlens structures with a smooth surface to enable optical imaging function, and grid-patterned biomimetic micro/nano hierarchical surface structures to produce underwater oil-resistance with a contact angle of 160.0° and a sliding angle of 1.5°. The resultant oil-repellent MLA exhibits underwater superoleophobicity and self-cleaning abilities in water. Meanwhile, it was demonstrated to have impressive imaging capability even after oil contamination. We believe that this novel resultant anti-oil MLA will be helpful for underwater detection and bioscience research, especially in oil polluted underwater workspaces.

Tetra-hyperbolic and tri-hyperbolic optical phases in anisotropic metamaterials without magnetoelectric coupling due to hybridization of plasmonic and magnetic Bloch high-k polaritons

In this paper we reveal the physics behind the formation of tri- and tetra-hyperbolic phases in anisotropic metamaterials without magnetoelectric coupling and describe the anti-crossing splitting phenomenon in the hyperbolic dispersion which arises due to the hybridization of the plasmonic and magnetic Bloch high-k polaritons. In hyperbolic metamaterials used for sensing, imaging, and other applications the high-k modes are purely magnetic or electric, which results in purely electric (magnetic) near-fields in response to electric (magnetic) sources. The hybridization predicted in this paper leads to the formation of high-k modes which feature both electric and magnetic fields. This can be used to induce magnetic near fields in response to electric dipole in realistic structures which opens novel avenues in the optical magnetism research. Our work considerably deepens the understanding of the high-k polaritons and the topology of the optical iso-frequency surfaces in k-space and will find applications in optical nano-resolution imaging, emission rate, directivity, and near-field control. To accomplish this, we develop a range of new techniques of theoretical optics for bianisotropic materials, including the quadratic index of refraction operator method, suitable to study the high-k polaritons with finite indices of refraction and the explicit expression for the characteristic matrix in generic bianisotropic media. We introduce the spatial stratification approach for the electric and magnetic responses of anisotropic homogeneous media to analyze the underlying Bloch waves. We believe that the formalisms developed here can be useful for the researchers in the field of theoretical optics of anisotropic and bianisotropic media in the future.

Ultra-Broadband Absorber Based on Metal-Insulator-Metal Four-Headed Arrow Nanostructure

We propose an ultra-broadband metamaterial absorber composed of a four-headed arrow-shaped top layer and titanium-bottom film spaced by a dielectric layer. The absorber attains an average absorption of 95.21% ranging from 300 to 2000 nm, and the peak absorptivity reaches up to 99.9%. The synergy of surface plasmon resonances, cavity modes, and lightning-rod effects lead to the ultra-broadband perfect absorption. We also demonstrate the proposed absorber is insensitive for both transverse electric and transverse magnetic polarization and can retain 90% absorption at a larger incident angle. The proposed ultra-broadband absorber holds promising potential in solar cells, optical imaging, polarization detectors, and other large-area applications.

Surface plasmon hole burning via doppler broadening

The hole burning phenomenon is investigated in a five-level atomic configuration at the interface of cesium and gold in the presence of Doppler broadening. The group index and refractive index of surface plasmon polaritons (SPPs) becomes equal in the hole burning region, which display that the phase and group velocities of SPPs are matched. The propagation length during absorption of SPPs decreases with the decrease of absorption, while there are increases with amplification of SPPs. This study could have significant applications in optical storage devices, telecommunication, imaging, and enhancement of plasmonster memory.

Graphdiyne:Structure of Fluorescent Quantum Dots.

Graphdiyne (GDY) as an emerging two-dimensional carbon allotrope exhibits excellent performance in energy chemistry, catalytic chemistry, optoelectronics, electronics, etc. because of the unique structure combining an sp- and sp2 -hybrid carbon network. However, the poor solubility of pristine GDY is a major obstacle to its applications in many fields. Proposed here is a facile strategy to control the preparation of GDY quantum dots (GDY-Py QDs), in which pyrene groups are covalently linked to GDY by using a Sonogashira cross-coupling reaction. The as-prepared GDY-Py QDs, with an average diameter of about 3±0.1 nm, show superior dispersibility in many organic solvents and water. The GDY-Py QDs display not only bright fluorescent with a high relative quantum yield (QY) of 42.82 %, but they are also well-behaved as contrast agents in cell imaging. The GDY-Py QDs are bestowed with high stability and non-cytotoxicity, and exhibit long fluorescent times, and have potential for optical imaging and biomedical applications.

Graphdiyne:Structure of Fluorescent Quantum Dots

AbstractGraphdiyne (GDY) as an emerging two‐dimensional carbon allotrope exhibits excellent performance in energy chemistry, catalytic chemistry, optoelectronics, electronics, etc. because of the unique structure combining an sp‐ and sp2‐hybrid carbon network. However, the poor solubility of pristine GDY is a major obstacle to its applications in many fields. Proposed here is a facile strategy to control the preparation of GDY quantum dots (GDY‐Py QDs), in which pyrene groups are covalently linked to GDY by using a Sonogashira cross‐coupling reaction. The as‐prepared GDY‐Py QDs, with an average diameter of about 3±0.1 nm, show superior dispersibility in many organic solvents and water. The GDY‐Py QDs display not only bright fluorescent with a high relative quantum yield (QY) of 42.82 %, but they are also well‐behaved as contrast agents in cell imaging. The GDY‐Py QDs are bestowed with high stability and non‐cytotoxicity, and exhibit long fluorescent times, and have potential for optical imaging and biomedical applications.

Designer Bloch plasmon polariton dispersion in grating-coupled hyperbolic metamaterials

Hyperbolic metamaterials (HMMs) represent a novel class of fascinating anisotropic plasmonic materials, supporting highly confined propagating plasmon polaritons in addition to surface plasmon polaritons. However, it is very challenging to tailor and excite these modes at optical frequencies by prism coupling because of the intrinsic difficulties in engineering non-traditional optical properties with artificial nanostructures and the unavailability of high refractive index prisms for matching the momentum between the incident light and the guided modes. Here, we report the mechanism of excitation of high-k Bloch-like Plasmon Polariton (BPPs) modes with ultrasmall modal volume using a meta-grating, which is a combined structure of a metallic diffraction grating and a type II HMM. We show how a 1D plasmonic grating without any mode in the infrared spectral range, if coupled to a HMM supporting high-k modes, can efficiently enable the excitation of these modes via coupling to far-field radiation. Our theoretical predictions are confirmed by reflection measurements as a function of angle of incidence and excitation wavelength. We introduce design principles to achieve a full control of high-k modes in meta-gratings, thus enabling a better understanding of light-matter interaction in this type of hybrid meta-structures. The proposed spectral response engineering is expected to find potential applications in bio-chemical sensors, integrated optics and optical sub-wavelength imaging.

Structural, morphological and optical properties of multifunctional magnetic-luminescent ZnO@Fe3O4 nanocomposite

In the present work, non-toxic luminescent ZnO nanoparticles (NPs) and magnetic Fe3O4 NPs were separately prepared by co-precipitation method. In order to get the [email protected]3O4 nanocomposite (NCs), both these NPs were embedded in silica matrix. Powder XRD reveals that the formation hexagonal wurzite structure of ZnO and cubic inverse spinel structure of Fe3O4. Both phases were combined in the prepared [email protected]3O4 NCs. FT-IR spectra showed the absorption peaks confirmed the presence of metal-oxygen stretching bands in ZnO NPs, Fe3O4 NPs and [email protected]3O4 NCs samples. VSM results showed both magnetite and [email protected]3O4 have superparamagnetic, whereas the saturation value for [email protected]3O4 NCs was tremendously decreased. Photoluminescence (PL) spectra of ZnO and [email protected]3O4 illustrated that both samples have very good luminescence property. PL intensity of [email protected]3O4 NCs has been reduced as compared to the intensity of bare ZnO NPs. However, [email protected]3O4 still hold very good luminescence property. The as-prepared [email protected]3O4 NCs were successfully demonstrated for magnetic resonance imaging contrast agent application. Hence, it can be simultaneously used for MRI contrast agent as well as optical imaging applications.

Turbulence profiling using pupil plane wavefront data derived Fried parameter values for a dynamically ranged Rayleigh beacon

Long-range optical imaging applications are typically hindered by atmospheric turbulence. The effect of turbulence on an imaging system can manifest itself as an image blur effect usually quantified by the phase distortions present in the system. The blurring effect can be understood on the basis of the measured strength of atmospheric optical turbulence along the propagation path and its impacts on phase perturbation statistics within the imaging system. One method for obtaining these measurements is by the use of a dynamically ranged Rayleigh beacon system that exploits strategically varied beacon ranges along the propagation path, effectively obtaining estimates of the aberrations affecting an optical imaging system. We developed a method for extracting tomographic turbulence strength estimations from a dynamically ranged Rayleigh beacon system that uses a Shack–Hartmann sensor as the phase measurement device. The foundation for extracting tomographic information from strategically range-varied beacon measurements obtained in rapid sequence is presented along with modeled example cases for typical turbulence scenarios. Additionally, the processing algorithm was used to simulate identification of isolated strong turbulence layers. We present the chosen processing algorithm’s foundation and provide discussion of the utility of this algorithm as an atmospheric turbulence profiling methodology.

NaGdF4:Yb,Er-Ag nanowire hybrid nanocomposite for multifunctional upconversion emission, optical imaging, MRI and CT imaging applications.

The effect of novel silver nanowire encapsulated NaGdF4:Yb,Er hybrid nanocomposite on the upconversion emission and bioimaging properties has been investigated. The upconvension nanomaterials were synthesised by polyol method in the presence of ethylene glycol, PVP and ethylenediamine. The NaGdF4:Yb,Er-Ag hybrid was formed with upconverting NaGdF4:Yb,Er nanoparticles of size ~ 80nm and silver nanowires of thickness ~ 30nm. The surface plasmon induced by the silver ion in the NaGdF4:Yb,Er-Ag nanocomposite resulted an intense upconversion green emission at 520nm and red emission at 660nm by NIR diode laser excitation at 980nm wavelength. The UV-Vis-NIR spectral absorption at 440nm and 980nm, the intense Raman vibrational modes and the strong upconversion emission results altogether confirm the localised surface plasmon resonance effect of silver ion in the hybrid nanocomposite. MRI study of both NaGdF4:Yb,Er nanoparticle and NaGdF4:Yb,Er-Ag nanocomposite revealed the T1 relaxivities of 22.13 and 10.39mM-1s-1, which are larger than the commercial Gd-DOTA contrast agent of 3.08mM-1s-1. CT imaging NaGdF4:Yb,Er-Ag and NaGdF4:Yb,Er respectively showed the values of 53.29 HU L/g and 39.51 HU L/g, which are higher than 25.78 HU L/g of the CT contrast agent Iobitridol. The NaGdF4:Yb,Er and NaGdF4:Yb,Er-Ag respectively demonstrated a negative zeta potential of 54mV and 55mV, that could be useful for biological application. The in vitro cytotoxicity of the NaGdF4:Yb,Er tested in HeLa and MCF-7 cancer cell line by MTT assay demonstrated a cell viability of 90 and 80 %, respectively. But, the cell viability of NaGdF4:Yb,Er-Ag slightly decreased to 80 and 78%. The confocal microscopy imaging showed that the UCNPs are effectively up-taken inside the nucleolus of the cancer cells, and it might be useful for NIR laser-assisted phototherapy for cancer treatment. Graphical abstract.

Excitation spectrum, nanoparticles, and their applications in cellular optical imaging

ABSTRACT The attractive photophysical properties of luminescent nanoparticles have prompted numerous studies on their synthesis and biological applications. Due to the complexity of components, sizes, morphologies, and strong light scattering of the nanoparticles the absorption spectrum alone is not enough for characterising and analysing the real absorption band of a nanoparticle product. Instead, the excitation spectrum is necessary for this purpose. To address the importance of the excitation spectrum in the utilisation of the photophysical properties of nanoparticles for cellular imaging, we compared the absorption and excitation spectra of a small organic molecule (rhodamine 6G) and commercially available nanoparticles (semiconductor quantum dots). Rhodamine 6G shows a good superimposition between its absorption and excitation spectra. However, the quantum dots do not, due to the presence of impurities and the polydispersity in nanoparticle size and shape. We demonstrated, by either spectrometer or cellular imaging, that excitation of the quantum dots at the maximum absorption peak will not result in the highest emission intensity. Instead, the best excitation wavelength for the nanoparticles can be revealed by the excitation spectrum. This has usually been overlooked by chemists and biologists.

All-dielectric bifunctional polarization converter with high transmission efficiency in near-infrared region.

In this paper, we demonstrate a polarization control device with different functions for oppositely propagating directions by a two-layer twisted silicon column array separated by a silica layer. The proposed structure can rotate the electric field directions of polarized linear wave backwards by 45º and serve as a linear-to-circular converter for the polarized linear wave forwards . The physical mechanism is discussed by the Jones matrix, and the numerical results show that the maximum transmissions ${ \gt }{0.9}$>0.9 for the two functions of the proposed structure are achieved in the near-infrared region. The high transmission originates from the all-dielectric materials, which is a major advance compared with previously reported bifunctional converters. The proposed simply shaped device with high transmission efficiency has potential applications in optical imaging, sensing, etc.

Enhanced Emission of Zinc Nitride Colloidal Nanoparticles with Organic Dyes for Optical Sensors and Imaging Application.

Herein, we have reported on the efficiency of inorganic Zn3N2 nanoparticles for labeling plant cells and animal cells toward imaging applications with negligible toxicity. We have synthesized zinc nitride (Zn3N2) colloidal nanoparticles with an average size of 25 nm at room temperature. The optical band gap of the prepared Zn3N2 nanoparticles is 2.8 eV and gives a visible range emission at 415 nm. With the addition of Zn3N2 colloids to organic dyes such as protoporphyrin, flavin adenine dinucleotide, fluorescein, and neutral red, the emission intensity of the organic dyes enhanced from 3 to 20 times. The molecular simulation and lifetime studies evidence the possibility of energy transfer from zinc nitride to organic dyes. The enhancement of dye intensity in the presence of Zn3N2 enhanced the vicinity of the cellular environment during confocal imaging of plant cells and animal cells. The detailed results suggested Zn3N2 for bioimaging and biosensor applications.

Reducing the dark current of cuprous oxide/Au schottky photodetector for high signal-to-noise ratio imaging

Photodetectors (PDs) as image sensors have been widely used in imaging system due to their outstanding photosensitivity. The improvement of imaging quality (signal-to-noise ratio (SNR)) can be realized by reducing the dark current of PDs. Conventionally, interfacial engineering can effectively suppress the dark current of PDs. Nevertheless, these techniques are hard to be applied in practical imaging systems owing to their complicated process. In this work, we proposed a facile method to reduce the dark current of Cu2O/Au Schottky PDs, and further demonstrated its application in high SNR imaging system. By applying a small external bias of −120 μV, the dark current of PDs decreases from 27 nA to 0.6 nA, with 4023% improvements of ON/OFF ratio. Additonaly, a model based on free carriers generated by rich trap-state and thermal excitation under asymmetric internal electric field was proposed to understand this phenomenon. Finally, a high-resolution image with high SNR (48 dB) was acquired, which is close to that of commercial Si-CDD and CMOS. Our results provide a convenient way to reduce the dark current and improve the image quality, also suggest Cu2O is potentially an attractive candidate to be applied in optical imaging applications.

Generation of novel partially coherent truncated Airy beams via Fourier phase processing.

We propose theoretically and numerically, for the first time, the generation of novel partially coherent truncated Airy beams (NPCTABs) with Airy-like distributions for both intensity and degree of coherence via Fourier phase processing. We demonstrate a clear link between the magnitude and frequency of intensity and degree of coherence distributions oscillations of generated beams, and the source coherence and the phase screen parameter. Thus, the source coherence and phase can serve as convenient parameters to control the intensity and degree of the coherence of NPCTABs. Furthermore, we discover that NPCTABs are more stable than the fully coherent truncated Airy beams (FCTABs) during their propagation in free space and can maintain their Airy-like profile for an extended propagation distance. The interesting and tunable characteristics of these novel beams may find applications in particle trapping, phase retrieval, and optical imaging.

Supercritical lens array in a centimeter scale patterned with maskless UV lithography.

Microlens arrays (MLAs) are widely used in optical imaging, dense wavelength division multiplexing, optical switching, and microstructure patterning, etc. However, the light modulation capability for both the conventional refractive-type MLA and planar diffractive-type MLA is still staying at the diffraction-limited scale. Here we propose and experimentally demonstrate a high numerical aperture (NA) supercritical lens (SCL) array which could achieve a sub-diffraction-limited focal spot lattice in the far field. The intensity distribution for all the focal spots has good uniformity with the lateral size around ${0.45}\lambda {\rm /NA}$0.45λ/NA (0.75X Airy unit). The elementary unit in the SCL array composes a series of concentric belts with a feature size in micrometer scale. By utilizing an ultrafast ultraviolet lithography technique, a centimeter scale SCL array could be successfully patterned within 10 mins. Our results may provide possibilities for the applications in optical nanofabrication, super-resolution imaging, and ultrafine optical manipulation.

Label-free optical imaging in developmental biology [Invited

Application of optical imaging in developmental biology marks an exciting frontier in biomedical optics. Optical resolution and imaging depth allow for investigation of growing embryos at subcellular, cellular, and whole organism levels, while the complexity and variety of embryonic processes set multiple challenges stimulating the development of various live dynamic embryonic imaging approaches. Among other optical methods, label-free optical techniques attract an increasing interest as they allow investigation of developmental mechanisms without application of exogenous markers or fluorescent reporters. There has been a boost in development of label-free optical imaging techniques for studying embryonic development in animal models over the last decade, which revealed new information about early development and created new areas for investigation. Here, we review the recent progress in label-free optical embryonic imaging, discuss specific applications, and comment on future developments at the interface of photonics, engineering, and developmental biology.

Dual-Wavelength Diffuse Optical Tomographic System for Direct Concentration Measurement

This article presents a promising dual-wavelength continuous wave (CW) diffuse optical tomography (DOT) system for direct estimation of concentrations and hemodynamic parameters for potential application in detection of rheumatoid arthritis (RA). The generalized curved-beam reconstruction technique is modified for direct estimation of hemodynamic parameters. The Rosenbrock’s function is fit to estimate the photon path as curved one followed by majority photons that enabled the use of modified Beer–Lambert law (MBLL) in differential form with assumption that unknown absorption coefficient ( $\mu _{a}$ ) varies from one path to another. The $\mu _{a}$ values are calculated and back-projected along the photon paths for image reconstruction without solving the inverse problem. Thus, stability is not an issue in image reconstruction. Also, there is no need for baseline measurement and prior information on perturbation, unlike the iterative methods used for dynamic imaging. The reconstructed images of the distal interphalangeal (DIP) and proximal interphalangeal (PIP) joints of a healthy male volunteer showed good consistency and are used for direct optical estimation of the physiological parameters. A novel application of optical imaging beyond biomedical applications is demonstrated by imaging the gradual dispersion of viscous Indian ink and glycerin mixture in turbid water with encouraging results.