Application Of Optical Tomography Research Articles

Ghost imaging influenced by a supersonic wind-induced random environment.

Near field airflow induced by wind is an important factor influencing imaging quality when the imaging system is placed on a moving platform with high speed, such as airborne imaging. In this Letter, ghost imaging through an airflow environment is experimentally and numerically investigated. The experiment is performed with a wind tunnel, and imaging quality decreases with wind velocity. The simulation model of ghost imaging through this kind of environment is proposed, and simulation results match well with experiments. With the model, imaging results are extended into the supersonic wind region with the effects of airflow factors discussed in detail, and a comparison between airflow and atmosphere turbulence is presented. The results can find potential applications in optical imaging and may be a powerful tool to estimate the effect of airflow on performance of the imaging system.

Intensity-based holographic imaging via space-domain Kramers–Kronig relations

Holography is a powerful tool to record waves without loss of information that has benefited optical, X-ray and electronic imaging applications by quantifying phase delays induced by light–matter interactions. However, holographic imaging is technically demanding in that it generally requires an interferometric setup, a coherent source and long-term stability. Here, we present holographic imaging in which a phase image is obtained directly from a single intensity measurement in oblique illumination. Our approach is based on space-domain Kramers–Kronig relations that transform the spatial variation in intensity to the spatial variation in phase. We demonstrate two-dimensional holographic imaging and three-dimensional refractive index tomography of microscopic objects and biological specimens from intensity images measured with an optical microscope and illumination control. The proposed method does not require iterative processes nor strict constraints and opens up a new approach to non-interferometric holographic imaging in various spectral regimes. An intensity-based holographic imaging via space-domain Kramers–Kronig relations is presented, allowing the phase image of an object to be obtained directly from a single intensity measurement with oblique illumination.

Far field superlensing inside biological media through a nanorod lens using spatiotemporal information

Far field superlensing of light has generated great attention in optical focusing and imaging applications. The capability of metamaterials to convert evanescent waves to propagative waves has led to numerous proposals in this regard. The common drawback of these approaches is their poor performance inside strongly scattering media like biological samples. Here, we use a metamaterial structure made out of aluminum nanorods in conjunction with time-reversal technique to exploit all temporal and spatial degrees of freedom for superlensing. Using broadband optics, we numerically show that this structure can perform focusing inside biological tissues with a resolution of λ/10. Moreover, for the imaging scheme we propose the entropy criterion for the image reconstruction step to reduce the number of required optical transducers. We propose an imaging scenario to reconstruct the spreading pattern of a diffusive material inside a tissue. In this way super-resolution images are obtained.

All-Dielectric Synthetic-Phase Metasurfaces Generating Practical Airy Beams.

Accelerating optical beams exhibit exotic features, such as nondiffractive propagation, self-acceleration, and self-healing, which have led their use in a wide range of photonics applications. However, spatial light modulator-based generators of such beams suffer from narrow operational bandwidth, high cost, low diffraction efficiency, and limited integration capability. Although recent metasurface-based approaches have yielded generators with significantly improved bandwidths and integration capacities, the resultant devices usually have ultrashort working distances and limited control over characteristic beam parameters, which decreases their utility in optical imaging and manipulation applications. Herein, we describe a synthetic-phase metasurface-based approach that overcomes these problems and increases the degrees of freedom to enable effective control of beam parameters by integrating a cubic phase profile and the phase of a Fresnel holographic lens into a single metasurface. We demonstrate this approach by using the synthetic metasurface to generate a series of Airy beams with controllable focal length (i.e., working distance), narrowed beam width, and extended propagation distance. Crucially, these beam parameters are fully adjustable, which makes these focal-length-modifiable Airy beams particularly appealing for use in high-resolution, large field-of-view imaging, and deep-penetration optical manipulation. Furthermore, we show that imposing the phase of a Dammann grating into a synthetic metasurface generates a 1 × 4 array of Airy beams that exhibit the aforementioned optical properties. These findings suggest that synthetic-phase metasurfaces may significantly broaden the application of accelerating optical beams in various fields, such as light-sheet microscopy, super-resolution stochastic optical-reconstruction microscopy, laser fabrication, and parallel processing and in the development of optical tweezers for use with live samples.

Fabry-Perot cavity enhanced three-photon luminescence of atomically thin platinum diselenide.

Two-dimensional materials, such as transition metal dichalcogenides (TMDs), exhibit intriguing physical properties that lead to both fundamental research and technology development. The recently emerged platinum diselenide (PtSe2), as a new member of the TMDs, has attracted increasing attention because of its good air stability, large refractive index and high electron mobility. However, being atomically thin significantly hinders its interaction with light, severely limiting the spontaneous or stimulated linear and nonlinear emission. Particularly, its nonlinear up-converted emission has not been fully exploited yet. Here, we experimentally observed the distinct enhancement of nonlinear up-converted luminescence of CVD-grown PtSe2 atomic layers on a SiO2/Si substrate with the assistance of the Fabry-Perot cavity resonance. The laser irradiance dependent luminescence study reveals the three-photon process of this nonlinear emission for the first time. Compared with non-resonant excitation, the luminescence enhancement can be up to six times because of the optical interference induced local field enhancement at the excitation wavelength. Leveraging this three-photon luminescence, nonlinear optical imaging and encryption were demonstrated for exploring information security applications. These results will pave the way for integrating nonlinear optical devices with the PtSe2 2D material.

Enzyme-activated probes in optical imaging: a focus on atherosclerosis.

Enzyme-activated probes enable complex biological processes to be studied in real-time. A wide range of enzymes are modulated in diseases, including cancer, inflammatory diseases and cardiovascular disease, and have the potential to act as vital diagnostic and prognostic biomarkers to monitor and report on disease progression. In this perspective article, we discuss suitable design characteristics of enzyme-activated fluorescent probes for ex vivo and in vivo optical imaging applications. With a particular focus on atherosclerosis imaging, we highlight recent approaches to report on the activity of cathepsins (K and B), matrix metalloproteinases (MMP-2 and MMP-9), thrombin, heme oxygenase-1 (HO-1) and myeloperoxidase (MPO).

Online simulation to monitor multiphase flow using laser source as transmitter

This research presents an application of optical tomography for the detection of gas bubbles flowing in a liquid medium. In order to visualise the material inside the pipeline, parallel beam projection had been selected. However, while producing the image, some constraints such as diffraction and reflection in liquid medium will happen, where it will affect the flow accuracy of the result. Therefore, a laser source is used to produce a better image resolution. The column is exposed to a homogeneous light beam and then the ray is detected with the use of optical wave guided detectors. By using parallel projection for 44 laser transmitters and photodiode receivers at the cross-sectional boundary, the existence of bubbles inside a vertical column pipeline is determined. The voltage drop at the sensor directly shows the existence of bubbles between the transmitter and receiver. Linear Back-projection (LBP) is the algorithm that is used to reconstruct the image in real-time. In conclusion, the technique of using parallel beam projection with a laser source can improve the image quality in liquid phase and enables the percentage size of bubbles to be determined.

Three-dimensional nonlinear optical holograms

The three-dimensional holography technique offers an efficient and convenient tool for storing depth information of the object and provides more realistic images compared to the two-dimensional case, which has been widely used in the fields of optical tweezers, image encryption, and optical microscopy. However, such a three-dimensional nonlinear holography technique is still lacking in the field of nonlinear optics. Here, we demonstrate the realization of three-dimensional nonlinear optical holograms. Without loss of generality, a second-order nonlinearity is used in our experiment and the generated second harmonic with multiplane patterns at different depths is dynamically realized. This study opens up the field of three-dimensional spatial nonlinear harmonic manipulation and may have applications in all-optical wave-band three-dimensional optical imaging, parallel micromachining, holographic displays, and so on.

Microscopic phase reconstruction of cervical exfoliated cell under partially coherent illumination.

Basic coherent diffraction imaging methods strongly rely on having a highly coherent illumination in order to reconstruct the phase accurately. However, regardless of considering the turbulent transport medium, the instability of the system or the generation mechanism of the light source, partially coherent illumination is more common in real case. In this paper, we proposed an efficient microscopic phase imaging method to study normal and abnormal cervical exfoliated cells. By applying three phase modulations in a single point of the sample's transmitted field, the phase can be retrieved with correspoding three intensities under partially coherent illumination. Compared with intensity map, we can efficiently and clearly judge the proportion of high density shrinking abnormal cells from the phase distributions, which provides a confident analysis and evaluation basis for early medical diagnosis of cervical cancer. This study also has potential applications in noninvasive optical imaging of dynamic biological tissues.

Versatile Multimodality Imaging System Based on Detectorless and Scanless Optical Feedback Interferometry-A Retrospective Overview for A Prospective Vision.

In this retrospective compendium, we attempt to draw a “fil rouge” along fifteen years of our research in the field of optical feedback interferometry aimed at guiding the readers to the verge of new developments in the field. The general reader will be moved at appreciating the versatility and the still largely uncovered potential of the optical feedback interferometry, for both sensing and imaging applications. By discovering the broad range of available wavelengths (0.4–120 μm), the different types of suitable semiconductor lasers (Fabry–Perot, distributed feedback, vertical-cavity, quantum-cascade), and a number of unconventional tenders in multi-axis displacement, ablation front progression, self-referenced measurements, multispectral, structured light feedback imaging and compressive sensing, the specialist also could find inspirational suggestions to expand his field of research.

A simple Mie-resonator based meta-array with diverse deflection scenarios enabling multifunctional operation at near-infrared

Abstract Deflection, a basic functionality of wavefront manipulation is usually associated with the phase-gradient metasurfaces and the classical blazed gratings. We numerically and experimentally demonstrate an unusually wideband and simultaneously wide-angle deflection achieved at near-infrared in reflection mode for a periodic (nongradient), ultrathin meta-array comprising only one silicon nanorod (Mie resonator) per period. It occurs in the range where only the first negative diffraction order and zero order may propagate. Deflection serves as the enabler for multifunctional operation. Being designed with the main goal to obtain ultra-wideband and wide-angle deflection, the proposed meta-array is also capable in spatial filtering and wide-angle splitting. Spatial filtering of various types can be obtained in one structure by exploiting either deflection in nonzero diffraction orders, or the specular-reflection (zero-order) regime. Thus, the role of different diffraction orders is clarified. Moreover, on–off switching of deflection and related functionalities is possible by changing polarization state of the incident wave. The suggested device is simple to fabricate and only requires cost-effective materials, so it is particularly appropriate for the large-area fabrication using nanoprint lithography. Ultra-wideband wide-angle and other deflection scenarios, along with the other functionalities, are promising for applications in optical communications, laser optics, sensing, detection, and imaging.

Patterned growth of β-Ga2O3 thin films for solar-blind deep-ultraviolet photodetectors array and optical imaging application

Solar-blind deep-ultraviolet (DUV) photodetectors based on Ga2O3 have attracted great attention due to their potential applications for many military and civil purposes. However, the development of device integration for optoelectronic system applications remains a huge challenge. Herein, we report a facile method for patterned-growth of high-quality β-Ga2O3 thin films, which are assembled into a photodetectors array comprising 8 × 8 device units. A representative detector exhibits outstanding photoresponse performance, in terms of an ultra-low dark current of ∼0.62 pA, a large Ilight/Idark ratio exceeding 104, a high responsivity of ∼0.72 A W−1 and a decent specific detectivity of ∼4.18 × 1011 Jones, upon 265 nm DUV illumination. What is more, the DUV/visible (250/400 nm) rejection ratio is as high as 103 with a sharp response cut-off wavelength at ∼280 nm. Further optoelectronic analysis reveals that the photodetectors array has good uniformity and repeatability, endowing it the capability to serve as a reliable DUV light image sensor with a decent spatial resolution. These results suggest that the proposed technique offers an effective avenue for patterned growth of β-Ga2O3 thin films for multifunctional DUV optoelectronic applications.

Controllable laser output of high-quality cylindrical vector beam through intra-cavity mode conversion

We experimentally demonstrate the controllable laser output of cylindrical vector (CV) beams, which feature flexibility, high efficiency, and good beam quality. Particularly, the CV laser beams have negligible radial components, distinguishing themselves from the extra-cavity-generated CV beams. The output state is controlled by an intra-cavity vortex half-wave plate (VWP). By changing the topological charge (l) of VWP, we produce l = 1 and l = 2 CV beams for example. Through rotating the half-wave plate inside the cavity, the laser outputs arbitrary CV beams around the equator of the corresponding high-order Poincaré spheres. For l = 1 and l = 2 CV beams, the polarization purities are as high as 97.8% and 96.7%, the sloping efficiencies are 15.5% and 5.4%, and the beam quality factors are 2.10 and 3.31, respectively. Our result provides a reliable CV laser source for advanced applications in optical imaging and optical manipulation.

Generation of subdiffraction longitudinal bifoci by shaping a radially polarized wave

Lenses with two or more foci along the longitudinal direction exhibit immense potential in several optical applications. In this study, we propose an approach for generating subdiffraction longitudinal bifoci by binary-phase bifocal super-oscillatory lenses (SOLs), which are realized by simple AND operation between two single-foci SOLs with different focal lengths. Three bifocal SOLs with radiusRlens=70λ are designed at an operating wavelength of λ=118.8µm. Simulation results demonstrate that the minimum full width at half maximum (FWHM) is 0.397λ, and the maximum FWHM is 0.449λ, which is still smaller than the Abbe diffraction limit of 0.510λ, while all the sidelobe ratios are small (<15.1%). By properly choosing the focal length of the single-foci SOLs in the design process, the distance between the two foci can be easily controlled. Significantly, the generated bifoci with relatively uniform intensity contain a strong longitudinal electric field, which indicates their excellent prospects in optical imaging, particle acceleration, and other optical applications. In addition, the proposed bifoci-SOLs are based on the binary phase modulation, which facilitates easy fabrication compared with other approaches. These outstanding properties indicate the wide application prospects of bifocal SOLs.

Perspective on optical imaging for functional assessment in musculoskeletal extremity trauma surgery.

.Significance: Extremity injury represents the leading cause of trauma hospitalizations among adults under the age of 65 years, and long-term impairments are often substantial. Restoring function depends, in large part, on bone and soft tissue healing. Thus, decisions around treatment strategy are based on assessment of the healing potential of injured bone and/or soft tissue. However, at the present, this assessment is based on subjective clinical clues and/or cadaveric studies without any objective measure. Optical imaging is an ideal method to solve several of these issues.Aim: The aim is to highlight the current challenges in assessing bone and tissue perfusion/viability and the potentially high impact applications for optical imaging in orthopaedic surgery.Approach: The prospective will review the current challenges faced by the orthopaedic surgeon and briefly discuss optical imaging tools that have been published. With this in mind, it will suggest key research areas that could be evolved to help make surgical assessments more objective and quantitative.Results: Orthopaedic surgical procedures should benefit from incorporation of methods to measure functional blood perfusion or tissue metabolism. The types of measurements though can vary in the depth of tissue sampled, with some being quite superficial and others sensing several millimeters into the tissue. Most of these intrasurgical imaging tools represent an ideal way to improve surgical treatment of orthopaedic injuries due to their inherent point-of-care use and their compatibility with real-time management.Conclusion: While there are several optical measurements to directly measure bone function, the choice of tools can determine also the signal strength and depth of sampling. For orthopaedic surgery, real-time data regarding bone and tissue perfusion should lead to more effective patient-specific management of common orthopaedic conditions, requiring deeper penetrance commonly seen with indocyanine green imaging. This will lower morbidity and result in decreased variability associated with how these conditions are managed.

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.