Application Of Optical Tomography Research Articles

Ghost Imaging Through a Supersonic Wind‐Induced Environment Under Weak Illumination

AbstractIn airborne imaging, wind‐induced random environment severely disturbs the imaging quality. Ghost imaging (GI) shows its potential application in airborne imaging due to the natural ability of anti‐interference and imaging at low light levels, however, the influence of wind‐induced random environment on GI is non‐negligible under low‐light detection. In this paper, GI through a wind‐induced random environment under low‐light detection is experimentally and numerically investigated. The experiment is performed with a wind tunnel, and the imaging quality decreases with wind velocity and detection signal‐to‐noise ratio (SNR). The simulation model of GI under low‐light detection through this kind of environment is proposed, and simulation results match well with experiments. With the theoretical model, imaging results for the binary and grayscale object under supersonic wind region are discussed in detail, and the critical wind velocity under the influences of boundary‐layer thickness and object size are obtained. These results can find potential applications in optical imaging and can be used to estimate the effect of airflow on the imaging performance.

Thermally stable broadband near-infrared emitting pyrochlore oxide phosphors codoped with Cr3+ and Yb3+ ions

The advance of portable and smart near-infrared (NIR) light sources has sparked significant interest. However, achieving high-performance NIR emission at longer wavelengths remains a formidable challenge. In this study, we prepared broadband NIR phosphors by codoping pyrochlore oxide Y2GaSbO7 (YGSO) with Cr3+ and Yb3+ ions using a conventional high-temperature solid-state reaction. Upon excitation by blue light, YGSO: 0.03Cr3+ exhibited a broadband NIR emission centered at 765 nm with a full width at half maximum (FWHM) of 160 nm. The purposeful incorporation of Yb3+ ions facilitated efficient energy transfer from Cr3+ to Yb3+, resulting in a newly observed NIR emission peak at 970 nm. Notably, the addition of Yb3+ improved the overall thermal quenching resistance owing to its inherent thermal stability. Furthermore, we encapsulated the as-obtained phosphors with commercial blue LED chips to create prototype phosphor-converted light-emitting diodes (pc-LEDs). The Cr3+ and Cr3+-Yb3+ codoped pc-LEDs achieved output powers of 120 mW@660 mA with a photoelectric conversion efficiency of 12.66%@30 mA, and 131.7 mW@1020 mA with a photoelectric conversion efficiency of 13.93%@30 mA, respectively. These broadband NIR pc-LEDs hold promise for optical imaging applications.

A Review of in vivo Toxicity of Quantum Dots in Animal Models.

Tremendous research efforts have been devoted to nanoparticles for applications in optoelectronics and biomedicine. Over the past decade, quantum dots (QDs) have become one of the fastest growing areas of research in nanotechnology because of outstanding photophysical properties, including narrow and symmetrical emission spectrum, broad fluorescence excitation spectrum, the tenability of the emission wavelength with the particle size and composition, anti-photobleaching ability and stable fluorescence. These characteristics are suitable for optical imaging, drug delivery and other biomedical applications. Research on QDs toxicology has demonstrated QDs affect or damage the biological system to some extent, and this situation is generally caused by the metal ions and some special properties in QDs, which hinders the further application of QDs in the biomedical field. The toxicological mechanism mainly stems from the release of heavy metal ions and generation of reactive oxygen species (ROS). At the same time, the contact reaction with QDs also cause disorders in organelles and changes in gene expression profiles. In this review, we try to present an overview of the toxicity and related toxicity mechanisms of QDs in different target organs. It is believed that the evaluation of toxicity and the synthesis of environmentally friendly QDs are the primary issues to be addressed for future widespread applications. However, considering the many different types and potential modifications, this review on the potential toxicity of QDs is still not clearly elucidated, and further research is needed on this meaningful topic.

Near-Infrared-Responsive Rare Earth Nanoparticles for Optical Imaging and Wireless Phototherapy.

Near-infrared (NIR) light is well-suited for the optical imaging and wireless phototherapy of malignant diseases because of its deep tissue penetration, low autofluorescence, weak tissue scattering, and non-invasiveness. Rare earth nanoparticles (RENPs) are promising NIR-responsive materials, owing to their excellent physical and chemical properties. The 4f electron subshell of lanthanides, the main group of rare earth elements, has rich energy-level structures. This facilitates broad-spectrum light-to-light conversion and the conversion of light to other forms of energy, such as thermal and chemical energies. In addition, the abundant loadable and modifiable sites on the surface offer favorable conditions for the functional expansion of RENPs. In this review, the authors systematically discuss the main processes and mechanisms underlying the response of RENPs to NIR light and summarize recent advances in their applications in optical imaging, photothermal therapy, photodynamic therapy, photoimmunotherapy, optogenetics, and light-responsive drug release. Finally, the challenges and opportunities for the application of RENPs in optical imaging and wireless phototherapy under NIR activation are considered.

Near-infrared switch effect of polarization modulation induced by guided-mode resonance in dielectric grating

Light intensity modulation is crucial for the development of optical imaging, optical sensing, and optical switch. Light intensity modulation methods, such as changing structural parameters, external temperature, or external voltage, make the control process time consuming and complex. The plasmonic polarization modulation is an effective strategy to modulate the light intensity, but this method is limited by the excitation of surface plasmons with transverse magnetic (TM) polarized light. Herein, we report another polarization modulation method for light intensity based on guided mode resonance in a dielectric grating excited by transverse electric (TE) polarized light. The nanosystem comprises a Si grating and a TiN substrate. By adjusting the polarization states of the incident light from TE to TM, the proposed nanosystem exhibits an outstanding light intensity modulation performance with a relative modulation depth of 25833%. The presented method provides another way for modulating the light intensity, which has potential applications in optical switching, optical imaging, and optical anti-counterfeiting.

Comparisons of 3D printed materials for biomedical imaging applications

ABSTRACT In biomedical imaging, it is desirable that custom-made accessories for restraint, anesthesia, and monitoring can be easily cleaned and not interfere with the imaging quality or analyses. With the rise of 3D printing as a form of rapid prototyping or manufacturing for imaging tools and accessories, it is important to understand which printable materials are durable and not likely to interfere with imaging applications. Here, 15 3D printable materials were evaluated for radiodensity, optical properties, simulated wear, and capacity for repeated cleaning and disinfection. Materials that were durable, easily cleaned, and not expected to interfere with CT, PET, or optical imaging applications were identified.

Towards practical single-shot phase retrieval with physics-driven deep neural network.

Phase retrieval (PR), a long-established challenge for recovering a complex-valued signal from its Fourier intensity-only measurements, has attracted considerable attention due to its widespread applications in optical imaging. Recently, deep learning-based approaches were developed and allowed single-shot PR. However, due to the substantial disparity between the input and output domains of the PR problems, the performance of these approaches using vanilla deep neural networks (DNN) still has much room to improve. To increase the reconstruction accuracy, physics-informed approaches were suggested to incorporate the Fourier intensity measurements into an iterative estimation procedure. Since the approach is iterative, they require a lengthy computation process, and the accuracy is still not satisfactory for images with complex structures. Besides, many of these approaches work on simulation data that ignore some common problems such as saturation and quantization errors in practical optical PR systems. In this paper, a novel physics-driven multi-scale DNN structure dubbed PPRNet is proposed. Similar to other deep learning-based PR methods, PPRNet requires only a single Fourier intensity measurement. It is physics-driven that the network is guided to follow the Fourier intensity measurement at different scales to enhance the reconstruction accuracy. PPRNet has a feedforward structure and can be end-to-end trained. Thus, it is much faster and more accurate than the traditional physics-driven PR approaches. Extensive simulations and experiments on an optical platform were conducted. The results demonstrate the superiority and practicality of the proposed PPRNet over the traditional learning-based PR methods.

Planar liquid crystal optics for axial focus shaping with an adjustable intensity and a high efficiency.

In this Letter, we report the application of planar liquid crystal (LC) devices in axial focus shaping, proving that LC diffractive optical elements (DOEs) can achieve continuous adjustment of a symmetrical axial light field by changing the ellipticity of the incident light and can flexibly and quickly achieve various axial light field designs through an axial iterative Fourier transform algorithm. The LC DOE achieves a quasi-continuous phase and an extremely high transmittance (98.6% at 1030 nm), which makes the focusing efficiency of the LC DOE with two segments of uniform focal depths as high as 84%. The experimental results demonstrate the accurate optical field shaping effect and the axial intensity adjustable ability of LC DOE, indicating potential applications in optical tomography and precision manufacturing, among others.

Recent advances of application of optical imaging techniques for disease detection in fruits and vegetables: A review

Fruits and vegetables are among the agricultural products that enjoy a high demand in the market. However, the most critical challenge in the production of fruits and vegetables is disease infections which can lead to economic loss. The current assessment method of disease infection still relies on conventional methods and laboratory analysis. The conventional methods although simple and easy are laborious and have less accuracy while laboratory analysis is costly and time-consuming. Over the last two decades, optical imaging techniques have emerged and are gaining interest in the agricultural and food industries. These techniques offer easy, rapid, accurate, reliable as well as user-friendly sensing tools for the identification of quality and disease infection in agricultural products. The fundamental aspect in the techniques is the interaction of light with the tissue and the manipulation of light when interacting with a surface. The integration of edge computing along with artificial intelligence has also reshaped the technology to another level. The use of other agricultural technologies such as drones or robots enables real-time monitoring and efficient farm management. Thus, this paper reviews recent advances in the application of optical imaging techniques for disease detection in fruits and vegetables. This includes computer vision, multispectral imaging, hyperspectral imaging, biospeckle and thermal imaging. The feasibility of the optical imaging techniques is discussed. Challenges and considerations for future research are also highlighted. This review provides a new insight into the recent application of optical imaging which is not only beneficial for the agricultural and food industries but also to other relevant industries.

Insights into solid dosage forms with nonlinear optical imaging

Microscopic chemical and solid-state structures and their changes in solid drugs and dosage forms can profoundly affect pharmaceutical performance and patient safety. Despite this, their detailed spatially-resolved analysis can be difficult or impossible with established analytical technologies. Multimodal non-linear optical imaging represents opportunities for sensitive and specific chemical and solid-state pharmaceutical imaging. Non-linear optical imaging encompasses several nonlinear optical phenomena, including coherent anti-Stokes Raman scattering (CARS), stimulated Raman scattering (SRS), and sum frequency/second harmonic generation (SFG/SHG). Imaging in 3D with (sub)micron resolution is rapid, non-destructive, possible in situ in aqueous media, and generally does not require prior sample preparation. This mini-review explores several applications of non-linear optical imaging for solid drug and dosage form analysis.

Biomimetic Compound Eyes with Gradient Ommatidium Arrays.

Compound eyes are high-performing natural optical perception systems with compact configurations, generating extensive research interest. Existing compound eye systems are often combinations of simple uniform microlens arrays; there are still challenges in making more ommatidia on the compound eye surface to focus to the same plane. Here, a biomimetic gradient compound eye is presented by artificially mimicking dragonflies. The multiple replication process efficiently endows compound eyes with the gradient characteristics of dragonfly compound eyes. Experimental results show that the manufactured compound eye allows multifocus imaging by virtue of the gradient ommatidium array arranged closely in a honeycomb pattern while ensuring excellent optical properties and compact configurations. Thousands of ommatidia showing a gradient trend at the millimeter scale while remaining relatively uniform at the micron scale have gradient focal lengths ranging from 260 to 450 μm. This gradient compound eye allows more ommatidia to focus on the same plane than traditional uniform compound eyes, which have experimentally been shown to capture more than 1100 in-plane clear images simultaneously, promising potential applications in micro-optical devices, optical imaging, and biochemical sensing.

Dual-mode dual-band circular polarization device based on three-layer plasmonic metasurface

In this work, we proposed a three-layer metasurface with rotated gold split-rings as a polarization device that has two adjacent operating bands in two different modes. The proposed metasurface can be used as a circular polarization selector in transmission mode as well as a circular polarization converter in reflection mode. In transmission mode, it can transmit right- and left-handed circularly polarized light at the corresponding wavelengths of 2130 and 3040 nm with transmission efficiencies of 85.3% and 83.8%, respectively. In reflection mode, it can convert two types of circularly polarized light into those of the orthogonal state with conversion efficiencies of 70.3% and 77.3% in the opposite bands, respectively. The results of the theoretical calculation by transfer matrix method are consistent with these simulation results, and the current distribution results illustrate the coupling mechanism under the proposed chiral structure. In addition, the influence of parameters on circular dichroism was investigated, demonstrating the strong robustness of the structure. The proposed metasurface provides a new degree of freedom for multifunctional photonic integrated devices, which can be used for applications in optical communication and imaging.

Modulating and identifying an arbitrary curvilinear phased optical vortex array of high-order orbital angular momentum

Vortex beams can be used in optical communication, imaging, and processing applications. In this study, we generate a phased optical vortex array with high-order orbital angular momentum (OAM) based on a phased Gaussian optical array and high-order phase multiplication. We then analyze the OAM mode distribution using the OAM spectrum expansion, and the number of high-order phase singularities in the array verified in interference experiments. Our results substantiate the feasibility of generating a high-order optical vortex array using this method. At the same time, because the phase Gaussian optics array that forms the phased optical vortex array is discrete and separable, we can use the phase Gaussian optics array with different phase differences to generate the phased optical vortex array with different phase gradients. The shape of the generated optical vortex array can be arranged along any curve. The phase singularity and OAM distributions at high orders are also detailedly analyzed. The ability to control the high-order OAM and phase structure has possible applications in particle manipulation and free-space optical communication.

Cr3+-activated broadband near-infrared mechanoluminescence in garnet compound

Near-infrared (NIR) mechanoluminescence (ML) materials have been of great interest within biological tissues due to their biocompatibility and suitability for biostress imaging. However, the reported NIR MLs have predominantly been featured with narrowband ML emissions, which may limit their further applications. In this work, a novel broadband NIR ML material of Lu3Ga4.88O12:0.12Cr3+ (FWHM > 120 nm) is reported. By substituting Al3+ for Ga3+, the local crystal field strength and the defect concentration are reasonably regulated, which further improves the NIR ML (650–1000 nm) intensity of Cr3+ ion by 475 %. In addition, by compounding polydimethylsiloxane with this phosphor, the obtained Cr3+ NIR ML film can penetrate 10 mm pork tissues quite well, indicating potential applications for stress distribution optical imaging within living organisms. Expectingly, broadband NIR ML from Cr3+ ions can be obtained by further solid-solution multiple lattice sites substitution, which may provide a new approach to improve the performance of NIR ML materials towards expanded biological applications.

Naphthalimide-Dyes Bearing Phosphine and Phosphorylamide Moieties: Synthesis and Optical Properties.

1,8-Naphthalimides (NIs) represent a class of organic dyes with interesting optical properties that has been extensively explored in the last decades in lighting devices, chemosensors, optical probes or medicinal chemistry. However, despite their remarkable potential, reports on organometallic dyes bearing NIs are scarce and virtually inexistent regarding palladium(II) complexes. Herein, we report the synthesis of NIs bearing phosphine and amine chelating moieties and the characterization of their optical properties both as single molecules and when complexed on Pd(II) ions. It is shown that the introduction of phosphine moieties in the naphthalimide core results in a marked increase in non-radiative processes, leading to a significant reduction of the emission efficiency and lifetime of these dyes, compared to amine-bearing counterparts. The complexation to Pd(II) sequesters the electronic contribution of chelating moieties, with complexes assuming an optical behavior similar to that of unsubstituted 1,8-naphthalimide. The complexation significantly increases the acidity of chelating secondary amines, giving rise to an unexpected intramolecular reaction that results in the formation of a novel 1,8-naphthalimide dye bearing a cyclic phosphorylamide moiety. The new dye exhibits good emission quantum yield, long fluorescence lifetime and sensitivity to basic media, evidencing potential for application in optical imaging and sensing scenarios.

Theoretical Modeling of Plasmon Resonance Induced by Hollow Nanoshell Spheres Assisted with a Graphene Shell for Use as an Efficient Narrowband Absorber

We present theoretical modeling of the local surface plasmon resonance (LSPR) induced by hollow nanoshell spheres assisted with a graphene shell, aiming to examine their potential for use as efficient narrowband absorbers in the infrared wavelength region. We investigate two designs of hollow nanoparticles; namely, a hollow graphene nanosphere with a single graphene shell, and a hollow nanosphere with double shells comprising a graphene shell wrapped around a silver shell. The electric field in each region of the nanoshell is determined by solving the Laplace equation of the potential within the electrostatic approximation (the nanoshell radius [Formula: see text]50[Formula: see text]nm). Using the calculated polarizability of nanoshells, we derive analytical expressions for the absorption and scattering cross-sections. We show that in both proposed nanocomposite models, the graphene shell affords an ultra-narrow LSPR with an absorption efficiency significantly higher than the scattering efficiency. In addition, the graphene-assisted LSPR can be tuned through the visible and infrared regions by changing the Fermi energy and thickness of the graphene layer. Another exciting finding is that the use of a silver shell in the hollow bi-shell nanoparticles provides another LSPR peak besides that induced by the graphene shell. Both LSPRs of graphene and silver shells can be overlapped by changing the optical properties of graphene and/or the geometrical parameters of the silver shell. The resulting LSPR is characterized by a dominant absorption cross-section and a significant narrowband. In both proposed nanoshell designs, the properties of LSPRs are promising for use in various optical imaging and phototherapy applications.

1.7 μm all-fiber figure-9 mode-locked laser based on a fiber Bragg grating

Abstract Fiber lasers operating at 1.7 μm have very important applications in biomedicine, optical imaging, laser welding, optical communication and other fields because of their rich spectral characteristics in the near-infrared band. We designed and experimentally implemented a 1.7 μm all-fiber figure-9 (F9) mode-locked laser, with a fiber Bragg grating (FBG) acting as both the mirror and the spectrum filter. The all-fiber F9 design made the laser work in the mode-locking state more efficiently. We obtained mode-locked pulses with a central wavelength of 1724.76 nm and a repetition rate of 14.39 MHz when the pump power was 1.1 W, and the pulse width was about 54 ps. Limited by the bandwidth of the FBG, the 3 dB bandwidth of the mode-locked spectrum was about 0.18 nm. The output power was 52 mW at a pump power of 2.5 W. The multi-pulse dynamics were studied by adjusting the pump power and the polarization controllers, and pulse trains of up to six pulses in a group were achieved. The 1.7 μm narrow-bandwidth all-fiber F9 mode-locked laser is simple in structure and easy to build, with potential application as a seed source in high-energy ultrashort pulse lasers.

Design and optimization of broadband metamaterial absorber based on manganese for visible applications

Metamaterial absorbers have been extensively researched due to their potential applications in photonics. This paper presents a highly efficient Broadband Metamaterial Absorber (BMA) based on a Manganese–Silica–Manganese three layer structure with a shaped pattern at the top layer. For maximum absorption efficiency, the geometrical parameters of the proposed absorber have been optimized based on Particle Swarm Optimization (PSO). The optimal structure with a thickness of 190 nm, can achieve more than 94% absorption spanning visible band (400–800) nm with 98.72% average absorption, and more than 90% absorption over the range from 365 to 888 nm. In the range from 447 to 717 nm, the design presented above 99% absorptivity, providing an ultra-wide bandwidth of 270 nm. The physical mechanism of absorption is illustrated through the exploration of the electric and magnetic field distributions. Additionally, the proposed structure maintains 85% absorption stability for wide incident angles up to 70° for both the TE and TM polarizations under oblique incidence. Further, the optimized absorber structure with excellent absorption capabilities makes it suitable for various applications, including optical sensors, thermal emitters, and color imaging applications.

Design of single-mode single-circularly polarized chiral anti-resonant fiber for the communication band

We propose a design of anti-resonant fiber (ARF) involving the introduction of chiral material into the inner regions of six germanium-doped silica glass cladding tubes, which can support the operation of single-mode single left-handed circular polarization in the communication band from 1.540 to 1.605 µm. In particular, the loss reaches a minimum value of 0.009 dB m−1 at 1.550 µm. The sign of the chiral parameter can control the handedness of polarization in the operation of single-mode single-circular polarization. In addition, the ARF possesses a good bending resistance performance. The minimum bending radius of the ARF is 10 to maintain the single-mode single left-handed circular polarization for 1.550 µm. We believe the novel ARF can find applications in optical communication, polarization imaging and chiral sensing.

Optimizing crystallinity to enhance X-ray excited persistent luminescence intensity of NaLuF4: Gd/Tb nanoparticles

Lanthanide doped fluoride nanoparticles (NPs) exhibit tunable X-ray excited persistent luminescence (XEPL), which show promising applications in optical imaging, cancer therapy and information storage. Although a few progresses have been achieved in enhancing the XEPL of lanthanide activators, there is no report about the influence of crystallinity on the XEPL intensity. In this work, we verify that the XEPL intensity can be improved by optimizing the NP crystallinity. Our results reveal that better crystallinity benefit the lower non-radiative relaxation possibility but also the restriction of the formation of Frenkel defects. This work provides important information for the development of lanthanide doped fluoride nanoparticles with superior XEPL performances.