Transverse Localization Research Articles

Submucosal tunneling endoscopic resection for large esophageal leiomyoma: technical aspects and risk of complications

This report demonstrates the advantages of tunnel dissection ensuring organ-sparing procedure with the best functional result. However, intra- and postoperative complications are possible after STER. The risk of complications and complexity of surgery depend on transverse size (>3.5 cm), shape and localization of tumor. Larger neoplasm is accompanied by more difficult surgery and higher risk of complications. Therefore, adequate selection of patients for STER is essential.

Review of a Decade of Research on Disordered Anderson Localizing Optical Fibers

Nearly a decade ago, transverse Anderson localization was observed for the first time in an optical fiber with a random transverse refractive index profile. This started the development of a whole new class of optical fibers that guide light, not in a conventional core-cladding setting based on total internal reflection, but utilizing Anderson localization, where light can guide at any location across the transverse profile of the fiber. These fibers have since been used successfully in high-quality endoscopic image transport. They also show interesting nonlinear and active (lasing) properties with promising applications. This review will cover a brief history of these fibers with personal accounts of the events that led to their development in our research groups. It will then follow with recent progress and future perspectives on science and applications of these fibers.

Learning-Based Image Transport Through Disordered Optical Fibers With Transverse Anderson Localization

Fiber-optic imaging systems play a unique role in biomedical imaging and clinical practice due to their flexibilities of performing imaging deep into tissues and organs with minimized penetration damage. Their imaging performance is often limited by the waveguide mode properties of conventional optical fibers and the image reconstruction method, which restrains the enhancement of imaging quality, transport robustness, system size, and illumination compatibility. The emerging disordered Anderson localizing optical fibers circumvent these difficulties by their intriguing properties of the transverse Anderson localization of light, such as single-mode-like behavior, wavelength independence, and high mode density. To go beyond the performance limit of conventional system, there is a growing interest in integrating the disordered Anderson localizing optical fiber with deep learning algorithms. Novel imaging platforms based on this concept have been explored recently to make the best of Anderson localization fibers. Here, we review recent developments of Anderson localizing optical fibers and focus on the latest progress in deep-learning-based imaging applications using these fibers.

Transverse Anderson localization of evanescent waves propagating in randomly layered media

We study theoretically the transverse Anderson localization of light in the simplest geometry, where the p-polarized wave propagates along the layers in the randomly stratified dielectric and evanesces exponentially in the direction across the layers. In this case, there exist two reasons for the localization of the wave in the direction transverse to its propagation: the usual evanescent wave confinement and the Anderson mechanism related to the randomness of the spatial distribution of permittivity. We solve the problem using the retarded-Green-function formalism in the Born approximation and show that, for fixed values of the wave frequency ω and wavenumber q, the random inhomogeneity results in the weakening of the wave localization. In the case of the surface plasmon-polaritons (SPPs) propagation, the Anderson mechanism changes the dispersion law for SPPs, moving the dispersion curves away from the light line. Therefore, the localization depth varies in different ways when increasing the disorder, depending on which of the values, wave vector q or frequency ω, is fixed. Namely, the localization depth increases for given q, but it decreases for given ω.

Transverse and Quantum Localization of Light: A Review on Theory and Experiments

Anderson localization is an interference effect yielding a drastic reduction of diffusion—including complete hindrance—of wave packets such as sound, electromagnetic waves, and particle wave functions in the presence of strong disorder. In optics, this effect has been observed and demonstrated unquestionably only in dimensionally reduced systems. In particular, transverse localization (TL) occurs in optical fibers, which are disordered orthogonal to and translationally invariant along the propagation direction. The resonant and tube-shaped localized states act as micro-fiber-like single-mode transmission channels. Since the proposal of the first TL models in the early eighties, the fabrication technology and experimental probing techniques took giant steps forwards: TL has been observed in photo-refractive crystals, in plastic optical fibers, and also in glassy platforms, while employing direct laser writing is now possible to tailor and “design” disorder. This review covers all these aspects that are today making TL closer to applications such as quantum communication or image transport. We first discuss nonlinear optical phenomena in the TL regime, enabling steering of optical communication channels. We further report on an experiment testing the traditional, approximate way of introducing disorder into Maxwell’s equations for the description of TL. We find that it does not agree with our findings for the average localization length. We present a new theory, which does not involve an approximation and which agrees with our findings. Finally, we report on some quantum aspects, showing how a single-photon state can be localized in some of its inner degrees of freedom and how quantum phenomena can be employed to secure a quantum communication channel.

Diffraction propagation of light wave and image distortionless transmission in ten-fold symmetric photonic quasicrystal lattices

Linear propagation behavior of light wave in two-dimensional ten-fold symmetric photonic quasicrystal lattices was studied numerically by using beam propagation method. The influences of structural characteristics and parameter changes of the quasicrystal lattices on the propagation and suppression of light wave diffraction are analyzed, and the results are also compared with those in periodic square lattices. We investigate the linear transverse light localization in the quasicrystal lattices without defects. The results indicate that the quasicrystal lattices are easier to achieve linear light localization than the periodic lattices. In addition, we demonstrate the distortionless transmission of light-spot images can be achieved in the quasicrystal lattices by numerical simulation. In this way, more complex light-spot images can be transmitted in photonic quasicrystal arrays which are consisting of multiple basic units of quasicrystal lattices. It has potential applications for optical information transmission and all optical signal processing.

TULUA Lipoabdominoplasty: No Supraumbilical Elevation Combined With Transverse Infraumbilical Plication, Video Description, and Experience With 164 Patients.

TULUA (transverse plication, undermining halted at umbilicus, liposuction [without restrictions], umbilicoplasty with a skin graft, and abdominoplasty with low transverse scar localization) is a fundamentally different lipoabdominoplasty technique intended to reduce the risk of vascular compromise, correct wall laxity through a unique plication, allow freedom in choosing the umbilical position, reduce tension on closure, and keep the final scar low. The objectives of this article were to describe the TULUA technique and its variations, delineate the indications and contraindications, show the expected results, and determine its safety profile. A series of 164 patients is presented. The technique's basic tenets were (1) infraumbilical wide transverse plication; (2) no undermining above the umbilicus; (3) unrestricted liposuction, including the supraumbilical tissues; (4) umbilical amputation and neoumbilicoplasty in the ideal position with a skin graft; and (5) low transverse scar placement. Complications were recorded and tabulated. Results were evaluated utilizing Salles' and the author's graded scales. Scores averaged 9.4 out of 10 on the Salles' scale and 5.6 out of 6 on the author's scale, demonstrating adequate correction of the abdominal contour and the wall and skin laxity, with properly placed scars and umbilici, and without compensatory epigastric bulging. Overall, 20% of the patients experienced a complication: 9.7% experienced a delay in either the healing or graft take of the umbilicus, 0.6% developed skin necrosis, 0.6% experienced a wound dehiscence, 2.4% had an infection, and 4.9% developed a seroma. The TULUA lipoabdominoplasty technique was found to improve abdominal wall laxity and aesthetics to a degree that is similar to traditional abdominoplasty, based on the evaluated parameters. The complications associated with the procedure are within the range of other abdominoplasty techniques, and the technique potentially has a reasonable safety profile with less risk of vascular compromise.

Numerical study of the transverse localization of waves in one-dimensional lattices with randomly distributed gain and loss: effect of disorder correlations

We study numerically the effects of short- and long-range correlations on the localization properties of the eigenstates in a one-dimensional disordered lattice characterized by a random non-Hermitian Hamiltonian, where the imaginary part of the on-site potential is random. We calculate the participation number versus strengths of disorder and correlation. In the short-ranged case and when the correlation length is sufficiently small, we find that there exists a critical value of the disorder strength, below which enhancement and above which suppression of localization occurs as the correlation length increases. In the region where the correlation length is larger, localization is suppressed in all cases. Similar behavior is obtained for long-range correlations as the disorder strength and the correlation exponent are varied. Unlike in the case of a long-range correlated real random potential, no signature of the localization transition is found in a long-range correlated imaginary random potential. In the region where localization is enhanced in the presence of long-range correlations, we find that the enhancement occurs in the whole energy band, but is strongest near the band center. In addition, we find that the anomalous localization enhancement effect occurs near the band center in the long-range correlated case.

Reciprocal skin effect and its realization in a topolectrical circuit

A system is non-Hermitian when it exchanges energy with its environment and non-reciprocal when it behaves differently upon the interchange of input and response. Within the field of metamaterial research on synthetic topological matter, the skin effect describes the conspiracy of non-Hermiticity and non-reciprocity to yield extensive anomalous localization of all eigenmodes in a (quasi) one-dimensional geometry. Here, we introduce the reciprocal skin effect, which occurs in non-Hermitian but reciprocal systems in two or more dimensions: Eigenmodes with opposite longitudinal momentum exhibit opposite transverse anomalous localization. We experimentally demonstrate the reciprocal skin effect in a passive RLC circuit, suggesting convenient alternative implementations in optical, acoustic, mechanical, and related platforms. Skin mode localization brings forth potential applications in directional and polarization detectors for electromagnetic waves.

Focal extent of scalar beams

The Andrejic focal extent measures, based on intensity, are an effective area in the focal plane, and an effective length of the focal region. The Cauchy–Schwartz inequality then provides lower bounds for both the transverse and longitudinal extents. Two families of monochromatic scalar beams, which share a tight-focus limit, are compared in their transverse and longitudinal focal extents. Both the beam families are characterized by a dimensionless parameter where is the wavenumber, and is a length. As increases from zero the transverse and longitudinal extents of both families increase monotonically. For large , the longitudinal extent becomes proportional to the length and the transverse localization is the same as for the Gaussian beam. For small , the two families have a confluent limit, the proto-beam. The Andrejic transverse extent lower bound is reached by the proto-beam, but the longitudinal extent lower bound is exceeded by the factor A hypothetical beam which reaches the longitudinal extent lower bound is shown to be non-physical.

Transverse localization of light in laser written designed disorder

Transverse Anderson localization provides the lateral confinement of electromagnetic waves in disordered systems that are invariant along the propagation direction. Here, we demonstrate a disorder induced confinement in glass microstructures where disorder is fabricated ad hoc by the femtosecond direct laser writing technique. By employing a high numerical aperture objective, we are able to write parallel arrays of tiny tubes with a refractive index higher than the surrounding glass and to arrange them in a disordered fashion in the transversal plane. We demonstrate that these paraxial scatterers are supporting transverse localization and that the confinement strength depends on the disorder properties. The proposed approach, which relies on a user-controlled positioning of individual scatterers, allows us to finely tune the structural design, maximizing the transversal confinement.

Percutaneous endoscopic transforaminal discectomy for L5~S1 disc herniation

Objective: To evaluate the clinical results of percutaneous endoscopic transforaminal discectomy (PETD) for L5~S1 lumbar disc herniation (LDH). Methods: One hundred and two cases of L5~S1 LDH from April 2016 to June 2018 were retrospectively analyzed, including 13 patients with high iliac crest. Pre-and postoperative pain was measured by Visual Analog Scale (VAS) and functional status was assessed by Oswestry Disability Index (ODI). Results: All the operations were successful and no severe complications occurred such as hemorrhages, infections, injury of nerves. The operation time was (87.6±21.0) min; the frequencies of intraoperative fluoroscopy were 29.1±11.7; the postoperative bedridden time was (4.6±1.1) hours and the hospital stay was (3.6±0.5) days. The mean VAS and ODI scores were significantly improved (P<0.01) postoperatively. The efficiency of 102 cases were excellent in 89 cases (87.3%), good in 8 cases (7.8%), fair in 4 cases (3.9%) and poor in 1 cases (1.0%). One patient (1.0%) relapsed at 6 months after surgery. Conclusions: PETD is a safe and effective method for treatment of L5~S1 LDH. The "transverse process localization method" might be an effective technique for patient with high iliac crest and/or hypertrophic transverse process.

Corrections to “Transverse Damage Localization and Quantitative Size Estimation for Composite Laminates Based on Lamb Waves”

In the above article [1] , the proposed Methods, Results, and Conclusions remain unchanged.

Subsurface Detection of Shallow Targets by Undersampled Multifrequency Data and a Non-Cooperative Source

Imaging buried objects embedded within electrically large investigation domains can require a large number of measurement points. This is impractical if long data acquisition time cannot be tolerated or the system is conceived to work at some stand-off distance from the air/soil interface; for example, if it is mounted over some flying platform. In order to reduce the number of spatial measurements, here, we propose a method for detecting and localizing shallowly buried scattering targets from under-sampled far-field data. The method is based on a scattering model derived from the equivalence theorem for electromagnetic radiation. It exploits multi-frequency data and does not require that the transmitter and receivers are synchronized, making the source non-cooperative. To provide a benchmark against which spatial data have to be reduced, first, the number of required spatial measurements is examined by analyzing the properties of the relevant scattering operator. Then, since under-sampling data produces aliasing artifacts, frequency diversity (i.e., multi-frequency data) is exploited to mitigate those artifacts. In particular, single-frequency reconstructions are properly fused and a criterion for selecting the frequencies to be used is provided. Numerical examples show that the method allows for satisfactory target transverse localization with a number of measurements that are much less than the ones required by other methods commonly used in subsurface imaging.

Kapitza light guiding in photonic mesh lattice.

We experimentally demonstrate the transverse confinement of light in the presence of a longitudinally periodic photonic potential with vanishing average. In agreement with Kapitza's original findings in classical mechanics, we confirm that light undergoes a transverse localization due to the action of an effective potential proportional to the square of the first derivative of the potential. Experiments are performed based on (1+1) D synthetic dimensions realized in a fiber loop system, allowing for complete control of the transverse and longitudinal distributions of the potential.

Effect of loss on transverse localization of light in 1D optical waveguide array in the presence of Kerr-type nonlinearity

In this paper we have comprehensive study on the interplay among radiation loss, transverse disorder (diagonal and off-diagonal) and Kerr-type nonlinearity on the light propagation in 1D array of optical waveguides. Our numerical results demonstrate the presence of three distinguished regimes of transverse light expansion at different propagation distances. At short propagation distance, the Kerr-type nonlinearity are dominated and results in the transverse localization of light through the self-trapping mechanism. Radiation loss, causes the light escape from the injected guides, affect the light expansion in middle distance via broadening the light beam width. At longer distance the disorder terms led to the transverse localization of light, again. Also, we compared the propagation of light in edge and middle modes in the presence of the above effects. Our results show that the propagation distance of first localized regime for edge modes is larger than the middle modes since the edge modes can exchange energy with one of the left or right waveguides, while for middle modes there are two ways for energy exchange. Therefore the discrete diffraction can be diminished the nonlinear effects in middle modes faster than the edge modes.

Group velocity distribution and short-pulse dispersion in a disordered transverse Anderson localization optical waveguide

Abstract We investigate the group velocity distribution of waveguide modes in the presence of disorder. The results are based on extensive numerical simulations of disordered optical waveguides using statistical methods. We observe that the narrowest distribution of group velocities is obtained in the presence of a small amount of disorder; therefore, the modal dispersion of an optical pulse is minimized when there is only a slight disorder in the waveguide. The absence of disorder or the presence of a large amount of disorder can result in a large modal dispersion due to the broadening of the distribution of the group velocities. We devise a metric that can be applied to the mode group index probability-density-function and predict the optimal level of disorder that results in the lowest amount of modal dispersion for short pulse propagation. Our results are important for studying the propagation of optical pulses in the linear regime, e.g., for optical communications; and the nonlinear regime for high-power short-pulse propagation.

Advances in the fabrication of disordered transverse Anderson localizing optical fibers [Invited

Disordered transverse Anderson localizing optical fibers have shown great promise in various applications from image transport to random lasing. Their success is due to their novel waveguiding behavior, which is enabled by the transverse Anderson localization of light. The strong transverse scattering from the transversely disordered refractive index structure results in transversely confined modes that can freely propagate in the longitudinal direction. Therefore, these fibers behave like large-core highly multimode optical fibers, with the peculiar property that most modes are highly localized. This property makes them ideal for such applications as image transport and spatial beam multiplexing. In this review paper, we will explore some of the recent advances in these fibers, especially those related to the material structure and fabrication methods.

Enhancement of the spontaneous emission rate of Rhodamine 6G molecules coupled into transverse Anderson localized modes in a wedge-type optical waveguide.

In this paper, the dynamics of the spontaneous emission rate of Rhodamine 6G dye molecules, coupled into disorder-induced optical cavities in a scattering medium, is investigated by a time-resolved spectroscopic technique. The system is a wedge-type wave-guiding system formed by a polymer with randomly positioned air inclusions. The scattering of light in the medium induces transverse Anderson localization, which gives rise to quasi-optical modes or Anderson-localized cavities. The presence of these modes strongly enhances the decay emission of the emitters. The waveguide is fabricated by a conventional fiber drawing technique inside a fused silica micro-rod. Localized optical modes are observed to appear in the form of sharp spectral resonance peaks at various frequencies throughout the photoluminescence spectrum of the dye molecules. The spontaneous emission rate of the molecules on resonance with the localized modes is measured to enhance by a factor of up to 6.8, which elucidates that the transverse Anderson localization enables an efficient way to alter the spontaneous emission rate of quantum emitters in an optically asymmetric simple wedge-type photonic waveguide, offering a moderate alternative to highly engineered sophisticated light-wave devices.

Disordered Anderson Localization Optical Fibers for Image Transport—A Review

Disordered optical fibers show novel waveguiding properties, enabled by the transverse Anderson localization of light, and are used for image transport. The strong transverse scattering from the transversely disordered refractive index structure results in transversely confined modes that can freely propagate in the longitudinal direction. In some sense, an Anderson localization disordered fiber behave like a large-core multimode optical fiber, with the advantage, that most modes are highly localized in the transverse plane, so any point in the cross section of the fiber can be used for localized beam transport. This property has been used for high-quality transportation of intensity patterns and images in these optical fibers. This review covers the basics and the history of the transverse Anderson localization in disordered optical fibers and captures the recent progress in imaging applications using these optical fibers.