Photonics

We propose a wide-field-of-view near-eye display featuring a dual-channel waveguide with cholesteric liquid crystal gratings. Our dual-channel waveguide is capable of splitting the field of view through the orthogonal polarization division multiplexing. To explain its mechanism, a diagram of k-domain, which factors into both the waveguide size and the number of pupils, is depicted. Our results demonstrate that the diagonal field of view reaches up to 80°, eye relief is 10 mm, exit pupil is 4 × 3 mm², and uniformity is 79%. Full article

In this work, we tested a new approach to assess the presence of inflammatory process in the implant area using spectral methods and the technique of fiber fluorescence analysis of photosensitizers in nanoform. First of all, the spectral characteristics of the photosensitizer when interacting with the porous surface of the implant, based on hydroxyapatite under in vitro and in vivo conditions, were determined. Thus, it was shown that spectral characteristics of photosensitizers can be used for judgement on the process of inflammation in the implant area and thus on the local presence of the immunocompetent cells. The analysis was performed at a sufficient depth in the biotissue by using the near-infrared spectral region, as well as two different methods: fiber-based laser spectroscopy and fiber-optic neuroscopy, which served to monitor the process and regular fluorescence diagnosis of the studied area. Fluorescence spectroscopic analysis was performed on experimental animals in vivo, i.e., under conditions of active immune system intervention, as well as on cell cultures in vitro in order to judge the role of the immune system in the interaction with the implant in comparison. Thus, the aim of the study was to determine the relationship between the fluorescence signal of nanophotosensitizers in the near infrared spectral region and its parameters with the level of inflammation and the type of surface with which the photosensitizer interacts in the implant area. Thus, fiber-optic control opens up new approaches for further diagnosis and therapy in the implant area, making immune cells a prime target for advanced therapies. Full article

An Optical Burst Switching (OBS) network is vulnerable to Burst Header Packet (BHP) flooding attack. In flooding attacks, edge nodes send BHPs at a high rate to reserve bandwidth for unrealized data bursts, which leads to a waste of bandwidth, a decrease in network performance, and massive data loss. Machine learning techniques are utilized to detect this attack in the OBS network. In this paper, we propose a particle swarm optimization–support vector machine (PSO-SVM) model for detecting BHP flooding attacks, in which the PSO is used to optimize the parameters of the SVM. We use the dataset provided by the UCI warehouse to train and test the model. The experimental results show that the detection accuracy of the PSO-SVM model reaches 95.0%, which is 9.4%, 9.6%, 20.7%, 8% higher than naïve Bayes, SVM, k-nearest neighbor, and decision tree. Although DCNN outperforms our model, it requires more processing and training time. Collectively, our approach is effective and high-efficiency in detecting flooding attacks in optical burst switching networks and maintaining network stability and security. Full article

We study the chaos and hyperchaos of Rydberg-dressed Bose–Einstein condensates (BECs) in a one-dimensional optical lattice. Due to the long-range, soft-core interaction between the dressed atoms, the dynamics of the BECs are described by the extended Bose-Hubbard model. In the mean-field regime, we analyze the dynamical stability of the BEC by focusing on the ground state and localized state configurations. Lyapunov exponents of the two configurations are calculated by varying the soft-core interaction strength, potential bias, and length of the lattice. Both configurations can have multiple positive Lyapunov exponents, exhibiting hyperchaotic dynamics. We show the dependence of the number of the positive Lyapunov exponents and the largest Lyapunov exponent on the length of the optical lattice. The largest Lyapunov exponent is directly proportional to areas of phase space encompassed by the associated Poincaré sections. We demonstrate that linear and hysteresis quenches of the lattice potential and the dressed interaction lead to distinct dynamics due to the chaos and hyperchaos. Our work is relevant to current research on chaos as well as collective and emergent nonlinear dynamics of BECs with long-range interactions. Full article

The tremendous development of both optical wireless communications (OWC) and implantable medical devices (IMDs) has recently enabled the establishment of transdermal optical wireless (TOW) links that utilize light waves to transfer information inside the living body to the outside world and conversely. Indeed, numerous emerging medical applications such as cortical recording and telemetry with cochlear implants require extremely high data rates along with low power consumption that only this new technology could accommodate. Thus, in this paper, a typical TOW link is investigated in terms of outage capacity which is a critical performance metric that has so far not been evaluated for such wireless systems in the open technical literature. More precisely, an outage capacity analysis is performed considering both skin-induced attenuation and stochastic spatial jitter, i.e., pointing error effects. Analytical expressions and results for the outage capacity are derived for a variety of skin channel conditions along with varying stochastic pointing errors which demonstrate the feasibility of this cross-field cooperation. Lastly, the corresponding simulation outcomes further validate our suggestions. Full article

By coherently combining advantages while largely avoiding limitations of two mainstream platforms, optical hybrid entanglement involving both discrete and continuous variables has recently garnered widespread attention and emerged as a promising idea for building heterogenous quantum networks. In contrast to previous results, here we propose a new scheme to remotely generate hybrid entanglement between discrete polarization and continuous quadrature optical qubits heralded by two-photon Bell-state measurement. As a novel nonclassical light resource, we further use it to discuss two examples of ways—entanglement swapping and quantum teleportation—in which quantum information processing and communications could make use of this hybrid technique. Full article

Sustainable development of the agricultural industry, in particular, the production of milk and feed for farm animals, requires accurate, fast, and non-invasive diagnostic tools. Currently, there is a rapid development of a number of analytical methods and approaches that meet these requirements. Infrared spectrometry in the near and mid-IR range is especially widespread. Progress has been made not only in the physical methods of carrying out measurements, but significant advances have also been achieved in the development of mathematical processing of the received signals. This review is devoted to the comparison of modern methods and devices used to control the quality of milk and feed for farm animals. Full article

The Young’s modulus and internal friction are two important parameters of materials. Self-mixing interferometry (SMI) is an emerging non-destructive sensing method that has been employed for various applications because of its advantages of simple structure, ease of alignment and high resolution. Some recent works have proposed the use of SMI technology to measure the Young’s moduli and/or internal frictions by measuring the resonance frequencies and damping factors of specimen vibrations induced by impulse excitation. However, the measurement results may be affected by frequencies of SMI fringes, and the implementation requires extra signal processing on SMI fringes. In this work, we developed an all-fiber SMI system without SMI fringes to measure the Young’s modulus and internal friction simultaneously. Simulations and experiments were carried out to verify the feasibility of the proposed method. Two specimens of brass and aluminum were tested. The experimental results show that the standard deviations of Young’s moduli for brass and aluminum are 0.20 GPa and 0.14 GPa, and the standard deviations of internal frictions are $4.0\times {10}^{-5}$ and $5.4\times {10}^{-5}$, respectively. This method eliminates the influences of the SMI fringe frequency on the resonant frequency and requires no signal processing on SMI fringes, contributing to its simplicity as a method for the measurement of the Young’s modulus and internal friction. Full article

Polylactide foaming as the key stage in laboratory preparation of highly porous biocompatible matrices used as scaffold prototypes was monitored based the effect of dynamic light scattering in expanding polylactide foams. Intensity fluctuations of scattered laser radiation in the course of foam expansion were analyzed using ensemble-averaged estimates of the speckle lifetime within a running window in the time domain. It was found that, in contrast to the commonly used correlation time of intensity fluctuations, the values of the average speckle lifetime are invariant with respect to the type of dynamics of phase fluctuations of partial components in scattered radiation. This makes it possible to relate this parameter to microscopic mobility of interphase boundaries in the foam in the absence of a priori information on the law of motion relating these boundaries at the microscopic level. The proposed approach in combination with the developed phenomenological model describing the relationship between the average speckle lifetime and the current values of the foam volume, as well as its first-time derivative made it possible to interpret the features of foam structure formation. Full article

Geometrical optics approximation is a classic method for calculating the optical trapping force on particles whose sizes are larger than the wavelength of the trapping light. In this study, the effect of the lens misalignment on optical force was analyzed in the geometrical optics regime. We used geometrical optics to analyze the influence of off-axis placement and the tilt of the lens on the trapping position and stiffness in an optical trap. Numerical calculation results showed that lens tilting has a greater impact on the optical trap force than the off-axis misalignments, and both misalignments will couple with each other and cause a shift of the equilibrium point and the asymmetry of the optical trap stiffness in different ways. Our research revealed the asymmetry in optical traps caused by lens misalignment and can provide guidance for optimize lens placement in future experiments. Full article

A versatile sensing scheme for gas and biomolecule detection has been proposed theoretically using optimized GaP/Au/Graphene/Silicon structures. A Gallium Phosphide (GaP) prism is used as a substrate in the proposed surface plasmon resonance based sensing scheme, which is designed to be in Kretschmann configuration. The thicknesses of different constituent layers have been optimized for the maximum values of the sensitivities of the gas and bio-sensing probes. To delineate the role of the silicon layer, sensing probes without a silicon layer have also been numerically modelled and compared. The present GaP/Au/Graphene/Silicon probes possess higher values of sensitivity for the detection of gas and biomolecules compared to the conventional SPR sensing probes reported in the literature. Full article

The polarization degree of objects in the marine background are affected by infrared radiation from sea surface. Taking into account the radiation coupling effect (RCE), a degree of linear polarization (DoLP) model is deduced. The DoLP of painted aluminum plates at different observation angles are simulated. The simulation results show the trend of the DoLP of the object decreases first and then increases as the observation angle ${\theta }_O$, with the minimum value at ${\theta }_O={53}^{\circ }$. Nevertheless, we get a monotonically increasing trend and the minimum value is at ${\theta }_O=0^{\circ }$ without considering RCE. The experimental results accord closely with those of the simulation with RCE. This conclusion is useful for the polarization detection and identification of infrared objects in the marine background. Full article

With the wide application of lidar in the future, the problem of crosstalk between lidars will become more serious. True random coding photon counting lidar with high anti-crosstalk ability will play an important role in solving this problem. In this paper, based on the working principle of Gm-APD, the detection probability theoretical model of true random coding photon counting lidar is built, and the impact of jitter on detection probability is considered for the first time. The influence of mean echo photon number, mean pulse count density, sequence length and pulse width on detection probability is analyzed. Monte Carlo simulation and experimental results are highly consistent with the theoretical model, which proves the correctness of the detection probability theoretical model. This theoretical model provides an effective means to evaluate the system performance. Full article

Quantum key distribution (QKD) has gained a lot of attention over the past few years, but the implementation of quantum security applications is still challenging to accomplish with the current technology. Towards a global-scale quantum-secured network, satellite communications seem to be a promising candidate to successfully support the quantum communication infrastructure (QCI) by delivering quantum keys to optical ground terminals. In this research, we examined the feasibility of satellite-to-ground QKD under daylight and nighttime conditions using the decoy-state BB84 QKD protocol. We evaluated its performance on a hypothetical constellation with 10 satellites in sun-synchronous Low Earth Orbit (LEO) that are assumed to communicate over a period of one year with three optical ground stations (OGSs) located in Greece. By taking into account the atmospheric effects of turbulence as well as the background solar radiance, we showed that positive normalized secure key rates (SKRs) up to $3.9\times {10}^{-4}$ (bps/pulse) can be obtained, which implies that satellite-to-ground QKD can be feasible for various conditions, under realistic assumptions in an existing infrastructure. Full article

In this study, we developed a remote gamma-ray spectroscopy system based on a fiber-optic radiation sensor (FORS) that is composed of an inorganic scintillator coated with reduced graphene oxide (RGO) and a plastic optical fiber (POF). As a preliminary experiment, we measured the transmitted light intensities using RGO membranes of different thicknesses with different wavelengths of emitted light. To evaluate the FORS performance, we determined the optimal thickness of the RGO membrane and measured the amounts of scintillating light and gamma energy spectra using radioactive isotopes such as ⁶⁰Co and ¹³⁷Cs. The amounts of scintillating light from the RGO-coated inorganic scintillators increased, and the energy resolutions of the gamma-ray spectra were enhanced. In addition, the gamma-ray energy spectra were measured using different types of RGO-coated inorganic scintillators depending on the lengths of the POFs for remote gamma-ray spectroscopy. It was expected that inorganic scintillators coated with RGO in FORS can deliver improved performance, such as increments of scintillating light and energy resolution in gamma-ray spectroscopy, and they can be used to identify nuclides remotely in various nuclear facilities. Full article

Optical gain and optical losses are separately measured in commercial laser diodes by simple analysis of spectral and electrical characteristics, and with no special specimen preparation or handling. The aim is to bring device analysis, for characterization and reliability purposes, closer to the intimate physical processes that rule over laser diode operation. Investigation includes resonating and non-resonating optical cavities. Full article

Phase retrieval utilizing Fourier amplitudes plays a significant role in image recovery. Iterative phase retrieval algorithms have been developed to retrieve phase information that cannot be recorded by detectors directly. However, iterative algorithms face the problem of being trapped in local minima due to the nonconvexity of phase retrieval, and most existing works addressed this by optimizing in multiple runs parallelly to improve the possibility that one of these could reach the global minimum. Alternatively, we propose in this work to increase the probability of reaching the global minimum with one arbitrary initial distribution by adapting simulated annealing in the standard hybrid input-output (HIO) algorithm. Numerical and experimental results demonstrate that the proposed method reconstructs images with mean square errors 50.12% smaller than those reconstructed by HIO. More importantly, the proposed method can be applied to any HIO-based algorithm with multiple runs to further improve the performance. Full article

The optical properties of biological systems can be measured by imaging and microscopy methodologies. The use of X-rays, γ-radiation and electron microscopy provides information about the contents and functions of the systems. The need to develop imaging methods and analyses to measure these optical properties is increasing. On the other hand, biological samples are easily penetrated by a high-energy input, which has revolutionized the field of tissue optical properties and has now reached a point where light can be applied in the diagnosis and treatment of diseases. To this end, developing methodologies would allow the in-depth study of optical properties of tissues. In the present work, we review the literature focusing on optical properties of biological systems and tissues. We have reviewed the literature for related articles on biological samples’ optical properties. We have reported on the theoretical concepts and the applications of Monte Carlo simulations in the studies of optical properties of biological samples. Optical properties of biological samples are of paramount importance for the understanding of biological samples as well as for their applications in disease diagnosis and therapy. Full article

The primary focus of this review article mainly emphasizes the light absorption enhancement for various nanostructured gratings assisted metal-semiconductor-metal photodetectors (MSM-PDs) that are so far proposed and developed for the improvement of light capturing performance. The MSM-PDs are considered as one of the key elements in the optical and high-speed communication systems for applications such as faster optical fiber communication systems, sensor networks, high-speed chip-to-chip interconnects, and high-speed sampling. The light absorption enhancement makes the MSM-PDs an ideal candidate due to their excellent performances in detection, especially in satisfying the high-speed or high-performance device requirements. The nano-grating assisted MSM-PDs are preordained to be decorous for many emerging and existing communication device applications. There have been a significant number of research works conducted on the implementation of nano-gratings, and still, more researches are ongoing to raise the performance of MSM-PDs particularly, in terms of enhancing the light absorption potentialities. This review article aims to provide the latest update on the exertion of nano-grating structures suitable for further developments in the light absorption enhancement of the MSM-PDs. Full article