Hasil untuk "Optics. Light"

Alireza Pourafzal, Hans Daniel Kaimre, Christian Hager et al.

Vertical-cavity surface-emitting lasers (VCSELs) are the dominant light sources in short-reach optical interconnects, where cost, efficiency, and scalability are critical. However, their modulation bandwidth, output power, and signal integrity degrade markedly as ambient temperature rises and self-heating increases, making accurate device-level temperature awareness indispensable. Existing approaches rely on embedded sensors or forward-voltage monitoring, which require calibration, additional hardware, or pilot overhead, and are therefore not well suited for in-service operation. This work introduces a <italic>pilot-free</italic> and <italic>sensor-free</italic> method for inferring VCSEL operating temperature directly from payload signals. We establish, through an electro&#x2013;thermal rate-equation model, that temperature rise manifests as a systematic reduction in the entropy of the optical waveform. Leveraging this property, we develop a regression-based estimator that achieves sub-5 <inline-formula><tex-math notation="LaTeX">$^{\circ }$</tex-math></inline-formula>C accuracy in simulation. The results demonstrate that entropy-based payload analysis provides a principled and low-cost proxy for junction temperature, with potential for integration into high-speed link management.

Heng Liu, Di Yang, Renfei Jia et al.

Distinguishing the severity of burned skin from structural optical coherence tomography (OCT) intensity maps remains a challenging task, and functional imaging from an elastic perspective can improve the accuracy of burned skin examination. As a functional extension of OCT, optical coherence elastography (OCE) can reveal the mechanical properties of samples while inheriting the imaging advantages of OCT. In this study, we used OCE to reveal the shear modulus and anisotropy parameters of burned skin before and after burning. A porcine skin burn model was constructed at a series of burned time durations and tested by elastic anisotropy imaging. Normal skin after hydration maintains good consistency in shear modulus. Interestingly, the shear modulus and longitudinal modulus of the burned skin show a tendency to stepwise increase with increasing burned times. A dataset was constructed by sampling the modulus parameters of burned skin maps through a scratch window, and its category was automatically identified by K-means and density peak clustering (DPC) algorithms with good agreement. The elastic anisotropy-based skin burn assessment method shows a prospect to be supplemented into the nondestructive means of burned skin examination.

M.Y. Kurbakov, V.V. Sulimova, O.S. Seredin et al.

An important step in determining the properties of carbon materials is the analysis of images from a scanning electron microscope (SEM). These images show the material surface after the application of metal nanoparticles. The order of these nanoparticles is a key characteristic that affects the material properties. We have previously proposed an approach to formalize the order features based on the identification of lines by nanoparticles in the SEM image. This paper proposes a novel approach to line allocation that is based on the concept of constructing a minimum spanning forest. Additionally, it introduces a set of novel ordering functions that are derived from this approach. The experimental study demonstrates that the combination of these new and previously extracted features improves the recognition quality of SEM images with ordered and disordered nanoparticles arrangements. This approach allows us to gain a better understanding of the nanoparticles arrangement and their effect on the material properties.

Yuanxiang Wang, Hanwen Luo, Tian Qiu et al.

To counter heterodyne measurements, correlation attacks, and known plaintext attacks, seed key refresh is critical to the security of a quantum noise stream cipher system. Integrated key distribution is an important means to reduce the deployment cost, as key exchange and public transmission are performed over the same channel. In this paper, we propose a novel method for integrated key distribution by optical steganography based on dither-remodulation in a bias controller of the Mach-Zehnder modulator. No extra wavelength or bandwidth is used for the stealth channel, which is transmitted together within the public channel. The concealing depth of the stealth signal reaches &#x2212;36.2 dB, and its steganographic effect provides additional security, which further improves the overall security of the optical physical layer. The bidirectional stealth transmission can support light-weight temporary key exchange mechanism, combined with asymmetric encryption algorithm, to achieve high security and forward&#x002F;backward security of seed keys. We experimentally demonstrate a real-time integrated key distribution via optical steganography in a QNSC system. The experimental results show that a real-time bidirectional stealth link is established at a rate of 1 kbps in a fiber transmission distance of 97 km for a public QNSC transmission at a rate of 32 Gbps, providing a seed key refresh frequency of over 1 Hz.

Junaid Khan, Matiullah Khan, Waqar Uddin et al.

Titanium dioxide (TiO2) has attracted much attention because of their desirable physicochemical properties especially in the water splitting process. In this work pure and Fe-doped TiO2 compounds are studies theoretically with the help of Generalized Gradient Approximation with the revised Pardew–Burke–Ernzerh (RPBE) exchange–correlation scheme. Total Density of States (TDOS) and Partial Density of States (DOS) were analyzed in detail which show that iron (Fe) and oxygen (O) orbitals hybridize, especially in the region of the doping system conduction band minima for both modes. Additionally, this interaction produces an energy level that effectively reduces the bandgap of the adsorbed system. Optical properties were elucidated which shows that Fe-doped TiO2 system results in high absorption and photoconductivity. Moreover, the results demonstrate low bandgap energy which is suitable for the reduction in water splitting without the need for external energy. Magnetic properties demonstrated that Fe-doped TiO2 systems show very low diamagnetic responses. The calculated elastic properties of Fe-doped TiO2 indicate ductile nature of the material with a strong average bond strength. Fe-doped TiO2 exhibited less microcracks with a mechanically stable composition.

Xiang Zhang, Jiajun Luo, Enguo Chen et al.

Abstract Hybrid tandem perovskite-organic LED has been developed to achieve high external quantum efficiency, narrow linewidth, and extended device lifespan, which shows great promise for future perovskite-EL-based commercial applications.

Yujie Miao, Lin Zhang, Dimeng Chen et al.

Broadband vortex arrays distributed in 2D n × n vortices are extremely needed for multiple microparticle manipulation, high‐capacity optical communication, and quantum information. Vortex arrays are usually generated with spatial light modulators, metamaterials; it is a big challenge to improve beam quality and output power. Herein, crisscross 2D n × n vortex arrays are converted from petal‐like Raman lasers with an astigmatic mode convertor. Efficient petal‐like lasers in the form of the Laguerre–Gaussian mode with zero radial index and l azimuthal index (LG0,l ) are irradiated in a Raman microchip laser (RML) by adjusting optimal beam waist and locating the position of focus spot of the annular pump beam. High‐beam‐quality LG0,9 petal‐like Raman laser oscillating at broadband wavelength (bandwidth: 16.2 nm) is generated with power of 773 mW and an efficiency of 10.6%. The conversion efficiency from petal‐like laser to crisscross vortex array is as high as 90%. The vortex array with 5 × 5 vortices operating around 1078 nm is generated with a power of 693 mW and an optical efficiency of 9.5%. Taking advantages of the broad emission spectrum of ytterbium‐doped laser materials and stimulated Raman scattering effect, RMLs are potential sources for generating flexible vortex arrays with desired 2D n × n vortices oscillating in Raman wavelengths.

Vasilisa E. Anikeeva, Kirill N. Boldyrev, Olga I. Semenova et al.

Vibrational and structural properties have an enormous influence on optoelectronic properties of hybrid halide perovskites CH3NH3PbX3 (X = I, Br, Cl), which are perspective materials for different photovoltaic applications. Here, we report results of the first high-resolution optical spectroscopy measurements of large CH3NH3PbBr3 single crystals in wide frequency (20–20 000 cm−1) and temperature (5–300 K) ranges. Fit of polarized far-infrared reflection spectra using Lorentz model of damped oscillators revealed parameters of three phonons at room temperature and 38 phonons at 10 K. An analysis of mid-infrared transmission spectra gave evidence of a strong anharmonicity in this hybrid perovskite. A splitting of some lines observed in the orthorhombic phase was presumably assigned to the tunneling of the CH3NH3+ cation molecule between several potential energy minima. The temperature behavior of the transmission spectra near the fundamental absorption edge was tentatively explained by the competition between two different exciton transitions in CH3NH3PbBr3. Positions of spectral lines and of the absorption edge measured at cooling and heating the sample demonstrate hysteresis loops in the vicinities of phase transitions around 237, 155, and 149 K, thus revealing the first-order nature of all three phase transitions in CH3NH3PbBr3.

Yuefeng Zhao, Jinxin Ding, Yong Han et al.

The spatiotemporal distributions and physical–optical properties of aerosols are of great scientific significance for the study of climate change and atmospheric environment. What are the characteristics of aerosols in constant high humidity? Continuous wet weather (CWW) is a special weather phenomenon that occurs frequently during the late winter and early spring in South China. In this study, the CALIPSO satellite data and the ERA5 and MERRA-2 reanalysis data are used to analyze the aerosol optical properties of a total of 68 CWW processes from 2012 to 2021 in the Guangdong–Hong Kong–Macau Greater Bay Area (GBA). We attempt to explore the variations in meteorological conditions and physical–optical properties of aerosols during the before-stage, wet-stage, and after-stage under different humidity levels. The results show that the prevailing wind direction is northeasterly and that the temperature and humidity are lower under the influence of cold high pressure in the before-stage. Moreover, the high aerosol optical depth (AOD) mainly results from regional transport. During the wet-stage, clean ocean airflow causes AOD to remain at a low level, whereas temperature and humidity increase significantly. The wet-stage ends with coldness when it is controlled by cold high pressure again. The atmospheric circulation in the after-stage is similar to that in the before-stage. However, a remarkable feature is that there is a temperature and humidity inversion layer, which results in a significant increase in AOD. This study reveals the physical–optical properties of aerosols during the three stages and the influence mechanism of meteorological factors on aerosols, which can provide a scientific basis for the study of CWW in the future.

Dongwei Li, Weiming Wang, Song Gao et al.

Optical self-healing is a repairing phenomenon of a beam in the propagation, as it is perturbed by an opaque object. In this work, we demonstrate experimentally and theoretically that the moiré distributed dual-microlens array enables to generate optical fields with better healing ability to withstand defects than their counterparts of a single microlens array. By utilizing the double parameter scanning method, the self-healing degree of the optical field is significantly affected by both the interval distance and the relative angle of the dual-microlens arrays. The self-healing level is decreased significantly by lengthening the interval between the two microlens array with a small twist angle, while increasing the angle enhances the self-healing degree. Further study manifests the self-healing process with respect to the size and central location of the obstacle. The research results provide a simple and effective method to generate self-healing optical wave fields, which have potential applications including optical communication, assisted imaging technology, and even intense laser physics.

Kashif Ammar Yasir, Lin Zhuang, Wu-Ming Liu

Abstract We investigate topological nonlinear optics with spin-orbit coupled Bose-Einstein condensate in a cavity. The cavity is driven by a pump laser and a weak probe laser. Both lasers excite Bose-Einstein condensate, in the presence of standard Raman process for spin-orbit coupling, to an intermediate storage level. We theoretically show that the quantum interference at the transitional pathways of dressed atomic states results in different types of optical transparencies, which get completely inverted in atomic damping induced gain regime. The synthetic pseudo-spin states also implant different phases in the probe field forcing modes in probe transparencies to form gapless Dirac cones, which become gapped in presence of Raman detuning. These features get interestingly enhanced in gain regime where the amplified part of probe transparencies appear as gapless topological edge-like states between the probe bulk modes and cause non-trivial phase transition. We illustrate that the nonlinear interactions of the pseudo-spin states also enhance the slow light features in probe transmission. The manipulation of dressed states for topological optical transparencies in our findings could be a crucial step towards topological photonics and their application in quantum computation.

Yachao Liu, Guo Ping Wang, John B. Pendry et al.

A robust negative index flat lens which collects all energy launched from the source is constructed with the ideal photonic Weyl metamaterials.

Xiaofan Xie, Yunfei Li, Gong Wang et al.

The anti-reflection properties of hard material surfaces are of great significance in the fields of infrared imaging, optoelectronic devices, and aerospace. Femtosecond laser processing has drawn a lot of attentions in the field of optics as an innovative, efficient, and green micro-nano processing method. The anti-reflection surface prepared on hard materials by femtosecond laser processing technology has good anti-reflection properties under a broad spectrum with all angles, effectively suppresses reflection, and improves light transmittance/absorption. In this review, the recent advances on femtosecond laser processing of anti-reflection surfaces on hard materials are summarized. The principle of anti-reflection structure and the selection of anti-reflection materials in different applications are elaborated upon. Finally, the limitations and challenges of the current anti-reflection surface are discussed, and the future development trend of the anti-reflection surface are prospected.

Ludwig Kunz, Marcin Jarzyna, Wojciech Zwoliński et al.

We consider a communication scenario where classical information is encoded in an ensemble of quantum states that admit a power series expansion in a cost parameter and converge to a single zero cost state with vanishing cost. For a given measurement scheme, we derive an approximate expression for mutual information in the leading order of the cost parameter. The general results are applied to selected problems in optical communication, where coherent states of light are used as input symbols and the cost is quantified as the average number of photons per symbol. We show that for an arbitrary individual measurement on phase shift keyed (PSK) symbols, the photon information efficiency is upper bounded by 2 nats of information per photon in the low-cost limit, which coincides with the conventional homodyne detection bound. The presented low-cost approximation facilitates a systematic analysis of few-symbol measurements that exhibit superadditivity of accessible information. For the binary PSK alphabet of coherent states, we present designs for two- and three-symbol measurement schemes based on linear optics, homodyning, and single photon detection that offer respectively 2.49% and 3.40% enhancement relative to individual measurements. We also show how designs for scalable superadditive measurement schemes emerge from the introduced low-cost formalism.

Sergej Orlov, Christian Huber, Christian Huber et al.

The knife-edge method is an established technique for profiling of even tightly focused light beams. However, the straightforward implementation of this method fails if the materials and geometry of the knife-edges are not chosen carefully or, in particular, if knife-edges are used that are made of pure materials. Artifacts are introduced in these cases in the shape and position of the reconstructed beam profile due to the interaction of the light beam under study with the knife. Hence, corrections to the standard knife-edge evaluation method are required. Here we investigate the knife-edge method for highly focused radially and azimuthally polarized beams and their linearly polarized constituents. We introduce relative shifts for those constituents and report on the consistency with the case of a linearly polarized fundamental Gaussian beam. An adapted knife-edge reconstruction technique is presented and proof-of-concept tests are shown, demonstrating the reconstruction of beam profiles.

William Hease, Alfredo Rueda, Rishabh Sahu et al.

Microwave photonics lends the advantages of fiber optics to electronic sensing and communication systems. In contrast to nonlinear optics, electro-optic devices so far require classical modulation fields whose variance is dominated by electronic or thermal noise rather than quantum fluctuations. Here we demonstrate bidirectional single-sideband conversion of X band microwave to C band telecom light with a microwave mode occupancy as low as 0.025±0.005 and an added output noise of less than or equal to 0.074 photons. This is facilitated by radiative cooling and a triply resonant ultra-low-loss transducer operating at millikelvin temperatures. The high bandwidth of 10.7MHz and total (internal) photon conversion efficiency of 0.03% (0.67%) combined with the extremely slow heating rate of 1.1 added output noise photons per second for the highest available pump power of 1.48 mW puts near-unity efficiency pulsed quantum transduction within reach. Together with the non-Gaussian resources of superconducting qubits this might provide the practical foundation to extend the range and scope of current quantum networks in analogy to electrical repeaters in classical fiber optic communication.

Long Jin, Zhiqiang Yang, Qiang Zhang

In this paper, we deduce the paraxial analytical expression for the Gaussian beam propagating in the sandwich slab system which contained double negative material based on light transfer matrix and generalized Huygens-Fresnel integral equation; the evolution properties of emerging Gaussian beam contour graph intensity distribution on the receiver plane, the relation between beam spot size and negative refractive index coefficient, and beam side transmission view in slab system changed with three negative refractive index parameters are illustrated through numerical examples. What is more, we propose a ring resonator sensor to measure the concentration of NaCl solution on the basis of above theory, of which the operating principle is deliberatively analyzed, the influence of the concave mirror curvature radius on the emerging beam evolution is acquired, the functional relation between the normalized central intensity of the emerging beam, the beam spot size, and NaCl solution concentration is further developed by fit linear method, and the mathematical statistics results reach high precision and linearity. It is expected that the proposed ring resonator sensor and the corresponding conclusions can be useful for precise optical measurement, especially for food safety inspection and medical services of health care.

Azusa Inoue, Yasuhiro Koike

We develop a graded-index plastic optical fiber (GI POF) that can significantly stabilize a multimode fiber (MMF) link with a vertical-cavity surface-emitting laser (VCSEL) subject to external optical feedback. It is demonstrated that the dominant mechanism for this stabilization effect is the strong mode coupling of the GI POF, which is closely related to the polymer-specific microscopic heterogeneities in the GI POF core material. Such mode coupling decreases correlation between the problematic reflected light field and VCSEL cavity field, increasing tolerance of the MMF link for external optical feedback. Our developed GI POF with specific microscopic heterogeneities prevents the external-optical-feedback-induced critical destabilization observed for silica GI MMFs. These results suggest that the stabilization effect can be controlled by microscopic properties regardless of the fiber attenuations and core refractive indices.

D. Pierce, R. Celotta, Gwo-Ching Wang et al.

Huaizhou Jin, Qipeng Lu, Shangzhong Jin et al.

The Raman spectra of human blood serum can be used to identify cancer or other diseases; however, obtaining a reliable surface enhanced Raman scattering (SERS) signal of human blood serum is difficult. Two primary factors that affect SERS measurement of serum are photodegradation and sample composition, which are investigated in this research. In the end, this research proposes a promising set of measurement conditions that can both acquire reliable serum Raman signals and avoid photodegradation.