Light Energy Flow Research Articles

Topological Structures of Energy Flow: Poynting Vector Skyrmions.

Topological properties of energy flow of light are fundamentally interesting and may introduce novel physical phenomena associated with directional light scattering and optical trapping. In this Letter, skyrmionlike structures formed by Poynting vectors are unveiled in the focal region of two pairs of counterpropagating cylindrical vector vortex beams in free space. The appearance of local phase singularities, and the distinct traveling and standing wave modes of different field components passing through the focal spot lead to a Néel-Bloch-Néel transition of Poynting vector skyrmion textures along the light propagating direction. By shaping the wave front of the incident beams with patterned amplitudes, the topological invariant of the Poynting vector skyrmions can be further tuned in a prospective area. This work expands the family of optical skyrmions and holds great potential in energy flow associated applications.

Photosystem II Tolerance to Excess Zinc Exposure and High Light Stress in Salvia sclarea L.

High light (HL) intensity has a substantial impact on light energy flow and partitioning within photosynthetic apparatus. To realize the impact of HL intensity on zinc (Zn) tolerance mechanisms in clary sage (Salvia sclarea L., Lamiaceae) plants, we examined the effect of the altered chlorophyll and nutrient uptake under excess Zn supply on the response mechanism of photosystem II (PSII) photochemistry. Eight-week-old clary sage plants were treated with 5 μM Zn (control) or 900 μM Zn in Hoagland nutrient solution. Leaf elemental analysis for Zn, Mn, Mg, and Fe was performed by inductively coupled plasma mass spectrometry (ICP-MS), whereas PSII functioning under HL was evaluated by chlorophyll fluorescence imaging analysis. Exposure of S. sclarea plants to 900 μM Zn increased leaf Zn accumulation and decreased leaf Mg and chlorophyll. The decreased non-photochemical quenching (NPQ) provided evidence of the photoprotection offered by the smaller light-harvesting antennae due to the reduced chlorophyll. The increased Mn after Zn exposure corresponded with higher efficiency of the oxygen-evolving complex (OEC) that was significantly correlated with the maximum efficiency of photosystem II (PSII) photochemistry (Fv/Fm). An increased electron transport rate (ETR) coincided with increased leaf Fe, which is known to play a vital role in the enzymes engaged in ETR. The decreased (32%) NPQ after an 8-day exposure to Zn caused an increased (10%) quantum yield of non-regulated energy loss in PSII (ΦNO), indicative of an increased singlet oxygen (1O2) production. It is suggested that the decreased NPQ induced acclimation responses of clary sage plants to HL and excess Zn by increasing 1O2 production. The reduced (18%) excess excitation energy (EXC) at PSII and the increased (24%) quantum yield of PSII photochemistry (ΦPSII) and ETR indicated improved photosynthetic efficiency under excess Zn and HL intensity. Therefore, the exposure of medicinal plants to excess Zn not only boosts their photosynthetic efficiency, enhancing crop yields, but can also improve Fe and Zn content, ameliorating the human health deficiency of these two essential micronutrients.

Band-division utilization of core-shell photocatalyst under condenser solar-light and enhancement of synergistic catalytic CO2 reduction

The synergistic effect of intrinsic photoelectrons and thermal effects, provided by intermediate- and long-wave solar energy, is considered as the linchpin in enhancing photo-thermal catalytic CO2 reduction performance. Recently, photocatalysts possessing photothermal conversion capabilities and photocatalytic systems with adjustable incident light energy flow density have garnered significant attention. The strong condensing property of the Fresnel lens was adopted in increasing the density of incident photoelectrons simultaneously, and raising the surface temperature of the photocatalyst significantly without an external heat source. A novel core–shell photocatalyst with the photothermal conversion effect was fabricated, consisting of amorphous TiO2 and CuxO active species on Fe3O4@SiO2 core. Under optimal incident energy flux density of 3200 mW cm−2, the photocatalyst was able to reduce CO2 to CO and CH4 with the production rate of 361.39 and 70.84 μmol g−1h−1, and the solar conversion efficiency reached 1.43 %. Furthermore, a simple reaction kinetic optimization based on Langmuir-Hinshelwood model well simulated the photothermal coupling effect under different incident energy flux densities. This work demonstrates an innovative technology for the full-spectrum utilization of photocatalysts and synergistic photothermal coupling catalysis. It proposes a future development scenario for the new field of efficient solar catalytic conversion to produce solar fuels.

Tunable heterostructural prism for planar polaritonic switch

The study of phonon polaritons in van der Waals materials at the nanoscale has gained significant attention in recent years due to its potential applications in nanophotonics. The unique properties of these materials, such as their ability to support sub-diffraction imaging, sensing, and hyperlenses, have made them a promising avenue for the development of new techniques in the field. Despite these advancements, there still exists a challenge in achieving dynamically reversible manipulation of phonon polaritons in these materials due to their insulating properties. In this study, we present experimental results on the reversible manipulation of anisotropic phonon polaritons in α-MoO3 on top of a VO2 film, a phase-change material known for its dramatic changes in dielectric properties between its insulating and metallic states. Our findings demonstrate that the engineered VO2 film enables a switch in the propagation of polaritons in the mid-infrared region by modifying the dielectric properties of the film through temperature changes. Our results represent a promising approach to effectively control the flow of light energy at the nanoscale and offer the potential for the design and fabrication of integrated, flat sub-diffraction polaritonic devices. This study adds to the growing body of work in the field of nanophotonics and highlights the importance of considering phase-change materials for the development of new techniques in this field.

LOCAL PROCESSING OF NON-METAL MATERIALS WITH CONCENTRATED ENERGY FLOW

In the present study, the peculiarities of local heat treatment with a concentrated light energy flow of non-metallic materials are traced. Mathematical dependences are presented for determining the surface density of the absorbed power - W(r), the thermal power - Po, and other characteristics in case of local thermal impact on the surface of non-metallic materials with a concentrated light energy flow.

Transverse energy flow in an optical Skyrmionic Hopfion.

The energy flow of light represents a natural way of investigating complex light fields with respect to their applicability. With the generation of a three-dimensional Skyrmionic Hopfion structure in light, which is a topological 3D field configuration with particle-like nature, we paved the way to employ optical, topological constructs. In this work, we present an analysis of the transverse energy flow in the optical Skyrmionic Hopfion, showing the transfer of the topological properties to the mechanical attributes such as the optical angular momentum (OAM). Our findings thus prepare topological structures to be applied in optical traps and data storage or communication.

Calculation of lateral optical energy flow in bound modes in organic light-emitting diodes

We investigate the lateral energy flow of light bound to an OLED (i.e., light that cannot be coupled to the substrate or air mode), with a focus on the attenuation characteristics. A methodology is developed for approximating the total bound field as a superposition of the individual guided modes constructed from multilayer eigenmodes with complex wave vectors. The field distribution and surface energy flow density obtained from our approximate expressions are found to be well matched to those calculated using the Green’s function formalism. The method presented in this study provides mode-based interpretation of the surface energy flow density versus distance characteristics, and can be used in designing OLEDs for applications where the optical energy transported by the bound field is of interest. • The complex photonic band structure of an OLED is calculated. • The bound-mode field of an OLED is constructed from eigenmodes with complex wave vectors. • The attenuation characteristics of the surface energy flow density are quantitatively described.

Light intensity imbalance in 2D magnetic photonic crystals with a real number in off-diagonal components of a dielectric tensor

Magneto-optical effects are caused by parameters of the off-diagonal components in the dielectric tensor of materials, which is a complex number. Because the real parts of off-diagonal components rotate the photo-induced polarization in the materials from the direction of the incident light electric field, the parts must become one of the effective parameters for light energy flow control in photonic crystals. In this study, we theoretically proposed a mechanism to realize light intensity imbalance to the left and right by inverting the sign of the real parts for 2D magnetic photonic crystals based on a finite-difference time-domain simulation and photonic band calculations. Our analyzes reveal that the maximal intensity peaks of light magnetic field distributions rotate ∼60∘ around the hole of the crystal at the Γ point in the Brillouin zone, and these rotations are caused by the real parts. The imbalance is caused by the deflections of light energy flow owing to the rotation, which are explained based on the following two mechanisms: the walk-off phenomenon and uneven bifurcation. Furthermore, the proposed mechanism was experimentally confirmed by observing the imbalance in the scattered light intensity from the surface of rough-cutting magnetic photonic crystals fabricated from a cerium-substituted yttrium iron garnet. The results of this study serve as a foundation for the development of light energy flow control by engineering photonic crystals using the real part of the off-diagonal components in dielectric tensors.

Subwavelength generation of orientation-unlimited energy flow in 4π microscopy.

Manipulation of light energy flow within the tight focus not only is important to the fundamental study of light-matter interactions but also underpins significant practical applications. However, the coupling between the electric and the magnetic fields of a focused light beam sets a fundamental barrier for independent control of these field components, restricting the focal energy flow primarily in the axial direction. In this paper, a 4π microscopic configuration is theoretically proposed to untangle the tight relation between the electric field and the magnetic field in a subwavelength-scale focal voxel. By independently altering the amplitudes of different field components in the focal region, energy flow with three-dimensionally unlimited orientation and ultra-high orientation purity (more than 90%) can be generated. This result expands the flexibility of energy flow manipulations and holds great potential in nanophotonics such as light scattering and optical force at subwavelength dimensions.

High performance electrochromic supercapacitors powered by perovskite-solar-cell for real-time light energy flow control

Electrochromic devices (ECDs) can alter their optical transmittances under external electrical power but are unable to spontaneously modulate the light flow in real-time along with the intensity change of surrounding light. To address this problem, a module of smart perovskite solar cell (PSC)-powered all-in-one gel ECDs was reported. The PSC-powered ECDs could modulate their transmittance swiftly in visible-infrared regions, hence regulating the photo energy flow in real time according to the surrounding light intensity. The ECD based on 4, 4′-(thiophene- 2, 5-diyl)bis(1-ethylpyridin-1-ium) diiodide (TEV) showed large optical contrast (79.7% at 570 nm, 64.9% at 908 nm), excellent coloration efficiency (231.2 cm2/C), and outstanding stability (only 1.1% ΔT change after 60,000 cycles). The PSC-powered ECDs showed fast response time (≤5 s) and high stability (negligible degradation after 5000 s consecutive switching between bright and dark conditions in air). Meanwhile, the stored power accompanied with the electrochromic process could drive a red LED with high cyclic stability (95.6% of areal capacitance maintained after 10,000 charging-discharging cycles), indicating that ECDs can serve as ideal electrochromic supercapacitors (ECSs). In addition, the fabricated ECD with large area (5.0 cm × 5.4 cm) showed excellent thermal regulation (7 °C of temperature difference between colored and bleached states). We expect this work would pave a new way to save energy and improve energy efficiency in modern buildings and automobiles.

Mechanism of formation of an inverse energy flow in a sharp focus

A reverse energy flow is theoretically demonstrated to occur in the interference pattern generated by four plane waves with linear polarization. In some regions of the interference pattern, the right-handed triplets of plane-wave vectors k $({k}_{z}g0)$, E, and H (comprising a wave vector and $\mathbf{E}$- and H-field vectors) sum up to form an electromagnetic field described by a right-handed triplet of vectors k $({k}_{z}l0)$, E, and H. It is in these regions that the negative propagation of light occurs. On the optical axis the orbital energy flow, proportional to the light intensity, is shown to be positive, while the spin flow is negative and exceeds the orbital flow in magnitude. That is why the on-axis summary energy flow is negative. The magnitude of the reverse flow on the optical axis is two times lower than that of the intensity. A similar mechanism may apply to the case of sharply focusing a laser beam with second-order polarization or phase singularity. Using two identical micro-objectives with a numerical aperture of 0.95, it has been demonstrated experimentally that the intensity on the optical axis near the focus of an optical vortex with a topological charge of 2 is zero for right circular polarization and nonzero for left circular polarization. This confirms that in the latter case there is the reverse flow of light energy on the optical axis, since in the center of the measured energy flow distribution there is a very weak local maximum (the Arago spot) aroused due to diffraction of the forward flow by a circle with a diameter of 300 nm (the diameter of the tube with the reverse flow). Comparing the numerical and experimental intensity distributions, it is possible to determine the diameter of a ``tube'' with the reverse flow. For a numerical aperture of 0.95 and a wavelength of 532 nm, the diameter of the tube of the reverse flow along the optical axis is 300 nm. It is also shown experimentally that when an optical beam with second-order cylindrical polarization is focused with a numerical aperture of 0.95, there is a circularly symmetric energy flow in the focus with a very weak flow in the center (the Arago spot), whose distribution is determined by diffraction of the forward flux by an $\ensuremath{\sim}300$-nm-diameter circular area, where the energy flow is reverse. This also confirms that in the latter case, there is a reverse energy flow on the optical axis.

Vortex energy flow in the tight focus of a non-vortex field with circular polarization

Using Richards-Wolf formulas, we show that an axisymmetric circularly polarized vortex-free field can be focused into a sharp subwavelength focal spot, around which there is a region where the light energy flow propagates along a spiral. This effect can be explained by the conversion of the spin angular momentum of the circularly polarized field into the orbital angular momentum near the focus, although the on-axis orbital angular momentum remains zero. It is also shown that a linearly polarized optical vortex with topological charge 2 forms near the focal plane an on-axis reverse energy flow (defined by the negative longitudinal component of the Poynting vector) whose amplitude is comparable with the direct energy flow.

Visualizing the Energy Flow of Tailored Light

AbstractExploiting the energy flow of light fields is an essential key to tailor complex optical multistate spin and orbital angular momentum (OAM) dynamics. With this work, the energy flow is identified and quantified by a novel approach that is based on the symmetry breaking induced by nonlinear light–matter interaction of OAM carrying beams at the example of Mathieu beams, showing transverse invariant intensity distributions. These complex scalar nondiffracting beams exhibit outstanding transverse energy flows on elliptic paths. Although their energy is continuously redistributed during linear propagation in homogeneous media, the beams stay nondiffracting. This approach to visualize the energy flow of light is based on the nonlinear self‐action in a nonlinear crystal. By this, the sensitive equilibrium is perturbed and accumulation of rotating high‐intensity spots is enabled. Intensity distributions on elliptic, chiral paths are demonstrated as a manifestation of the energy flow. Furthermore, the formation of corresponding refractive index modulations that may be implemented as chiral waveguides, is controlled via the beam power and structure size.

Angular momentum density of a circularly polarized paraxial optical vortex

We obtain general analytic expressions for the angular momentum density of a vectorial circularly polarized paraxial optical vortex. It is shown that for any vortex field with the rotational symmetry and circular polarization, an effect of the “angular tractor” takes place, which means that the flow of light energy rotates around the optical axis clockwise or counter-clockwise at different radii in the beam cross section. It is also shown that on the circles of these radii in the beam cross section, the axial component of the angular momentum density of the vortex light field changes its sign. Thus, microparticles trapped in the vortex beam at different radii will rotate either clockwise or counterclockwise.

Influence of the variation potential on photosynthetic flows of light energy and electrons in pea.

Local damage (mainly burning, heating, and mechanical wounding) induces propagation of electrical signals, namely, variation potentials, which are important signals during the life of plants that regulate different physiological processes, including photosynthesis. It is known that the variation potential decreases the rate of CO2 assimilation by the Calvin-Benson cycle; however, its influence on light reactions has been poorly investigated. The aim of our work was to investigate the influence of the variation potential on the light energy flow that is absorbed, trapped and dissipated per active reaction centre in photosystem II and on the flow of electrons through the chloroplast electron transport chain. We analysed chlorophyll fluorescence in pea leaves using JIP-test and PAM-fluorometry; we also investigated delayed fluorescence. The electrical signals were registered using extracellular electrodes. We showed that the burning-induced variation potential stimulated a nonphotochemical loss of energy in photosystem II under dark conditions. It was also shown that the variation potential gradually increased the flow of light energy absorbed, trapped and dissipated by photosystem II. These changes were likely caused by an increase in the fraction of absorbed light distributed to photosystem II. In addition, the variation potential induced a transient increase in electron flow through the photosynthetic electron transport chain. Some probable mechanisms for the influence of the variation potential on the light reactions of photosynthesis (including the potential role of intracellular pH decrease) are discussed in the work.

Wireless Communication with Nanoplasmonic Data Carriers: Macroscale Propagation of Nanophotonic Plasmon Polaritons Probed by Near-Field Nanoimaging.

The ability to control the energy flow of light at the nanoscale is fundamental to modern communication and big-data technologies, as well as quantum information processing schemes. However, since photons are diffraction-limited, efforts of confining them to dimensions of integrated electronics have so far proven elusive. A promising way to facilitate nanoscale manipulation of light is through plasmon polaritons-coupled excitations of photons and charge carriers. These tightly confined hybrid waves can facilitate compression of optical functionalities to the nanoscale but suffer from huge propagation losses that limit their use to mostly subwavelength scale applications. With only weak evidence of macroscale plasmon polaritons, propagation has recently been reported theoretically and indirectly, no experiments so far have directly resolved long-range propagating optical plasmons in real space. Here, we launch and detect nanoscale optical signals, for record distances in a wireless link based on novel plasmonic nanotransceivers. We use a combination of scanning probe microscopies to provide high resolution real space images of the optical near fields and investigate their long-range propagation principles. We design our nanotransceivers based on a high-performance nanoantenna, Plantenna, hybridized with channel plasmon waveguides with a cross-section of 20 nm × 20 nm, and observe propagation for distances up to 1000 times greater than the plasmon wavelength. We experimentally show that our approach hugely outperforms both waveguide and wireless nanophotonic links. This successful alliance between Plantenna and plasmon waveguides paves the way for new generations of optical interconnects and expedites long-range interaction between quantum emitters and photomolecular devices.

Increase the absorption plasm and the flow of light energy in ultra-thin films gaas solar nano-structured metal

The silicon thin film solar cells in the visible region, The low absorption which reduces its efficiency. The use of metallic nanostructures help, to increase light absorption and reduce the size of the entire structure will be. The process of light absorption in solar cells is one of the factors in improving the performance of solar cells. Silicon thin film solar cells, in the visible region, the absorption is low. Using arrays of metallic nanostructures, Semiconductors such as silicon or germanium on, Radiation absorption, a significant amount used in the top layer. Metal nanostructures for their ability to excite PLASMONS, (Collective oscillations of free electrons) are being considered. PLASMONS, surface electromagnetic waves, They are strictly limited to the field level, And that's why the border field strength is high, As a result, the surface PLASMON excitation, Square in the vicinity of heavily reinforced silicon and thus the absorption of light, The silicon layer is increased significantly. Keyword: Plasmon light energy; NANO-structured metal

Graphene plasmonic lens for manipulating energy flow

Manipulating the energy flow of light is at the heart of modern information and communication technologies. Because photons are uncharged, it is still difficult to effectively control them by electrical means. Here, we propose a graphene plasmonic (GP) lens to efficiently manipulate energy flow by elaborately designing the thickness of the dielectric spacer beneath the graphene sheet. Different from traditional metal-based lenses, the proposed graphene plasmonic lens possesses the advantages of tunability and excellent confinement of surface plasmons. It is found that the proposed lens can be utilized to focus and collimate the GP waves propagating along the graphene sheet. Particularly, the lens is dispersionless over a wide frequency range and the performance of lens can be flexibly tuned by adjusting the bias voltage. As an application of such a lens, the image transfer of two point sources with a separation of λ0/30 is demonstrated.

Investigate the Method on Measurement Transparence of Tissue Engineered Cornea

With the development of construction tissue engineered cornea by using biomaterials and seed cells,how to measurement transparence of tissue engineered cornea need to be solved. Purpose of the paper is bringing forward a new method to measurement transparence of tissue engineered cornea. According to the definition of corneal transparence, a beam of light is divided into equal two beams of light by spectroscope. In which a beam of light pass through cornea. Ratio of light energy flow that light passed cornea and the other one is calculated. The usual optical and measuring instruments were used, such as sensors for illumination and Data acquisition (DAQ) card. The real-time measuring device for corneal transparence is designed and implemented. The method and device are effective to real-time measurement of tissue engineered cornea transparence through the elements analysis and experiment.

Ultrabroadband nonreciprocal transverse energy flow of light in linear passive photonic circuits

Using a technique, analogous to coherent population trapping in an atomic system, we propose schemes to create transverse light propagation violating left-right symmetry in a photonic circuit consisting of three coupled waveguides. The frequency windows for the symmetry breaking of the left-right energy flow span over 80 nm. Our proposed system only uses linear passive optical materials and is easy to integrate on a chip.