In this study, simulated by using Finite-Difference Time-Domain method, and applied to spin-coating titanium dioxide (TiO2) solution onto the indium tin oxide (ITO) conductive glass films, and gold nanoparticles (AuNPs) are modified on the TiO2 glass films by using self-assembly method. The sensing element is immersed in five different concentrations of glucose solution, including 0 mg/dl, 50 mg/dl, 100 mg/dl, 150 mg/dl and 200 mg/dl. The results show that the resonance wavelength λSPR was shifted by changing the polarization state of the incident light for the purpose of copper ion (Cu2+) concentration sensing.
Toroidal moment, induced by currents flowing on the surface of a torus, plays an important role in the fundamental physics of light-matter interaction. However, natural toroidal response was usually overlooked due to weak interaction with other electromagnetic resonances. Recently, toroidal moments can be effectively excited in artificial metamaterial by utilizing complex nanostructures or special light sources. Here, we have proposed periodic amorphous silicon cylinders embedded in spin-on-glass layer that can successfully generate transverse toroidal dipole (TD) in optical regime under normal incident illumination. Both experimental and simulation results indicate that such TD mode sustains a large structural tolerance and can be spectrally tuned by stretching the cylindrical axis perpendicular to the light polarization. In addition, the excited TD mode also displays ultrahigh refractive index sensitivity. This approach provides a simple and straightforward way to implement TD metamaterials and serves a powerful platform for high-sensitivity biosensors and nonlinear optics.
In this study, the pseudospectral time-domain (PSTD) simulation technique is employed to model light propagation through a virtual chicken cornea tissue model. We construct a collagen-rich stromal layer model and simulate light impinging upon it. The transmittance through the cornea at different wavelengths is acquired. Factors that may affect optical transparency are explored and investigated. Simulation findings of this research may provide essential information that contribute to chicken cornea transparency.
In this research, the finite-difference time-domain (FDTD) simulation technique is employed to analyze the optical characteristics of the following creatures: Morpho menelaus, Euprymna scolopes, Dynastes hercules, Hoplia coerulea, and Paracheirodon innesi. The layered geometries are simulated to decipher the effect on color appearances, including: thickness of the periodic layered structure, spacing between layers and the number of layers. Furthermore, we compare the biological structures of various creatures; research findings suggest that the color appearances may be accounted for by the specific geometrical nanostructure.
We employ the pseudospectral time-domain (PSTD) simulation to model light propagation through a cluster of dielectric cylinders and investigate the transmission of light. Specifically, we model light propagation through a cornea-like geometry vs. a sclera-like geometry. Simulations show that due to light wave interference, light can be transmitted through a cluster geometry, or, it can be blocked by the cluster geometry, depending on the specific geometrical structure. We explore factors that may contribute to this phenomenon; the simulation findings may provide essential information to analyze this problem.
We report an effective approach to analyze the effect of different amplitude patterns on image quality of asymmetric illumination-based differential phase contrast (AIDPC) microscope. Specifically, we investigate how the amplitude pattern can enhance the imaging quality. Two types of amplitude patterns are tested by the pseudospectral time-domain (PSTD) simulation. Preliminary simulation show promising results. Furthermore, the reported simulation may enhance the AIDPC system by helping researchers to optimize the optical system and facilitate new optical imaging strategies on AIDPC imaging.
We employ the pseudospectral time-domain (PSTD) algorithm to model light propagation through a macroscopic scattering medium. We show that with specific amplitude and phase, light can propagate through scattering media and focus. We model explore the feasibility to propagate light the scattering medium with imprecise amplitude or phase. Based upon the numerical experiment, we analyze the degradation due to such imprecision.
Both consist of collagen fibrils, sclera is opaque whereas cornea is transparent for optical wavelengths. By employing the pseudospectral time-domain (PSTD) simulation technique, we model light impinging upon cornea and sclera, respectively. To analyze the scattering characteristics of light, the cornea and sclera are modeled by different sizes and arrangements of the non-absorbing collagen fibrils. Various factors are analyzed, including the wavelength of incident light, the thickness of the scattering media, position of the collagen fibrils, size distribution of the fibrils.
By means of numerical solutions of Maxwell’s equations, we model the complex light scattering phenomenon. Light propagation through scattering medium is a deterministic process; with specific amplitude and phase, light can propagate to the target position via multiple scattering. By means of numerical solutions of Maxwell’s equations, the complex light scattering phenomenon can be accurately analyzed. The reported simulation enables qualitative and quantitative analyses of the effectiveness of directing light through turbid media to a targeted position
The pseudospectral time-domain (PSTD) simulation technique is employed to obtain numerical solutions of Maxwell’s equations. Amplitude and phase of the outgoing light is recorded and later used to generate phase-conjugated light which back-propagates through the scattering medium. By changing the angular span of the region of phase-conjugated light, we can analyze back-propagation of light for different angular spans. The simulation results may help determine the optimal angular span for practical back-propagation of light.
Optical coherence tomography (OCT) provides high resolution, cross-sectional image of internal microstructure of biological tissue. We use the Finite-Difference Time-Domain method (FDTD) to analyze the data acquired by OCT, which can help us reconstruct the refractive index of the biological tissue. We calculate the refractive index tomography and try to match the simulation with the data acquired by OCT. Specifically, we try to reconstruct the structure of melanin, which has complex refractive indices and is the key component of human pigment system. The results indicate that better reconstruction can be achieved for homogenous sample, whereas the reconstruction is degraded for samples with fine structure or with complex interface. Simulation reconstruction shows structures of the Melanin that may be useful for biomedical optics applications.
The ability to focus light in most tissue degrades quickly with depth due to high optical scattering. Recently, researchers have found they can concentrate light tightly despite these scattering effects by using a guidestar and optical phase conjugation to focus light to greater distances in tissue. An optical or probe signal is transmitted through a scattering medium and its resulting wavefront is detected. The wavefront is then conjugated and utilized as a new optical source or delivery wave that focuses back to the guidestar's location with minimal scattering. The power in the delivery wave may be greatly increased for enhanced energy delivery at the focus. Modulation by an ultrasound (US) beam may be utilized to generate the guidestar dynamically and allow for US-resolution at depths of several millimeters. The delivery wave is successful at focusing light back at the guidestar because it creates constructive interference at the desired focus. However, if the phases of the field contributions change, we expect the delivered power at the focus to be reduced. This paper will analyze the robustness of this method when the probe beam is at one wavelength and the delivery wave is at another. This will allow us to characterize the deleterious effects of varying the phase contributions at the focus.
High scattering in biological turbid media limits the applicability of optical imaging techniques, such as optical coherence tomography (OCT). Accurate and robust simulations are required due to the complexity of optical wave propagation in these tissues. Recent computational simulations make use of finite-difference time-domain (FDTD) method to exactly solve the scattered electromagnetic field distribution. We propose a method to isolate and selectively remove energy from portions of the scattered field in these simulations. This technique will involve placing an absorber in the medium that consists of convolutional perfectly matched layers (CPML). The performance of the absorber as an optical target is analyzed.
Here we attempt to simulate the macroscopic light scattering phenomenon involving digitally
time-reversed ultrasound-encoded light, which combines optical phase conjugation with ultrasound
encoding, for deep-tissue imaging. By using the focused ultrasound, we can create a virtual source of
light frequency shifted due to the acousto-optic effect. Frequency-shifted light emanating from this
source is then recorded, and can be used to retrace to the virtual source to form an optical focus deep
inside biological tissues. The simulation is done by numerical solutions of Maxwell’s equations, which
can accurately account for phase and amplitude of light. The reported simulation enables qualitative
and quantitative characterization that may provide important information for enhancement.
In this paper we attempted to simulate the macroscopic light scattering phenomenon of optical coherence
tomography. Numerical solutions of Maxwell’s equations were computed to accurately account for phase and
amplitude of light. According to the simulation results, the qualitative and quantitative characterization may provide
important information for future development of this technique, especially on the index mapping of biological cells.
The light scattering effects of turbid media causing opacity may be undone via Optical Phase Conjugation (OPC). Here
we rigorously simulate light scattering through a macroscopic random using the pseudospectral time-domain (PSTD)
technique. The OPC phenomenon of multiply scattered light can be quantitatively analyzed which is not feasible
otherwise. Specifically, factors affecting the electromagnetic energy propagation and refocusing phenomenon is
analyzed. The reported simulation study allows accurate characterization of the optical properties of the OPC
phenomenon for practical biomedical applications.
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