Light scattering

About: Light scattering is a research topic. Over the lifetime, 37721 publications have been published within this topic receiving 861581 citations.

Light scattering from dipole and quadrupole nanoshell antennas

Abstract: Metal nanoshells are nanoscale optical components that allow for the controllable redirection of electromagnetic radiation via careful engineering of their multilayer structures. By varying the core size and shell thickness of these nanoparticles, nanoscale “antennas” are constructed that can be selectively driven into a dipolar or quadrupolar oscillation pattern. With scattering cross sections many times larger than their physical cross section, these antennas efficiently couple to the incident electromagnetic wave. These structures can focus, redirect, or split the incident light with subwavelength precision, and may find useful applications in the remote coupling of electromagnetic signals into nanoscale machines or devices.

Dependence of tissue optical properties on solute-induced changes in refractive index and osmolarity.

Abstract: Additions of a solute/carbohydrate in tissue affect the size of tissue cells and the refractive indexes of the extra- and intracellular fluids, and thus the overall tissue scattering properties. We use both the Rayleigh- Gans and Mie theory approximation in calculating effects of the osmolarity and refractive indexes on the reduced scattering coefficient of tissue, and employ photon diffusion theory to associate the reduced scattering coefficient to the mean optical path length. The calculations show that changes of scattering in tissue depend not only on the change in extracellular refractive index but also on the change in osmolarity, and thus on the change in cell size and volume fraction. Experimentally, we have utilized time-domain and frequencydomain NIR techniques to measure the changes of optical properties caused by an addition of a solute in tissue models and in perfused rat livers. The temperature-dependent path length measurement of the perfused liver confirms the dependence of tissue scattering on the tissue cell size. The results obtained from the liver with three kinds of carbohydrate perfusion display different scattering aspects and can be well explained by changes in cell size and in extracellular as well as intracellular refractive indexes. The consistency between the theoretical and experimental results confirms the dependence of optical properties in (liver) tissue on both tissue osmolarity and relative refractive indexes between the extracellular and intracellular compartments. This study suggests that the NIR technique is a novel and useful tool for noninvasive, physiological monitoring.

Flow-cytometric light scattering measurement of red blood cell volume and hemoglobin concentration.

Abstract: A light scattering technique for simultaneously determining the volume (V) and hemoglobin concentration (HC) of individual sphered red blood cells (RBCs) is described. Light scattered into two angular intervals yields measurements S1 and S2, respectively. Since a sphered RBC is essentially a homogeneous dielectric sphere having a complex refractive index that is linear in HC, with a proper choice of detector acceptance angles, tables relating V and HC to S1 and S2 can be computed via Mie theory. Absolute calibration is possible using droplets of water-immisible oils of accurately known refractive index. Results of experimental tests of the method are compared with those obtained from hematological reference measurements.

Mueller matrix decomposition for extraction of individual polarization parameters from complex turbid media exhibiting multiple scattering, optical activity, and linear birefringence

Abstract: Linear birefringence and optical activity are two common optical polarization effects present in biological tissue, and determi- nation of these properties has useful biomedical applications. How- ever, measurement and unique interpretation of these parameters in tissue is hindered by strong multiple scattering effects and by the fact that these and other polarization effects are often present simulta- neously. We have investigated the efficacy of a Mueller matrix decom- position methodology to extract the individual intrinsic polarimetry characteristics linear retardance and optical rotation , in particu- lar from a multiply scattering medium exhibiting simultaneous linear birefringence and optical activity. In the experimental studies, a pho- toelastic modulation polarimeter was used to record Mueller matrices from polyacrylamide phantoms having strain-induced birefringence, sucrose-induced optical activity, and polystyrene microspheres- induced scattering. Decomposition of the Mueller matrices recorded in the forward detection geometry from these phantoms with con- trolled polarization properties yielded reasonable estimates for and parameters. The confounding effects of scattering, the propagation path of multiple scattered photons, and detection geometry on the estimated values for and were further investigated using polarization-sensitive Monte Carlo simulations. The results show that in the forward detection geometry, the effects of scattering induced linear retardance and diattenuation are weak, and the decomposition of the Mueller matrix can retrieve the intrinsic values for and with reasonable accuracy. The ability of this approach to extract the indi- vidual intrinsic polarimetry characteristics should prove valuable in diagnostic photomedicine, for example, in quantifying the small opti- cal rotations due to the presence of glucose in tissue and for monitor- ing changes in tissue birefringence as a signature of tissue abnormality. © 2008 Society of Photo-Optical Instrumentation Engineers. DOI: 10.1117/1.2960934

Improved SERS Sensitivity on Plasmon-Free TiO2 Photonic Microarray by Enhancing Light-Matter Coupling

Abstract: Highly sensitive surface-enhanced Raman scattering (SERS) detection was achieved on plasmon-free TiO2 photonic artificial microarray, which can be quickly recovered under simulated solar light irradiation and repeatedly used. The sensitive detection performance is attributed to the enhanced matter-light interaction through repeated and multiple light scattering in photonic microarray. Moreover, the SERS sensitivity is unprecedentedly found to be dependent on the different light-coupling performance of microarray with various photonic band gaps, where microarray with band gap center near to laser wavelength shows a lower SERS signal due to depressed light propagation, while those with band gap edges near to laser wavelength show higher sensitivity due to slow light effect.