TY - JOUR
T1 - Merging Mie solutions and the radiative transport equation to measure optical properties of scattering particles in optical phantoms
AU - Baez-Castillo, L.
AU - Ortiz-Rascón, E.
AU - Bruce, N. C.
AU - Garduño-Mejía, J.
AU - Carrillo-Torres, R. C.
AU - Álvarez-Ramos, M. E.
N1 - Publisher Copyright:
© 2020 Optical Society of America.
PY - 2020/11/20
Y1 - 2020/11/20
N2 - We present a new method to calculate the complex refractive index of spherical scatterers in a novel optical phantom developed by using homemade monodisperse silica nanospheres embedded into a polyester resin matrix and an ethanol–water mixture for applications in diffuse imaging. The spherical geometry of these nanoparticles makes them suitable for direct comparison between the values of the absorption and reduced scattering coefficients (µa and µs0, respectively) obtained by the diffusion approximation solution to the transport equation from scattering measurements and those obtained by the Mie solution to Maxwell’s equations. The values of the optical properties can be obtained by measuring, using an ultrafast detector, the time-resolved intensity distribution profiles of diffuse light transmitted through a thick slab of the silica nanosphere phantom, and by fitting them to the time-dependent diffusion approximation solution to the transport equation. These values can also be obtained by Mie solutions for spherical particles when their physical properties and size are known. By using scanning electron microscopy, we measured the size of these nanospheres, and the numerical results of µa and µs0 can then be inferred by calculating the absorption and scattering efficiencies. Then we propose a numerical interval for the imaginary part of the complex refractive index of SiO2 nanospheres, ns, which is estimated by fixing the fitted values of µa and µs0, using the known value of the real part of ns, and finding the corresponding value of Im(ns ) that matches the optical parameters obtained by both methods finding values close to those reported for silica glass. This opens the possibility of producing optical phantoms with scattering and absorption properties that can be predicted and designed from precise knowledge of the physical characteristics of their constituents from a microscopic point of view.
AB - We present a new method to calculate the complex refractive index of spherical scatterers in a novel optical phantom developed by using homemade monodisperse silica nanospheres embedded into a polyester resin matrix and an ethanol–water mixture for applications in diffuse imaging. The spherical geometry of these nanoparticles makes them suitable for direct comparison between the values of the absorption and reduced scattering coefficients (µa and µs0, respectively) obtained by the diffusion approximation solution to the transport equation from scattering measurements and those obtained by the Mie solution to Maxwell’s equations. The values of the optical properties can be obtained by measuring, using an ultrafast detector, the time-resolved intensity distribution profiles of diffuse light transmitted through a thick slab of the silica nanosphere phantom, and by fitting them to the time-dependent diffusion approximation solution to the transport equation. These values can also be obtained by Mie solutions for spherical particles when their physical properties and size are known. By using scanning electron microscopy, we measured the size of these nanospheres, and the numerical results of µa and µs0 can then be inferred by calculating the absorption and scattering efficiencies. Then we propose a numerical interval for the imaginary part of the complex refractive index of SiO2 nanospheres, ns, which is estimated by fixing the fitted values of µa and µs0, using the known value of the real part of ns, and finding the corresponding value of Im(ns ) that matches the optical parameters obtained by both methods finding values close to those reported for silica glass. This opens the possibility of producing optical phantoms with scattering and absorption properties that can be predicted and designed from precise knowledge of the physical characteristics of their constituents from a microscopic point of view.
UR - http://www.scopus.com/inward/record.url?scp=85097749732&partnerID=8YFLogxK
U2 - 10.1364/AO.403388
DO - 10.1364/AO.403388
M3 - Artículo
C2 - 33361994
AN - SCOPUS:85097749732
SN - 1559-128X
VL - 59
SP - 10591
EP - 10598
JO - Applied Optics
JF - Applied Optics
IS - 33
ER -