Differential description and irreversibility of depolarizing light-matter interactions

The widely-used Jones and Mueller differential polarization calculi allow non-depolarizing deterministic polarization interactions, known to be elements of the $SO^+(1,3)$ Lorentz group, to be described in an efficient way. In this Letter, a stochastic differential Jones formalism is shown to provide a clear physical insight on light depolarization, which arises from the interaction of polarized light with a random medium showing fluctuating anisotropic properties. Based on this formalism, several "intrinsic" depolarization metrics naturally arise to efficiently characterize light depolarization in a medium, and an irreversibility property of depolarizing transformations is finally established

Generalized Jones matrices for anisotropic media

The interaction of arbitrary three-dimensional light beams with optical elements is described by the generalized Jones calculus, which has been formally proposed recently [Azzam, J. Opt. Soc. Am. A 28, 2279 (2011)]. In this work we obtain the parametric expression of the 3×3 differential generalized Jones matrix (dGJM) for arbitrary optical media assuming transverse light waves. The dGJM is intimately connected to the Gell-Mann matrices, and we show that it provides a versatile method for obtaining the macroscopic GJM of media with either sequential or simultaneous anisotropic effects. Explicit parametric expressions of the GJM for some relevant optical elements are provided

Mueller matrix differential decomposition for direction reversal: application to samples measured in reflection and backscattering

Mueller matrix differential decomposition is a novel method for analyzing the polarimetric properties of optical samples. It is performed through an eigenanalysis of the Mueller matrix and the subsequent decomposition of the corresponding differential Mueller matrix into the complete set of 16 differential matrices which characterize depolarizing anisotropic media. The method has been proposed so far only for measurements in transmission configuration. In this work the method is extended to the backward direction. The modifications of the differential matrices according to the reference system are discussed. The method is successfully applied to Mueller matrices measured in reflection and backscattering

Depolarizing differential Mueller matrices

The evolution of a polarized beam can be described by the differential formulation of Mueller calculus. The nondepolarizing differential Mueller matrices are well known. However, they only account for 7 out of the 16 independent parameters that are necessary to model a general anisotropic depolarizing medium. In this work we present the nine differential Mueller matrices for general depolarizing media, highlighting the physical implications of each of them. Group theory is applied to establish the relationship between the differential matrix and the set of transformation generators in the Minkowski space, of which Lorentz generators constitute a particular subgroup

FDTD-based Transcranial Magnetic Stimulation model applied to specific neurodegenerative disorders

Non-invasive treatment of neurodegenerative diseases is particularly challenging in Western countries, where the population age is increasing. In this work, magnetic propagation in human head is modelled by Finite-Difference Time-Domain (FDTD) method, taking into account specific characteristics of Transcranial Magnetic Stimulation (TMS) in neurodegenerative diseases. It uses a realistic high-resolution three-dimensional human head mesh. The numerical method is applied to the analysis of magnetic radiation distribution in the brain using two realistic magnetic source models: a circular coil and a figure-8 coil commonly employed in TMS. The complete model was applied to the study of magnetic stimulation in Alzheimer and Parkinson Diseases (AD, PD). The results show the electrical field distribution when magnetic stimulation is supplied to those brain areas of specific interest for each particular disease. Thereby the current approach entails a high potential for the establishment of the current underdeveloped TMS dosimetry in its emerging application to AD and PD

Singlet oxygen prediction in gold nanoparticles-assisted PDT applied to a squamous cell carcinoma in the esophagus

A predictive model for PDT singlet oxygen production in esophageal squamous cell carcinomas with gold nanoparticles is proposed. Differences enhance the ¹O₂ -mediated oxidative damage due to the optical absorption improvement by gold nanoparticles.This work has been partially supported by the project MAT2012-38664-C02-01 of the Spanish Ministery of Economy and Competitiveness

Predictive model for Photodynamic Therapy with gold nanoparticles as vehicle for the photosensitizer delivery

Photodynamic Therapy offers multiple advantages to treat nonmelanoma skin cancer compared to conventional treatment techniques such as surgery, radiotherapy or chemotherapy. Among these advantages are particularly relevant its noninvasive nature, the use of non ionizing radiation and its high selectivity. However the therapeutic efficiency of the current clinical protocol is not complete in all the patients and depends on the type of pathology. Emerging strategies to overcome its current shortcomings include the use of nanostructures that can act as carriers for conventional photosensitizers and improve the treatment selectivity and provide a controlled release of the photoactive agent. In this work, a model for photodynamic therapy combined with gold nanocarriers for a photosensitizer commonly used in dermatology is presented and applied to a basal cell carcinoma in order to predict the cytotoxic agent spatial and temporal evolution.This work has been partially supported by the project MAT2012-38664-C02-01 of the Spanish Ministery of Economy and Competitivenss and by San Cándido Foundatio

Comparative numerical analysis of magnetic and optical radiation propagation in adult human head

In this work, magnetic and optical propagation in human head are modeled by FDTD and Monte Carlo methods. Both of them use a realistic high-resolution three-dimensional human head mesh. The numerical methods are applied to the analysis of magnetic and optical radiation distribution in the brain using different sources. The results show the characteristics of both types of stimulation, and highlight the spatial selectivity achieved by optical sources, which entails a high potential for illuminating specific brain regions. The presented approach can be applied for predictive purposes in magnetic stimulation techniques and in the emerging field of optical brain stimulation

Polarized light Monte Carlo analysis of birefringence-induced depolarization in biological tissues

In this work we analyze the impact of linear birefringence on biological tissues depolarization, which is essential for correctly interpreting experimental results. Our approach is based on the polarized light Monte Carlo method in transmission. We present a comparative analysis of light depolarization in biological tissues with different values of linear birefringence and particle sizes, in order to evaluate its impact on the calculated parameters

Mueller matrix differential decomposition

We present a Mueller matrix decomposition based on the differential formulation of the Mueller calculus. The differential Mueller matrix is obtained from the macroscopic matrix through an eigenanalysis. It is subsequently resolved into the complete set of 16 differential matrices that correspond to the basic types of optical behavior for depolarizing anisotropic media. The method is successfully applied to the polarimetric analysis of several samples. The differential parameters enable one to perform an exhaustive characterization of anisotropy and depolarization. This decomposition is particularly appropriate for studying media in which several polarization effects take place simultaneously