Fundamental understanding of the light-matter interaction in the context of nano-particles is immensely benefited by the study of geometry dependent tunable Localized Surface Plasmon Resonance (LSPR) and has been demonstrated to have potential applications in various areas of science. The polarization characteristics of LSPR in addition to spectroscopic tuning can be suitably exploited in such systems as contrast enhancement mechanisms and control parameters. Such polarization characteristics like diattenuation and retardance have been studied here using a novel combination of Muller-matrix polarimetry with the T-matrix matrix approach for silver nano-rods to show unprecedented control and sensitivity to local refractive index variations. The study carried out over various aspect ratios for a constant equal volume sphere radius shows the presence of longitudinal (dipolar and quadrupolar) and transverse (dipolar) resonances; arising due to differential contribution of polarizabilities in two directions. The overlap regions of these resonances and the resonances themselves exhibit enhanced retardance and diattenuation respectively. The spectral and amplitude tunability of these polarimetric parameters through the aspect ratios to span from the minimum to maximum ([0, 1] in the case of diattenuation and [0, π] in the case of retardance) presents a novel result that could be used to tailor systems for study of biological media. On the other hand, the high sensitivity of diattenuation dip (caused by equal contribution of polarizabilities) could be possibly used for medium characterization and bio-sensing or bio imaging studies.
In this work, we report a wavelet based multi-fractal study of images of dysplastic and neoplastic HE- stained
human cervical tissues captured in the transmission mode when illuminated by a laser light (He-Ne 632.8nm
laser). It is well known that the morphological changes occurring during the progression of diseases like cancer
manifest in their optical properties which can be probed for differentiating the various stages of cancer. Here,
we use the multi-resolution properties of the wavelet transform to analyze the optical changes. For this, we have
used a novel laser imagery technique which provides us with a composite image of the absorption by the different
cellular organelles. As the disease progresses, due to the growth of new cells, the ratio of the organelle to cellular
volume changes manifesting in the laser imagery of such tissues. In order to develop a metric that can quantify
the changes in such systems, we make use of the wavelet-based fluctuation analysis. The changing self- similarity
during disease progression can be well characterized by the Hurst exponent and the scaling exponent. Due to the
use of the Daubechies' family of wavelet kernels, we can extract polynomial trends of different orders, which help
us characterize the underlying processes effectively. In this study, we observe that the Hurst exponent decreases
as the cancer progresses. This measure could be relatively used to differentiate between different stages of cancer
which could lead to the development of a novel non-invasive method for cancer detection and characterization.