Controlled modulation of depolarization in laser speckle

Abstract

A new technique based on superposition of two speckle patterns is proposed and demonstrated for controlled modulation of the spatial polarization distribution of the resultant speckle. It is theoretically and experimentally demonstrated that controlled modulation of the spatial polarization distribution of laser speckle can be achieved by proper choice of the polarization states as well as the average spatial intensity of the constituent speckles. It is shown that the proposed technique is useful to generate different speckle patterns with sinusoidal variation in their degree of polarization, which can be tuned from zero to unity. This technique can find application in sensing, biomedical studies, and in determining the rotation of an electric field vector after passing through a scattering medium.

Spatial statistics of superposition of two uncorrelated speckle patterns with polarization diversity

“…3 are similar to the results reported in Ref. [27], it is important to mention that the characteristics of the object speckle patterns used in these two studies are completely different. In the present study, the object speckle patterns are fully mutually correlated, whereas in case of Ref.…”

“…In the present study, the object speckle patterns are fully mutually correlated, whereas in case of Ref. [27], the correlation between the object speckle patterns varies depending on the filtered polarization [9]. Hence, the present study also establishes that modulation of the spatial CP property of the superposed speckle pattern is independent of the mutual correlation of the object speckle patterns.…”

Non-invasive tracking of polarization rotation from speckle contrast using uncorrelated speckle patterns

“…Let us consider that the propagation of a monochromatic, linearly polarized sample field (SF) with the polarization vector oriented at an angle ϕ with respect to the x-axis through a scattering layer results in a sample random field (SRF), E S (r, t), at the observation plane. As a scattering layer does not change the polarization of the input field, E S (r, t) has the same polarization as the input SF [27][28][29]. The SRF, E S (r, t), at the transverse observation plane, r can be written as…”

Polarization-based intensity correlation of a depolarized speckle pattern

“…Apart from the aforementioned applications, the intensity correlation technique is also reported to be a very useful tool to investigate the spatial coherence-polarization property, another important characteristics, of a speckle pattern. The spatial coherence-polarization property of a speckle pattern is characterized from the study of the spatial degree of coherence (DoC) and degree of polarization (DoP), which are determined from the two-point intensity correlation function of the speckle pattern [10,11]. The speckles, based on their spatial coherence-polarization property, are categorized into intensity speckle (with uniform spatial polarization distribution) and polarization speckle (with non-uniform spatial polarization distribution).…”

“…Although the polarization speckle has tremendous potential application in various branches of science, not much attention have been paid to characterize the polarization speckle properly, until recently. Different techniques based on the interferometric approach have been proposed to generate and control the depolarization of the speckles [10,12]. Separately, polarization speckle has also been reported to be generated using a bulk scattering medium or a spiral phase plate [13,14].…”