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We report the characterization and photoluminescence ͑PL͒ of newly synthesized deformed helix ferroelectric liquid crystal ͑DHFLC͒ material having short pitch and high spontaneous polarization. We observed ninefold enhancement in PL intensity in gold nanoparticles doped DHFLC material. This enhancement in the PL intensity has been attributed to the coupling of localized surface plasmon resonance from metal nanoparticles with DHFLC molecules, resulting in the increase in excitation and emission rate of the liquid crystal molecules in the localized electromagnetic field. These studies would provide a cutting edge tool in the realization of enhanced photoluminescent liquid crystal display devices.

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We report significant speckle reduction in a laser illumination system using a vibrating multimode optical fiber bundle. The optical fiber bundle was illuminated by two independent lasers simultaneously. The beams from both lasers were first expanded and collimated and were further divided into multiple beams to illuminate the fiber optic bundle with normal and oblique incidence. Static diffusers were also placed at the input and output faces of the fiber bundle, thus introducing the spatial as well as angular diversity of illumination. Experiments were carried out both in free space and in imaging geometry configuration. Standard deviation, speckle contrast and signal-to-noise ratio of the images were computed, and the results were compared with those of white light illumination. Speckle contrast close to that of white light was obtained using a vibrating fiber bundle with combined temporal, spatial, and angular diversities of the illumination.

Nonvolatile memory effect based on gold nanoparticles ͑GNPs͒ doped deformed helix ferroelectric liquid crystal ͑DHFLC͒ has been observed. This observed memory effect has been attributed to electric field induced charge transfer from liquid crystal molecules to the GNPs and the stabilization of helix deformation of DHFLC material, which occurs on the application of electric field beyond a critical field. The memory effect has been analyzed by polarizing optical microscopy, high-resolution transmission electron microscopy, and dielectric spectroscopy. The observed memory effect combines two active research areas: nanotechnology and liquid crystal.

In this Letter, we demonstrate quantitative phase imaging of biological samples, such as human red blood cells (RBCs) and onion cells using narrow temporal frequency and wide angular frequency spectrum light source. This type of light source was synthesized by the combined effect of spatial, angular, and temporal diversity of speckle reduction technique. The importance of using low spatial and high temporal coherence light source over the broad band and narrow band light source is that it does not require any dispersion compensation mechanism for biological samples. Further, it avoids the formation of speckle or spurious fringes which arises while using narrow band light source.

Semen quality assessed by sperm count and sperm cell characteristics such as morphology and motility, is considered to be the main determinant of men’s reproductive health. Therefore, sperm cell selection is vital in assisted reproductive technology (ART) used for the treatment of infertility. Conventional bright field optical microscopy is widely utilized for the imaging and selection of sperm cells based on the qualitative analysis by experienced clinicians. In this study, we report the development of a highly sensitive quantitative phase microscopy (QPM) using partially spatially coherent light source, which is a label-free, non-invasive and high-resolution technique to quantify various biophysical parameters. The partial spatial coherence nature of light source provides a significant improvement in spatial phase sensitivity and hence reconstruction of the phase of the entire sperm cell is demonstrated, which was otherwise not possible using highly spatially coherent light source. High sensitivity of the system enables quantitative phase imaging of the specimens having very low refractive index contrast with respect to the medium like tail of the sperm cells. Further, it also benefits with accurate quantification of 3D-morphological parameters of sperm cells which might be helpful in the infertility treatment. The quantitative analysis of more than 2500 sperm cells under hydrogen peroxide (H 2 O 2 ) induced oxidative stress condition is demonstrated. It is further correlated with motility of sperm cell to study the effect of oxidative stress on healthy sperm cells. The results exhibit a decrease in the maximum phase values of the sperm head as well as decrease in the sperm cell’s motility with increasing oxidative stress, i.e., H 2 O 2 concentration. Various morphological and texture parameters were extracted from the phase maps and subsequently support vector machine (SVM) based machine learning algorithm is employed for the classification of the control and the stressed sperms cells. The algorithm achieves an area under the receiver operator characteristic (ROC) curve of 89.93% based on the all morphological and texture parameters with a sensitivity of 91.18%. The proposed approach can be implemented for live sperm cells selection in ART procedure for the treatment of infertility.

We present the results of the fast electro-optic response of multiwalled carbon nanotubes ͑MWCNTs͒-doped deformed helix ferroelectric liquid crystal ͑DHFLC͒. The fastening of the response in MWCNTs-doped DH-FLC has been attributed to the decrease in rotational viscosity and increase in anchoring energy. The decrease in the former is due to the experience of the torque both by MWCNTs and DHFLC and perturbation of order parameter of the DHFLC while the increase in the latter is due to the -electrons stacking between the MWCNTs, DHFLC molecules, and alignment layers. The increase in conductance in doped cells has also been observed. DOI: 10.1103/PhysRevE.80.012701 PACS number͑s͒: 61.30.Ϫv, 42.70.Df, 42.79.Kr, 77.84.Nh The field of carbon nanotubes ͑CNTs͒ has drawn a great deal of interest in fundamental and applied research since their discovery by Iijima in 1991 ͓1͔ because they possess fascinating electrical, dielectric, thermal, mechanical, and electronic properties. The CNTs have proved their importance in employing the devices as field-effect transistors ͓2͔, memory storage devices ͓3͔, sensors and actuators ͓4,5͔, and field emission sources ͓6͔. The doping of CNTs ͓either single walled ͑SW͒ or multiwalled ͑MW͔͒ in liquid crystals ͑LCs͒, in order to have fast electro-optic devices, has been pursued by various groups around the world for improving their electro-optical properties ͓7-10͔, dynamic response ͓11͔, and other physical parameters ͓12,13͔. But much of the reported work has been focused on nematic liquid crystals ͑NLCs͒ ͓8-10,13͔ and twisted NLC ͓7,12͔. The doping of CNTs in ferroelectric liquid crystals ͑FLCs͒ is rarely reported in literature. It has also been found that thermotropic ͓14-16͔ as well as lyotropic ͓17͔ LCs have been used as a solvent providing a simple, versatile, and reproducible way to control the order in SWCNTs and MWCNTs. Some studies have been carried out on the translational motion of CNTs dispersed in NLC under an ac and in-plane field ͓18,19͔. Among many intrinsically physical parameters of LC material, the response time is the most important for addressing the fast LC display devices. Lee et al. ͓7͔ demonstrated the effect of CNTs on LC to improve the switching behavior. Faster electro-optical response characteristics of carbonnanotubes-nematic suspension have been studied by Chen et al. ͓8͔. The CNTs-doped LC optically compensated birefringent cells were studied by Lu and Chien ͓10͔ for improvement in response time. The deformed helix FLCs ͑DHFLCs͒ are very useful and have much applications in display devices because of their low driving voltage, gray scale generation capability, easily achievable alignment, fast response, etc. ͓20,21͔. The bistability or memory effect has also been demonstrated by us ͓22,23͔ in DHFLCs. In this brief report, the improvement ͑almost 50%͒ in response time, in MWCNTs ͑we referred CNTs throughout the paper͒-doped DHFLC material has been reported. The improvement in the response time has been attributed to the decrease in rotational viscosity a...