Sudipta Saha

Transverse spin and transverse momentum in scattering of plane waves

We study the near field to the far field evolution of spin angular momentum (SAM) density and the Poynting vector of the scattered waves from spherical scatterers. The results show that at the near field, the SAM density and the Poynting vector are dominated by their transverse components. While the former (transverse SAM) is independent of the helicity of the incident circular polarization state, the latter (transverse Poynting vector) depends upon the polarization state. It is further demonstrated that the interference of the transverse electric and transverse magnetic scattering modes enhances both the magnitudes and the spatial extent of the transverse SAM and the transverse momentum components.

Outcome of Surgery for Benign Prostatic Hyperplasia-Is It Predictable?

AIM The study was done to evaluate the pre-operative and intra operative factors which influence the post-operative outcome in patients undergoing surgery for Benign Prostatic Hyperplasia (BPH). SETTING AND DESIGN It was carried out prospectively at a university college hospital in northern India. MATERIAL & METHODS The study was carried out prospectively in 31 patients who underwent surgery for BPH (TURP - 50, Open Prostatectomy - 10). Various pre-operative and intra-operative parameters were studied by means of a detailed history and examination, IPS score, urodynamic evaluation & cystoscopic examination. Their effect on post-operative outcome was evaluated by measuring changes in IPSS, maximum and average flow rates, and fall in PSA values. STATISTICAL ANALYSIS Repeated measure ANNOVA was applied to calculate the significance of preoperative factors on post operative outcome (IPSS, Q max and Q av). RESULTS All parameters studied in the patients improved significantly following surgery. Patients who had pre-operative urinary retention and catheter at the time of surgery had significant improvement in both subjective (IPSS ,p=.oo4) and objective (maximum & average flow rates p=.04) parameters studied. Patients with larger prostrate had a significantly better maximum flow rate (p=.03) and IPSS at 3 months post-operatively. Similarly, patients with larger bladder capacity (more than 150 ml), better compliance (more than 6 ml per cm of water) and lower post-voidal residue (less than 60ml) had better post-operative outcome. CONCLUSION Patients with pre-operative urinary retention, shorter duration of bladder catheterization, lower post voidal residue, high IPSS score, larger prostrate, larger bladder capacity and compliance had a significantly better outcome following surgery for BPH as assessed by various parameters studied.

Probing intrinsic anisotropies of fluorescence: Mueller matrix approach

Abstract. We demonstrate that information on “intrinsic” anisotropies of fluorescence originating from preferential orientation/organization of fluorophore molecules can be probed using a Mueller matrix of fluorescence. For this purpose, we have developed a simplified model to decouple and separately quantify the depolarization property and the intrinsic anisotropy properties of fluorescence from the experimentally measured fluorescence Mueller matrix. Unlike the traditionally defined fluorescence anisotropy parameter, the Mueller matrix-derived fluorescence polarization metrics, namely, fluorescence diattenuation and polarizance parameters, exclusively deal with the intrinsic anisotropies of fluorescence. The utility of these newly derived fluorescence polarimetry parameters is demonstrated on model systems exhibiting multiple polarimetry effects, and an interesting example is illustrated on biomedically important fluorophores, collagen.

Effects of mode mixing and avoided crossings on the transverse spin in a metal-dielectic-metal sphere

We study transverse spin in a sub-wavelength metal-dielectric-metal (MDM) sphere when the MDM sphere exhibits avoided crossing due to hybridization of the surface plasmon with the Mie localized plasmon. We show that the change in the absorptive and dipersive character near the crossing can have significant effect on the transverse spin. An enhancement in the transverse spin is shown to be possible associated with the transparency (suppression of extinction) of the MDM sphere. The effect is attributed to the highly structured field emerging as a consequence of competition of the electric and magnetic modes.

Unusual Cause of Orocutaneous Fistula in the Neck

A case of orocutaneous fistula secondary to submandibular sialolithiasis, which was masquerading clinically as branchial fistula is presented. This case highlights the importance of conducting fistulogram in the evaluation of discharging lesions in the neck.

Cavity enhanced interference of orthogonal modes in a birefringent medium

Abstract Interference of orthogonal modes in a birefringent crystal mediated by a rotator is known to lead to interesting physical effects (Solli et al., 2003). In this paper we show that additional feedback offered by a Fabry–Perot cavity (containing the birefringent crystal and the rotator) can lead to a novel strong interaction regime. Usual signatures of the strong interaction regime like the normal mode splitting and avoided crossings, sensitive to the rotator orientation, are reported. A high finesse cavity is shown to offer an optical setup for measuring small angles. The results are based on direct calculations of the cavity transmissions along with an analysis of its dispersion relation.

Enhancing transverse spin and transverse spin momentum in micro- and nano-optical systems

We show that scattering of plane waves leads to helicity-independent transverse spin angular momentum (SAM) and helicity-dependent transverse Poynting vector components. The in uence of plasmon resonance and avoided crossing for a sphere on these quantities is studied.

Consequences of nonreciprocity in reflection from a truncated spatial Kramers–Kronig medium

We study the truncated Kramers-Kronig (KK) medium to reveal the effects of nonreciprocity in reflection on the scattering and the wave guiding properties. We focus on the simplest possible spatial profile mimicking the dielectric response. We show that a finite slab of KK medium can support only one sided null scattering under bidirectional identical illumination. However, for a phase lag between the two incident beams it is possible to have null scattering on the other side. This is shown to be a consequence of the nonreciprocity in reflection due to the inherent asymmetry of the KK medium. We further look at the possibility of surface modes for unidirectional illumination. For specific range of parameters, we show the existence of TM polarized surface plasmons only for illumination from one side. The origin of such modes is traced to the inhomogeneous metal like layer with negative real part of the permittivity in the KK medium.