Nabamita Goswami

Surface plasmon enhanced reflected second harmonic generation in periodically poled whispering gallery resonator

This paper analytically describes the surface plasmon enhanced very low threshold second harmonic generation formed by a 29 nm thin gold layer is sandwiched between a BK7 prism plane and 20 nm thin GaAs layer. Here the electric field with incident optical radiation of picowatt level is amplified upto milliwatt level through surface plasmon phenomenon at off resonance condition. This amplified output further coupled to a whispering gallery resonator, which facilitates the generation of second harmonic for an incident optical radiation of picowatt level. In this proposed configuration with an incident optical power of 94.6 pW generated second harmonic through whispering gallery resonator found to be 14.6 mW.

Enhanced lateral shifts with Gaussian beam and Laguerre-Gaussian beam in presence of surface plasmon resonance

First time a theoretical approach towards the enhancement of spatial and angular Goos-Hanchen (GH) shift and Imbert-Fedorov (IF) shift for a Gaussian beam and Laguerre-Gaussian beam are observed, designed and simulated in four layer Kretschmann-Raether geometry at a free space wavelength of 1550 nm. Here the proposed configuration comprises a ZnSe prism and a liquid crystal layer of E44 between two silver layers through which spatial and angular GH shift and IF shift can be observed for Gaussian beam as well as Laguerre-Gaussian beam whereas the exact output beam position can only be accurately identified with the composite effect of spatial and angular GH shift and IF shift. Here with the variation of incident angle from 400 to 500, the spatial and angular GH shift and IF shift have been calculated for two types of beams. This idea expedites the concept of optical tuning at μm ranges and reveals the exact output beam position for every experiments with different beams.

Polarization tunable spatial and angular Goos-Hänchen shift and Imbert-Fedorov shift using long range surface plasmon

A new proposal towards the polarization tunable Goos-Hänchen (GH) and Imbert-Fedorov (IF) spatial and angular shifts is explored analytically in a four layer Kretschmann-Raether geometry comprising a ZnSe prism, a dielectric layer of PMMA-DR1 (Polymethylmthacryalate-Disperse red) and two metal layers of silver having thicknesses of 50 nm and 200 nm respectively. Observations from the different graphical representations reveal that in correspondence of the long range surface plasmon (LRSP) resonant angle both spatial and angular GH shifts get appreciably enhanced in case of p polarized light whereas negligible or very less amplification of spatial and angular GH shifts are obtained for s polarized light. With the switching of polarization of the incident light beam on the proposed configuration through the half wave plate, the spatial and angular GH shift is tuned from -17.35 μm to 0.105 μm and -0.631 μrad to 4.28 nrad respectively and the spatial and angular IF shift is tuned from 94.16 μm to -53.58 μm and about 7.774 μrad to -11.17 μrad respectively. To the best of our knowledge, several articles have been devoted for depicting the GH shift without considering the IF shift, whereas the exact beam position of the output beam can only be identified with the composite effect of GH and IF spatial and angular shifts. The above new proposal can be implemented in the field of fine tuning of optical switching at the μm ranges with varying polarization, optical sensors applications and serves interesting opportunities to make atomic mirrors.

Long range surface plasmon enhanced tunable Goos-Hanchen shift in ZnSe prism

This paper first time observed, designed and simulated the surface plasmon enhanced tunable Goos-Hanchen shift with varying refractive index of the dielectric layer in Kretschmann-Reather geometry formed by a ZeSe prism,50 nm silver layer, 4.5 μm liquid crystal layer (as dielectric layer) and 200 nm thin silver layer. Here the Goos-Hanchen shift is tuned from (10-72) nm with the change in refractive index of the liquid crystal layer with varying applied voltage.