We
report the photocurrent generation in reduced graphene oxide–cadmium
zinc sulfide (RGO–Cd0.75Zn0.25S) nano
composite material under simulated solar light irradiation, where
the photocurrent increases linearly with increasing incident light
intensity. We also report the temperature dependent electrical conductivity
and conductivity relaxation in RGO–Cd0.75Zn0.25S composite. At low frequency, the real part of conductivity
is independent of frequency, and above a characteristic crossover
frequency, the conductivity decreases with the increase in frequency,
which indicates the onset of a relaxation phenomenon. The dc conductivity
of the RGO–Cd0.75Zn0.25S composite shows
Arrhenius behavior. From the scaling of real part of conductivity
spectra, we have observed that the dynamic process occurring at different
temperatures have the same thermal activation energy. The RGO–Cd0.75Zn0.25S composite shows an enhancement of photo
catalytic activity in comparison to control sample under simulated
solar light irradiation to degrade Rhodamine B. The RGO sheets prolong
the separation of photo induced electrons and holes in Cd0.75Zn0.25S, which hinder the electron–hole recombination
and subsequently enhances the photocurrent generation and photocatalytic
activity under simulated solar light irradiation.
We report a 1D planar optical waveguide with transverse distribution of inhomogeneous loss profile, which exhibits an exceptional point (EP). The waveguide hosts two leaky resonant modes; where the interaction between them in the vicinity of the EP is controlled by proper adjustment of the inhomogeneity in attenuation profile only. We study the adiabatic dynamics of propagation constants of the coupled modes by quasi-static encirclement of control parameters around the EP. Realizing such an encirclement with the inhomogeneous loss distribution along the direction of light propagation, we report the breakdown of adiabatic evolution of two coupled modes through the waveguide in presence of an EP. Here, during conversion the output mode is irrespective of the choice of input excited mode but depends on the direction of light transportation. This topologically controlled, robust scheme of asymmetric mode conversion in the platform of the proposed all-lossy waveguide structure may open up an extensive way-out for implementation of state-transfer applications in chirality driven waveguide-based devices.
We report a specially configured non-Hermitian optical microcavity, imposing spatially imbalanced gain-loss profile, to host an exclusively proposed next nearest neighbor resonances coupling scheme. Adopting scattering matrix (S-matrix) formalism, the effect of interplay between such proposed resonance interactions and the incorporated non-Hermiticity in the microcavity is analyzed drawing a special attention to the existence of hidden singularities, namely exceptional points (EP s); where at least two coupled resonances coalesce. We establish adiabatic flip-of-states phenomena of the coupled resonances in the complex frequency plane (k-plane) which is essentially an outcome of the fact that the respective EP is being encircled in system parameter plane. Encountering such multiple EP s, the robustness of flip-of-states phenomena have been analyzed via continuous tuning of coupling parameters along a special hidden singular line which connects all the EP s in the cavity. Such a numerically devised cavity, incorporating the exclusive next neighbor coupling scheme, have been designed for the first time to study the unconventional optical phenomena in the vicinity of EP s.
Exploiting scattering matrix (S-matrix) formalism, a unique route for manipulating the exceptional points (EPs) has been reported in a trilayer open optical microcavity with non-uniform real refractive index. The boundaries of the intermediate index layer are appropriately tapered. The cavity is partially pumped by a transverse distribution of a balanced gain-loss profile. With the strict restriction of balanced gain-loss, controlling infinitesimally small variation of gain-coefficient with simultaneous tapering parameter an EP has been encountered; which is being encircled in cavity parameter space to study dynamics of the coupled states around the EP in the context of robust selective flip-of-state phenomena with lower-asymmetry in state conversion efficiencies. Such a specialty trilayer microcavity with tunable width is reported for the first time; which turns out to be a specific approach to achieve maximum efficiency in conversion with minimum asymmetry. Considering suitable state-of-the-art techniques, this exclusive proposal may open up a fabrication feasible platform for device level implementation of system control exploiting EPs.
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