AbstractIt has long been recognized that emission of radiation from atoms is not an intrinsic property of individual atoms themselves, but it is largely affected by the characteristics of the photonic environment and by the collective interaction among the atoms. A general belief is that preventing full decay and/or decoherence requires the existence of dark states, i.e., dressed light-atom states that do not decay despite the dissipative environment. Here, we show that, contrary to such a common wisdom, decoherence suppression can be intermittently achieved on a limited time scale, without the need for any dark state, when the atom is coupled to a chiral ring environment, leading to a highly non-exponential staircase decay. This effect, that we refer to as intermittent decoherence blockade, arises from periodic destructive interference between light emitted in the present and light emitted in the past, i.e., from delayed coherent quantum feedback.
AbstractStrong electromagnetic coupling among plasmonic nanostructures paves a new route toward efficient manipulation of photons. Particularly, plasmon-waveguide systems exhibit remarkable optical properties by simply tailoring the interaction among elementary elements. In this paper, we propose and demonstrate a freestanding bilayer plasmonic-waveguide structure exhibiting an extremely narrow transmission peak with efficiency up to 92%, the linewidth of only 0.14 nm and an excellent out of band rejection. The unexpected optical behavior considering metal loss is consistent with that of electromagnetic induced transparency, arising from the destructive interference of super-radiative nanowire dipolar mode and transversal magnetic waveguide mode. Furthermore, for slow light application, the designed plasmonic-waveguide structure has a high group index of approximately 1.2 × 105 at the maximum of the transmission band. In sensing application, its lowest sensing figure of merit is achieved up to 8500 due to the ultra-narrow linewidth of the transmission band. This work provides a valuable photonics design for developing high performance nano-photonic devices.
AbstractIn the paper, one input optical gates i.e., INVERTER and BUFFER have been designed using some basic assumption to analyze with the help of Semi-conductor Optical Amplifier based Mach–Zehnder Interferometer structure. The results are optimized by iterative process. The proposed design of optical gates presents low complexity, high scalability and more feasible to evaluate through digital Boolean analyzation. The digital Boolean analyzation is analyzed by some basic Boolean rules and assumptions which makes the design more digital so that it can be compatible for more than one input optical gates also. Optical Gate is designed to get constructive and destructive interference for pump and probe as they are injected into SOA simultaneously. The phase modulation is converted into intensity modulation which gives a Boolean result. The paper is optimized by Eye diagram, Q factor, wavelength spectrum and frequency chirp for both the gates. The comparative results of extinction ratio for both the gates have also been discussed. The design is supported by theoretical analysis, simulation tool (Optsim) and Boolean explanation. The proposed designs are constructed with same pattern which supports the same Boolean analysis.
For wave loads on cylinders constituting a long but finite array in the presence of incident waves, variations in the magnitude of the load with the non-dimensional wavenumber exhibit interesting features. Towering spikes and nearby secondary peaks (troughs) associated with trapped modes have been studied extensively. Larger non-trapped regions other than these two are termed Region III in this study. Studies of Region III are rare. We find that fluctuations in Region III are regular; the horizontal distance between two adjacent local maximum/minimum points, termed fluctuation spacing, is constant and does not change with non-dimensional wavenumbers. Fluctuation spacing is related only to the total number of cylinders in the array, identification serial number of the cylinder concerned and wave incidence angle. Based on the interaction theory and constructive/destructive interference, we demonstrate that the fluctuation characteristics can be predicted using simple analytical formulae. The formulae for predicting fluctuation spacing and the abscissae of every peak and trough in Region III are proposed. We reveal the intrinsic mechanism of the fluctuation phenomenon. When the diffraction waves emitted from the cylinders at the ends of the array and the cylinder concerned interfere constructively/destructively, peaks/troughs are formed. The fluctuation phenomenon in Region III is related to solutions of inhomogeneous equations. By contrast, spikes and secondary peaks are associated with solutions of the eigenvalue problem. This study of Region III complements existing understanding of the characteristics of the magnitude of wave load. The engineering significances of the results are discussed as well.
We study the transport properties of electrons in a quantum wire with side-coupled quantum dots in Coulomb blockade regime by the use of the equivalent single-particle multi-channel network and Landauer formula. At low temperatures the calculated dependence of the conductance on the gate voltage of dots exhibits two dips, indicating the destructive interference of the wave directly transmitted through the wire and the wave reflected from the dots. In a wire with more than one side-coupled dots the suppression of conductance is a simple summation of the effects of scattering of all the dots. The possibility of fabricating tunable switch devices by using such structures is discussed.