Comparative study of surface plasmon scattering by shallow ridges and grooves

We revisit the scattering of surface plasmons by shallow surface defects for both protrusions and indentations of various lengths, which are deemed infinite in one-dimension parallel to the surface. Subwavelength protrusions and indentations of equal shape present different scattering coefficients when their height and width are comparable. In this case, a protrusion scatters plasmons like a vertical point-dipole on a plane, while an indentation scatters like a horizontal point-dipole on a plane. We corroborate that long and shallow asymmetrically-shaped surface defects have very similar scattering, as already found with approximate methods. In the transition from short shallow scatterers to long shallow scatterers the radiation can be understood in terms of interference between a vertical and a horizontal dipole. The results attained numerically are exact and accounted for with analytical models

Effect of defect depth on surface plasmon scattering by subwavelength surface defects

10 páginas, 13 figuras, 1 tabla.-- PACS number(s): 42.82.EtSurface plasmon scattering by bidimensional indentations and protrusions is examined, mainly in the optical regime. The width of the defects is fixed, while their height is varied. Both individual defects and arrays of defects are considered. Protrusions mainly reflect the incident plasmons in the optical range. Indentations mainly radiate the incident plasmon out of plane. An indentation produces maximum reflection and out-of-plane radiation at the same wavelength when its interaction with the incident surface plasmon is resonant. Protrusions, in general, exhibit maximum reflection and radiation at different wavelengths. Shallow arrays of either defects produce a photonic band gap, whose spectral width can be broadened by increasing the defects height or depth. At wavelengths inside the band gap, ridge arrays reflect surface plasmon polaritons (SPP’s) better than groove arrays while groove arrays radiate SPP’s better than ridge arrays.The authors acknowledge financial support from the Spanish Ministry of Science and Innovation under Grant Nos. MAT2008-06609-C02, AP2005-5185, and CSD2007- 046-Nanolight.es.Peer reviewe

Nonlinear quantum optics in the (ultra)strong light-matter coupling

The propagation of $N$ photons in one dimensional waveguides coupled to $M$ qubits is discussed, both in the strong and ultrastrong qubit-waveguide coupling. Special emphasis is placed on the characterisation of the nonlinear response and its linear limit for the scattered photons as a function of $N$, $M$, qubit inter distance and light-matter coupling. The quantum evolution is numerically solved via the Matrix Product States technique. Both the time evolution for the field and qubits is computed. The nonlinear character (as a function of $N/M$) depends on the computed observable. While perfect reflection is obtained for $N/M \cong 1$, photon-photon correlations are still resolved for ratios $N/M= 2/20$. Inter-qubit distance enhances the nonlinear response. Moving to the ultrastrong coupling regime, we observe that inelastic processes are \emph{robust} against the number of qubits and that the qubit-qubit interaction mediated by the photons is qualitatively modified. The theory developed in this work modelises experiments in circuit QED, photonic crystals and dielectric waveguides.Comment: Comments are wellcom

Scattering coefficients of surface plasmon polaritons impinging at oblique incidence onto one-dimensional surface relief defects

4 pages, 4 figures.-- PACS number(s): 73.20.Mf, 78.67. n, 41.20.JbWe present a theoretical analysis of surface plasmon polariton (SPP) scattering by shallow one-dimensional surface relief defects for oblique incidence, applying both surface impedance boundary conditions and Rayleigh expansion. Using this method, nontrivial angular dependences for transmission, reflection, and out-of-plane scattering are obtained. For the case of a defect with rectangular shape, we give an analytical description of the interference phenomena caused by the SPP diffraction for both a single defect (either protrusion or indentation) and a finite array of them.The authors acknowledge financial support from the INTAS YS Grant No. 05-109-5206, the European Network of Excellence Plasmo-Nano-Devices (Grant No. FP6-2002-IST- 1-507879 , the STREP “Surface Plasmon Photonics” Grant No. FP6-NMP4-CT2003-505699), and the Spanish MCyT Project No. MAT2005-06608-C02.Peer reviewe

One- and two-photon scattering from generalized V-type atoms

The one- and two-photon scattering matrix S is obtained analytically for a one-dimensional waveguide and a point-like scatterer with N excited levels (generalized V -type atom). We argue that the two-photon scattering matrix contains sufficient information to distinguish between different level structures which are equivalent for single-photon scattering, such as a V -atom with N = 2 excited levels and two two-level systems. In particular, we show that the scattering with the V -type atom exhibits a destructive interference effect leading to two-photon Coupled-Resonator-Induced Transparency, where the nonlinear part of the two-photon scattering matrix vanishes when each incident photon fulfills a single-photon condition for transparency

Single photons by quenching the vacuum

Heisenberg's uncertainty principle implies that the quantum vacuum is not empty but fluctuates. These fluctuations can be converted into radiation through nonadiabatic changes in the Hamiltonian. Here, we discuss how to control this vacuum radiation, engineering a single-photon emitter out of a two-level system (2LS) ultrastrongly coupled to a finite-band waveguide in a vacuum state. More precisely, we show the 2LS nonlinearity shapes the vacuum radiation into a nonGaussian superposition of even and odd cat states. When the 2LS bare frequency lays within the band gaps, this emission can be well approximated by individual photons. This picture is confirmed by a characterization of the ground and bound states, and a study of the dynamics with matrix product states and polaron Hamiltonian methods.Comment: 9 pages, 10 figure

Propiedades topológicas en nanofotónica: materiales de anchura atómica en presencia de nanoestructuras metálicas

En este trabajo se combinan los materiales bidimensionales o de anchura atómicas con las estructuras metálicas perforadas con el objetivo de desarrollar un modelo teórico capaz de abarcar los resultados experimentales que estos sistemas han producido: C. Genet et al. en ACS Photonics, 5(4):1281–1287, January 2018. <br /

Phase Magnitude Diagram for Linear Systems With Delay

[Abstract] Transfer functions can be viewed as complex functions where the magnitude and the phase of a system depend on complex numbers. In our previous work, we have developed a graphical tool where transfer functions are represented in a four-dimensional space. The magnitude is represented in decibels in the third dimension and a color code is applied to represent the phase in a fourth dimension. Level curves are used to compare points with the same magnitude or phase. This tool, which is called Phase Magnitude diagram, makes it more intuitive to understand complex functions. This representation allows the user to visually obtain the phase and the gain that have to be added to a system to meet some design specifications. After that, any control approach can be employed. The application to systems with delay is discussed in this paper. It is demonstrated that the Phase Magnitude diagram can be efficiently applied to design an ideal PD controller for a system with delay. In addition, it is deduced that this instrument is not limited to this class of system.https://doi.org/10.17979/spudc.978849749808