Ricardo Tellez-Limon

Theoretical analysis of Bloch mode propagation in an integrated chain of gold nanowires

The eigenmodes analysis of Bloch modes in a chain of metallic nanowires (MNWs) provides a significant physical understanding about the light propagation phenomena involved in such structures. However, most of these analyses have been done above the light line in the dispersion relation, where the Bloch modes can only be excited with radiative modes. By making use of the Fourier modal method, in this paper we rigorously calculate the eigenmode and mode excitation of a chain of MNWs via the fundamental transverse magnetic (TM) mode of a dielectric waveguide. Quadrupolar and dipolar transversal Bloch modes were obtained in an MNW chain embedded in a dielectric material. These modes can be coupled efficiently with the fundamental TM mode of the waveguide. Since the eigenmodes supported by the integrated plasmonic structure exhibit strong localized surface plasmon (LSP) resonances, they could serve as a nanodevice for sensing applications. Also, the analysis opens a direction for novel nanostructures, potentially helpful for the efficient excitation of LSPs and strong field enhancement.

Topological terahertz circuits using semiconductors

Topological insulator-based devices can transport electrons/photons at the surfaces of materials without any back reflections, even in the presence of obstacles. Topological properties have recently been investigated using non-reciprocal materials, such as gyromagnetics, or using bianisotropy. However, these effects usually saturate at the optical frequencies and limit our ability to scale down the devices. In order to implement topological devices that we introduce in this paper for the terahertz range, we show that the semiconductors can be utilized via their cyclotron resonance in combination with small magnetic fields. We propose two terahertz operating devices such as the topological tunable power splitter and the topological circulator. This work opens up the perspectives in designing the terahertz integrated devices and circuits with high functionality.

Directive and enhanced spontaneous emission using shifted cubes nanoantenna

Recent studies have demonstrated that nano-patch antennas formed by metallic nanocubes placed on top of a metallic film largely enhance the spontaneous emission rate of quantum emitters due to the confinement of the electromagnetic field in the small nanogap cavity. The popularity of this architecture is, in part, due to the ease in fabrication. In this contribution, we theoretically demonstrate that a dimer formed by two metallic nanocubes embedded in a dielectric medium exhibits enhanced emission rate compared to the nano-patch antenna. Furthermore, we compare the directivity and radiation efficiency of both nanoantennas. From these characteristics, we obtained information about the “material efficiency” and the coupling mismatch efficiency between a dipole emitter and the nanoantenna. These quantities provide a more intuitive insight than the Purcell factor or localized density of states, opening new perspectives in nanoantenna design for ultra-directive light emission.

Integrated metaphotonics: symmetries and confined excitation of LSP resonances in a single metallic nanoparticle

Using numerical simulations, we demonstrate that the dipolar plasmonic resonance of a single metallic nanoparticle inserted in the core of a dielectric waveguide can be excited with higher order photonic modes of the waveguide only if their symmetry is compatible with the charge distribution of the plasmonic mode. For the case of a symmetric waveguide, we demonstrate that this condition is only achieved if the particle is shifted from the center of the core. The simple and comprehensive analysis presented in this contribution will serve as basis for applications in integrated nanophotonic/metamaterials devices, such as optical filters, modulators and mode converters.

Integrated and steerable vortex laser using bound states in continuum (Conference Presentation)

Steering the beam of a wave source has been demonstrated using mechanical and non-mechanical techniques. While mechanical techniques are bulky and slow, non-mechanical techniques rely on breaking the symmetry of the refractive index profile either using asymmetric structure or injecting a non-uniform current. In this contribution, we theoretically and experimentally demonstrated a new type of topological steering of light sources in which the phase offset is provided by Floquet-Bloch phase in periodic structure. It was shown that in periodic structures, there exist singular states in the radiation region of the band diagram that exhibit diverging quality factor. Thus light sources can operate at these states with lower power threshold. The existence of these singular states are topologically protected, and their momentum are very sensitive to any small perturbations, which is used to control the steering angle. By uniformly controlling some parameters in the system, such as a physical dimension or injecting current uniformly, the beam of the light source steers. Our experimental demonstrations open new paradigm in the implementation of light steering with applications in data communications, bio imaging and sensing.

Functional topological THz devices using semiconductors

We showed that cyclotron resonance of semiconductors can be utilized in Topological devices to break the time-reversal symmetry for unidirectional propagation in THz. To demonstrate, we proposed a tunable power splitter based on topological effect.

Numerical analysis of tip-localized surface plasmon resonances in periodic arrays of gold nanowires with triangular cross section

In this contribution, we numerically study the tip enhancement of localized surface plasmons in periodic arrays of gold nanowires with triangular cross section under different illumination configurations. We found that the plasmonic resonance in a single nanowire is excited with a transverse magnetic (TM) plane wave impinging from the substrate at the critical angle, whereas grazing angles are required for the excitation of resonant propagating modes in periodic arrays of triangular-shaped nanowires. Moreover, we found that resonant plasmonic quasi-Bloch modes are efficiently excited with the fundamental TM mode of a dielectric waveguide placed underneath the array. The integrated plasmonic structure allows a strong enhancement of the electromagnetic field at the tip of the nanowires, hence its potential application in the development of new nanophotonic devices.

Modal analysis of LSP propagation in an integrated chain of gold nanowires

Light propagation in an integrated chain of metallic nanowires (MNW) is theoretically investigated by means of rigorous coupled wave analysis. First, we analyze the nanowires chain immersed in a dielectric homogeneous medium and we compute the eigenmodes dispersion relation and their field profiles. Depending on the nanowire aspect ratio, in addition to the longitudinal and the transversal chain modes, we found a new mode characterized by quadrupolar-like localized surface plasmons resonances well identified at the edge of the first Brillouin zone. We then consider the vertical coupling of the MNW chain with the fundamental TM0 mode of a planar dielectric waveguide. We demonstrate that high energy transfer can be obtained, by computing near field maps and spectral responses (transmission, reflection, and absorption) of the structure consisting in a finite number of nanowires. The coupling mechanism between the dielectric waveguide and the MNW chain is rigorously explained through the analysis of the eigenmodes dispersion relation.