Two-dimensional phase-space picture of the photonic crystal Fano laser

The recently realized photonic crystal Fano laser constitutes the first demonstration of passive pulse generation in nanolasers [Nat. Photonics $\boldsymbol{11}$, 81-84 (2017)]. We show that the laser operation is confined to only two degrees-of-freedom after the initial transition stage. We show that the original 5D dynamic model can be reduced to a 1D model in a narrow region of the parameter space and it evolves into a 2D model after the exceptional point, where the eigenvalues transition from being purely to a complex conjugate pair. The 2D reduced model allows us to establish an effective band structure for the eigenvalue problem of the stability matrix to explain the laser dynamics. The reduced model is used to associate a previously unknown origin of instability with a new unstable periodic orbit separating the stable steady-state from the stable periodic orbit.Comment: 12 pages, 7 figures, journal, Phys. Rev. A, before editorial correctio

Design and fabrication of ridge waveguide-based nanobeam cavities for on-chip single-photon sources

We report on the design of nanohole/nanobeam cavities in ridge waveguides for on-chip, quantum-dot-based single-photon generation. Our design overcomes limitations of a low-refractive-index-contrast material platform in terms of emitter-mode coupling efficiency and yields an outcoupling efficiency of 0.73 to the output ridge waveguide. Importantly, this high coupling efficiency is combined with broadband operation of 9 nm full-width half-maximum. We provide an explicit design procedure for identifying the optimum geometrical parameters according to the developed design. Besides, we fabricate and optically characterize a proof-of-concept waveguide structure. The results of the microphotoluminescence measurements provide evidence for cavity-enhanced spontaneous emission from the quantum dot, thus supporting the potential of our design for on-chip single-photon sources applications

Eccentrically-Layered Active Coated Nano-Particles for Directive Near- and Far-Field Radiation

The present work shows how the eccentricity in active nano-particles may lead to very interesting and rather directive near- and far-field radiation patterns. The nano-particle is of a three-layer type and consists of a silica core, a free-space middle layer and an outer silver shell and is excited by a magnetic line source. The constant frequency gain model is included in the silica core, and the eccentricity is introduced through appropriate displacements of the core. It is shown that the eccentricity in a nano-particle, which was initially designed to excite a strong dipole mode, causes a progressively larger excitation of several other (including higher order) modes, this being more so the larger the core displacement. Specifically, eccentric nano-particles are identified with comparable simultaneous excitations of dipole and quadrupole modes, with associated large values of the radiated power and, even more notably, enhanced and directive near- and far-field radiation patterns. The main beam of these patterns is shown to be effectively tailored (enhanced, reshaped and steered) by the direction and amount of the core displacement. The eccentric nano-particles can be additionally gain optimized to boost their near-field response and the radiated power, while retaining the directivity of the gain unoptimized eccentric cases. Owing to their very directive nearand far-field patterns, the proposed eccentric, active three-layer nano-particles may provide alternative strategies towards the design of directive nano-antennas relative to several of the existing solutions

Effects of layer eccentricity on the super-resonant states of active cylindrical core-shell nano-particles

This work reports on the effects of layer eccentricity on the resonant properties of active cylindrical core-shell nano-particles excited by a near-by exterior magnetic line source. The core-shell particles consist of a silver core layered with a silica shell. For a fixed over-all radius of the nano-particle equal to 30 nm, we investigate designs with relatively small (radius equal to 6 nm) and large (radius equal to 24 nm) silver cores and we quantify their performance characteristics in terms of the near- and far-field properties. Our results show that the super-resonances, known to exist in the concentric version of these nano-particles, are significantly influenced by introducing eccentricity (through displacements of the silver core relative to the silica shell). In particular, their amplitude responses are found to diminish significantly for silver core displacements ≥ 3 nm for the small core case, and even for displacements ≥ 1 nm for the large core case. The present results are useful from the experimental point of view since slight displacements of the centers of the core and shell parts of the investigated nano-particles are likely to occur in standard fabrication processes

Effects of layer eccentricity on the super-resonant states of active cylindrical core-shell nano-particles

This work reports on the effects of layer eccentricity on the resonant properties of active cylindrical core-shell nano-particles excited by a near-by exterior magnetic line source. The core-shell particles consist of a silver core layered with a silica shell. For a fixed over-all radius of the nano-particle equal to 30 nm, we investigate designs with relatively small (radius equal to 6 nm) and large (radius equal to 24 nm) silver cores and we quantify their performance characteristics in terms of the near- and far-field properties. Our results show that the super-resonances, known to exist in the concentric version of these nano-particles, are significantly influenced by introducing eccentricity (through displacements of the silver core relative to the silica shell). In particular, their amplitude responses are found to diminish significantly for silver core displacements ≥ 3 nm for the small core case, and even for displacements ≥ 1 nm for the large core case. The present results are useful from the experimental point of view since slight displacements of the centers of the core and shell parts of the investigated nano-particles are likely to occur in standard fabrication processes

Active coated nano rod antennas for enhanced and directive scattering phenomena

The scattering properties of a range of symmetric and asymmetric active coated nano rod antennas are investigated numerically. The active nano rods are composed of a silica dioxide nano-core coated with a silver nano-shell, and with a canonical gain model implemented into their nano-core regions. The asymmetric nano rods are obtained through suitable perforations of their nano-shell and/or nano-core regions. In all cases, active nano rods are found to exhibit super-resonant phenomena with significantly enhanced scattered fields for an incident plane wave having the magnetic field parallel to the rod axis. While the dipole-mode response in the symmetric cases is only weakly directive, the asymmetric cases stimulate an abundant emission of higher order modes furnishing rather enhanced and directive near-fields. As the length of the symmetric nano rods decreases, more gain is needed to achieve a super-resonant response, which also was found to be blue-shifted. For asymmetric cases, the gain was lowered, and the response got blue-shifted as the asymmetry increased. The proposed active nano rod antennas provide a new class of antennas with desirable wavelength tunability and polarization-dependent scattering properties; this makes them interesting candidates for many nano-photonic applications. Moreover, the proposed geometries bridge the important gap between the two often considered canonical geometries, namely, spherical and infinitely long cylindrical particles. The detailed knowledge of gain values and resonant wavelengths provided in here is crucial for a successful combination of such particles with realistic gain materials

Active coated nano rod antennas for enhanced and directive scattering phenomena

The scattering properties of a range of symmetric and asymmetric active coated nano rod antennas are investigated numerically. The active nano rods are composed of a silica dioxide nano-core coated with a silver nano-shell, and with a canonical gain model implemented into their nano-core regions. The asymmetric nano rods are obtained through suitable perforations of their nano-shell and/or nano-core regions. In all cases, active nano rods are found to exhibit super-resonant phenomena with significantly enhanced scattered fields for an incident plane wave having the magnetic field parallel to the rod axis. While the dipole-mode response in the symmetric cases is only weakly directive, the asymmetric cases stimulate an abundant emission of higher order modes furnishing rather enhanced and directive near-fields. As the length of the symmetric nano rods decreases, more gain is needed to achieve a super-resonant response, which also was found to be blue-shifted. For asymmetric cases, the gain was lowered, and the response got blue-shifted as the asymmetry increased. The proposed active nano rod antennas provide a new class of antennas with desirable wavelength tunability and polarization-dependent scattering properties; this makes them interesting candidates for many nano-photonic applications. Moreover, the proposed geometries bridge the important gap between the two often considered canonical geometries, namely, spherical and infinitely long cylindrical particles. The detailed knowledge of gain values and resonant wavelengths provided in here is crucial for a successful combination of such particles with realistic gain materials