The non-Drude-like behavior of the real part of the photoinduced permittivity Re epsilon(P) of GaAs and Si samples in the gigahertz range is detected by direct cavity measurements under conditions of fiber-optic irrad...
详细信息
The non-Drude-like behavior of the real part of the photoinduced permittivity Re epsilon(P) of GaAs and Si samples in the gigahertz range is detected by direct cavity measurements under conditions of fiber-optic irradiation at a wavelength of lambda = 0.97 microns with changing power P in the range of 0-1 W. It is shown that, in accordance with the hypothesis of the exciton mechanism of photoinduced microwave dielectric permittivity, Re epsilon P increases with increasing P (approaching saturation above P = 200 mW) instead of decreasing within the framework of free-charge carriers according to Drude. The generality of the behavior of the real parts of the photoinduced permittivity observed in semiconductors of different types (direct-gap GaAs and indirect-gap Si) in different electrodynamic systems (waveguides, cavities, metastructures) testifying to the universality of the exciton mechanism is demonstrated. Optically controlled metastructures in the GHz band containing resonant electrically conductive elements filled with GaAs and Si samples are proposed for the first time: a metastructure based on linear dipoles and a half-wave electric dipole based on a multipass spiral. The gigahertz responses of the metastructures and transformation of the responses associated with changes in the dielectric permittivity of Si and GaAs during photoexcitation are measured for the first time. Based on the hypothesis put forward about the effect of excitons on photoexcitation, the observed saturation effect of gigahertz photoinduced permittivity is discussed.
Graphene has the potential to manipulate surface modes in frequency bands from THz to mid-IR regions. Typically, due to single -atom thickness and low charge -carrier density, the thermal response of graphene is ineff...
详细信息
Graphene has the potential to manipulate surface modes in frequency bands from THz to mid-IR regions. Typically, due to single -atom thickness and low charge -carrier density, the thermal response of graphene is ineffective. Temperature -sensitive materials (TSMs) can play an active role in enhancing the thermal response of graphene-based devices. In the present work, graphene-based temperature -sensitive metafilms have been proposed for thermally tunable propagation of electromagnetic surface modes. A detailed analytical and numerical solution for temperature -dependent electromagnetic surface (even and odd) modes supported by the graphene-based temperature -sensitive metafilm has been studied. The Kubo's formulation has been used to model optical conductivity ( sigma g ) while the hybrid Drude's model is implemented to realize the indium antimonide (InSb) as temperature -sensitive material. To simulate the metafilm, the waveguide modal analysis approach was implemented, while the realization of the graphene sheets was achieved by the use of impedance boundary conditions (IBCs). The propagation characteristics for even/odd surface modes were analyzed under different values of temperature (T), chemical potential ( mu c ), and thickness of metafilm (d). Further, the numerical results for even and odd surface modes under two phases of InSb [Insulator phase (T = 200 K) and metallic phase (T = 300 K)] were compared under different values of chemical potential ( mu c ) and TSM film thickness (d). It is concluded that the propagation characteristics of surface modes are sensitive to the external temperature and can be tailored by tuning the temperature, chemical potential ( mu c ), and TSM film thickness (d). Moreover, the degeneracy of the even and odd modes can be controlled by varying the temperature and TSM film thickness. The work is suitable for designing temperature -assisted dual channel waveguides, THz optical switches, THz optical logic designs, and flexible the
In this work, electromagnetic propagating modes within a planar waveguide featuring a cholesteric elastomer core whose helical axis is oriented perpendicular to the planar boundaries are analysed. The Maxwell equation...
详细信息
In this work, electromagnetic propagating modes within a planar waveguide featuring a cholesteric elastomer core whose helical axis is oriented perpendicular to the planar boundaries are analysed. The Maxwell equations and the constitutive equation are used to establish a novel configuration, enabling the tuning of mechanical stress through elastic strain in the perpendicular stretching along the helix axis. The derived set of equations is numerically solved, presuming the waveguide to be surrounded by either air or a vacuum medium. The corresponding band structure and the ratio between electric and magnetic modes have been plotted as a function of angular frequency. The amplitudes of the electromagnetic field profiles are also investigated as functions of position. The ratio of Transverse Electric and Transverse Magnetic modes, along with the cut-off frequencies, is also examined as functions of strain. Finally, the mixing of transverse electric and magnetic modes to generate new eigenmodes, as well as the investigation of their propagation conditions within the waveguide, is examined in this study.
The design for a metadevice on an optical platform combining two different applications is reported, namely optical filter and optical splitter. The platform is based on a dropping cavity placed in two-dimensional squ...
详细信息
The design for a metadevice on an optical platform combining two different applications is reported, namely optical filter and optical splitter. The platform is based on a dropping cavity placed in two-dimensional square photonic crystal (2D-PC). The PC-based optical filter consists of a periodic disposition of silicon (Si) cylinders in air, of radius r = 0.2a and a dielectric constant epsilon = 12, while the PC-based splitter is composed of square alumina rods (Al2O3) in air, of radius r = 0.2a and a dielectric constant epsilon = 8.9. The two dropping PC waveguides, having the size w, are coupled via a cavity-ring resonator of thickness g. By controlling the geometrical parameters w and g, the incoming wavelength can be shifted or extinct.
Development of the Mach-Zender electrooptic modulator with adjustable extinction coefficient provided by electrical tuning of the input splitter based on multimode interferometer. Electrooptical bandwidth of the modul...
详细信息
Development of the Mach-Zender electrooptic modulator with adjustable extinction coefficient provided by electrical tuning of the input splitter based on multimode interferometer. Electrooptical bandwidth of the modulators was higher than 32 GHz, modulus of electric signal reflectance from the input was not higher than -12 dB within the range up to 43 GHz, half-wave voltage was equal to 2.8 V at 1550 nm. However, electrical tuning of the input splitter extended the extinction ratio of the modulator from the initial 21.5-29.5 dB.
The T-15MD tokamak is equipped with a gyrotron set-up, which currently includes one gyrotron with an operating output frequency of 82.6 GHz and a power of 1 MW. The length of the waveguide path from the gyrotron to th...
详细信息
Waveguide quantum electrodynamics represents a powerful platform to generate entanglement and tailor photonic states. We consider a pair of identical qubits coupled to a parity invariant waveguide in the microwave dom...
详细信息
Waveguide quantum electrodynamics represents a powerful platform to generate entanglement and tailor photonic states. We consider a pair of identical qubits coupled to a parity invariant waveguide in the microwave domain. By working in the one- and two-excitation sectors, we provide a unified view of decay processes and show the common origin of directional single-photon emission and two-photon directional bunching. Unveiling the quantum trajectories, we demonstrate that both phenomena are rooted in the selective coupling of orthogonal Bell states of the qubits with photons propagating in opposite directions. We comment on how to use this mechanism to implement optimized post-selection of Bell states, heralded by the detection of a photon on one side of the system.
Excitation equations for waveguides and cavities excited by extraneous sources are used for solving problems in electrodynamics, microwave and terahertz electronics. In some monographs authors suggest an algorithm for...
详细信息
In this study, we demonstrate direct femtosecond laser writing of -BaB2O4 crystal waveguides in the inside of 47,5BaO-5Al2O3-47,5B2O3 glass. The propagating mode profile was evaluated in the near field as Gaussian wit...
详细信息
ISBN:
(纸本)9781665418768
In this study, we demonstrate direct femtosecond laser writing of -BaB2O4 crystal waveguides in the inside of 47,5BaO-5Al2O3-47,5B2O3 glass. The propagating mode profile was evaluated in the near field as Gaussian with slightly elliptical cross-section.
Astrophotonics is a burgeoning field that lies at the interface of photonics and modern astronomical instrumentation. Here we provide a pedagogical review of basic photonic functions that enable modern instruments, an...
详细信息
Astrophotonics is a burgeoning field that lies at the interface of photonics and modern astronomical instrumentation. Here we provide a pedagogical review of basic photonic functions that enable modern instruments, and give an overview of recent and future applications. Traditionally, optical fibres have been used in innovative ways to vastly increase the multiplex advantage of an astronomical instrument, e.g. the ability to observe hundreds or thousands of stars simultaneously. But modern instruments are using many new photonic functions, some emerging from the telecom industry, and others specific to the demands of adaptive optics systems on modern telescopes. As telescopes continue to increase in size, we look to a future where instruments exploit the properties of individual photons. In particular, we envisage telescopes and interferometers that build on international developments in quantum networks, the so-called quantum internet. With the aid of entangled photons and quantum logic gates, the new infrastructures seek to preserve the photonic state and timing of individual photons over a coherent network.
暂无评论