The use of enhanced electromagnetic fields in nanophotonic structures is moving from plasmonic to all-dielectric platforms in order to overcome the intrinsic Ohmic losses from metal inclusions. In this work, we demonstrate that strong electromagnetic fields may be generated in the infrared without heating the nearby molecules by exciting anapole modes in a slotted all-dielectric cylinder on a glass substrate surrounded by water. Numerical calculations are used to prove that the platform is useful to manipulate small biomolecules without heating.
We show a strategy to design polarization-insensitive electro-optical modulators based on the use of single-layer graphene sheets working at the ε-near-zero (ENZ) regime. An external voltage is used to change the optical properties of graphene at will, allowing dynamical tuning of the permittivity between dielectric and metallic behavior. As a proof of concept, we designed an ultra-compact modulator, with a minimum length of 5.22 µm, to produce a 3 dB modulation depth when working at the center of the optical C-band (λ = 1550 nm). The modulation principle is based on the high electromagnetic absorption associated to the ENZ mode of graphene. Our approach can be used for highly integrated, cost-effective and energy-efficient nanophotonic circuits in future optical communication networks.
We present a new proposal for enhancing the transverse magneto-optical Kerr effect (TMOKE) in the transmission mode using dielectric magneto-optical (MO) ribs deposited on a high-refractive-index (HRI) slab. Our concept is based on the phase-matching condition between the MO grating and the slab to produce extraordinary TMOKE amplitudes, which are superior to the most successful plasmonic approaches, and at least one order of magnitude higher than using dielectric MO gratings. It is also significant that there was almost no loss in the structure proposed owing to the low level of losses from the constituent materials. These features can be exploited in sensing and biosensing, as we demonstrated by considering the nanostructure in a typical liquid medium.
We report on the design of an all-dielectric quasiperiodic grating coupler with rectangular Si ribs on a SiO2 substrate. The structure consists of ten periods built by alternating Si ribs and air according to the S4 step of the Fibonacci series, i.e., the period was made as ABAAB, where A (B) can be used as Si (air) or air (Si). The thicknesses of air and Si ribs were taken as 315 nm, with a total length for the unit cell of 1575 nm. The finite- difference time-domain (FDTD) technique was used to obtain the numerical data within the commercial software Lumerical FDTD. Multiple coupling efficiency peaks were observed owing to self-similarity effects. Furthermore, we show numerically that optimum wavelengths and coupling efficiency amplitudes can be tailored by varying the ribs’ etch-depth and the angle of incidence from the optical fiber, which makes the proposal relevant for efficient, broadband optoelectronic circuits.
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