arXiv subjects

Janderson Rocha Rodrigues

Publications and source records attributed to Janderson Rocha Rodrigues.

4 recordsLinked to original sources

arXiv2026

Antireflection by design in bilayer metasurfaces

Antireflection coatings are ubiquitous in optical systems, where they maximize transmission and suppress undesirable reflections by impedance-matching uniform interfaces. Extending this principle to metasurfaces, however, is fundamentally more challenging because wavefront control requires a library of geometrically distinct meta-atoms, each locally imposing a prescribed phase that is tethered to its transmittance. Here, we show that vertical integration resolves this constraint by allowing bilayer meta-atoms to operate simultaneously as a phase shifter and an impedance-matching stack. Using an effective thin-film model, we derive a design rule that links the effective indices of two independently patterned layers and identifies antireflective bilayer libraries with full $0$-$2π$ transmission-phase coverage. We realize this concept in a free-standing TiO$_2$/TiO$_2$ metalens operating at 1310 nm, which suppresses reflectance below that of bare glass while preserving diffraction-limited focusing. These results establish bilayer metasurfaces as a framework for co-engineering optical impedance and wavefront response at the meta-atom level.

physics.optics↗

arXiv2018

Optimization of radiation pressure in dielectric nanowaveguides

Stimulated Brillouin scattering (SBS) processes have been allowing important technological breakthroughs in integrated photonics and nano-optomechanics, by exploiting light-sound (photon-phonon) interactions at the nanoscale. These nonlinear processes are created by two main effects: radiation pressure and electrostriction; however, the former is the predominant one in high-index-contrast nanowaveguides. In this letter, we derive a simple set of analytical expressions that can be used for optimizing the radiation pressure on the waveguide boundaries, for any optical mode, polarization, and wavelength. We observe a very strong influence of the waveguide geometric parameters on the optimal radiation pressure value. Furthermore, we explain how the existence of such optimal geometric dimensions is physically related to the minimization of the electromagnetic momentum flow in the propagation direction. This work provides a novel and robust method, yet simple, to optimize the radiation pressure in dielectric nanowaveguides, which may be of great relevance for designing integrated photonic-phononic devices.

physics.optics↗

arXiv2017

Dynamic Sensitivity Study of MEMS Capacitive Acceleration Transducer Based on Analytical Squeeze Film Damping and Mechanical Thermoelasticity Approaches

The dynamic behavior of a capacitive micro-electro-mechanical (MEMS) accelerometer is evaluated by using a theoretical approach which makes use of a squeeze film damping (SFD) model and ideal gas approach. The study investigates the performance of the device as a function of the temperature, from 228 K to 398 K, and pressure, from 20 to 1000 Pa, observing the damping gas trapped inside de mechanical transducer. Thermoelastic properties of the silicon bulk are considered for the entire range of temperature. The damping gases considered are Air, Helium and Argon. The global behavior of the system is evaluated considering the electro-mechanical sensitivity (SEM) as the main figure of merit in frequency domain. The results show the behavior of the main mechanism losses of SFD, as well as the dynamic sensitivity of the MEMS transducer system, and are in good agreement with experimental dynamic results behavior.

physics.app-ph↗

arXiv2016

Analytical solutions for optical forces between two dielectric planar waveguides immersed in dielectric fluid media

We investigate optical (transverse gradient) forces between two high-index dielectric planar waveguides immersed in low-index dielectric fluid media. Complimentary to previous studies, we extend optical forces calculations, in order to take into account a non-vacuum (and non-air) background medium, by using the Minkowski stress tensor formulation; we derived a very simple set of equations in terms of the effective refractive indexes of the waveguide eigenmodes. We also used a normalized version of the dispersion relation method to calculate the optical forces, in order to validate our results for different dielectric fluid media. Excellent agreement between the two methods was obtained for all analyzed cases. We show that, due to slot-waveguide effect, the TM modes are more sensitive to changes in the fluid refractive index than the TE ones. Furthermore, the repulsive optical force of the antisymmetric TM1 mode becomes stronger for higher refractive indexes, whereas the attractive force of the symmetric TM0 mode becomes weaker. The methodology and results presented in this work provide a rigorous analysis of nano-optomechanical devices actuated by optical forces in a broader range of materials and applications.

physics.optics↗