Search

As the optical characteristics of several materials such as vanadium oxide (VO 2 ) and lithium niobate (LiNbO 3 ) exhibit electrostatic and/or thermal dependences, these materials can be exploited in the design of multicontrollable optical devices. We simulated the visible/near-infrared spectrums of the specular reflectances and absorptances of a bicontrollable metasurface absorber with pixelated meta-atoms. Each meta-atom is a 3 × 3 array of pixels, some patched with VO 2 , some with LiNbO 3 , some with copper, and the remaining unpatched. The VO 2 pixels provide thermal control, the LiNbO 3 pixels electrostatic control.

This article presents the comparative analysis of antennas for Ground Penetration Radars (GPR) that operate in the VHF/UHF band around 200 MHz. Three types of antennas are optimized to improve bandwidth, obtain a gain greater than 5 dB while analyzing their Half Power Beam Width-HPBW, and front to back levels. These antennas are candidates to be implemented on a 2×2 array for a double polarized GPR to improve its resolution and range. This radar conducts non-invasive explorations to obtain data from Caral’s archaeological center in the city of Lima, Peru. The geometry design, simulation results, and optimization of the antennas were calculated using the ANSYS-HFSS software. The simulation results have indicated that the Antipodal Vivaldi antenna showed better results than the Log Periodic Dipole Arrays and the DGS Vivaldi antennas.

Aluminum nitride (AlN), which belongs to the family of the III-V semiconductors, is a material of great interest in the microelectronics industry due to its high decomposition temperature, good chemical stability, wide bandgap and CMOS compatibility. Moreover, AlN is known by its Pockels coefficients, which makes it very suitable for various non-linear optical devices. In this work, a study of a design space exploration of fundamental mode polarization in an AlN pedestal waveguide is proposed. The current work performs a dispersion analysis of this type of waveguide by varying the dimensions of the core and the pedestal. Lastly, electrode design for phase shifting analysis is also proposed. The data obtained with the exhibited work will allow the device designer to have a design space with light polarization control to stimulate the adequate electro-optic coefficient, with potential applications in modulators, switches, multiplexers, phase shifters, among others. A feasibility study will also be provided.

Coupling between monomode silicon waveguides and Ge photodetectors is challenging due to the size mismatch between both components. This work proposes a non-linear tapered coupling device to couple light from a silicon on insulator waveguide to an SOI Ge photodetector. For our 32.1 µm non-linear spot-size converter, the simulated transmission coefficients in the SCL band for 1550 nm, 1460 nm, and 1625 nm wavelength are -0.0113, -0.059, -0.0092 dB, respectively; while state of the art linear spot-size converters of the same transmission coefficients are around 211% bigger.

Silicon modulators paved the way for silicon photonics to take control of optical interconnects. Since its popularization, most works use the 1-D diode model approximation to design the horizontal PN junction, which estimates the modulator bandwidth and efficiency. Some works do not even consider the effects of fringe capacitance, alleging that the junction’s dimensions are large. The 1-D model is suitable for vertically uniform PN junctions. However, there are essential deviations for the typical rib waveguide used in most horizontal-junction silicon modulators. Our work aims to quantify such deviations incorporating details from 2D model simulations and offer a corrected 1-D model for estimating modulation bandwidth. This study was carried out as follows: firstly, we incorporated an improved scheme for phase shifting and loss for different junction locations and widely used doping concentrations. Next, we analyzed the generation-recombination effects and their impact on the depletion width at the top and bottom of the waveguide. We calculated the depletion width via the 1-D model and the two-dimensional Poisson’s equation finite-element calculation for the rib and identified an important mismatch. Lastly, we propose and demonstrate an accurate equivalent circuit with our 1-D model corrections. Our model considers the total depletion capacitance, the fringe capacitance, the capacitance due to the wider depletion widths at the top and bottom surfaces of the diode, and other capacitive effects at the border of the rib as a result of high reverse bias. We found that although the 1-D model is well-suited for small reverse biases, higher voltages and extreme junction locations affect the bandwidth’s estimation dramatically.

Silicon photonics is the leading platform for pho-tonic integrated circuits (PICs) because of its low fabrication cost and a small area on-chip, which allows the forefront of the industry to develop low-energy consuming devices. For the implementation of PICs, among passive devices, the most used because of its functionality is the power splitter. Y-junctions are power splitters that are compact and can deliver relatively wide-band frequency responses. In order to respond to the current demands of silicon photonics foundries, this work proposes a method based on the Particle Swarm Optimization to design always-feasible and mass-production oriented Y-junctions. We have achieved transmittances above 49%, and a flat frequency response in the SCL optical communications band.

Thin-film polymer-on-silicon modulators are efficient devices which have shown potential for integration scalability due to chromophore-based electro-optic constant engineering. Assembling them into hybrid silicon-photonics integrated circuits poses an interesting challenge in terms of bandwidth and footprint. Accordingly, we propose the first, to the best of our knowledge, sub-wavelength silicon tapered structures to couple light vertically from a polymer film platform to a silicon-on-insulator chip. By designing horizontally tapered and longitudinally segmented waveguides in the subwavelength regime to couple light vertically, we can overcome the bandwidth limitations of grating couplers while still have considerable footprint reduction when compared to continuous linearly tapered evanescent vertical coupling. Our simulation results show that silicon-on-insulator-compatible linearly tapered segmented waveguides offer losses bellow 0.5 dB in the C and L bands with four times smaller coupling length than their continuous counterpart. Preliminary studies show that there is good horizontal misalignment tolerance up to 1.5 micrometers.

Optical antennas/nanoantennas are optical elements that have gained highlight in this decade and have potential application in several branches of photonics/plasmonics, such as, optical sensors, lasers, solid state lighting, photovoltaics, microscopy, etc. Additionally, the dipole nanoantennas have been the antennas elements mostly studied in proposals for those applications and, in special, for free-space communication based on plasmonic circuits. Here we report some advantages of dielectric resonator nanoantennas (DRNAs) as elements for coupling light to plasmonic-based circuits. Fundamental antenna parameters such as reflection coefficient, gain, efficiency, among others, are evaluated and its advantages are highlighted for nanophotonics applications. A study about an optical link for circuits based on metal-dielectric-metal-dielectric (MDMD) nanostrip waveguides operating at the central wavelength of λ0 = 1.55 μm is evaluated. We studied the coupling of near- and far-fields of a DRNA matched to an MDMD nanostrip waveguide. The results show the advantage of it as an element for optical coupling from/to free-space as well as to establish a wireless optical link for inter-chip communication.