We present a non-intuitive but still practically implementable silicon meta-atom with strong electrical tunability. We used topological optimization on a 20×20-variable silicon-on-insulator grid and achieved tunability by using JRD1, a stable electrooptic polymer. The electric potential is applied on two ITO electrodes, and a peak shift of 0.6 nm V−1 is achieved in the optical communication E and S bands. The proposed device can be regarded as a demultiplexer or channel selector on a coarse wavelength-division-multiplexing system, with an extinction ratio between adjacent channels of ∼14 dB.
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.
In this work, we analyze passive parameters for a band of 1500 to 1600 nm in microring resonators (MRRs). Such analysis can be vital for estimating an appropriate parameter design exploration with potential applications on Wavelength Division Multiplexing (WDM) solutions. Using a coupled mode theory-based method, we found optimal design spaces for MRRs with radii from 5 to 10 µm and bus-ring gap from 0.12 to 0.21 µm. For All-Pass MRRs, we found an optimal design space where the transmittances in the resonant frequencies are down to 8% in the Through port, while for the Add-Drop MRRs, we found an optimal design space where for transmittances in the Drop port are from 0.77 to 1. We also found optimal design spaces for Q-factors between 2000 and 3800. To find the optimal ring/radius and bus-ring gap values inside the design spaces, we use the particle swarm optimization technique. The data obtained with the exhibited work also shows a modal analysis for the supermodes formed by the cross-section of the bus-ring interface and the impact of UV-lithography common fabrication errors, even due to wafer die positioning. With the latter, our work provides a comprehensive design space exploration and helps designers to know the effect that typical structural fabrication errors will have on the passive resonance.
III-V materials with quantum wells or quantum dot active regions have proven to be relatively efficient devices for amplifying light. However, integration and scaling of many other functions are moving towards the development of ever more complex photonic integrated circuits (PICs). Assembling these devices into hybrid/heterogeneous PICs poses a challenge in terms of bandwidth and footprint. In this work, we propose a Particle Swarm Optimized methodology to generate non-intuitive structures that couple light vertically from a III-V platform to a silicon-on-insulator chip. By designing heuristically optimized III-V and silicon tapers, we can overcome the limitations of typical linearly-varying spot-size converters in terms of footprint, without sacrificing bandwidth. Furthermore, the optimization parameters are adjusted to fit the usual design rule constraints that are ready for mass production, namely UV-lithography limits.
The Genetic Algorithm (GA) is one of the most popular heuristic methods due to its natural and fast implementation. However, at the same time, it has the disadvantage of poor optimization. To improve performance, it’s necessary avoid stuck in local maximums throught choosing proper methods and parameters that vary for each application. In photonic devices, although the GA has been recently used to optimize passive silicon Y-branches, its performance is still trailing behind other optimization algorithms based on swarms, for instance. In this work, we present a new three-part heuristic method for optimizing Y-branches. We used the Finite-difference Time-domain (FDTD) method and the Particle Swarm Optimization (PSO) to generate an optimal data set as initial population for the GA. Considering an adequate population model, we demonstrate improvement in the performance for the design of a Y-branch through the GA. Next, we used a variation of a gradient-based search method to fine-tune the final parameters to find the absolute maximum. As a result, we produced new non-intuitive Y-branch devices with on-chip areas smaller than 2µm2 and excess loss down to 0.05 dB @1550 nm for the TE mode. A complete study of fabrication feasibility and uv-lithography typical fabrication errors and its effects on the bandwidth will be shown at the time of the conference. Our method will be compared against other widely-used heuristic methods in photonic device design in terms of number of iterations.
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.
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.
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.
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.
We present the results of the theoretical study and two-dimensional frequency domain finite-element simulation of tapered segmented waveguides. The application that we propose for this device is an adiabatically tapered and chirped PSW transmission, to eliminate higher order modes that can be propagated in a multimode semiconductor waveguide assuring mono mode propagation at 1.55μm. We demonstrate that by reducing the taper functions for the design of a segmented waveguide we can filter higher order modes at pump wavelength in WDM systems and at the same time low coupling losses between the continuous waveguide and the segmented waveguide. We obtained the cutoff wavelength as a function of the duty cycle of the segmented waveguide to show that we can, in fact, guide 1.55μm fundamental mode over a silicon-on-insulator platform using both, silica and SU-8 as substrate material. For the two-dimensional finite element analysis a new module over a commercial platform is proposed. Its contribution is the inclusion of the anisotropic perfectly matched layer that is more suitable for solving periodic segmented structures and other discontinuity problems.
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