Elastic Wave Eigenmode Solver for Acoustic Waveguides

A numerical solver for the elastic wave eigenmodes in acoustic waveguides of inhomogeneous cross-section is presented. Operating under the assumptions of linear, isotropic materials, it utilizes a finite-difference method on a staggered grid to solve for the acoustic eigenmodes of the vector-field elastic wave equation. Free, fixed, symmetry, and anti-symmetry boundary conditions are implemented, enabling efficient simulation of acoustic structures with geometrical symmetries and terminations. Perfectly matched layers are also implemented, allowing for the simulation of radiative (leaky) modes. The method is analogous to eigenmode solvers ubiquitously employed in electromagnetics to find waveguide modes, and enables design of acoustic waveguides as well as seamless integration with electromagnetic solvers for optomechanical device design. The accuracy of the solver is demonstrated by calculating eigenfrequencies and mode shapes for common acoustic modes in several simple geometries and comparing the results to analytical solutions where available or to numerical solvers based on more computationally expensive methods

Finite line-number equi-spaced resonances based on coupled cavity resonators

We investigate a linear configuration of coupled cavity resonators based on tri-diagonal Kac matrix which enables such cavities to support finite equi-spaced comb of resonances. Such resonator may allow designing cavities which decouple cavity size from comb spacings.Accepted manuscrip

Frequency translating add/drop filters based on electro-optically modulated photonic molecules

We demonstrate a new category of optical add-drop filters, with a frequency- translated drop-port response. Comprising modulated coupled resonators, they support Butter- worth, Chebyshev and other passband shapes typical to linear high-order filters.Accepted manuscrip

Can one critically couple to a multimode, coupled-cavity finite equispaced comb resonator?

A finite-equispaced-comb resonator based on N “Kac-matrix” coupled cavities could be an important photonic building block. To maximally excite all comblines: there’s a best cavity to couple to the bus waveguide; and, we “critically couple” the geometric mean of the supermode escape rates.Accepted manuscrip

Minimum Drop-Loss Design of Microphotonic Microring-Resonator Channel Add-Drop Filters

Abstract-Microring-resonator filters have important applications as filtering elements in microphotonic circuits. In this paper, we address the question of optimum design of resonatorbased add-drop filters in the presence of finite losses, and show that symmetric coupling provides the optimum design. This conclusion contravenes previous work on this subject, and the oft-cited critically coupled resonator case. While the minimum bandwidth of a resonant filter is ultimately limited by intrinsic losses, i.e. the intrinsic Q, we show that the symmetric design can approach twice as narrow a linewidth as a critically coupled design for the same losses, in principle. We present a coupledmode theory (CMT) model, and a complete electromagnetic device design example based on finite-difference time-domain field simulations which validates our conclusions

Wide-band On-chip Four-Wave Mixing via Coupled Cavity Dispersion Compensation

Abstract: We demonstrate a dual-cavity resonant structure that employs frequency splitting at one of three resonances to structurally compensate dispersion. We show seeded four-wave mixing across the largest free spectral range to our knowledge of 26nm. On-chip four-wave mixing (FWM) has received much attention recently for applications from wavelength conversion [1] to quantum photonic circuits In this paper, we propose and demonstrate FWM in a dispersion compensating device consisting of two coupled resonators referred to as the 'primary' and 'auxiliary' cavities with different FSRs as illustrated i

High Directivity, Vertical Fiber-to-Chip Coupler with Anisotropically Radiating Grating Teeth

Abstract: Efficient vertical grating-coupler designs are proposed that allow near 50:1 up/down directivity using only two lithographic layers, without top/bottom mirrors, in high-index-contrast silicon waveguides. FDTD simulations predict single-mode-fiber-coupling efficiencies of 75% even for non-apodized gratings. The concept of using periodic structures such as gratings to couple out-of-plane light into waveguides has seen a revived interest recently for high index-contrast (HIC) microphotonics due to the strong HIC scattering that enables all input light to be coupled out vertically over a 10μm grating length, which is close to the mode field diameter of standard single-mode fiber, a necessary condition for efficient coupling to it We propose in this paper an out-of-plane fiber-to-chip coupler design with a high out-of-plane directivity (preference for upward radiation over downward radiation), achieved by engineering of the tooth shape, through a minimum of lithographic layers (two), and without any need for top or bottom reflector layers required by previous designs By modeling each sub-tooth as a point scatterer, Δθ upward is defined as the phase difference between radiation scattered upward by the both sub-teeth and Δθ downward is that for radiation scattered downward, then Δθ upward = θ v -θ h and Δθ downward = θ v + θ h (se