Superscattering of electromagnetic waves from subwavelength dielectric structures.

Superscattering, corresponding to the scattering cross section of a scatterer being significantly larger than its single-channel limit, has attracted increasing attention due to its huge potential for practical applications. The realization of superscattering relies on the overlapping of multiple resonance modes in a scatterer. Accordingly, superscattering phenomena have been observed primarily in alternating plasmonic/dielectric layered structures which support surface plasmons.

Tailored compliant mechanisms for reconfigurable electromagnetic devices.

Reconfigurable electromagnetic devices, specifically reconfigurable antennas, have shown to be integral to the future of communication systems. However, mechanically robust designs that can survive real-world, harsh environment applications and high-power conditions remain rare to this day. In this paper, the general framework for a field of both discrete and continuously mechanically reconfigurable devices is established by combining compliant mechanisms with electromagnetics.

Continuous-discontinuous Galerkin time domain (CDGTD) method with generalized dispersive material (GDM) model for computational photonics.

The discontinuous Galerkin time domain (DGTD) method and its recent flavor, the continuous-discontinuous Galerkin time domain (CDGTD) method, have been extensively applied to simulations in the radio frequency (RF) and microwave (MW) regimes due to their inherent ability to efficiently model multiscale problems. We propose to extend the CDGTD method to nanophotonics while exploiting its advantages which have already been established in the RF and MW regimes, such as domain decomposition, non-conformal meshing, high-order elements, and hp-refinement. However, at optical frequencies many materials are highly dispersive, so the modeling of nanophotonic devices requires accurate handling of different dielectric functions, including those of plasmonic elements, dielectrics, and tunable materials.

Realizable design of field taper via coordinate transformation.

Complex electromagnetic structures can be designed by exploiting the concept of spatial coordinate transformations. In this paper, we define a coordinate transformation scheme that enables one to taper the electric field between two waveguides of different cross-sections. The electromagnetic field launched from the wide input waveguide is compressed in the proposed field tapering device and guided into the narrow output waveguide.

Multi-element, multi-frequency lens transformations enabled by optical wavefront matching.

Transformation optics (TO) has brought forth a renewed interest in gradient-index (GRIN) optics due to its ability to allow arbitrary geometries to electromagnetically mimic the behaviors of more conventional structures via a spatially-inhomogeneous refractive index profile. While quasi-conformal transformation optics (qTO) has seen great success at microwave and RF frequencies, it is inherently limited to single frequency transformations: an immediate shortcoming for designs in the optical regime. Also, achieving desirable solutions from multi-element transformations is difficult for qTO.

Analytical surrogate model for the aberrations of an arbitrary GRIN lens.

Current analytical expressions between Gradient-Index (GRIN) lens parameters and optical aberrations are limited to paraxial approximations, which are not suitable for realizing GRIN lenses with wide fields of view or small f-numbers. Here, an analytical surrogate model of an arbitrary GRIN lens ray-trace evaluation is formulated using multivariate polynomial regressions to correlate input GRIN lens parameters with output Zernike coefficients, without the need for approximations. The time needed to compute the resulting surrogate model is over one order-of-magnitude faster than traditional ray trace simulations with very little losses in accuracy, which can enable previously infeasible design studies to be completed.

Size, weight, and power reduction regimes in achromatic gradient-index singlets.

By analyzing the limitations that achromatic gradient-index (GRIN) lens solutions in the radial and axial extremes place on lens thickness and surface curvature, a radial-axial hybrid GRIN theory is developed in order to overcome these restrictions and expose a larger solution space. With the achromatic hybrid GRIN theory, the trade-offs between thickness, curvature, and GRIN type can be directly studied in the context of size, weight, and power (SWaP) reduction. Finally, the achromatic solution space of a silicon-germanium-based material system is explored, and several designs are verified with ray tracing.

Modularization of gradient-index optical design using wavefront matching enabled optimization.

This paper proposes a new design paradigm which allows for a modular approach to replacing a homogeneous optical lens system with a higher-performance GRadient-INdex (GRIN) lens system using a WaveFront Matching (WFM) method. In multi-lens GRIN systems, a full-system-optimization approach can be challenging due to the large number of design variables. The proposed WFM design paradigm enables optimization of each component independently by explicitly matching the WaveFront Error (WFE) of the original homogeneous component at the exit pupil, resulting in an efficient design procedure for complex multi-lens systems.

Transformation-optics-inspired anti-reflective coating design for gradient index lenses.

Recent developments in transformation optics have led to burgeoning research on gradient index lenses for novel optical systems. Such lenses hold great potential for the advancement of complex optics for a wide range of applications. Despite the plethora of literature on gradient index lenses, previous works have not yet considered the application of anti-reflective coatings to these systems.