Search for: All records

The inverse design of meta-optics has received much attention in recent years. In this paper, we propose a GPU-friendly inverse design framework based on improved eigendecomposition-free rigorous diffraction interface theory, which offers up to 16.2 × speedup over the traditional inverse design based on rigorous coupled-wave analysis. We further improve the framework’s flexibility by introducing a hybrid parameterization combining neural-implicit and traditional shape optimization. We demonstrate the effectiveness of our framework through intricate tasks, including the inverse design of reconfigurable free-form meta-atoms.

This work presents a novel approach to achieve directional and normal thermal emission from epsilon‐near–zero (ENZ) materials. ENZ materials exhibit near–zero permittivity at the ENZ point, resulting in some unique properties compared to conventional optical materials including infinite wavelength, constant phase distribution, and decoupling of spatial and temporal fields inside the ENZ material. These properties are used to engineer the far‐field thermal emission from optical antennas fabricated on ENZ film in the mid‐infrared. By coupling the antenna resonance mode with the Berreman mode of the ENZ material, highly directional and normal emission is demonstrated. This approach could have significant implications for thermal management, energy conversion, and sensing applications.

Highly doped semiconductor “designer metals” have been shown to serve as high-quality plasmonic materials across much of the long-wavelength portion of the mid-infrared. These plasmonic materials benefit from a technologically mature semiconductor fabrication infrastructure and the potential for monolithic integration with electronic and photonic devices. However, accessing the short-wavelength side of the mid-infrared is a challenge for these designer metals. In this work we study the perspectives for extending the plasmonic response of doped semiconductors to shorter wavelengths by leveraging charge confinement, in addition to doping. We demonstrate, theoretically and experimentally, negative permittivity across the technologically vital mid-wave infrared (3–5 $\mathrm{\mu <\#comment/>}$m) frequency range. The semiconductor composites presented in our work offer an ideal material platform for monolithic integration with a variety of semiconductor optoelectronic devices operating in the mid-wave infrared.

We report the theoretical prediction and experimental realization of the optical phenomenon of “ballistic resonance.” This resonance, resulting from the interplay between free charge motion in confining geometries and periodic driving electromagnetic fields, can be utilized to achieve negative permittivity at frequencies well above the bulk plasma frequency. As a proof of principle, we demonstrate all-semiconductor hyperbolic metamaterials operating at frequencies 60% above the plasma frequency of the constituent doped semiconductor “metallic” layer. Ballistic resonance will therefore enable the realization and deployment of various applications that rely on local field enhancement and emission modulation, typically associated with plasmonic materials, in new materials platforms.

Remarkable systems have been reported recently using the polylithic integration of semiconductor optoelectronic devices and plasmonic materials exhibiting epsilon-near-zero (ENZ) and negative permittivity. In traditional noble metals, the ENZ and plasmonic response is achieved near the metal plasma frequency, limiting plasmonic optoelectronic device design flexibility. Here, we leverage an all-epitaxial approach to monolithically and seamlessly integrate designer plasmonic materials into a quantum dot light emitting diode, leading to a$5.6\times <\#comment/>$enhancement over an otherwise identical non-plasmonic control sample. The device presented exhibits optical powers comparable, and temperature performance far superior, to commercially available devices.

We demonstrate coupling to and control over the broadening and dispersion of a mid-infrared leaky mode, known as the Berreman mode, in samples with different dielectric environments. We fabricate subwavelength films of AlN, a mid-infrared epsilon-near-zero material that supports the Berreman mode, on materials with a weakly negative permittivity, strongly negative permittivity, and positive permittivity. Additionally, we incorporate ultra-thin AlN layers into a GaN/AlN heterostructure, engineering the dielectric environment above and below the AlN. In each of the samples, coupling to the Berreman mode is observed in angle-dependent reflection measurements at wavelengths near the longitudinal optical phonon energy. The measured dispersion of the Berreman mode agrees well with numerical modes. Differences in the dispersion and broadening for the different materials is quantified, including a 13 cm^-1red-shift in the energy of the Berreman mode for the heterostructure sample.