Novel Material Engineering in III-IV Semiconductor Platforms: Metamaterials with Quantum Cascade Structures

Abstract

In this work, inspired by the emerging applications of metamaterials in imaging, we engineered and studied the optical properties of novel metamaterial devices in III-IV semiconductor platforms with quantum cascade (QC) structures. The first type of devices we investigated are multilayered plasmonic metamaterials that exhibit negative refraction in the mid-infrared range, but suffer from great optical loss due to strong resonance in the highly-doped layers. We addressed this problem by replacing the undoped layers in the original architecture with QC structures as gain media near the resonance frequency of the plasmonic metamaterial. We designed, fabricated, and characterized the active plasmonic metamaterials that are capable of preserving negative refraction in the presence of gain media interleaved between the plasmonic structures. Our work provides insight into the possibility of electronically manipulating the optical properties of mid-IR metamaterials, and it is also a successful demonstration of biasing interleaved high doped layers and QC structures that exhibit negative refraction, which opens up the possibility of further engineering the structure for different applications. We also studied a second type of device consisting of hyperuniform (DHU) structures on a metasurface. Inspired by the optical computation capability of metasurfaces with photonic crystal (PC) structures, we designed and fabricated DHU metasurfaces that can be used for spatial differentiation. Although optical differentiators with PC structures have been proposed for applications in object identification and edge detection, the intrinsic properties of PC such as anisotropy and small band gap width greatly limit the maximum numerical aperture and the frequency range of operation in real applications. Our proposal of replacing PC with DHU structures overcomes those theoretical limitations. In this work, we performed photonic band calculation as well as image transfer modeling in order to design, study, and optimize various DHU structures. We fabricated DHU metasurfaces and demonstrated experimentally for the first time the isotropic band gaps in various 2-d DHU photonic structures in the mid-IR range. This is a critical step towards image differentiation with these materials. The development of DHU quasi-materials will enable fast, real-time, large-area, multi-color image processing and enhance applications such as biomedical imaging.