Exploring the Frontier of Photonic Device Size, Speed, and Efficiency Limits with Gain-enhanced Multifuncional Metamaterials

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Abstract title: Exploring the Frontier of Photonic Device Size, Speed, and Efficiency Limits with Gain-enhanced Multifuncional Metamaterials Abstract: (Non-technical)Metal-dielectric composites hold significant promise as the building blocks of next-generation information, communication, and sensing systems. The combination of metals and dielectrics offers unprecedentedly small volumes, fast speeds, and enhancements to nonlinear effects in photonic devices such as light sources, waveguides, and switches. Generally, however, the incorporation of metals necessarily increases the energy dissipated as heat in such devices, consequently reducing the energy carried by useful signals. We propose to create metal-dielectric and metal-semiconductor composites with the primary goal of demonstrating optical signal transmission without energy loss. Semiconducting materials may be engineered to emit and absorb light over a very broad color range, and their properties may be tuned by external electronics. We aim to develop the theoretical underpinning and experimental knowledge on the role of active semiconductors in enabling propagation of optical signals without loss of energy, while still retaining the small footprint and fast operation of the metal-dielectric-based photonic devices. We additionally plan to explore, both theoretically and experimentally, the enhancement of nonlinear effects in such devices, due both to the local enhancement of electromagnetic fields and to the cascaded nonlinearities present at the interfaces between the constituent materials. (Technical) Hyperbolic metamaterials offer unique and enhanced functionalities compared to conventional optical materials. For example, hyperbolic metamaterials exhibit highly localized electric fields in deeply subwavelength volumes, enabling field-enhanced nonlinear polarization, as well as broadband Purcell enhancement of the spontaneous emission rate. By introducing external strain, the band-structure of the constituent materials can be further modified, enabling multi-scale engineering of the hyperbolic metamaterials's linear and nonlinear optical responses. Unfortunately, hyperbolic metamaterials typically suffer from considerable Ohmic losses, preventing their applicability to practical devices. To overcome this deficiency, optical gain may be introduced for improved device performance. To date, most research on gain-compensated metamaterials has focused on dye molecules as a gain medium because they are easy to incorporate in proof-of-concept experiments and can be accurately modeled using simple two-level systems. In contrast, inorganic semiconductors and their heterostructures are attractive as gain media because their absorption/emission resonances may be engineered from terahertz to ultraviolet frequencies. Additionally, semiconductor hyperbolic metamaterials may be electrically injected with charge carriers, allowing for a more direct and reliable control of their functionality. And lastly, inorganic semiconductors offer distinct advantages over dyes in terms of robustness, lifetime, and integrability with guided wave devices. The overall goal of this proposal is to advance the science and technology of Gain Enhanced Multifunctional Metamaterials. Specifically, we aim to comprehensively understand and experimentally demonstrate: (1) lossless propagation in waveguide-based Gain Enhanced Multifunctional Metamaterials, (2) field-enhanced second- and third-order nonlinear effects in Gain Enhanced Multifunctional Metamaterials, and (3) strain-enhanced nonlinear effects in Gain Enhanced Multifunctional Metamaterials, all mediated by semiconductor gain. For specificity, we focus on the near-infrared part of the spectrum, but we stress that the lessons learned from our work may easily be extended to ultraviolet and terahertz frequencies alike. Gain Enhanced Multifunctional Metamaterials offer an avenue for achieving unprecedented nonlinear conversion efficiencies with lossless signal transmission. Due to their extremely small footprint and potentially fast operation, Gain Enhanced Multifunctional Metamaterials will become strong candidates for integrated nonlinear devices of future photonic circuits. The proposed research will not only advance the basic science and technology of active semiconductor metamaterials, but will also set an example for the investigation of physical phenomena in which the self-consistent treatment of electronic, electromagnetic, and mechanical interaction becomes crucially important. We anticipate that Gain Enhanced Multifunctional Metamaterials will find applications in data- and telecommunications, graph-processing, computation, biomedical imaging, and chemical sensing.