The objective of this proposal is to develop novel photonic devices and artificial materials-appropriately engineered to display properties not found in nature. A new approach that exploits the complex dielectric permittivity plane in its entirety will be employed. This will be achieved by judiciously controlling both absorption and gain-especially in integrated optical arrangements based on semiconductor wafers. To carry out this task, an interdisciplinary team composed of engineers, physicists, material scientists, and mathematicians with complementary skills and know-how has been assembled.

The intellectual merit of this activity is based on very recent developments in optics that make use of space-time reflection. The non-Hermitian potentials involved in such arrangements break the spatial symmetry, thus allowing a wave to distinguish left from right. This leads to non-reciprocal wave behavior in both space and time. The team will investigate: (i) non-reciprocal light propagation in linear and nonlinear non-Hermitian structures as a means to realize compact optical isolators and circulators; (ii) wavefront and energy propagation for on-chip beam deflectors; (iii) non-Hermitian absorbers and amplifiers by manipulating the propagation properties of light; and (iv) unidirectional invisibility induced by non-Hermitian gratings.

The broader impact of this work will be on educating students to drive tomorrow?s advancements in photonics. They will be trained in modeling, material growth, device fabrication, and optical characterization and through constant interactions with their peers at the partner institutions. The team will organize workshops to engage the photonics community at large in non-Hermitian optics.

Project Report

Intellectual Merit: This project investigated a new way to develop the linear and nonlinear optical properties of nitride quantum wells. The ability to produce high quality p-doped nitride quantum wells has been a road block to nitride based photonics. This is because it has been based on using Mg doping which results in poor optical quality. To overcome this road block we have investigated and achieved p-doped nitride quantum wells using a trick based on the strong internal polalization of the material. By grading the Al composition we introduced a polarization gradient. The gradient of fixed charge is designed to attract positive charge in order to neutralize the negative fixed charge thereby producing a effective p-doping of the nitride quantum well for the first time. This approach is novel, was published, and avoids the poor quality that results from Mg impurities. This same technique was then used to make n-p wavegiudes with the potenial for gain to be used to study parity-time or PT nonlinear optics. We are now investigating its nonlinear optical properties. Broader Impacts: During this project a graduate student learned how to grow and process optical waveguides using molecular beam epitaxy and dual ion beam-electron beam processing. The student also worked closely with the theorists on the project and learned how to model PT nonlinear waveguides. The student will graduate with a PhD in one year.

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University of Arkansas at Fayetteville
United States
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