This project has advanced a comprehensive multi-physics study of the complex physics phenomena behind the excitation and electro-optical control of charge density waves, i.e. Surface Plasmon Polaritons (SPPs), at high-gradient, heavily doped semiconductor PN⁺-junctions. A step-by-step process is implemented in which theory is matched to a set of control experiments, providing the critical data needed to refine and develop a unique Surface Plasmon Diode (SPD). In the design phase of this project, two Figures of Merit (FoM) have been used to characterize the tradeoff between the SPP propagation losses and mode confinement for operation frequencies in the mid- to far-IR spectral range and semiconducting materials and compounds consistent with the experimental capabilities. Comprehensive steady-state and time-dependent I/O studies has led to in-depth understanding of the unique switching mechanism behind the SPD, and have helped to guide and accelerate the development of a prototype. The experimental efforts have led to Proof of Concept devices based on highly doped Silicon-on-Insulator (SOI) and lattice matched In_0.53Ga_0.47As materials systems. Bulk material growth/fabrication and characterization was used to inform the theoretical model, which in turn guides the fabrication and experimental characterization of the prototype. This multi-pronged approach was accomplished through an iterative process in which devices with added complexity are manufactured and tested, seeking to refine the SPD design for improved operation. The steady-state and transient response of the prototypes has be experimentally tested using a direct detection method (IR-detector) for modulation rates ranging from low (kHz) to moderate and high frequencies (hundreds of MHz). These experimental measurements, in conjunction with the theory, have defined the physical limitations and scaling laws governing the SPD operation establishing a clear roadmap toward direct, electro-optical signal modulation at rates from a few kHz up to 10GHz.

The training of future engineers, scientists and educators was an integral component of this project. Those that have been affected include undergraduate and graduate students at the PI?s Institutions; STEM underrepresented minority students at Louisiana Tech University (LA Tech) and K-12 students and teachers in the State of Louisiana and Texas. As part of this project?s broader impact, the LA Tech group has reached out to K-12 students and educators through the Speaking of Science (SoS) outreach program. The SoS is managed by the Louisiana Experimental Program to Stimulate Competitive Research (LA EPSCoR) and aims to increase public awareness and showcase the State?s leading scientists and their cutting-edge research to K-12 institutions and the general public. As part of this program the LA Tech group has presented lecture-demo series entitled ?The Magic of Science or How to Make the Harry Potter Invisibility Cloak? at low performing, high minority, and high poverty schools throughout the State of Louisiana. The presentations focused on explaining to the attending students and teachers the basic physics principles behind ?why we see? and how these principles can be used to make objects invisible to the naked eye. Furthermore, three sets of hand-on demonstrations were performed showcasing invisibility due to camouflage, refractive index matching and total internal reflection. In total 20 lectures, demonstrations and workshops were delivered in front of more than 380 students, 48 teachers and 12 parents. The UT group has reached out to the local Austin K-12 community, developing and performing outreach activities and modular exercises in local schools and at UT outreach events. The UT group participated in the UT Girl Day event twice over the course of the program. All of the group?s graduate students worked to assemble a hands-on activity entitled ?Painting with Heat?, where visitors to the group?s set-up were able to paint with hot or cold water on a canvas and view the thermal image of their painting projected to a screen in real time. The PI and graduate students worked with the K-12 visitors to explain the concept of thermal energy and thermal imaging. In addition, the UT group has participated in the CDCM MRSEC?s RET program, working with a local elementary school teacher over the summer of 2019 to develop new hands-on activities for the classroom. 

Figure (A) Transfer magnetic (TM) and transfer electric (TE) reflectivity spectra of the In_0.53Ga_0.47As grating device (see insert) under zero bias. The experimental data (solid-lines) is compared to self-consistent electro-optic simulations (dashed lines). The local magnetic and electric field intensities across the device for the two incident light polarizations; (B-D) transverse magnetic and (C, E) transverse electric. The electromagnetic mode profiles unambiguously shows the excitation of SPP at the PN⁺⁺- junction interface for incident wavelength of .

Last Modified: 09/30/2020
Modified by: Daniel Wasserman