Semiconducting Carbon Nanotube Polaritonic Devices
Abstract
The overarching goal of this project is to realize room-temperature, polaritonic devices and ultralow-threshold lasers based on semiconducting single-walled carbon nanotubes. Polaritons are quasiparticles that emerge in semiconductor microcavities due to strong light-matter coupling between a cavity photon mode and semiconductor excitons. They possess properties inherited from both of these constituents such as the small effective mass of the photon and the strong nonlinear character of the exciton. These properties can be harnessed for transformative optoelectronic devices such as low threshold lasers and ultra-efficient optical switches. For example, the relaxation of polaritons towards their energetic minimum can produce a state akin to a Bose-Einstein condensate, which emits coherent radiation. The ability to do this without requiring population inversion can allow for the realization of ultralow power coherent light sources. While most polariton devices have focused on microcavities containing group III-V or II-VI quantum wells at cryogenic temperatures, recent research has turned towards systems that will readily allow for room-temperature operation. For example, transition metal dichalcogenides, organic semiconductors, and hybrid organic-inorganic materials all possess highly stable excitons with binding energies >100 meV and large oscillator strengths Ð thereby enabling the exploitation of polariton phenomena at room-temperature. One of the most promising routes, which is only beginning to be explored, is the use of carbon nanotubes for polaritonics. Carbon nanotubes are highly stable and easily processed, have large exciton binding energy (0.3 eV), large oscillator strength, narrow homogeneous linewidth, and tunable bandgap that can be tailored from 1000 Ð 2000 nm, which is a spectral range of importance for communications and remote sensing technologies. NanotubesÕ strong exciton-phonon scattering characteristics and sizeable third-order susceptibility are expected to promote rapid polariton relaxation Ð critical for realizing ultralow thresholds and overcoming the relaxation bottleneck that has limited many material systems. The materials science of semiconducting carbon nanotubes has matured substantially over the last 10 years. It is now possible to prepare highly monodisperse, electronics-grade semiconducting nanotubes with nearly a singular bandgap in quantities useful for devices. Nanotubes can be integrated onto almost any substrate via simple solution-phase processing, allowing for polariton optoelectronic device integration with conventional technological platforms (e.g., Si, III-V) without the challenges of heteroepitaxial crystal growth. This project will exploit selective, conjugated polymer wrappers as a means for producing single chirality semiconducting nanotube populations from heterogeneous as-produced mixtures and integrate these nanotubes into high quality (Q) factor microcavities with lifetimes >> 100 fs. The ultimate goal will be to realize compact, electrically-driven, ultralow threshold, near-infrared, polariton lasers. To achieve this goal, research will be pursued in four inter-related thrusts that focus on: (A) High Q microcavity fabrication; (B) Polariton dispersion and nanotube thin film engineering; (C) Polariton dynamics, emission, and lasing; and (D) Hybrid optical/electrical and direct electrical pumping schemes. This work builds on ArnoldÕs leading expertise in the preparation of nanotubes purified by their bandgap, diameter, chirality, and electronic-type (semiconducting versus metallic) and their integration into high-performance electronic and optoelectronic devices and KŽna-CohenÕs expertise in polariton lasers, polariton superfluids, and optical nonlinearities in microcavities using organic semiconductors and atomic monolayers of metal transition dichalcogenides.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Sep 11, 2018
- Source ID
- W911NF1810149
Entities
People
- Michael S Arnold
Organizations
- Army Contracting Command
- United States Army
- University of Wisconsin–Madison