Large Area Planck Radiators for Mid-Infrared Optical Communications
Abstract
This proposed effort aims to investigate the use of multilayered graphene (~100 layers thick) to control the Planckian (i.e., blackbody) emission from a solid body. In our previous ONR-funded effort, we developed a device that demonstrates the ability to modulate the thermal emissivity of multilayer graphene by the reversible electrochemical intercalation of ionic liquids (e.g., [EMIM+][TFSI-]). By applying just 4 Volts, we can modulate the apparent temperature of these surfaces by #T = 12oC, as measured by a thermal imaging camera sensitive over the range from 7 - 14 µm. This change in the thermal emissivity arises from a two-order-of-magnitude shift in the free carrier concentration upon intercalation, which ultimately modulates the complex dielectric function of the material (i.e., ############i##). While our previous efforts were limited to relatively small area devices (1# x 1#), our proposed work will explore several strategies to scale this material/device up to larger areas. In particular, we will use a large-diameter chemical vapor deposition system, tiling many smaller devices to cover a larger area, and a spray-coating method using graphene ink. Our previous work also demonstrated optical communications up to 100 bits per second using free space optics in the mid-IR wavelength range using small devices 1# x 1# over a transmission distance of 10 meters. In the proposed work, we will design, fabricate, test and demonstrate larger area devices (up to 14#) capable of transmitting 1 kbps across a free-space range of 100 meters. In addition, we will conduct a fundamental study of the intercalation and diffusion dynamics to explore several aspects of the intercalation process thatremain poorly understood. Along with thermal camera imaging, time-resolved Raman scattering spectroscopy/microscopy with an AC lock-in technique will be utilized to provide structural information about the intercalated device. The full temperature dependence of the intercalation/deintercalation dynamics will be investigated, including the use of smaller ions such as Li+, which are smaller than ionic liquids and, therefore, expected to result in faster intercalation and support higher operation speeds. Other ionic liquids will also be examined, including ionic liquid-based propellants (e.g., AF-M315E) currently utilized by the military. The thickness dependence of the MLG material (ranging from 20 nm to up to 100 nm) will also be explored, which have applications as thermal switches for thermal management purposes. Ultimately, our goal is to ascertain the fundamental limit of how extensively we can modify the thermal emissivity profile, apparent temperature #T, and understand the fundamental limits of how quickly we can modulate these devices. A small portion of our effort will focus on finite-difference time-domain (FDTD) simulations, which will help to guide device design and interpret experimental data.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jan 13, 2025
- Source ID
- N000142512083
Entities
People
- Jonathan Habif
Organizations
- Office of Naval Research
- United States Navy
- University of Southern California