No abstract

Wavelength-selective thermal emitters (WS-EMs) are of high interest due to the lack of cost-effective, narrow-band light sources in the mid-to long-wave infrared. Cost-effective WS-EMs can be realized via Tamm plasmon polariton (TPP) structures supported by distributed Bragg reflectors (DBRs) on metal layers, however, optimizing TPP-WS-EMs is challenging because of the large number of parameters to optimize.To address this challenge, we use stochastic gradient descent (SGD) to optimize TPP-WS-EMs composed of an aperiodic DBR deposited on doped cadmium oxide (CdO) plasmonic films. While the SGD-optimized, aperiodic DBR offers extensive spectral control, the material choice, i.e., plasma-frequency-tunable doped CdO, enables the design capabilities not accessible with noble metals. Here, the individual layer thickness and carrier density of CdO are optimized by our SGD inverse design strategy. The resultant experimental designs demonstrate TPP-WS-EMs exhibiting isolated, high-Q (narrow bandwidth), and structures featuring multiple emission bands for applications such as free-space communications and gas sensing. Furthermore, we illustrate the deterministic design capability within the infrared, such as user-designated Q-factors (28 -10,127) at a desired frequency, multi-band emitters with user-defined Q, and the ability to directly match arbitrary chemical absorption spectra. Thus, the combination of our SGD inverse design and the broadly tunable plasma frequency of CdO enables lithography-free, CMOS-compatible, and wafer-scale solutions for WS-EMs with unprecedented spectral control.

No abstract

No abstract

Antireflection (AR) coatings with graded refractive index profiles approaching air offer unparalleled AR performance but lack a scalable fabrication process that would enable them to be used more widely in applications such as architecture and solar energy conversion. This work introduces a sputtering-based sacrificial porogen process to fabricate multilayer nanoporous SiO 2 coatings with tunable refractive index down to n eff = 1.11. Using this approach, we demonstrate a step-graded bilayer AR coating with outstanding wide-angle AR performance (single side average reflectivity in the visible spectrum ranges from 0.2% at normal incidence to 0.7% at 40°), good adhesion, and promising environmental durability. These results open up a path to produce ultrahigh performance AR coatings over large area by using industrial-scale magnetron sputtering systems.