Broadband Epsilon-Near-Zero Perfect Absorption in the Near-Infrared

Perfect absorption (PA) of incident light is important for both fundamental light-matter interaction studies and practical device applications. PA studies so far have mainly used resonant nanostructures that require delicate structural patterning. Here, we realize tunable and broadband PA in the near-infrared region using relatively simple thin film coatings. We adjust the growth condition of an ITO film and control its epsilon-near-zero (ENZ) wavelength. We show that this results in highly tunable PA in the telecommunication window. Then, using an ITO multilayer of different ENZ wavelengths, we demonstrate broadband PA that covers a wide range of near-infrared wavelengths. The use of ENZ coatings makes PA adjustable during the film growth and does not require any structural patterning afterward. It also facilitates the chip-scale integration of perfect absorbers with other device components. Broadband PA relaxes the single wavelength condition in previous PA studies, and thus it is suitable for many practical device applications, including sensors, photodetectors, and energy harvesting devicesopen0

Admittance matching analysis of perfect absorption in unpatterned thin films

We perform a detailed analysis of perfect absorption in unpattemed thin films by invoking admittance matching conditions. We consider a single, absorptive layer coated on a reflective substrate and investigate perfect absorption conditions for normal and oblique incidences of light. For normal incidence, it is found that we need larger optical losses as the film gets thinner. But, for oblique incidence, perfect absorption can be achieved even for very small losses especially around the epsilonnear-zero frequency of the film. We consider the oblique incidence case in two different configurations (termed Berreman and ATR configurations). In both cases, we show that perfect absorption involves critical coupling to TM modes existing in thin films. We also evaluate actual light absorption and the electric field distribution in ITO films using the transfer matrix method, and show that it agrees well with our analytic theory. Finally, we present a versatile diagram that visualizes the admittance matching process in thin film structures. Our work presents an in-depth analysis of light absorption in thin films and provides design principles for various thin film devices, such as sensors, optical filters, optical modulators, and thermal emitters. (C) 2014 Elsevier B.V. All rights reservedclose5

Design of epsilon-near-zero coherent perfect absorption with indium tin oxide thin films using admittance matching method

In this study, we report ITO thin film designs for epsilon-near-zero coherent perfect absorption in near infrared wavelength regime using an admittance matching" method and investigate their optical properties

Tunable and broadband perfect absorption in epsilon-near-zero indium tin oxide thin films at near infrared wavelengths

In this study we demonstrate tunable and broadband perfect absorption in epsilon-near-zero ITO thin films and multilayers at near infrared wavelengths and investigate their optical, electrical, and structural properties

Electromagnetic Nanocommunication Networks : Principles, Applications, and Challenges

Funding Information: This work was supported by Sejong University through the Faculty Research Program under Grant 20212023.Peer reviewedPublisher PD