MEMS terahertz-to-infrared band converter using frequency selective planar metamaterial

Abstract

A MEMS terahertz-to-infrared converter has been developed based on the unique properties of metamaterials that allow for selective control of the absorptivity and emissivity of the sensors. The converter consists of a sensing element structurally made of planar metamaterial membranes, connected to a substrate frame by four symmetrically-located thermal insulators. Upon THz absorption, the temperature of the sensing element increases and the outward infrared flux from the backside of the element is read by a commercial long-wave infrared camera. Two configurations were designed and fabricated with metamaterial absorptivity optimized for 3.8 THz and 4.75 THz quantum cascade lasers. The first sensor, fabricated with an oxidized aluminum backside, exhibits higher responsivity, but lower conversion efficiency than the second sensor, fabricated with a metamaterial backside. The spectral characteristics of the metamaterial on the two sides can be optimized to improve both responsivity and sensitivity, while keeping the sensors’ thermal time constant sufficiently small for real time imaging. No dedicated electronics or optics are required for readout making metamaterial-based MEMS THz-to-IR converters very attractive for THz imaging as means of a simple attachment to commercial IR cameras.

Ultrastrong Light–Matter Coupling in Deeply Subwavelength THz LC Resonators

“…The resonant behavior, occurring into highly subwavelength volumes, generates high electromagnetic field intensities, which, as pointed out by the seminal paper of Pendry et al, are crucial to implement artificial electromagnetic properties of a macroscopic ensemble of meta-atoms. Moreover, the ability to control and enhance the electromagnetic field at the nanoscale is beneficial for optoelectronic devices, such as nanolasers, electromagnetic sensors, − and detectors. − For instance, metamaterial architectures have led to a substantial decrease of the thermally excited dark current in quantum infrared detectors, resulting in higher temperature operation. , …”

Design and Fabrication of Substrate-Free Au/SiNx/Au Metafilm for THz Sensing Application

“…To verify the universality of the Asym2sig model ( 6), parameter estimation from the third part of the experimental data is critical to the desired model. The experimental absorption-frequency data at the different length of the Al/SiO x /Al metafilm absorber were taken from the papers [21,25]. The theoretical curves of absorption-frequency were obtained after the nonlinear least squire curve fitting of the Asym2sig model ( 6) on experimental data and shown in Fig.…”

“…Integrating metafilm absorbers with bi-material cantilevers can enhance the absorption of THz energy and subsequently transfers the absorbed energy into the deformation of the bimaterial cantilevers [21][22][23][24]. This detection unit can be arranged in an array to form a metamaterial focal plane array (MFPA), which can be used in THz real-time imaging systems [25,26] when incorporated with an optical readout system. This optical readout imaging system has lower self-heating, longer integration times, and better signal-to-noise ratio than the electronic readout system.…”

“…This optical readout imaging system has lower self-heating, longer integration times, and better signal-to-noise ratio than the electronic readout system. Alves et al [21,22,25] reported THz SiO 2 /Al bi-material cantilever sensors with Al/SiO x /Al metafilm for THz optical readout system. The sensors operated in a frequency range >3 THz.…”

Design of a Broadband Solar Thermal Absorber Using a Deep Neural Network and Experimental Demonstration of Its Performance

“…By inducing electromagnetic resonance, subwavelength-sized nanostructures have great potential for use in tailoring the radiative properties of system, especially the absorption spectrum 1–4 . Well-designed nanostructures with desirable radiative properties can be utilized as selective 1,3,4 and broadband absorber 5 . In designing subwavelength-sized nanostructures, precise prediction of the corresponding radiative properties resulting from light-structure interactions is crucial.…”