The realization of high-performance tunable absorbers for terahertz frequencies is crucial for advancing applications such as single-pixel imaging and spectroscopy. Based on the strong position sensitivity of metamaterials' electromagnetic response, we combine meta-atoms that support strongly localized modes with suspended flat membranes that can be driven electrostatically. This design maximizes the tunability range for small mechanical displacements of the membranes. We employ a micro-electromechanical system technology and successfully fabricate the devices. Our prototype devices are among the best-performing tunable THz absorbers demonstrated to date, with an ultrathin device thickness (~1/50 of the working wavelength), absorption varying between 60% and 80% in the initial state when the membranes remain suspended, and fast switching speed (~27 μs). The absorption is tuned by an applied voltage, with the most marked results achieved when the structure reaches the snap-down state. In this case, the resonance shifts by 4200% of the linewidth (14% of the initial resonance frequency), and the absolute absorption modulation measured at the initial resonance can reach 65%. The demonstrated approach can be further optimized and extended to benefit numerous applications in THz technology.

Vertical minority carrier electron transport parameters in p-type InAs/GaSb type-II superlattices for long wavelength infrared (LWIR) detection have been extracted from magnetic field dependent geometrical magneto-resistance. The measurements, performed at low electric fields and at magnetic field intensities up to 12 T, exhibited multiple-carrier conduction characteristics that required mobility spectrum analysis for the extraction of individual carrier mobilities and concentrations. Within the common operating temperature range for LWIR photodiodes (80 to 150 K), the conductivity was found to be dominated by three distinct carriers, attributed to majority holes (μ=280±27 cm2/Vs), minority electrons (μ=2,460±75 cm2/Vs), and parasitic sidewall inversion layer electrons (μ=930±55 cm2/Vs). A miniband energy gap of 140 ± 15 meV for the 14/7-monolayer InAs/GaSb superlattice was estimated from the thermal activation of the minority carrier electron density.

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This paper presents the design, fabrication, and optical characterization of silicon-based thin film Fabry-Pérot filters for spectroscopic sensing applications at shortwave infrared (SWIR: 1.5-2.5 µm) and mid-wave infrared (MWIR: 3-5 µm) wavelengths. Filter performance is enhanced using distributed Bragg reflectors composed of silicon and air-gap layers for enhanced refractive index contrast. A peak-topeak surface variation of less than 20 nm in the fabricated micromachined structures was achieved across a large spatial area of 1 mm × 1 mm. Spectral measurements on released Fabry-Pérot filters show excellent agreement with optical simulations. The fabricated Fabry-Pérot filters demonstrate peak transmittance values greater than 50% across all spectral ranges, with measured full width at half maximum values in the range of 50 nm rendering them suitable for use in spectral sensing and imaging in the SWIR and MWIR wavelength ranges.

Evolving from past black‐and‐white images, through present red‐green‐blue spectral colors, future remote imaging systems promise spectroscopic functionalities extending well beyond the visible wavelengths. This allows real‐time spectral information to be gathered from multiple wavelength bands that is applicable to numerous remote sensing spectroscopy/imaging applications and aids target recognition. This paper reviews the wavelength tunable microelectromechanical systems (MEMS) optical filter technologies developed for the important infrared and the emerging terahertz wavelength bands of the electromagnetic spectrum with the fabrication effort being enabled by the Western Australian Node of the Australian National Fabrication Facility. A low size, weight and power (SWaP) platform solution is demonstrated delivering mechanically robust, field‐portable, spectroscopic, chem/bio sensing suitable for deployment in remote sensing and imaging applications.