Metamaterial absorbers have attracted considerable attention for applications in the terahertz range. In this Letter, we report the design, fabrication, and characterization of a terahertz dual band metamaterial absorber that shows two distinct absorption peaks with high absorption. By manipulating the periodic patterned structures as well as the dielectric layer thickness of the metal–dielectric–metal structure, significantly high absorption can be obtained at specific resonance frequencies. Finite-difference time-domain modeling is used to design the structure of the absorber. The fabricated devices have been characterized using a Fourier transform IR spectrometer. The experimental results show two distinct absorption peaks at 2.7 and $5.2\mathrm{THz}$, which are in good agreement with the simulation. The absorption magnitudes at 2.7 and $5.2\mathrm{THz}$ are 0.68 and 0.74, respectively.

A Caughey–Thomas-like mobility model with temperature and composition dependent coefficients is used in this work to describe the dependence of electron and hole mobilities on temperature, doping concentration, and alloy composition. Appropriate parameter sets are given for a large number of III–V binary and ternary compounds, including: GaAs, InP, InAs, AlAs, GaP, ${\mathrm{Al}}_{\mathrm{0.3}}{\mathrm{Ga}}_{\mathrm{0.7}}\mathrm{As},$ ${\mathrm{In}}_{\mathrm{0.52}}{\mathrm{Al}}_{\mathrm{0.48}}\mathrm{As},$ ${\mathrm{In}}_{\mathrm{0.53}}{\mathrm{Ga}}_{\mathrm{0.47}}\mathrm{As},$ and ${\mathrm{In}}_{\mathrm{0.49}}{\mathrm{Ga}}_{\mathrm{0.51}}\mathrm{P}.$ Additionally, physically justifiable interpolation schemes are suggested to find the mobilities of various ternary and quaternary compounds (such as ${\mathrm{Al}}_x{\mathrm{Ga}}_{\text{1−x}}\mathrm{As},$ ${\mathrm{In}}_{\text{1−x}}{\mathrm{Ga}}_x\mathrm{P},$ ${\mathrm{In}}_{\text{1−x}}{\mathrm{Ga}}_x\mathrm{As},$ ${\mathrm{In}}_{\text{1−x}}{\mathrm{Al}}_x\mathrm{As},$ and ${\mathrm{In}}_{\text{1−x}}{\mathrm{Ga}}_x{\mathrm{As}}_y{\mathrm{P}}_{\text{1−y}})$ in the entire range of composition. The models are compared with numerous measured Hall data in the literature and very good agreement is observed. The limitations of the present model are also discussed. The results of this work should be extremely useful in device simulation packages, which are currently lacking a reliable mobility model for the above materials.

We present the simulation, implementation, and measurement of a polarization insensitive broadband resonant terahertz metamaterial absorber. By stacking metal-insulator layers with differing structural dimensions, three closely positioned resonant peaks are merged into one broadband absorption spectrum. Greater than 60% absorption is obtained across a frequency range of $1.86\mathrm{THz}$ where the central resonance frequency is $5\mathrm{THz}$. The FWHM of the device is 48%, which is two and half times greater than the FWHM of a single layer structure. Such metamaterials are promising candidates as absorbing elements for bolometric terahertz imaging.

We present the simulation, implementation, and measurement of a polarization insensitive resonant metamaterial absorber in the terahertz region. The device consists of a metal/dielectric-spacer/metal structure allowing us to maximize absorption by varying the dielectric material and thickness and, hence, the effective electrical permittivity and magnetic permeability. Experimental absorption of 77% and 65% at $2.12\mathrm{THz}$ (in the operating frequency range of terahertz quantum cascade lasers) is observed for a spacer of polyimide or silicon dioxide respectively. These metamaterials are promising candidates as absorbing elements for thermally based terahertz imaging.

We show the experimental realization of a 108-GHz planar Gunn diode structure fabricated in GaAs/AlGaAs. There is a considerable interest in such devices since they lend themselves to integration into millimeter-wave and terahertz integrated circuits. The material used was grown by molecular beam epitaxy, and devices were made using electron beam lithography. Since the frequency of oscillation is defined by the lithographically controlled anode-cathode distance, the technology shows great promise in fabricating single chip terahertz sources.

Terahertz (THz) oscillators based on resonant tunneling diodes (RTDs) have relatively low output power, tens to hundreds of microwatts. The conventional designs employ sub-micron sized RTDs to reduce the device self-capacitance and, as a result, realise higher oscillation frequencies. However, reducing the RTD device size leads to lower output power. In this paper we present RTD oscillators which can employ one or two RTD devices of relatively large size, 9 - 25 μm2, for high power and, at the same time, can oscillate at THz frequencies. This is achieved through low resonating inductances realized by microstrip or coplanar waveguide (CPW) transmission line short stubs with low characteristic impedances (Z0), which have lower inductance values per unit length and so compensate the increase of the self-capacitance of large area RTD devices. Thus, fabrication using only photolithography is possible. It is also shown that device sizing, which is limited only by bias stability considerations, does not limit device bandwidth. Further, we report a new way to estimate the RTD oscillator output power with frequency. A series of oscillators with oscillation frequencies in the 245 - 309 GHz range and output powers from 0.1 - 1 mW have been demonstrated showing the feasibility of the proposed approach.