Smart control is an attracting and important function for modern electromagnetic wave absorber. This paper presents the design, fabrication, and measurement of a frequency and bandwidth tunable metamaterial absorber (MA) in X-band. The unit cell of the MA consists of a microstrip resonator loaded with the varactors. Simulation and measurement results show that by tuning the bias voltage on the varactors, the peak absorption frequency can be tuned by 0.44 GHz with the peak absorption greater than 95%. Field and circuit model analysis is conducted to reveal the working mode and predict the absorbing frequency. After that, by specially designing the bias circuit so as to adjust the bias voltage on neighboring unit cells separately, dual resonance and absorption peaks occur, and the overall absorption bandwidth can thus be tuned conveniently by controlling the difference of the two resonance frequencies. The center absorbing frequency can also be tuned. Simulation and experiment results show that the 75% absorption (À6 dB reflection) bandwidth can be tuned from 0.40 GHz to 0.74 GHz, which is a two-fold tuning range. This work is believed to improve the state-of-the-art smart metamaterial absorber. V C 2015 AIP Publishing LLC.

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Recently, compressive sensing has been introduced to confocal Raman imaging to accelerate data acquisition. In particular, unsupervised compressive imaging methods do not require a priori knowledge of an object’s spectral signatures, and they are thus applicable to unknown or dynamically changing systems. However, the current methods based on either spatial or spectral undersampling struggle between spatial and spectral fidelities at high compression ratios. By exciting a sample with an array of focused laser beams and randomly interleaving the projection locations of the scattering, we simultaneously demonstrate a single-acquisition confocal Raman hyperspectral imaging with a high fidelity and resolution in spatial and spectral domains, at a compression ratio of 40–50. The proposed method is also demonstrated with suppressed noise and a smooth transition at the boundaries.