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Terahertz compressive imaging with metamaterial spatial light modulators

Abstract

Imaging at long wavelengths, for example at terahertz and millimetre-wave frequencies1, is a highly sought-after goal of researchers2,3 because of the great potential for applications ranging from security screening4 and skin cancer detection5 to all-weather navigation6 and biodetection7. Here, we design, fabricate and demonstrate active metamaterials that function as real-time tunable, spectrally sensitive spatial masks for terahertz imaging with only a single-pixel detector. A modulation technique permits imaging with negative mask values, which is typically difficult to achieve with intensity-based components. We demonstrate compressive techniques allowing the acquisition of high-frame-rate, high-fidelity images. Our system is all solid-state with no moving parts, yields improved signal-to-noise ratios over standard raster-scanning techniques8, and uses a source orders of magnitude lower in power than conventional set-ups9. The demonstrated imaging system establishes a new path for terahertz imaging that is distinct from existing focal-plane-array-based cameras.

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Figure 1: Metamaterial-based SLM and imaging schematic.
Figure 2: Comparison of reconstruction techniques for an inverse cross aperture.
Figure 3: Compressive imaging of inverse cross.
Figure 4: Increase of imaging frame rate using compressive techniques.

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Acknowledgements

The research presented in this work was performed at Boston College and was supported by funding from the Office of Naval Research (US Navy contract no. N00014-11-1-0583; Compressive Sensing Algorithms) and the National Science Foundation (contract no. ECCS-1309966; Phase Contrasted Mask for Hadamard Imaging). The University of New Mexico acknowledges support from Sandia National Laboratories (contract no. 433420 and grant no. 37250) and the Center for Integrated Nanotechnologies. Boston College also acknowledges support from K. Lowrie for her assistance in programming the field programmable gate array.

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Contributions

W.J.P. conceived the idea and S.K. helped develop the device realization scheme. J.M. developed the fabrication protocols and fabricated the spatial light modulator. D.S. performed simulations and D.S. and C.M.W. characterized the device. G.L. and J.H. provided insight on the computational reconstructions of the images. T.S. assisted with the apparatus set-up and data processing. C.M.W. conducted imaging measurements and experiments, and performed analysis of all experiments. All authors contributed to analysis and interpretation of the results and contributed to writing the manuscript.

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Correspondence to Willie J. Padilla.

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The authors declare no competing financial interests.

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Watts, C., Shrekenhamer, D., Montoya, J. et al. Terahertz compressive imaging with metamaterial spatial light modulators. Nature Photon 8, 605–609 (2014). https://doi.org/10.1038/nphoton.2014.139

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