Fig. 11From: Terahertz spectroscopy in biomedical field: a review on signal-to-noise ratio improvementa Schematic view of an antenna on SI-GaAs with TiO2 layer coating. The green arrows indicate the micrometer controlled alignment of the substrate on the HRFZ Si-lens. b SEM image of the uncoated and TiO2-coated antenna on the same substrate. c and d show the zoomed-in images of the regions marked by the green and the red squares in (b), respectively (90° rotated) [68]Back to article page