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(a) Second-generation terahertz SLM
(b) SLM fabrication mask (zoom-in view)
Figure 5.5 : (a) The second-generation terahertz SLM is a 32×32 array of individual
pixels in Figure 5.6(a). Each pixel is independently controlled by an external voltage
between the respective Schottky electric pad and the ohmic contacts (L-shaped pads
at the four corners). The 256 Schottky pads on each side control all the pixels in one
quadrant (triangular-shaped). (b) The active area of each pixel is 880 μm×860 μm
and the spacing between pixels is about 200 μm. The connecting wires between the
pixels are 6 μm in width and 4 μm apart.
voltage. Chen et al. demonstrate a 55% modulation depth in amplitude transmission
at a 16V bias on a terahertz modulator based on this SRR design [12].
5.5 Characterization experiments and results
Characterization of the two identical second-generation THz SLM samples (SLM 1
and SLM 2) uses a terahertz time-domain spectroscopy system with fiber-coupled
photoconductive antennae for both terahertz generation and detection. A control
circuit system synchronizes the THz SLM with the terahertz measurement system
(see Appendix B). Figure 5.7 (a) and (b) show the terahertz amplitude transmission