xiv
5.4 Measured (solid curves) differential fringe patterns produced by the
transmission of the THz beam through the THz SLM in two
double-slit configurations, compared with analytical calculations
(dashed curves). The insets show the “on” and “off” configurations of
the 16 pixels, with zero bias on the gray pixels, and the white pixels
modulated with a 3-kHz square signal alternating between O and 14V. 47
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.................................... 49
5.6 Geometry of (a) one SLM pixel and (b) one metamaterial SRR
element of the SLM. Each single pixel (880 μm×860 μm) contains a
10×10 element array of metamaterial SRRs. Each SRR element is 88
μm×86 μm, with 6 μm-wide metal and 2 μm split gaps........ 50
5.7 Frequency-dependent terahertz transmission amplitude for a typical
terahertz SLM pixel at various reverse gate biases for terahertz
polarization (a) parallel to and (b) perpendicular to the connecting
wires. Maximum modulation observed is 25% at 0.42 THz in (a) and
is 20% at 0.37 THz in (b)......................... 51