The name is absent

48

of the double slit are a result of the fact that the illuminating THz beam is not an
ideal plane wave. To our knowledge, this is the first demonstration of fast dynamical
modulation of a THz wave front.

5.4 Second-generation 32 × 32 SLM design

The first-generation SLM only has 16 pixels. Imaging and other SLM applications
such as terahertz beam focusing and beam steering require a terahertz SLM with a
larger number of pixels.

The second-generation terahertz SLM contains a 32×32 array of pixels, where
each pixel is a 1.062× 1.062 mm² array of metameterial split-ring resonator (SRR)
elements, as shown in Figure 5.5. More precisely, each pixel have an active area
of 880 μm×860 μm, which comprises of 100 metamaterial SRRs (see Figure 5.5(b)
and 5.6(a)), and is separated from each neighboring pixel by a 200-μm space filled
with connecting wires. The connecting wires between the pixels are 6 μm in width
and 4 μm apart. The breakdown voltage of air is above 300 V for gaps larger than
about 5 μm, and it decreases linearly with gap length. Thus, the SLM with 4-μm
gaps between the wires should be safe at the intended operation voltage, 16V. The
SLM design is 4-fold symmetric. The 256 schottky electric pads on each side of the
SLM control all the pixels in the respective triangular quadrant. The ohmic contacts
placed at the four corners of the SLM are connected together by wires interdigitated
between the pixels. The fabricated chip is 4cm × 4cm in size, and 635-μm thick.

The design of the second-generation terahertz SLM uses SRRs with split gaps
located at the four outer corners, as shown in Figure 5.6(b). Each SRR element is 88
μm×86 μm, and has 200 μm gold thickness, 6 μm line width, 2 μm split gap spacing
such that the device has a resonant transmission around 0.4 THz upon application of a

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