86
4 Scalable Interdigitated Photoconductive Emitters for the Electrical …
4.4.4 Experimental Results
Upon measuring some initial polarisation-resolved time-domain waveforms, it was
clear that biasing the horizontally emitting or vertically emitting pixels only did
not produce fully circularly polarised pulses as intended, due to the device being
misaligned from 45
◦ when it was mounted onto the prism. However the design
and operation of the multi-pixel devices allows for easy rectification of any device
misalignment; a small bias voltage can be applied to the orthogonally emitting pixels
to correct for any error in the original orientation angle. To find the optimal voltages
Fig. 4.7 Polarisation-resolved time-domain traces for THz pulses emitted from the multi-pixel
interdigitated photoconductive emitter mounted on a Si prism, in order to generate a right-hand
circularly polarised pulses (ψ R = 8 ◦ ) and b left-hand circularly polarised pulses (ψ R = 98 ◦ ). c
Frequency-dependent Stokes parameter V for the right- and left-hand circularly polarised pulses,
normalised by the Stokes parameter I of each pulse