Roggenbuck, A ; Langenbach, M ; Thirunavukkuarasu, K ; Schmitz, H ; Deninger, A ; Mayorga, I Camara ; Güsten, R ; Hemberger, J ; Grüninger, M
In a continuous-wave terahertz
system based on photomixing, the measured amplitude of the terahertz signal
shows an uncertainty due to drifts of the responsivities of the photomixers and
of the optical power illuminating the photomixers. We report on a simple method
to substantially reduce this uncertainty. By normalizing the amplitude to the
DC photocurrents in both the transmitter and receiver photomixers, we achieve a
significant increase of the stability. If, e.g., the optical power of one laser
is reduced by 10%, the normalized signal is expected to change by only 0.3%,
i.e., less than the typical uncertainty due to short-term fluctuations. This
stabilization can be particularly valuable for terahertz applications in
non-ideal environmental conditions outside of a temperature-stabilized
laboratory.
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