Abstract-Enhancing the stability of a continuous-wave terahertz system by photocurrent normalization

Axel Roggenbuck, Malte Langenbach, Komalavalli Thirunavukkuarasu, Holger Schmitz, Anselm Deninger, Iván Cámara Mayorga, Rolf Güsten, Joachim Hemberger, and Markus Grüninger  »View Author Affiliations

http://www.opticsinfobase.org/josab/abstract.cfm?uri=josab-30-6-1397

In a continuous-wave terahertz system based on photomixing, the measured amplitude of the terahertz signal shows a variability due to drifts of the responsivities of the photomixers and of the optical power illuminating the photomixers. We report a simple method to substantially reduce this variability. By normalizing the amplitude to the DC photocurrents in both the transmitter and receiver photomixers, we achieve a significant increase in 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 nonideal environmental conditions outside of a temperature-stabilized laboratory.

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