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Antenna-coupled photomixers, serving as emitters and receivers of terahertz (THz) radiation, are the central active components of coherent optoelectronic THz systems. Here, we focus on the continuous-wave modality, which finds ample use for spectroscopy, sensing, and ranging and plays a major role in upcoming ultrahigh-frequency telecommunication applications. We demonstrate with planar receivers based on low-temperature-grown GaAs that the use of interdigital graphene electrodes instead of metal fingers enhances the responsivity by more than one order of magnitude. The increase in responsivity leads to a strongly enlarged dynamic range and doubles the frequency range covered in the detection process. We show by simulations that these improvements are a consequence of the transparency of the finger electrodes for visible/near-infrared laser radiation, which also activates the area under the fingers for the mixing process, not only their edges as in conventional devices with metal electrodes.

[ES] Este trabajo estudia las posibilidades de abordar directamente el problema de la desadaptación de las impedancias de un sistema continuo de generación de ondas (CW) de terahercios (THz) a partir de diferentes configuraciones, tanto convencionales como nano fotomezcladores. Aquí se investigan dos diseños de antena, las antenas de banda ancha y de resonancia. Una antena log-periódica se elige para un amplio rango de frecuencias, y el dipolo de onda completa para la antena de resonancia. Se discuten las posibilidades de implementar una red de adaptación de elementos concentrados. Los valores obtenidos de los elementos coincidentes son, para el fotomezclador interdigital L = 7,93 pH y C = 1,88 fF, y para el fotomezclador con hilo simple L = 50 pH y C = 0,3 fF. La baja transferencia de energía entre el fotomezclador y la antena se centra en le hecho de que las redes distribuidas clásicas de adaptación basadas en líneas de transmisión no son adecuadas para esa aplicación. Los elementos adaptados se calculan tanto para los fotomezcladores convencionales como para los nanofotomezcladores. Además, el uso de nanomateriales como los electrodos puede mitigar significativamente el rendimiento de eficiencia cuántica baja de los fotoconductores optoelectrónicos de terahercios. Esto mejora la eficiencia de la conversión óptica a terahercios de emisores fotoconductores de terahercios. En conclusión, este estudio permite comprender mejor los distintos roles del fotomezclador y la integración de la antena y, por lo tanto, optimizar independientemente estos componentes., [EN] This work studies the possibilities of directly addressing the impedance mismatch problem of a continuous wave (CW) terahertz (THz) generation from different both configuration of conventional and nano photomixers. Two antenna designs are investigated here, the broadband and resonance antennas. A logperiodic antenna design is chosen for broad frequency range, and full-wave dipole for resonance antenna. The possibilities of implementing a lumped element matching network are discussed. The values obtained of the matching elements are, for the interdigital photomixer L = 7.93 pH and C = 1.88 fF, and for the single nanowire L = 50 pH and C = 0.3 fF. The low power transfer between the photomixer and antenna focuses in which classical distributed matching networks based in transmission lines are not suitable for this application. The matching elements are calculated for both conventional and nano photomixers. Moreover, the use of nanomaterial as electrodes can significantly mitigate the low-quantum efficiency performance of photoconductive terahertz optoelectronics. This enhances the optical-to-terahertz conversion efficiency of photoconductive terahertz emitters. In conclusion, this study allows to understand better the distinct roles of the photomixer and antenna integration and, hence, independently optimize these components.

Continuous-wave terahertz emitters based on photomixers with hybrid nanoelectrodes are investigated. The nanoelectrodes consist of a nitrogen-doped single layer of graphene and silver nanowires, placed on low-temperature-grown (LTG) GaAs as photoconductive material. Due to the high transparency of graphene and the low fill factor of nanowire nanoelectrodes, high photocurrents in the range from 260 µA to 1.8 mA can be reached. Despite their very small size nanoelectrodes provide the capability of handling rather high currents, leading to THz output signals reasonably three times higher than for conventional interdigitated finger electrodes for the whole measurement range. Measurement results of generated photocurrents and THz output signals are presented, showing the increased performance of our approach while maintaining highly reliable operation of the devices.

[ES] Este trabajo consiste en el diseño y fabricación de una antena de banda ancha para el rango de THz, entre 300GHz y 3THz. La antena se utilizará en fuentes de THz (fotomezcladores). La tecnología utilizada combina técnicas tanto en el rango de las microondas como en el de fotónica., [EN] This work consists of designing and fabricating a broadband antenna in the Terahertz range, between 300 GHz and 3 THz. The antenna will be used in Terahertz sources (photomixers). The used technology combines both work in microwave and photonic range.