Interdigitated terahertz emitters

Acuna, Guillermo P.; Buersgens, F.; Lang, C.; Kersting, R.

doi:10.1109/icimw.2007.4516827

Cited by 1 publication

(1 citation statement)

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“…Several variants of this conventional LPE targeting higher conversion efficiencies were demonstrated. Instead of an additional cover layer, the substrate in every second region can be removed [3, 4]. This way, lower dark currents result, but a higher conversion efficiency is not to be expected.…”

Section: Introductionmentioning

confidence: 99%

Terahertz emission based on large‐area photoconductive emitters illuminated via beam interference

et al. 2015

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The use of beam interference in combination with a large-area photoconductive emitter for the generation of pulsed terahertz (THz) radiation is presented. An interference pattern with a period twice that of the THz emitter is generated with a transmission phase grating, placed directly in front of the photoconductive emitter. This way, efficient THz generation is achieved with a single metallisation layer and a single lithography step in the fabrication technology of the THz emitter.Introduction: The efficient generation and detection of broadband tera hertz (THz) radiation has evolved as the driving force for future high speed THz time domain systems. Different generation mechanisms based on ultra short optical pulses such as optical rectification and photoconductive antennas have been investigated intensively during the past. Amplified high energy pulses with kilohertz pulse repetition rates are able to create ultra broadband THz radiation by optical rectifi cation in nonlinear crystals [1]. However, for many applications a higher data acquisition speed is favoured, thus higher pulse repetition frequen cies (>MHz) should be used. These setups are mostly equipped with photoconductive emitters, which rely on linear infrared (IR) absorption and offer a high IR to THz conversion efficiency at moderate pulse energies. The emitted THz radiation in a single antenna is limited by the maximum thermal load and the breakdown voltage of the antenna. Power scaling was demonstrated via large area photoconductive emitters (LPEs) based on a periodic interdigitated metal semiconductor metal structure [2]. To prevent destructive inter ference of THz radiation in the far field from regions with inversed bias fields, every second electrode spacing needs to be covered with an additional electrically isolated opaque material. This way, uni directional charge carrier acceleration over the illuminated area is ensured. Unfortunately, the additional metallisation reduces the amount of absorbed light by a factor of 2. Several variants of this con ventional LPE targeting higher conversion efficiencies were demon strated. Instead of an additional cover layer, the substrate in every second region can be removed [3,4]. This way, lower dark currents result, but a higher conversion efficiency is not to be expected. By implementing a micro lens array in front of the emitter structure, the amount of absorbed light is increased by a factor of 3 [5]. Further large area emitters rely on lateral photocurrents via the lateral photo Dember effect or Schottky fields at multiple asymmetric metal semiconductor junctions [6,7]. A fundamentally different approach relies on locally enhanced fields and absorption due to plasmonic effects [8 10]. Despite being very promising in terms of efficiency, plas monic structures need to be simulated and grown with high accuracy and are sensitive to the polarisation of the incident IR light.The approach presented here is based on a biased LPE that is illu minated by a tailored interference pattern. This concept allows...

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Section: Introductionmentioning

confidence: 99%