Novel photmixers with one-dimensional and two-dimensional nanocontacts for terahertz generation

近年来，太赫兹元件和系统的新发展为新的安全应用提供了有吸引力的机会，例如隐藏物体的成像测量、有害物质的光谱和无线宽带系统中的防窃听通信。然而，仍然需要获得频率高达几太赫兹的稳定高性能连续波源，这将允许非常简单的系统架构。传统技术在可实现的太赫兹输出功率和频率方面有很大的局限性。拟议的研究项目建立在创新的1D或2D纳米触点上，具有可靠的高光电流bbb30 3 mA和小器件电容< 0.5 fF。因此，可以在< 2太赫兹的频率下实现更高的太赫兹输出功率> 100µW，甚至可以从远程物体进行成像测量，并且覆盖最高太赫兹频率> 5太赫兹，可以轻松识别不同有害物质的光谱吸收线。此外，材料和食品的质量研究是可能的。高太赫兹输出功率和高信噪比将允许比传统的光电混合器更快的测量。首先，将研究商用纳米线（如银线）和多层石墨烯片作为LT-GaAs接触电极的适用性。将确定附着力和可靠的功率密度。在这些结果的基础上，将设计和制造第一批横向和垂直太赫兹光敏器，并对最初高达2太赫兹的光敏器进行测量和建模。所得到的光度计等效电路允许优化选择的天线概念，以用于紧凑的太赫兹源。纳米接触光敏器也开启了减小有源光敏器面积的可能性，同时保持高光电流和太赫兹输出功率，以集成bbb20太赫兹的天线概念。再加上较小的电容，可以实现高信噪比的高频bbb50 THz。在800 nm的系统中，将对太赫兹输出功率、截止频率和新photomixer的可靠性进行现实电位分析。该技术也可以很容易地应用于800 nm的系统，具有廉价和紧凑的垂直腔面发射激光器（VCSELs），以及1.55 μ m的系统，具有电信激光器，大大简化了系统架构。

New developments of THz components and systems in recent years offer attractive opportunities for new security applications such as imaging measurements of hidden objects, spectroscopy of hazardous substances and tap-proof communication in wireless broadband systems. However, it is still necessary to obtain stable and high performance continuous-wave sources for frequencies up to several THz, which will allow very simple system architectures. The conventional technologies have significant limitations with respect to the achievable THz output power and frequencies. The proposed research project builds on innovative 1D or 2D nano-contacts with reliable high photocurrents > 3 mA and small device capacitance < 0.5 fF. Thus, much higher THz output power > 100 µW can be achieved at frequencies < 2 THz to perform imaging measurements even from remote objects and covers highest THz frequencies > 5 THz, which can easily identify the spectral absorption lines of different hazardous substances. Additionally, a quality study of materials and foods is possible. The high THz output power and the high signal-to-noise ratio will allow much faster measurements than with conventional photomixers. At the beginning, commer-cial nanowires (e.g. silver wires) and multilayer graphene sheets will be investigated for their suitability as a contact electrode on LT-GaAs. The adhesion and the reliable power density will be determined. On the basis of these results, first lateral and vertical THz photomixers will be designed and manufactured as well as measured and modeled initially up to 2 THz. The resulting equivalent circuit of the photomixer allows the optimization of selected antenna concepts to use in compact THz sources. The nano-contacted photomixer also opens the possibility to reduce the active photomixer area while maintaining high photocurrents and THz output power to integrate antenna concepts for > 2 THz. Together with the smaller capacitance high frequencies > 5 THz with high signal-to-noise ratio can be achieved. The realistic potential analysis with regard to the THz output power, the cut-off frequency and the reliability of the new photomixer will be carried out at an 800 nm system. This technology can also be applied easily to an 800 nm system with cheap and compact vertical-cavity surface-emitting lasers (VCSELs) and to a 1.55 µm system with telecom lasers to greatly simplify the system architecture.