Abstract-Experimental Comparison of UTC- and PIN-Photodiodes for Continuous-Wave Terahertz Generation

• S. Nellen, 
• T. Ishibashi 
• A. Deninger, 
• R. B. Kohlhaas, 
• L. Liebermeister, 
• M. Schell, 
• B. Globisch
• • 
    

https://link.springer.com/article/10.1007/s10762-019-00638-5

We carried out an experimental comparison study of the two most established optoelectronic emitters for continuous-wave (cw) terahertz generation: a uni-traveling-carrier photodiode (UTC-PD) and a pin-photodiode (PIN-PD). Both diodes are commercially available and feature a similar package (fiber-pigtailed housings with a hyper-hemispherical silicon lens). We measured the terahertz output as a function of optical illumination power and bias voltage from 50 GHz up to 1 THz, using a precisely calibrated terahertz power detector. We found that both emitters were comparable in their spectral power under the operating conditions specified by the manufacturers. While the PIN-PD turned out to be more robust against varying operating parameters, the UTC-PD showed no saturation of the emitted terahertz power even for 50 mW optical input power. In addition, we compared the terahertz transmission and infrared (IR) blocking ratio of four different filter materials. These filters are a prerequisite for correct measurements of the absolute terahertz power with thermal detectors.

Abstract-Silicon–plasmonic integrated circuits for terahertz signal generation and coherent detection

T. Harter, S. Muehlbrandt, S. Ummethala, A. Schmid, S. Nellen, L. Hahn, W. Freude,  C. Koos,

https://www.nature.com/articles/s41566-018-0237-x

Optoelectronic signal processing offers great potential for generation and detection of ultra-broadband waveforms in the terahertz range (so-called T-waves). However, fabrication of the underlying devices still relies on complex processes using dedicated III–V semiconductor substrates. This severely restricts the application potential of current T-wave transmitters and receivers and impedes co-integration of these devices with advanced photonic signal processing circuits. Here, we demonstrate that these limitations can be overcome by plasmonic internal-photoemission detectors (PIPEDs). PIPEDs can be realized on the silicon photonic platform, which allows exploiting the enormous opportunities of the associated device portfolio. In our experiments, we demonstrate both T-wave signal generation and coherent detection at frequencies up to 1 THz. To prove the viability of our concept, we monolithically integrate PIPED transmitters and receivers on a common silicon chip and use them to measure the complex transfer impedance of an integrated T-wave device.

Abstract-Fiber-coupled, photoconductive heterodyne receiver operating at frequencies up to 1 THz

S. Nellen,  B. Globisch,   R. Kohlhaas,   D. Stanze,   T. Göbel,   J. O'Gorman ,  L. Barry,   M. Schell

http://ieeexplore.ieee.org/document/8084080/

An optoelectronic InGaAs-based terahertz (THz) receiver for heterodyne detection up to 1 THz is demonstrated for the first time operating at 1.5 μm. This wavelength allows for a fully fiber-coupled heterodyne system, which simplifies applications spectroscopy and THz communications.

Abstract-Terahertz detectors from Be-doped low-temperature grown InGaAs/InAlAs: Interplay of annealing and terahertz performance

B. Globisch1,a), R. J. B. Dietz1, S. Nellen1, T. Göbel1 and M. Schell1
http://scitation.aip.org/content/aip/journal/adva/6/12/10.1063/1.4971843?TRACK=RSS
1 Fraunhofer Institute for Telecommunications, Heinrich Hertz Institute, Einsteinufer 37, 10587 Berlin, Germany
a) Electronic mail: Bjoern.Globisch@hhi.fraunhofer.de
AIP Advances 6, 125011 (2016); http://dx.doi.org/10.1063/1.4971843

The influence of post-growth annealing on the electrical properties, the transient carrier dynamics and the performance as THz photoconductive receiver of Beryllium (Be) doped InGaAs/InAlAs multilayerheterostructures grown at 130 °C in a molecular beam epitaxy (MBE) system was investigated. We studied samples with nominally Be doping concentrations of 8 ×10 17 cm-3 – 1.2 ×1019 cm3 annealed for 15 min. – 120 min. at temperatures between 500 °C – 600 °C. In contrast to previous publications, the results show consistently that annealing increases the electron lifetime of the material. In analogy to the annealing properties of low-temperature grown (LTG) GaAs we explain our findings by the precipitation of arsenic antisite defects. The knowledge of the influence of annealing on the material properties allowed for the fabrication of broadband THz photoconductive receivers with an electron lifetime below 300 fs and varying electrical properties. We found that the noise of the detected THz pulse trace in time-domain spectroscopy (TDS) was directly determined by the resistance of the photoconductive receiver and the peak-to-peak amplitude of the THz pulse correlated with the electron mobility.