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Erzeugung von Dauerstrich THz-Strahlung / CW-THz Generation

Prof. Dr. Eng. Dr. h. c. mult H. L. Hartnagel

Prof. Dr.-Ing. Franko Küppers

PD Dr.-Ing. habil. Oktay Yilmazoglu

PD Dr.-Ing. Shihab Al-Daffaie

Assoc. Prof. Dr. Vadim Sirkeli, AvH-Fellow

The main target of this research topic is the generation of THz radiation by optical heterodyning, as well as using quantum cascade lasers (QCLs) and resonant tunneling diodes (RTDs). This approach is based on CW operation and allows wide tuneability as well as high resolution. Cooperation partners are the group of Prof. Elsässer at the TU Darmstadt and the group of Prof. Roskos at the University of Frankfurt.

The underlying principle of THz generation by optical heterodyning is the mixing of two single mode laser beams which will generate an optical beat signal with the difference frequency. A material with very low carrier lifetimes is needed that allows the optical beat signal to modulate its carrier concentration. GaAs can provide these low carrier lifetimes with sufficient mobility when grown under special conditions. In contrast to conventional growth temperatures of about 580°C LTG-GaAs (Low temperature grown Gallium Arsenide) is grown at about 200°C to allow arsenic excess. When this material is annealed after growth it provides carrier lifetimes below 1 ps, high resistivity and sufficient mobility.

Metallisation for planar antennas and photomixers is processed on top of the LTG-GaAs to make use of the THz power as efficient as possible.

Schematic of the photoconductive setup
Schematic of the photoconductive setup

CW-THz Setup

The photoconductive CW-THz setup provides:

  • Frequency range up to 3 THz
  • Line width < 5 MHz
  • S/N Ratio of 1000
  • opt. modulation depth > 90%
  • max. power about 50 nW

These properties make it ideal for spectroscopy measurements and characterisation of material at THz frequencies.

Description of the picture:

In the upper left and upper right corner the two parabolic mirrors are displayed which focus the radiation. Below them the two PCB holders for the LTG-GaAs Chips are shown which have to be illuminated by the two-color laser beam.

QCL and RTD structures for terahertz generation at room temperature

The increase of operation temperature of terahertz quantum cascade lasers (THz QCLs) resonant tunneling diodes (RTDs) up to room temperature and above is a crucial issue. Here for the first time a design is presented that allows quantum cascade structures to generate THz signals at or even above room temperature. The suggested THz QCL is based on ZnSe/Zn1–xMgxSe material systems employing alternating barriers with variable heights.

Veröffentlichungen / Publications

2017

Sirkeli, V. P. and Yilmazoglu, O. Küppers, F. and Hartnagel, H. L. :
Room-temperature terahertz emission from ZnSe-based quantum cascade structures: A simulation study
[Online-Edition: https://doi.org/10.1002/pssr.201600423]
In: physica status solidi (RRL) – Rapid Research Letters, 11, pp. 1-4.
[Article], (2017)

2016

Hartnagel, H. L. and Al-Daffaie, S. and Yilmazoglu, O. :
Plasmonics in semiconductors and in Ag submicron wires and graphene.
[Online-Edition: http://dx.doi.org/10.3952/physics.v55i4.3225]
In: Lithuanian Journal of Physics, 55 (4)
[Article], (2016)

Schildbach, Christian and Ong, Duu Sheng and Hartnagel, Hans and Schmidt, Lorenz-Peter :
Estimation of frequency conversion efficiency of THz devices using a ballistic electron wave swing circuit model.
[Online-Edition: http://dx.doi.org/10.1088/0268-1242/31/6/065003]
In: Semiconductor Science and Technology, 31 (065003) pp. 1-7. ISSN 0268-1242
[Article], (2016)

2015

Al-Daffaie, S. and Yilmazoglu, O. and Küppers, F. and Hartnagel, H. :
Fully integrated vertical nanocontact photomixer for continuous-wave terahertz generation.
[Online-Edition: http://dx.doi.org/10.1109/IRMMW-THz.2015.7327568]
In: 40th International Conference on Infrared, Millimeter, and Terahertz waves (IRMMW-THz).
[Conference or Workshop Item], (2015)

Damm, C. and Schwefel, H. G. L. and Sedlmeir, F. and Hartnagel, H. and Preu, S. and Weickhmann, C. :
Selected emerging thz technologies.
[Online-Edition: http://dx.doi.org/10.1002/9781118920411]
In: Semiconductor Terahertz Technology: Devices and Systems at Room Temperature Operation. John Wiley & Sons, Chichester, UK , pp. 340-382.
[Book Section], (2015)

Evtukh, Anatoliy and Hartnagel, Hans and Yilmazoglu, Oktay and Mimura, Hidenori and Pavlidis, Dimitris:
Quantum Electron Sources for High Frequency Applications.
[Online-Edition: http://dx.doi.org/10.1002/9781119037989.ch9]
Wiley Online Library, pp. 375-446.
[Book], (2015)

Carpintero, Guillermo and Garcia-Munoz, Luis Enrique and Hartnagel, Hans and Preu, Sascha and Räisänen, Antti:
Semiconductor TeraHertz Technology: Devices and Systems at Room Temperature Operation.
[Online-Edition: http://dx.doi.org/10.1002/9781118920411]
John Wiley & Sons ISBN 978-111-892-039-8 ; 978-111-892-040-4 ; 978-111-892-042-8 (print)
[Book], (2015)

Yilmazoglu, O. and Al-Daffaie, S. and Küppers, F. and Hartnagel, H. L. :
New photocathodes for THz vacuum microelectronic devices.
[Online-Edition: http://www.emnmeeting.org/VE/]
In: Energy, Materials, Nanotechnology (EMN) Meeting on Vacuum Electronics, Las Vegas, NV USA.
[Conference or Workshop Item], (2015)

Hartnagel, H. L., Sontea, Victor and Tiginyanu, Ion (eds.) :
Plasmonic Effects for Enhanced Optical Mixing in View of THz Signal Generation.
[Online-Edition: http://dx.doi.org/10.1007/978-981-287-736-9_46]
In: 3rd International Conference on Nanotechnologies and Biomedical Engineering: ICNBME-2015, Chisinau, Republic of Moldova. 3rd International Conference on Nanotechnologies and Biomedical Engineering: ICNBME-2015, September 23-26, 2015, Chisinau, Republic of Moldova Springer Singapore
[Conference or Workshop Item], (2015)

Yilmazoglu, O. and Al-Daffaie, S. and Küppers, F. and Hartnagel, H. L. and Neo, Y. and Mimura, H. :
Ultrafast photocathodes based on n-doped graphene emitters on compound semiconductor photoswitches.
[Online-Edition: http://dx.doi.org/10.1109/IVNC.2015.7225573]
In: 28th International Vacuum Nanoelectronics Conference (IVNC).
[Conference or Workshop Item], (2015)

Hartnagel, H. L. and Al-Daffaie, S. and Yilmazoglu, O. :
Plasmonics and Graphene for THz Generation by Optical Mixing.
[Online-Edition: https://www.researchgate.net/publication/280223417_Plasmonic…]
In: The 4th Russia-Japan-USA Symposium on Fundamental & Applied Problems of Terahertz Devices & Technologies, At IMT, ISSP, Chernogolovka, Russia.
[Conference or Workshop Item], (2015)

Al-Daffaie, S. and Yilmazoglu, O. and Küppers, F. and Hartnagel, H. L. :
1-D and 2-D Nanocontacts for Reliable and Efficient Terahertz Photomixers.
[Online-Edition: http://dx.doi.org/10.1109/TTHZ.2015.2399772]
In: IEEE Transactions on Terahertz Science and Technology, 5 (3) pp. 398-405. ISSN 2156-342X
[Article], (2015)

Hartnagel, H. L. and Al-Daffaie, S. and Yilmazoglu, O. :
Plasmonics in semiconductors and in Ag submicron wires and graphene.
[Online-Edition: http://dx.doi.org/10.3952/physics.v55i4.3225]
In: Lithuanian Journal of Physics, 55 (4) pp. 287-291.
[Article], (2015)

Ong, Duu Sheng and Hartnagel, Hans L. :
THz radiation by quasi-ballistic electron reflection in AlSb/InAs/AlSb heterostructures.
[Online-Edition: http://dx.doi.org/10.1209/0295-5075/109/38004]
In: EPL, 109 (2015) p. 38004.
[Artikel], (2015)