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Photoinitiated dynamics studied in the femtosecond to picosecond time and the THz/IR – PHz frequency domain: PIDID a multi institutional initiative

In the frame of the German-Russian collaboration on

“Development and use of accelerator-based photon sources“

(Coordinator: Prof. Dr. J. Heberle, FU Berlin)

The PIDID project (click for further information) will substantially improve the experimental opportunities for accelerator based time-resolved measurements in Germany. The proposed development of the experimental infra-structures at FELBE and FLASH will establish a complementary instrumentation that allows the contributing groups for the first time to perform their research in an unprecedented combination of fs – ns time- and THz – PHz frequency domain. The close collaboration of German and Russian partners will carry out the development which will master solutions to the problems that presently inhibit a routine user program at the two facilities.

To provide for the required single-pulse photon diagnostic and alignment of the temporal overlap, the AG Hübers is responsible for the development of single-pulse detectors to be used at FLASH and FELBE and collaborating with partners from DESY, HZDR and the Budker institute (WP5). The beam monitor detector will be realized on the basis of a gallium and antimony doped compensated Germanium crystals (Ge:Ga:Sb)

Responsivity of an unstressed (blue) and a stressed (red) Ge:Ga detector measured with a Fourier transform spectrometer. Unixaial stress (along [100]) extends the long-wavelength response to about 200 µm.

The response time of the detector material was determined with a pump-probe technique in cooperation with the group of Prof. Shastin. The experiments were performed at the free electron laser FELBE by exciting the carriers into the valence band (Ge:Ga) or conduction band (Ge:Sb).

a) Pump-probe signals of a Ge:Sb sample for different pump-pulse energies. Inset: Dependence of the maximum of the relative transmission on the pump pulse energy at 2.85 THz excitation frequency. The temperature of the Ge:Sb sample was ~5 K. b) Dependence

In order to improve the speed, Ge:Ga with a particular compensation and concentration of recombination centers were grown by the Institute for Crystal Growth.

a) Fast Germanium detector system mounted on the cold plate of a liquid Helium cryostat b) Typical dependences of free electron decay times on the energy of the pump pulse (frequency is 2.85 THz) for the photoinduced THz transmittance in n-Ge:Sb:Ga and p-



[1]      N. Deßmann, S. G. Pavlov, V. N. Shastin, R. K. Zhukavin, V. V Tsyplenkov, S. Winnerl, M. Mittendorff, N. V. Abrosimov, H. Riemann, and H.-W. Hübers, “Time-resolved electronic capture in n-type germanium doped with antimony,” Phys. Rev. B, vol. 89, no. 3, p. 35205, 2014.

[2]      S. G. Pavlov, N. Deßmann, V. N. Shastin, R. K. Zhukavin, B. Redlich, A. F. G. van der Meer, M. Mittendorff, N. V. Abrosimov, H. Riemann, and H.-W. Hübers, “Terahertz Stimulated Emission from Silicon Doped by Hydrogenlike Acceptors,” Phys. Rev. X, vol. 4, no. 2, p. 21009, Apr. 2014.

[3]      N. Deßmann, S. G. Pavlov, M. Mittendorff, S. Winnerl, R. K. Zhukavin, V. V Tsyplenkov, D. V Shengurov, V. N. Shastin, N. V. Abrosimov, H. Riemann, and H.-W. Hübers, “Fast relaxation of free carriers in compensated n- and p-type germanium,” in Infrared, Millimeter, and Terahertz Waves (IRMMW-THz), 2013 38th International Conference on, 2013, pp. 1–2.

[4]      N. Deßmann, S. G. Pavlov, V. N. Shastin, R. K. Zhukavin, S. Winnerl, M. Mittendorff, and H.-W. Hübers, “Time-resolved electronic capture in germanium doped with hydrogen-like impurity centers,” in Infrared, Millimeter, and Terahertz Waves (IRMMW-THz), 2012 37th International Conference on, 2012, pp. 1–2.

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