Search

Your search keyword '"Fobbe F"' showing total 147 results
Start Over Author "Fobbe F"
147 results on '"Fobbe F"'

1. Electron spin dynamics of Ce$^{3+}$ ions in YAG crystals studied by pulse-EPR and pump-probe Faraday rotation

Author

Azamat, D. V., Belykh, V. V., Yakovlev, D. R., Fobbe, F., Feng, D. H., Evers, E., Jastrabik, L., Dejneka, A., and Bayer, M.

Subjects
Condensed Matter - Materials Science, Condensed Matter - Mesoscale and Nanoscale Physics, Physics - Optics
Abstract

The spin relaxation dynamics of Ce$^{3+}$ ions in heavily cerium-doped YAG crystals is studied using pulse-electron paramagnetic resonance and time-resolved pump-probe Faraday rotation. Both techniques address the 4$f$ ground state, while pump-probe Faraday rotation provides also access to the excited 5$d$ state. We measure a millisecond spin-lattice relaxation time $T_1$, a microsecond spin coherence time $T_2$ and a $\sim 10$ ns inhomogeneous spin dephasing time $T_2^*$ for the Ce$^{3+}$ ground state at low temperatures. The spin-lattice relaxation of Ce$^{3+}$ ions is due to modified Raman processes involving the optical phonon mode at 125 cm$^{-1}$. The relaxation at higher temperature goes through a first excited level of the $^{2}$F$_{5/2}$ term at about $\hbar \omega \approx 228$ cm$^{-1}$. Effects provided by the hyperfine interaction of the Ce$^{3+}$ with the $^{27}$Al nuclei are observed., Comment: 10 pages, 13 figures

Published
2017
Full Text
View/download PDF

2. Extended pump-probe Faraday rotation spectroscopy of the submicrosecond electron spin dynamics in n-type GaAs

Author

Belykh, V. V., Evers, E., Yakovlev, D. R., Fobbe, F., Greilich, A., and Bayer, M.

Subjects
Condensed Matter - Mesoscale and Nanoscale Physics, Quantum Physics
Abstract

We develop an extended pump-probe Faraday rotation technique to study the submicrosecond electron spin dynamics with picosecond time resolution in a wide range of magnetic fields. The electron spin dephasing time $T_2^*$ and the longitudinal spin relaxation time $T_1$, both approaching $250$ ns in weak fields, are measured thereby in $n$-type bulk GaAs. By tailoring the pump pulse train through increasing the contained number of pulses, the buildup of resonant spin amplification is demonstrated for the electron spin polarization. The spin precession amplitude in high magnetic fields applied in the Voigt geometry shows a non-monotonic dynamics deviating strongly from a mono-exponential decay and revealing slow beatings. The beatings indicate a two spin component behavior with a $g$-factor difference of $\Delta g \sim 4\times10^{-4}$, much smaller than the $\Delta g$ expected for free and donor-bound electrons. This $g$-factor variation indicates efficient, but incomplete spin exchange averaging., Comment: 5 pages, 3 figures

Published
2016
Full Text
View/download PDF

7. Wissenschaftliche Ausstellung

Author

Sachs, M., Encke, A., Wenisch, H. J. C., Hanisch, E., Keller, H., Jung, M., Weber, Th., Heller, K., Buia, A., Eichhorn, J., Klein, C., Howaldt, H.-P., Becker, H.-P., Schmidt, R., Gutcke, A., Gerngroß, H., Willy, C., Minholz, R., Wieja, G., Melzer, A., Kipfmüller, K., Stöckel, D., Schurr, M. O., Russ, D., Kunert, W., Steiner, R., Buess, G., Schaeff, B., Gutt, C., Kanngießer, P., Paolucci, V., Hinkelbein, W., Wagner, A. K., Fobbe, F., Boese-Landgraf, J., Schill, S., Lorenz, E. P. M., Albrecht, D., Bumm, R., Lehr, L., Siewert, J. R., Stangl, M. J., Anthuber, M., Berger, H., Weiss, M., Jauch, K. W., Schildberg, F. W., Bödeker, H., Berger, M., Linnemann, U., Gebhardt, Ch., Schultheis, K.-H., Wünsch, P.-H., Ernst, M., Wondzinski, A., Germer, C. T., Heiniche, A., Buhr, H. J., Hasse, C., Stinner, B., Geks, J., Rothmund, M., Hochstein, P., Becker, S., Kuhn, A., Wentzensen, A., Krabatsch, Th., Fleck, E., Hetzer, R., Minor, Th., Isselhard, W., Yamaguchi, T., Klauke, H., Müller, G., Mayer, G., Mühlbach, K., Stumptner, K., Kolbert, G., Shekarriz, H., Wenk, H., Neumann, M., Neumann, K., Steinau, H. U., Markel, D. C., Willis, S., Allescher, H.-D., Classen, M., Schumpelick, V., Vatankhah, M., Blesse, J., Volbracht, A., Schleef, J., Hebestreit, A., Willital, G. H., Walter, M., Wolters, U., Pichlmaier, H., Maiwald, G., Meyer, G., Walli, A., Seidel, D., Schildberg, F.-W., Mann, S., Martens, O., Mann, U., Zirngibl, H., Nustede, R., Streich, R., Becker, H., Henrichs, Ch., Gebhardt, H., Schaube, H., Fändrich, F., Jonas, J., Junginger, Th., Viebahn, R., Metzdorf, B., Eisenberger, C., Lauchart, W., Morlion, B. J., Holzgreve, A., Meffert, R., Wrenger, K., Pohle, T., Lippert, H., Schulz, H.-U., Schmidt, D., Kunz, D., Struy, H., Klose, G., Pommer, S., Frei, S., Nägeli, J., Sege, D., Lange, J., Hartel, W., editor, and Hierholzer, G.

Published
1995
Full Text
View/download PDF

30. Optical rectification of a 100??W average power mode-locked thin-disk oscillator

Author

Meyer, F., Hekmat, N., Mansourzadeh, S., Fobbe, F., Aslani, F., Hoffmann, M., and Saraceno, C. J.

Abstract

We demonstrate terahertz (THz) generation at megahertz repetition rate by optical rectification in GaP crystals, using excitation average power levels exceeding 100 W. The laser source is a state-of-the-art diode-pumped Yb:YAG SESAM-mode-locked thin-disk laser, capable of generating 580 fs pulses at an average power up to 120 W and a repetition rate of 13.4 MHz directly from a one-box oscillator, without the need for any extra amplification stages. In this first demonstration, we measure a maximum THz average power of 78 μW at a central frequency of 0.8 THz. Our results show that optical rectification of state-of-the-art high average power ultrafast sources in nonlinear crystals is within reach and paves the way toward high average power, ultrafast laser pumped THz sources.

Published
2018

50. Minimally invasive catheter implantation for regional chemotherapy of the liver: a new percutaneous transsubclavian approach.

Author

Wacker, Frank, Boese-Landgraf, Jochen, Wagner, Armin, Albrecht, Dirk, Wolf, Karl-Jürgen, Fobbe, Franz, Wacker, F K, Boese-Landgraf, J, Wagner, A, Albrecht, D, Wolf, K J, and Fobbe, F

Abstract

Purpose: Development of a percutaneously implantable catheter system for regional chemotherapy of liver metastases and its application in patients with surgically implanted but dislocated catheters.Methods: Thirty-three patients with liver metastases of colorectal tumors were submitted to percutaneous puncture of the subclavian artery and insertion of a catheter whose tip was placed in the proper hepatic artery and whose end was subcutaneously connected with an infusion pump.Results: The mean duration of therapy via the percutaneously inserted catheter was 27 weeks (+/-14 weeks). The most frequent complication was disconnection of the therapy catheter from the tube of the infusion pump. Eighty percent of all complications were corrected by reintervention. The therapy drop-out rate due to catheter-associated complications was 9%.Conclusion: Percutaneous insertion of a catheter for regional chemotherapy of the liver is a relatively uncomplicated method with high patient acceptance and simple access for reintervention. [ABSTRACT FROM AUTHOR]

Published
1997
Full Text
View/download PDF

Catalog

Books, media, physical & digital resources
See catalog results