Dresden 2003 – wissenschaftliches Programm

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HL: Halbleiterphysik

HL 32: Spinabh
ängiger Transport II

HL 32.3: Vortrag

Mittwoch, 26. März 2003, 15:00–15:15, POT/81

Spectrally resolved measurements of the Faraday rotation induced by spin polarized electrons — •Jochen Müller, Markus Beck, Claus Metzner, Stefan Malzer, and Gottfried H. Döhler — Institut für Technische Physik I, Universität Erlangen Nürnberg, Erlangen, Germany

One approach for the determination of spin relaxation times in semiconductors is time resolved Faraday rotation using femtosecond pump and probe measurements. Instead of femtosecond pulses with one common, relatively broad wavelength spectrum, we use two cw laser diodes whose wavelengths can be tuned independently. One diode continuously excites spin polarized carriers, whereas with the second one, we probe the spin orientation, making use of the Faraday rotation. The determination of spin relaxation times by means of spatially resolved measurements will be discussed in a different contribution, whereas here, we concentrate on the dependence of the obtained Faraday rotation on the cw pump and probe photon energies.

We have studied the spectral dependence of the Faraday rotation in n-type GaAs and in n-doped InGaAs quantum wells. Since the Faraday rotation ist closely linked to the difference between the absorption coefficients for right and left circular polarized light via Kramers-Kronig transformation, the energy spectrum reveals information both about the density and the spin polarization of the photoexcited carriers.