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MA: Fachverband Magnetismus

MA 35: Spin-Dynamics / Spin-Torque IV

MA 35.16: Vortrag

Donnerstag, 26. März 2009, 19:15–19:30, HSZ 04

Ultrafast Spin Noise Spectroscopy — •Sebastian Starosielec and Daniel Hägele — AG Spektroskopie der kondensierten Materie, Ruhr-Universität Bochum, D-44801 Bochum, Germany

Optical spin noise spectroscopy based on cw laser probe has proved to be a powerful method for determining e.g. spin lifetimes with only minimally perturbing the electronic system [1]. The accessible frequency range is however limited to typically below 1 GHz by the detection electronics. Here we propose a new scheme based on pairs of fs laser pulses that allows for measuring noise spectra up to 10 THz [2]. Monte-Carlo-simulations including photon shot noise show that smooth spectra can be obtained within a total observation time of only a few seconds. In addition, ultrafast noise spectroscopy can measure broad signals that are centered around zero frequency where traditional Raman- or Brillouin spectroscopy is notoriously difficult or even impossible. We give analytic expressions for the quality of ultrafast spin noise spectra in terms of observation time, photon shot noise, electrical noise, and the spin-noise level. A time-resolved version of noise spectroscopy for detecting noise after a pump event follows naturally from the scheme.

[1] M. Oestreich, M. Römer, R. J. Haug and D. Hägele, Phys. Rev. Lett. 95, 2166003 (2005).

[2] S. Starosielec and D. Hägele, Appl. Phys. Lett. 93, 051116 (2008).