Regensburg 2010 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 33: Poster I: Transport, including Magnetic-Field Effects

HL 33.14: Poster

Tuesday, March 23, 2010, 18:30–20:30, Poster D1

Linear and non-linear noise spectroscopy of fluctuating signals — •Rachel Fainblat, Sebastian Starosielec, Jörg Rudolph, and Daniel Hägele — AG Spektroskopie der kondensierten Materie, Ruhr-Universität Bochum, Germany

Spin noise spectroscopy has recently become a popular tool for studying incoherent dynamics in semiconductor spin systems. The usually measured (linear) noise power spectrum however can not discriminate between noise mechanisms that yield e.g. either Gaussian or non-Gaussian noise. An extension to non-linear noise spectroscopy is therefore highly desirable. We have implemented a real-time measurement systems that apart from the linear noise spectrum also calculates a non-linear noise spectrum. The non-linear spectrum is based on the square of the original noise signal and contains expectation values up to the fourth order. The non-linear spectrum is especially sensitive to correlations between spectral frequency components and non-Gaussian behaviour of the noise amplitude. As a demonstration we measure strong frequency correlations in the signal of FM radio broadcasting. On the contrary, the white photon shot noise of a laser above threshold shows no frequency correlations within the measured range from 0 to 90 MHz. We also performed measurements on biased and unbiased resistors (industrial metal-film and carbon) exhibiting white and 1/f-noise, respectively. The possible application of non-linear fluctuation spectroscopy for studying magnetic phase-transitions will be pointed out.