Subharmonic lock-in detection and its optimisation for femtosecond noise correlation spectroscopy

Although often viewed as detrimental, fluctuations carry valuable information about the physical system from which they emerge. Femtosecond noise correlation spectroscopy (FemNoC) has recently been established to probe the ultrafast fluctuation dynamics of thermally populated magnons by measurement...

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Bibliographic Details
Published inarXiv.org
Main Authors Weiss, M A, Herbst, F S, Eggert, S, Nakajima, M, Leitenstorfer, A, Goennenwein, S T B, Kurihara, T
Format Paper Journal Article
LanguageEnglish
Published Ithaca Cornell University Library, arXiv.org 14.03.2024
Subjects
Data acquisition
Demodulation
Magnons
Mathematical models
Parameter identification
Physics - Instrumentation and Detectors
Physics - Optics
Physics - Other Condensed Matter
Signal to noise ratio
Spectroscopy
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Summary:Although often viewed as detrimental, fluctuations carry valuable information about the physical system from which they emerge. Femtosecond noise correlation spectroscopy (FemNoC) has recently been established to probe the ultrafast fluctuation dynamics of thermally populated magnons by measurement of their amplitude autocorrelation. Subharmonic lock-in detection is the key technique in this method, allowing to extract the pulse-to-pulse polarisation fluctuations of two femtosecond optical pulse trains transmitted through a magnetic sample. Here, we present a thorough technical description of the subharmonic demodulation technique and of the FemNoC measurement system. We mathematically model the data acquisition process and identify the essential parameters which critically influence the signal-to-noise ratio of the signals. Comparing the model calculations to real datasets allows validating the predicted parameter dependences and provides a means to optimise FemNoC experiments.
ISSN:2331-8422
DOI:10.48550/arxiv.2403.09829