Freiburg 2019 – scientific programme

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FM: Fall Meeting

FM 56: Entanglement: Many-Body Dynamics II

FM 56.2: Talk

Wednesday, September 25, 2019, 14:30–14:45, 2004

Development of a software based lock-in amplifier for phase-modulated spectroscopy — •Daniel Uhl, Friedemann Landmesser, Ulrich Bangert, Marcel Binz, Lukas Bruder, and Frank Stienkemeier — Institute of Physics, University of Freiburg, Germany

Recently, many-body effects of interacting molecules doped on rare gas clusters have been observed [1]. Detecting these weak higher order signals requires a particularly sensitive measurement scheme. We established such a method based on a phase modulated quantum beat experiment combined with lock-in detection to isolate multiple-quantum coherences (MQCs) in a low density alkali vapor [2,3]. Here, the MQC signatures show up at higher harmonics of the modulation frequency and can be extracted with harmonic lock-in detection. Hence, it is possible to simultaneously isolate several MQC signals in a single measurement using multiple lock-in amplifiers (LIA). To further improve our detection scheme we developed a software based LIA. This opens the possibility to demodulate our signal at different harmonics and thus gives us the advantage to observe any desired separate multiphoton processes in the pre-analysis. The algorithm is mainly based on a digital phase locked loop to detect the phase and frequency of the incoming reference signal. Hence, it is possible to demodulate the signal for different harmonics by conserving the phase information.

[1] S. Izadnia et al., J. Phys Chem Lett 8, 2068 (2017)

[2] L. Bruder et al., Phys. Rev. A 92, 053412 (2015)

[3] L. Bruder et al., Phys. Chem. Chem. Phys. 21, 2276 (2019)