Freiburg 2024 – wissenschaftliches Programm

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MO: Fachverband Molekülphysik

MO 7: Poster: Spectroscopy

MO 7.16: Poster

Dienstag, 12. März 2024, 17:00–19:00, Tent C

Phase-sensitive detection of photons — Lucas Ludwig, •Sanchayeeta Jana, Simon Durst, and Markus Lippitz — Chair for experimental physics III, Universität Bayreuth, Bayreuth, Germany

In quantum optics, the measured signal is often photon detection events. Modulation and phase-sensitive detection of photons is essential for many applications. Even though phase-sensitive or lock-in detection is a compelling technique invented over 90 years ago, all commercial lock-in detectors use an analog voltage measured by a detector (e.g., a photodiode) as the input signal. Thus, one cannot use a commercial lock-in detector with photon counters for phase-sensitive detection of photons. For this reason, we have developed a method for lock-in detection of photons, which we use for measuring 2D spectra of single molecules.

We employ AOMs to phase-modulate four optical pulses for the fluorescence-detected two-dimensional electronic spectroscopy (F-2DES) experiment. A reference diode detects the interference signal, and the output goes to an FPGA, where three phase lock loops (PLL) lock the phase difference between the pulses and send the trigger pulse to a time tagger. A single photon counting detector detects the fluorescence signal from the molecules after excitation with the four phase-modulated pulses. These photons are also registered by the time tagger, thus enabling phase-sensitive detection of photons.

This work will discuss the construction of PLLs in FPGA and their characteristics.

Keywords: FPGA; 2D spectroscopy; lock-in detection; phase locked loop (PLL); single photon counting