Transient absorption microscopy setup with multi-ten-kilohertz shot-to-shot subtraction and discrete Fourier analysis

Robert Schwarzl, Pascal Heim, Manuela Schiek, Dario Grimaldi, Andreas Hohenau, Joachim R. Krenn, Markus Koch*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

Recording of transient absorption microscopy images requires fast detection of minute optical density changes, which is typically achieved with high-repetition-rate laser sources and lock-in detection. Here, we present a highly flexible and cost-efficient detection scheme based on a conventional photodiode and an USB oscilloscope with MHz bandwidth, that deviates from the commonly used lock-in setup and achieves benchmark sensitivity. Our scheme combines shot-to-shot evaluation of pump–probe and probe–only measurements, a home-built photodetector circuit optimized for low pulse energies applying low-pass amplification, and a custom evaluation algorithm based on Fourier transformation. Advantages of this approach include abilities to simultaneously monitor multiple pulse modulation frequencies, implement the detection of additional pulse sequences (e.g., pump–only), and expand to multiple parallel detection channels for wavelength-dispersive probing. With a 40 kHz repetition-rate laser system powering two non-collinear optical parametric amplifiers for wide tuneability, we find that laser pulse fluctuations limit the sensitivity of the setup, while the detection scheme has negligible contribution. We demonstrate the 2-D imaging performance of our transient absorption microscope with studies on micro-crystalline molecular thin films.

Original languageEnglish
Pages (from-to)34385-34395
Number of pages11
JournalOptics Express
Volume30
Issue number19
DOIs
Publication statusPublished - 12 Sept 2022

Keywords

  • Diffraction limit
  • Laser beams
  • Laser sources
  • Laser systems
  • Optical amplifiers
  • Wire grid polarizers

ASJC Scopus subject areas

  • Atomic and Molecular Physics, and Optics

Fields of Expertise

  • Advanced Materials Science

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