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Frequency-domain ultrafast coherent multidimensional spectroscopy has made possible a family of fully coherent spectroscopies that can create and interrogate characteristic superpositions of the quantum-mechanical states of a system under investigation. Typical applications include the resolution of couplings and dynamics among multiple electronic states in atoms, molecules, and materials. These methods require scanning the wavelengths of multiple, ultrafast light sources—often optical parametric amplifiers (OPAs). Spectral calibration of the OPA output (a.k.a. wavelength-tuning) involves optimizing the OPA output intensity by adjusting the angles of its component nonlinear crystals and motorized delay stages. When the spectral range addressed in the experiment is large, optimization and control of the one or more OPAs become complex. This work describes an automated calibration strategy that measures the multidimensional configuration-space of a typical 800-nm OPA over all angular and delay degrees-of-freedom in order to create a global tuning curve that spans its dynamic spectral range with optimal power and smooth interpolation. To accomplish this task, the optimization assesses the wavelength-dependent variations to the temporal and spatial characteristics of the OPA output caused by material dispersion so that compensations may be applied during a wavelength scan.
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This content will become publicly available on July 7, 2026
Algorithmic approaches to automate OPA tuning for frequency domain spectroscopy
Frequency domain nonlinear spectroscopies are a useful probe of linear and non-linear transitions in a variety of biological, chemical, and materials systems. They require scanning of optical parametric amplifiers (OPAs). Each OPA contains multiple motors that move to prerecorded positions to optimize output at each desired color. OPA optimization and color accuracy are crucial for frequency domain experiments, where OPA color is scanned. Such performance is highly sensitive to environmental fluctuations, so motor positions must be regularly optimized and tuned. Despite the widespread availability of motorized OPAs, this frequent maintenance can make frequency domain spectroscopy a cumbersome and time-consuming process. We have found that fully automated approaches to tuning are invaluable when scanning OPAs. Here, we report four algorithms that accurately and robustly tune a variety of ultrafast laser systems—picosecond and femtosecond, homebuilt and commercial OPAs. Using case studies from previously published work, we illustrate how these four algorithms can be combined to tune all motors of an ultrafast laser system. These algorithms are available through open-source software and can be applied to existing instruments, significantly lowering the threshold for executing frequency domain spectroscopy.
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- Award ID(s):
- 2203290
- PAR ID:
- 10634980
- Publisher / Repository:
- AIP Publishing1305 WALT WHITMAN RD, STE 300, MELVILLE, NY 11747-4501
- Date Published:
- Journal Name:
- The Journal of Chemical Physics
- Volume:
- 163
- Issue:
- 1
- ISSN:
- 0021-9606
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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