Spectrally Selective Time-Resolved Emission through Fourier-Filtering (STEF).

Area of Science:

• Optics and Photonics
• Biophotonics
• Spectroscopy

Background:

• Conventional methods for separating multiple emitters often rely on filters, which can be limiting.
• Resolving the dynamics of multiple species with overlapping spectral signatures is challenging.

Purpose of the Study:

• To introduce a novel method, Spectrally selective Time-resolved Emission through Fourier-filtering (STEF), for demixing multiple emitter signatures.
• To demonstrate the capability of STEF in filtering unwanted signals and resolving complex biological samples.

Main Methods:

• Utilizing a fixed path-length imbalanced Mach-Zehnder interferometer to selectively cancel or enhance spectral signatures.
• Combining the interferometer with time-correlated single photon counting (TCSPC) or confocal imaging.
• Developing a calibration procedure to correct for Mach-Zehnder interferometer imperfections.

Main Results:

• Successfully filtered laser scatter from a sample.
• Separated and measured fluorescence lifetimes from a binary chromophore mixture with overlapping spectra.
• Confocally imaged and resolved distinct fluorescent stains in cellular samples (bovine pulmonary endothelial cells and RAW 264.7 cells).

Conclusions:

• STEF offers a robust and tunable approach for spectral balancing and signal sorting.
• The method enables the separation of multiple emitter dynamics without conventional spectral filters.
• STEF demonstrates broad utility in filtering, lifetime measurements, and bio-imaging applications.