Hyperspectral imaging via labeled excitation light and background-free absorption spectroscopy

We introduce a new method of hyperspectral imaging which encodes a varying temporal intensity modulation onto the excitation (or illumination) power spectrum. Functionally, we have moved the spectrometer from the back end of an experiment to the front, where intensity modulations uniquely label wavelengths within the excitation power spectrum at different frequencies, thereby creating a temporal light label which we can identify after subsequent light-matter interactions. To demonstrate this method, we acquire two-dimensional micrographs of background-free absorption spectra by capturing the intensity modulations transferred from the excitation spectrum into the emitted fluorescent intensity. Both the temporal light labeling method and the demonstrated excitation-labeled fluorescence application are readily adaptable to hyperspectral acquisition rates far beyond the frame rates of high-speed cameras. (C) 2015 Optical Society of America