Probing microscopic chemical environments with high-intensity chirped pulses

By varying the chirp of high-intensity pulses, we can use the chirp-condition-dependent fluorescence yield to distinguish among different molecules or the same molecule in different microenvironments. As an example of the latter we show that SNAFL-2, a well-known pH-sensitive dye, shows large modulation in fluorescence yield in response to both variation in acidity and variation in chirp condition. Future application of this technique as a novel contrast mechanism within fluorescence microscopy is discussed.