J. Grace*, S. Edlou, J. Foss, C. Hodgson, J-P Rheault, and K Sieber, IDEX Health and Science, LLC. 1180 John St., West Henrietta, NY 14586 (*presenting author)

In fluorescence microscopy and related applications, fluorescence from optical elements in the system can be a limiting factor in achieving low background levels. Evaluating low-level “autofluorescence” from optical elements requires a high-sensitivity measurement method. We present a straightforward approach to making sensitive fluorescence measurements using a chopped laser and phase-lock detection scheme. Using high-quality optical filters in the excitation and detection paths, the trade-off between spectral information and ultimate sensitivity is controlled by the choice of filter edge locations and bandwidths. We discuss details of the measurement technique and present results demonstrating sensitivity to ~ 1 pW optical power.