We present the Resonator, a simple optical device that provides quasi-simultaneous fluorescence imaging with multiple excitation wavelengths. The device uses a resonant scanning mirror to periodically displace the sample image on a camera sensor at a rate that is much faster than the image acquisition rate. The excitation light is synchronized with the scanner motion to create two laterally shifted copies of the image, each containing the fluorescence excited by a single wavelength. The additional information is then encoded either into the point-spread function of the imaging or as multiple distinct images. Since this multiplexing is performed at very high rates, our design can eliminate or mitigate artifacts caused by temporal aliasing in conventional sequential imaging. We demonstrate the use of our system for the monitoring of fast light-induced dynamics in single quantum dots and for the imaging of Ca2 signalling in hippocampal neurons.

Upconverting nanoparticles are a rising class of non-linear luminescent probes burgeoning since the beginning of the 2000’s, especially for their attractiveness in biology. However, the precise quantification of the light delivered remains a hot problem in order to estimate the impact in biology, resulting in the development by a few teams of sophisticated photophysical measurements (operable under NIR excitation). Here, we present the first attempt towards a simple and cheap photochemical approach consisting of a pseudo-actinometric characterization of the green emission of NaYF4:Yb,Er. Using the recently calibrated actinometer 1,2-bis(2,4-dimethyl-5-phenyl-3-thienyl)-3,3,4,4,5,5-hexafluoro-1-cyclopentene operating in the green region of the visible spectra, we propose simple photochemical experiments to get an accurate estimation of the efficiency of these green-emitting “nanolamps”. The agreement of the collected data with the previous published results validates this approach.