This cube combines the detection of two calcium indicators (GCaMP and red fluorophores) with the activation of red opsins. It integrates dichroic mirrors to combine fluorophores excitations, isolate the fluorescence emissions, and let opsin stimulation light through. At the same time, narrow bandpass filters limit the excitation and detection spectral bands:

• 400-410 nm, 410-420 nm, 421-433 nm, or 433-445 nm for GCaMP isosbestic point excitation
• 460-490 nm for GCaMP excitation
• 500-540 nm for GCaMP fluorescence detection
• 555-570 nm for red fluorophore excitation
• 580-600 nm for red fluorescence detection
• 628-642 nm for red opsins activation

Compared to Fluorescence Mini Cubes with only FC connectors on all ports, the ones with integrated photodetectors provide a 100% better signal-to-noise ratio (30% signal increase and a 40% noise reduction). Moreover, in the latest version of Mini Cubes, LEDs and LED drivers are integrated as well to reduce the number of connections and the system’s overall footprint. In his version, it is also possible to replace the excitation filter (to adjust the isosbestic excitation from 405 nm to 410 nm for instance) and decrease the excitation power by adding attenuating filters (for low power photometry).