Modifications to allow 2-Photon imaging on the MD Sarastro 2000

The Molecular Dynamics Sarastro 2000 has a simple light path that makes it ideal for conversion to a 2-photon scope. We retained the ability to use the microscope in the 1-photon, confocal mode by replacing mirror 2 with a beamsplitter that passes IR from the Mira 900 or reflects visible excitation from the on-board 25 mW argon-ion laser. Mirror 3 and the two scanning mirrors were replaced with broad-band mirrors for better IR throughput. We installed a plate that blocks the IR laser beam whenever the lid is opened to change filters, for safety. That is it–No more modifications necessary! To use in the 2-Photon mode, the on-board laser is turned off, the Mira 900 IR laser is turned on, the primary dichroic wheel is rotated to a 680 SP (Chroma) mirror, and the excitation filter and aperture wheels are rotated to the “open” settings. To improve rejection of excitation light, a barrier filter (680 SP, Chroma) is used in the detector housing.

Aerial view of lightpath, from pump laser to IR laser, to microscope:

Light path of the Sarastro 2000, with the IR beam entering through the auxillary port, from the left: