Adaptive Optics and Two-Photon Microscopy
The 2P-AO Microscope incorporates Thorlabs' MPM-2PKIT Multiphoton Essentials Kit and a gold-coated, 140 actuator, Multi-Deformable Mirror (DM140-35-UM01). As shown on the right two-photon excitation light from an OCTAVIUS-2P femtosecond laser (not included) is directed towards the deformable mirror via a polarizing beamsplitter and λ/4 wave plate. The excitation light reflects off of the deformable mirror, passes back through the wave plate and beamsplitter, and is coupled to the Multiphoton Scan Head of the Essentials Kit.
The two-photon emission light from the sample is diverted to a two-channel, non-descanned, detection module via a dichroic mirror cube. This module incorporates GaAsP PMTs, which are connected to a control/interface box and computer. The PMT and scanner signals are used to produce high-sensitivity two-photon images. These images are then used in a closed-loop feedback fashion to drive the necessary wavefront correction. The feedback system enables continuous compensation of the wavefront between acquired image frames.
By combining deep imaging via two-photon microscopy and aberration correction by incorporating adaptive optics, improved imaging deep into live tissue samples is possible.
Results Without Adaptive Optics
When the adaptive optics system is off, the deformable mirror in the figure above is flat. Input laser light reflects from the deformable mirror with an unchanged wavefront. The light is directed onto the sample by relay lenses, galvo steering mirrors, and the objective. The focused spot size within the sample will be larger than the theoretical minimum due to aberrations caused by the optical system as well as the sample itself, resulting in the low-resolution image shown on the left.
Results with Adaptive Optics
As the Adaptive Optics system engages, the deformable mirror's actuators deform the surface of the mirror until the intensity measured by the PMT module is at a maximum. The deformed mirror yields a wavefront which is corrected to form a minimized spot size in the sample. The image to the right shows the results: both the contrast and brightness are increased when compared to the same image without the adaptive optics system.
For More Information
For more information on deformable mirrors, including detailed tutorials on adaptive optics and aberrations, lists of publications, and detailed specifications for the deformable mirrors, please visit our deformable mirrors product presentation.