Large-scale femtosecond holography for near simultaneous optogenetic neural modulation.

For better understanding of brain functions, optogenetic neural modulation has been widely employed in neural science research. For deep tissue in vivo applications, large-scale two-photon based near simultaneous 3D laser excitation is needed. Although 3D holographic laser excitation is nowadays common practice, the inherent short coherence length of the commonly used femtosecond pulses fundamentally restricts the achievable field-of-view. Here we report a technique for near simultaneous large-scale femtosecond holographic 3D excitation. Specifically, we achieved two-photon excitation over 1.3 mm field-of-view within 1.3 milliseconds, which is sufficiently fast even for spike timing recording. The method is scalable and compatible with the commonly used two-photon sources and imaging systems in neuroscience research.