180 fs High power megahertz Ytterbium fiber chirped pulse amplifier for in-vivo high-speed functional imaging

摘要: Imaging tools that allow for high resolution high-speed network-level brain activity mapping are of interest in neuroscience and other biomedical applications studying biological population dynamics scattering tissues vivo. Currently nonlinear optical microscopy plays a key role imaging neural behaving animals. In tissue, two-photon combination with raster scanning approaches have been widely applied, but one the most difficult challenges is to achieve sufficient image contrast deep samples[1]. Due limited number emitted photons available reconstruction, accessing neuronal temporal large-scale volumetric measurements tissue challenging. For multiphoton imaging, fundamentally speed limit set by pulse repetition rate femtosecond laser used, i.e. at least must be used per pixel. practice, this also ruled compromise inertia beam steering hardware, as well maximum allowed incident power on sample avoid damage or excessive heating. On hand, peak intensity operation wavelength driving source play significant achieving imaging. To counteract decrease depth, order maintain focus depths media, it increase energy excitation pulse. Yb-fiber chirped amplifiers providing femtosecond, multi μJ-level pulses very rates attractive functional work, we present μJ-level, MHz all-fiber integrated amplifier delivering clean ∼180 fs (Fig. 1 (a-c)), enabled us demonstrate new approach fast microscopy, using focusing [2] produce an enlarged point spread function 5×5×10 μm (matching typical size neurons mouse cortex) single vowel [3]. This important because allows volumes minimally required voxels, which leads faster volume sampling higher signal-to-noise ratios same average power. The large stretching ratio change output system over range, without compromising fidelity. At rate, obtained up 10 W from less than 60% pump power, 100 kHz, compression (10 μ J energy) similar system, stretcher, efficient gratings yielded 160 [4]. With 4 600 nJ energy, performed living, awake mice, microscope sculpted focal μm3 (xyz) through focusing. We neuron-resolution three-dimensional in-vivo, GCamp6 jRGECKO1 labelled neurons, FOVs (up 500×500×500 μm) multi-Hertz (3–6 Hz) update see Fig. (d) (e).