Compact diode laser source for multiphoton biological imaging

We demonstrate a compact, pulsed diode laser source suitable for multiphoton microscopy of biological samples. The center wavelength is 976 nm, near the peak of the two photon cross section of common fluorescent markers such as genetically encoded green and yellow fluorescent proteins. The laser repetition rate is electrically tunable between 66.67 kHz and 10 MHz, with 2.3 ps pulse duration and peak powers >1 kW. The laser components are fiber coupled and scalable to a compact package. We demonstrate >600 mm depth penetration in brain tissue, limited by laser power. Two photon imaging to a depth of 1000 mm in living brains by use of a Ti:Al2O3 regenerative amplifier," Opt.  1022 1024 (2003) 2. F. Helmchen and W. Denk, "Deep tissue two photon microscopy,"  (2005) 3. D. Kobat, M. E. Durst, N. Nishimura, A. W. Wong, C. B. Schaffer, and C. Xu, "Deep tissue multiphoton microscopy using longer wavelength excitation," Opt. Express 17, 13354 13364 (2009) 4. N. G. Horton, K. Wang, D. Kobat, C. 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