Flexible multiphoton tomography with femtosecond pulse hollow-core fiber delivery

Multiphoton imaging has advanced the traditional fluorescence microscopy with non-invasive label-free 3D-imaging capability and high penetration depth. However, currently available systems are often bulky and employ non-flexible optical setups due to the need of a free-beam delivery with hard-to-exchange light sources. The use of an optical fiber for beam delivery offers the possibility to locate bulky and expensive components away from the point of measurement and therefore allows imaging devices to become more compact and flexible. We report on the use of a kagome hollow core photonic-crystal fiber to deliver laser pulses between laser and imaging system which enables high flexibility regarding the type of laser excitation source and its positioning. The fiber can deliver ultrashort pulses within a broadband range in the near infrared region without inducing significant spectral or temporal pulse distortions. The fiber-delivery capabilities are demonstrated with four different lasers and by employing fiber-delivered pulses for fluorescence intensity as well as lifetime imaging of human skin with a modified clinical multiphoton tomograph.