Delivery of nanojoule femtosecond pulses through large-core microstructured fibers

We investigate femtosecond-pulse propagation through large-core microstructured fibers. Although these fibers are highly multimode, excitation of the fundamental mode is readily achieved, and coupling to higher-order modes is weak even when the fiber is bent or twisted. For prechirped input pulses with energies as large as 3 nJ, pulses as short as 140 fs were produced at the output of the fiber. Such a system could prove to be extremely useful for applications such as in vivo multiphoton microscopy and endoscopy that require delivery of femtosecond pulses and collection of fluorescence.