Ultrabroadband continuum generation by hollow fiber cascading

Summary form only given. We report on a technique which allows one to generate an ultrabroadband continuum by cascading two gas-filled hollow fibers. 25-fs pulses are coupled into an argon-filled (gas pressure 0.2 bar) hollow fiber; the slightly spectrally broadened pulses are then compressed to /spl sim/10 fs by chirped mirrors. Such pulses are then injected into a second argon-filled (gas pressure <0. 1 bar) hollow fiber. The output spectrum, extends from /spl sim/370 nm to >1000 nm (the cutoff in the infrared region is due to the spectrometer used in the measurement). The output beam presents excellent spatial characteristics (single-mode operation), and is diffraction limited. Output pulse energy is 90 pJ. It is worth pointing out that by using a single gas-filled hollow fiber it turns out to be impossible to achieve the same spectral broadening.