Reported from optic.org:
A new design of hollow-core photonic crystal fiber (HC PCF) has been developed by an international team led by Fetah Benabid of Bath University in the UK. One immediate result has been a method to produce attosecond laser pulses more efficiently than previous techniques.
The fiber's unique properties have led directly to a second breakthrough, the efficient generation of a broad spectrum of ultrafast pulses from a hydrogen-filled PCF through stimulated Raman scattering.
The conventional technique to create attosecond pulses is high-harmonic generation (HHG), which produces central wavelengths in the XUV or soft X-ray region through the firing of a very intense laser pump pulse into a gas. Benabid's fiber was able to produce ultrashort pulses more simply using through stimulated Raman scattering. Benabid's fiber is claimed to require a pump pulse with power levels six orders of magnitude lower and five orders of magnitude longer than those previously needed for HHG.