Number 172 (Story #4), April 7, 1994 by Phillip F. Schewe and Ben Stein FEMTOSECOND LASERS keep getting better. In just the past three years typical laser power has increased by a factor of ten and pulse size has shrunk by a factor of three. Practical devices can now generate 10-20 fsec pulses. Light chopped up in parcels this small has a variety of uses such as for observing chemical reactions or melting in real time, or for studying photosynthesis. Henry Kapteyn and Margaret Murnane of Washington State University believe that the pulse-size limit for titanium-doped sapphire lasers, commonly used in this research, will be 3 fsec, which constitutes about 1 cycle of light at a wavelength of 800 nm. To produce shorter pulses, they say, will require the use of shorter-wavelength light such as x rays. (Optics and Photonics News, March 1994.)