Margaret Murnane and Henry Kapteyn are leaders in the development of ultrafast laser technologies. Their group demonstrated the first sub-10 femtosecond mode-locked Ti:sapphire laser that is now a standard fixture in thousands of laboratories around the world, including several here at JILA. Their group also developed technologies to amplify very short pulses to high peak powers that incorporate cryo-cooling of the amplifier crystal and pulse-shaping techniques to optimize the interaction of light with quantum systems. These techniques are also being adopted worldwide for many applications in science and technology.

Many current projects involve generating and using ultrashort "laserlike" beams of short wavelength light 10-1000 times shorter than visible light. Until now the generation of fully spatially coherent laser light has been limited to the visible/ultraviolet and longer wavelength regions of the spectrum. Because short-wavelength light sources such as electron impact sources, synchrotron sources, X-ray lasers, and free-electron lasers do not use resonators, they generate only partially coherent light. In contrast, the process of high harmonic generation generates X-ray beams that are fully coherent or laserlike. In this process, a high-intensity femtosecond laser is focused into a gas. Odd harmonics of the exciting laser frequency (i.e., 3ω, 5ω, etc.) are produced in a directed narrow-divergence beam, with photon energies that can extend from the UV up to > 1keV. This process coherently upshifts a femtosecond pulse from the visible into the EUV region of the spectrum using an extreme nonlinear optical process.

The Kapteyn/Murnane group has demonstrated that laserlike beams can be generated only by focusing the femtosecond laser into a hollow waveguide filled with gas. The waveguide guides the laser beam and ensures that the EUV beam that emerges is well collimated and truly laserlike. Such an EUV source, with good beam quality and high spatial coherence, can be used for experiments in femtosecond holography, high-precision metrology, inspection of optical components for EUV lithography, and for microscopy with nanometer resolution. Furthermore, the time duration of the EUV radiation is a few femtoseconds, which allows molecular imaging, EUV microscopy, and holography to be performed with ultrahigh time resolution. This technology may become a critical "enabling" technology for developing an EUV lithography process that will make possible continued progress in designing faster and more complex computer chips.

Such applications will require the highest possible source brightness. Therefore, the Kapteyn/Murnane group is exploring the field of extreme nonlinear optics to develop new methods for increasing the conversion efficiency of laser light into coherent X-rays. Approaches that have yielded promising results thus far include the use of modulated waveguides that force the laser beam and X-ray beams to travel with the same phase velocity down the waveguide. Other exciting approaches use the idea that the radiating electron wave function can be controlled and manipulated on subangstrom spatial scales with subfemtosecond temporal precision.

For additional information please see http://jilawww.colorado.edu/kmgroup