ROCKY MOUNTAIN SECTION OPTICAL SOCIETY OF AMERICA
                              &
           IEEE LASERS AND ELECTROOPTICS SOCIETY


                       March Meeting

Date:  Thursday, 20 Mar. 2003
Time:  7 PM refreshments, 7:30 PM talk
Place: Engineering 100
       Colorado State University, Fort Collins

Title: Generation of Extreme Ultraviolet Radiation Using High 
Harmonic Generation

       Randy Bartels
       ECE, CSU
       Fort Collins, CO


Abstract:

Until recently, the generation of fully coherent beams has 
been limited to the visible/ultraviolet and longer wavelength 
regions of the spectrum. I will discuss the use of extreme 
nonlinear optics to generate laser beams in the extreme 
ultraviolet region of the spectrum. The extreme nonlinear 
optical process of high harmonic generation (HHG) is a useful 
way of generating coherent light throughout the ultraviolet 
and extreme ultraviolet (EUV) regions of the spectrum. In 
HHG, extremely short duration pulses can be produced by 
focusing a high intensity femtosecond laser pulse into a gas. 
Odd harmonics of the exciting laser are produced in a 
directed, narrow-divergence beam, with photon energies that 
can extend up to > 500eV (corresponding to harmonic orders > 
300). This process thus coherently up-shifts a femtosecond 
pulse from the visible into the EUV region of the spectrum. 
However, experiments to date have shown that the HHG 
radiation is only partially spatially coherent, and does not 
retain the full coherence of the fundamental driving beam. In 
this talk, we show that EUV radiation generated by phase-
matched HHG in a hollow core fiber has nearly perfect spatial 
coherence. Such an EUV source, with good beam quality and 
high spatial coherence, can be used for experiments in high-
precision metrology, inspection of optical components for EUV 
lithography, and microscopy and holography with nanometer 
resolution. This source, with its short-wavelength and 
diffraction-limited output, represents the smallest inherent 
effective source-size of any light source yet created. I will 
discuss the measurement of the spatial coherence of phase-
matched EUV light generated in a fiber using the process of 
high-harmonic generation. Coupled with previous measurements 
that demonstrate that coherent control techniques can be 
applied to obtain nearly-full temporal coherence from these 
sources, this means that fully spatially and temporally 
coherent laser-Iike beams of EUV light can now be generated. 
Furthermore, because HHG is generated using a table -top 
setup, this EUV source will be particularly useful for a 
variety of application including nanoscale probes and 
imaging, and for precision metrology of EUV optical 
components for the next generation of optical lithography. 
Imaging applications will also be discussed.


Biography:

Prof. Bartels received his B.S. in Electrical Engineering 
from Oklahoma State University in 1997. In January of 1996, 
Prof. Bartels was invited by Lawrence Livermore National 
Laboratory to work on the development of diode-pumped solid 
state lasers. He then went on to the University of Michigan, 
Ann Arbor, where he joined the research group of Professors 
Margaret Mumane and Henry Kapteyn and received both a GAANN 
Graduate Fellowship and a National Defense Science and 
Engineering Graduate Fellowship from the Department of 
Defense. During his tenure in the Kapteyn/Murnane group, they 
moved to JILA at the University of Colorado, Boulder where he 
performed his research for which he received a number of 
awards including the New Focus Student Research Award, the 
IEEE/LEOS Graduate Student Award, and the JILA Scientific 
Achievement Award. Prof. Bartels received his M.S. in 1999, 
and his Ph.D. in 2002, both in Electrical Engineering. Prof. 
Bartels joined the ECE Department at Colorado State 
University in January 2003.