11·î22Æü(ÌÚ)  14:30 -- 15:30  Johannes Elschner
                              (Weierstrass-Institute for Applied Analysis 
                               and Stochastics, Germany)
             ``Inverse problems for diffraction gratings''

¡ã¸¦µæȯɽÍ×»Ý(Prof. J. Elschner)¡ä
 We consider the 2D TE and TM diffraction problems for a time harmonic plane 
wave incident on a periodic grating structure. An inverse diffraction problem
is to determine the grating profile from measured reflected and transmitted 
waves away from the structure. We present a new approach to this problem
which is based on the material derivative with respect to the variation of the
dielectric coefficient. This leads to local stability estimates in the case 
of interfaces with corner points. Another application concerns the optimal 
design problem for diffraction gratings.
  The talk presents joint work with Gunther Schmidt.