Dynamics in the dimerized and the high-field incommensurate phase of CuGeO3

Temperature ($2.3<T<\mathrm{}40\mathrm{}$ K) and magnetic-field ($0<B<\mathrm{}17\mathrm{}$ T) dependent far-infrared-absorption spectroscopy on the spin-Peierls coumpound CuGe${\mathrm{O}}_3$ has revealed several interesting absorption processes in both the dimerized and high-field phase of CuGe${\mathrm{O}}_3$. These results are discussed in terms of the modulation of the CuGe${\mathrm{O}}_3$ structure. At low fields this is the well-known spin-Peierls dimerization. At high fields the data strongly suggest a field-dependent incommensurate modulation of the lattice as well as of the spin structure.