Shinki NAKAMURA^*, Naoya TAKASAWA, Takeshi SAEKI and Yahei KOYAMADA

Department of Media and Telecommunications Engineering, Faculty of Engineering, Ibaraki University, 4-12-1, Nakanarusawa-cho, Hitachi-shi 316-8511, Japan

(Received December 18, 2002; Accepted January 14, 2004)

We have analyzed the induced phase modulation (IPM) for ultrashort (74 fs) two-pulse propagation in a silica fiber by the extended finite-difference time-domain (FDTD) method, considering all exact Sellmeier-fitting values and nonlinear polarization P_NL involving the Raman response function. We show that nonlinear polarization causes several phenomena in spectral characteristics of propagated pulses, such as self-phase modulation (SPM), self-steepening, Raman response and IPM, by the extended FDTD method. To the best of our knowledge, this is the first IPM calculation by the extended FDTD method for the simultaneous propagation of two ultrashort (74 fs) laser pulses in a silica fiber.

Key words: FDTD, fiber, nonlinear propagation, ultrafast, femtosecond, induced phase modulation, cross-phase modulation, self-phase modulation, self-steepening, Raman effect

^*E-mail address: nakamura@mx.ibaraki.ac.jp