Recent Studies on InGaAsP and TiO_2/Si Planar Asymmetric Coupled Waveguides as Dispersion Compensators(Special Issue on Ultrafast Optical Signal Processing and Its Application)

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Two planar asymmetric coupled waveguides were fabricated by using different materials (lnGaAsP and TiO_2/Si) and tested as dispersion compensators (or pulse compressors). Compression of a more-than-l0-ps chirped pulse is experimentally demonstrated by using an InGaAsP planar asymmetric coupled waveguide whose group velocity dispersion (GVD) is enhanced by structural optimization and is spectrally tuned to an input pulse as precisely as possible. A large polarization dependence of the pulse compression was also observed and indicates that the observed pulse compression results from dispersion compensation due to the GVD associated with supermodes. A new planar, asymmetric coupled waveguide with a large difference in refractive indices of the two waveguides was fabricated by using a combination of dielectric (TiO_2) and semiconductor (Si) materials in order to obtain better GVD characteristics than semiconductor (for example, LnGaAsP) asymmetric coupled waveguides. A preliminary experiment on pulse compression using the TiO_2/Si planar asymmetric coupled waveguide was conducted. A 2.8-ps blue chirped pulse was compressed down to about 1 ps by a 1-mm-long waveguide (compression ratio : 0.375, which is better than those of the previous InGaAsP planar asymmetric coupled waveguides). This compression ratio agrees well with a theoretical result obtained by a numerical model based on a supermode's GVD.
社団法人電子情報通信学会の論文
2002-01-01