Blue phases (BPs) are known to exhibit optical stop bands in a visible range because they have a three-dimensional cubic structure with lattice periods of several 100 nm. Furthermore, since the diffracted wavelength of BPs can be shifted by external electric fields. BPs are expected to be applied for tunable photonic crystals. We have succeeded in expanding a temperature range of BPs from generally ca. 1 <SUP>o</SUP>C to 11 <SUP>o</SUP>C on heating when an asymmetric dimer with mesogenic- and nonmesogenic-groups was added to BP. In this study, we investigated structural analyses and electric-field response behaviors of BPs with an extended temperature range.