Growth of 3D photonic crystals by photolysis of CrO2Cl2

A method of three-dimensional (3D) holography is used for the growth of photonic crystals of sub-micron cell parameters by gas decomposition in a 3D interference field of UV laser light. Either amorphous or crystalline chromium oxides are obtained by photolysis of chromyl chloride CrO2Cl2 for different experimental conditions. The most interesting product is obtained for a photolysis of CrO2Cl2 at low pressure, on a cooled TiO2 single-crystal substrate and for a higher beam energy. The growth begins with the formation of epitaxial CrO2 metastable phase which is partly transformed into Cr2O3 under UV irradiation. Due to crystallographic orientational relationships between CrO2 and Cr2O3, the growth of a well organized 3D photonic crystal of Cr2O3 phase goes on according to the 3D periodic modulations of electromagnetic energy of the interference field. In the present case, the Cr2O3 phase exhibits four sets of equivalent crystallographic orientations with respect to the single-crystal substrate. From such a result, one can expect to produce in a further work photonic crystals constituted of single-crystalline Cr2O3 phase in epitaxy onto a Cr2O3 or sapphire Al2O3 substrate.