Study On The Optical Properties Of（TiO₂/MgF₂）_n1D Photonic Crystal Heterostructure

Photonic crystal is a multilayer microstructure that is composed of two or more different dielectric materials in terms of the structure. In most cases, it is artificially designed and manufactured. In the three kinds of dimensional photonic crystals, a one-dimensional photonic crystal has a lot of advantages such as simple structure, easy preparation, low cost and become a research focus in this field. But due to the dielectric constant limitation of the materials, the appropriate materials which are applied to the photonic crystal in optical wavelengths are very few. Thus, photonic band gap of the structure in visible light wavelengths has some shortcomings, such as narrow photonic band gap, low reflectivity photonic band gap, and high absorption rate. To achieve broad, comprehensive and high reflectivity photonic band gap, and high transmittance narrow peak, there are two main methods. One is the selection of suitable high and low dielectric constant of the material, the other is the adjustment of the multilayer structure including encapsulation, nesting, superposition, introduction of defects, multi-quantum well. In recent years, the heterostructure and multi-quantum well (MQW) has been an effective method for broadening the band gap. The methods of superposition of two or more than photonic crystals and light quantum well structure can effectively change the structure of one-dimensional photonic crystal. The heterostructure composed of two or more than photonic crystals may get high reflectivity of omni-directional band gap. The light quantum well structure not only enables the one-dimensional photonic crystals but also possess multi-channel, high transmission rate and the narrow transmission peak with half peak width.In this paper, the multi-layer heterostructures and multiple quantum well structures composed of TiO2and MgF2are designed. The optical properties of photonic band gap and defect modes in visible wavelengths of the structures are studied by the transfer matrix method. Firstly, the optical properties of the multi-layer heterostructure (AB)m(CD)n(EF)1composed of TiO2and MgF2are researched. The photonic band gap of the structure can cover the entire visible wavelengths. Thus, this structure can be applied to visible wavelengths omni-directional reflection devices. Based on the above research, the multi-layer heterostructure (AB)n[Bi4Ge3O12](BA)n composed of TiO2, MgF2and Bi4Ge3O12, the temperature sensor can be used in visible light wave band; meanwhile the multi-layer heterostructure (AB)n(BA)m(CD)n and (AB)q(BA)q(CD)p(DC)p composed of TiO2and MgF2are researched. The visible light band filter (AB)n(BA)m(CD)n can obtain the green wave filter with high transmittance.The visible light band filter (AB)q(BA)q(CD)p(DC)p can also obtain the characteristics of narrow half peak width, red, green, and blue three-channel filter to be used for white LED; and the multiple quantum well (AB)m(CD)n(AB)m composed of TiO2and MgF2are studied, the structure can be applied to high transmittance multi-channel filter. The above research results can provide guidance for study of one-dimensional photonic crystal.