Abstract
The fabrication of photonic crystal heterostructures is important for the applications in the fields of integrated photonic crystal chips and multi-frequency optical Bragg filters or mirrors; here we report on the fabrication and characterization of opal-based photonic crystal heterostructures. These heterostructures are created by using multilayer deposition of silica and polystyrene spheres. In the specific the fabricated structures involved both different lattice constant and dielectric function. Scanning electron microscopy (SEM) and VIS-NIR transmittance and reflectance spectroscopy are used to characterize the systems. The SEM images show good ordering of the two-layer colloidal crystals constituting the heterostructures. The transmittance and reflectance spectra measured from the (111) plane of the heterostructure show that the composite colloidal photonic crystals have double photonic stop bands that matches the stop bands of the individual photonic crystals. This behaviour can be seen as a superposition of the properties of each individual layer.
Highlights
Photonic crystals have attracted great interests since the pioneering works of Yablonovitch and John [1,2]
The fabrication of photonic crystal heterostructures is important for the applications in the fields of integrated photonic crystal chips and multi-frequency optical Bragg filters or mirrors; here we report on the fabrication and characterization of opal-based photonic crystal heterostructures
For the case of the opal constituted by SiO2 NPs, reported in Figure 1(b), it is possible to observe the presence of an intense diffraction peak at about 700 nm in agreement with the position of the calculated pseudo gap along the Γ-L direction
Summary
Photonic crystals have attracted great interests since the pioneering works of Yablonovitch and John [1,2] These materials have the feature of the photonic bandgap (PBG) that forbids the propagation of the light in a particular range of frequencies through the structure. Top-down methods such as nanolithography, holography and direct laser writing can successfully design 3D PC, the high cost and the complex process have led to the development of efficient bottom-up techniques based on the colloidal crystals consisting of highly organized monodispersed colloidal particles [13,14,15,16] It has been demonstrated from a theoretical point of view [17], as well as through experimental results [18], that these nanoparticles self-assemble in a face-centered cubic structure with the (111) plane parallel to the underlying substrates. Morphological and optical assessment of the systems realized is discussed
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