A novel technique was proposed to fabricate a three-dimensional photonic crystal by self-assembling microspheres and the autocloning technology. The autocloning thin-film layers were superimposed on the prepared two-dimensional structural substrates using self-assembled microspheres. The thin-film process allows the three-dimensional periodic structure to be easily modified in the thickness dimension to structure as needed. We analyzed the etching effect using the unified process model according to the surface movement and surface velocity of the film to achieve the surface profile of the SiO2 adjusting layer. Finally, 17 layers of Ta2O5/SiO2 multilayers were stacked on the SiO2 adjusting layer successfully.
A novel design of photonic-crystal polarization filter was demonstrated with dual-band and wide working wavelength
range. The structure of the filter is a 2-dimensional wavy structure of multilayer thin films consisted with a number of
alternate high and low refractive indices transparent dielectric layers deposited sequentially on a periodic structured
substrate. The fabrication of the photonic-crystal polarization filter is based on an autocloning method which integrated
the techniques of lithography and thin film deposition. Different from the traditional polarizing beam splitters, the
photonic-crystal polarization filter is a flat type of polarizer with normal incident angle. The transmission and
reflectance spectra were analyzed using finite-difference time-domain method (FDTD). From the analysis result, we
found the photonic bandgap was happened at transverse electric (TE) mode and the passband at transverse magnetic (TM) mode. So, the photonic crystal polarization filter can separate TE mode and TM mode effectively as the field is incident normally. We design the working wavelength range of the photonic-crystal polarization filter at both visible and near infrared regions, and have wide polarization separated band at normal incident. Finally, the bandwidth is about 100 nm in visible region and 300 nm at near infrared region. The extension ratio is about 20 both in visible region and near infrared region.
The triangle shape of two dimensional photonic crystals were fabricated based on autocloning technique, and preserved
the periodic surface corrugation after the deposition of multilayer stacks using an E-beam gun evaporation with ion-assisted
deposition (IAD). Drude model has been applied to analyze the effective refractive indices of the structural
single-layer and multilayer autocloning films with triangle shape in the visible range which divided into several periodic
parts. The advantage of using the model of effective refractive index is the optical properties of structural multilayer
films can be analyzed easily. The effective refractive indices have been calculated based on this model, and simulated
the reflectance and transmittance of the different incident angles. The influences of the structure period on the
reflectance and transmittance were also analyzed.
Autocloning technique is an attractive deposition method to make photonic crystals since it can produce various photonic crystals by changing the substrate periodicity and the structure of the stacking materials. We report a novel method to fabricate autocloned photonic crystals. This method has better step-coverage, higher deposition rate and large deposition area than the sputtering method. We successfully preserved the periodic surface corrugation after the deposition of multilayer stacks by using an E-beam gun evaporation with ion-assisted deposition (IAD). Freedoms of the shaping process can be controlled by the power of IAD and the time of the ion source etching. The ion source etching is a physical etching process without any chemical reaction and dangerously reactive gas. The process parameters were described in this paper. During the deposition process, the refractive index can be adjusted by changing the deposition rate and the substrate temperature. The deposition rate was about 0.7~1 nm/s for SiO<sub>2</sub> which is almost ten times faster than the sputtering method. So this method is good for the mass production of photonic crystals.