In the optimization of the stereolithgrapic parameters, the exposure power influences toward the layer thicknesses and size tolerances were compared and investigated systematically in the formed acryl objects with the different mixing ratio of the metallic and oxide glasses. The cross sectional object of 14.5 and ±3 μm in layer thickness and size tolerance were created by micro patterning of 700 mJ/cm2
in exposure power for the mixed slurry composed of the acrylic resin, metallic and oxide glass particles of 60, 17 and 23% in volume fractions, respectively. The photo polymerization depth should be over 10 μm of the stacking layer thickness with restraining the exposure right scatters. Figure 4
a shows the magnetophotonic crystals with the diamond lattices fabricated by the stereolithography. The size tolerance between the designed model and formed sample was converged within ±3 μm. The sintered diamond lattice structure with 500 μm in lattice constant is shown in Figure 4
b. The micrometer order periodic lattices were formed successfully. The liner shrinkage ratios of horizontal and vertical axis were 10.2% and 12.5%, respectively. These results can be fed back successfully for the computer graphic designing to realize the isotropic arrangement of diamond lattice. Figure 5
shows the microstructure of the sintered metallic glass and oxide glass composite lattice. The metallic glass particles dispersed homogeneously in the oxide glass matrix. The X-ray diffraction patterns of metallic glass particles before and after the heat treatments were analyzed as shown in Figure 6
. The metallic glass was not crystallized during the dewaxing and sintering heat treatments. Figure 7
shows the measured terahertz wave transmission spectrum for the magnetophotonic crystal. The black and gray lines show the measured and calculated results, respectively. These transmission spectra have good agreement. The theoretical visualization of the electromagnetic wave propagation could verify the forbidden gap was exhibited by the wave diffraction. The electromagnetic band gap can be formed from 0.2 to 1.0 THz in wave frequency. Between the lower and higher band gap edges, the electromagnetic waves from 300 to 1500 μm in wavelengths create standing vibrations in the periodic arrangements of magnetophotonic lattices and realize the total reflections for the incident direction through the Bragg diffractions. Figure 8
shows the magnetophotonic crystal with a structural defect fabricated by using the micro pattering stereolithography and the low temperature heat treatment. A round hole of 200 μm in diameter was opened as the defect cavity exactly into the diamond lattice structure for perpendicularity direction toward the crystal face shown in Figure 8
. The terahertz wave was propagated toward the parallel direction to the opened hole, and the transmission spectrum was obtained as shown in Figure 9
. The black and gray spectra show the measured and calculated ones, respectively. The localized modes of the transmission peaks were formed in the band gaps. At the peak frequencies of 0.72, 0.75 and 0.79 THz, the half wavelengths of 208, 200 and 189 were comparable to the cavity diameter of defect hole, and the standing waves should be formed by multiple reflections between the diffraction lattices. The amplified terahertz waves could be transmitted selectively toward the opposite side of the magnetophotonic crystal. Because the opened hole has uneven surface, the similar wavelengths could resonate in the cavity, and the three localized modes were considered to be formed in the band gap as shown in Figure 9
. The electromagnetic fields profiles of these localized modes were calculated and visualized in the cylindrical cavity. Moreover, the intentional shifts of the band gap frequency and localized mode peaks could be simulated through the lattice permeability modulations supposing the static magnetic field application toward the magnetophotonic crystal.
An acryl diamond lattice with metallic glass (Fe72B14.4Si9.6Nb4) and oxide glass (B2O3·Bi2O3) particles dispersion fabricated by the stereolithography (a) and a magnetophotonic crystal after dewaxing and sintering (b).
A microstructure of the oxide glass lattice with the metallic glass particles dispersion observed by a scanning electron microscopy.
A X-ray diffraction patterns of the metallic glass particles before and after the dewaxing and sintering heat treatments under the transition temperature from the amorphous structure for the crystal phase.
An electromagnetic band gap formation in a transmission spectrum of the terahertz wave through the magnetophotonic crystal with the diamond lattice structure. The black and gray lines show the measured and calculated results, respectively.
The magnetophotonic crystal with a structural defect in the periodic lattice of the diamond structure. The round hole was opened as the defect cavity for the perpendicularly direction toward the crystal face.
Localized modes formation in the electromagnetic band gap. The terahertz waves with the selected wavelengths can resonate with the defect cavity and transmit the crystal. The black and gray lines show the measured and calculated results, respectively.