Product Code: PIC06_M203
Void Generation and Three-dimensional Photonic Crystal Fabrication in a Lithium Niobate Crystal by Use of Micro-explosion
Guangyong Zhou, Swinburne University of Technology; Hawthorn, VIC Australia
Min Gu, Swinburne University of Technology; Hawthorn Australia
Presented at PICALO 2006
Smooth void dots and void channels have been generated efficiently in some low refractive index materials such as polymers and glasses by use of a femtosecond laser induced microexplosion method and have been used to fabricate 3D photonic crystals. In order to get complete bandgap, a high refractive index material need to be used. Lithium niobate (LiNbO3) crystal is a good candidate because of its high refractive index (2.2) and broad transparent range (0.5-5 µm). However, the large refractive index mismatch between the crystal and the immersion oil produces a strong spherical aberration at the focal point and therefore distort the focal point. In this work, we report two methods to reduce the side lobe effect. One is a so-called near threshold fabrication method. By carefully choose the laser power slight above the threshold, one can eliminate the effect of side lobes and fabricate relative spherical voids. The other is a wave front correction method by using a liquid crystal phase modulator. By carefully modifying the wave front, one can remove the side lobes and reshape the focal point. By using these two methods, we fabricate 16-layer FCC photonic crystals. Confocal microscrope images and photonic bandgap spectra shows that the quality of voids fabricated by use of the phase modification method is much better than that fabricated by use of the near-threshold fabrication method.
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