Focused ion beam fabricated bragg grating filters in relaxor ferroelectrics

In this paper, we discuss the fabrication and characterization of optical waveguide Bragg filters in ion-implanted PMN-32PT [68Pb (Mg1/3Nb2/3)-32PbTiO3] single crystal substrates. PMN-32PT posses exceptionally high piezoelectric and electro-optic properties and has immediate applications in on-chip optical circuitry. We use commercial modeling programs to design the waveguide filter and fabricate the device using ion-implantation and nano-fabrication techniques. First, slab waveguides are created in <001> mirror polished substrates through He+ ion-implantation process. He+ implantation creates an optical barrier with reduced refractive index. Second, ridge waveguides on the slab are fabricated through standard photolithography and dry etching techniques. Third, Periodic refractive index modulation (grating) on the top of the ridge waveguide is achieved through Focused Ion Beam [FIB] milling which is controlled by Nanometer Pattern Generation System [NPGS]. Photonic bandgaps are observed in 1480–1580 nm wavelength range in these filters. The experimental data shows excellent agreement with the theory.