Fabrication of micro patterns on BaTiO3:Er3+/Yb3+ perovskite films by femtosecond laser micromachining

Abstract

Femtosecond lasers currently show much promise as potential sources for the fabrication of optical and photonic devices, displaying high performance due to their high resolution, excellent geometric flexibility, and low collateral damage. In particular, devices displaying high performance based on BaTiO3:Er3+/Yb3+ (BTEY) films have been widely investigated, promising for the innovation of perovskite patterning applications. Herein, we fabricated BTEY perovskite films by spin coating at room temperature. XRD pattern and Raman spectroscopy analysis of the BTEY films revealed a tetragonal crystal structure. The study of Williamson-Hall's method calculated the strain and crystallite size for the BTEY film. Different parameters in the exploiting cylindrical focusing of an fs-laser were adopted to modulate the crater cavity of patterning, which gives the opportunities to evaluate their impact on the energy ablation threshold (Eth). It was found that cavity radius is proportional to the energy cross-section, thus providing wide range dependence of damaged spot size versus pulse energy. The Eth was measured using Liu's method, determining a value of Eth that decreased from 33.4 nJ to 22.4 nJ when the number of applied laser pulses per spot increased. It is found that the number of pulses per spot low possesses the best performance, successfully producing highly uniform patterning. Moreover, the evolution with the number of pulses also revealed changes in the surface morphology of the crater cavity via AFM and scanning confocal fluorescence microscopy (SCFM) analysis. These results are crucial for determining the Eth required to damage the material, understating the driving mechanism of formations of cavity profile surfaces, and changes in their optics properties in the edges owing to the balling effects and structural defects.