The Surface and Interface Engineering Multi-Layered Nanopore Films for Enhanced Fabry-Pérot Interferences

摘要： In this study, a broadly-tunable nanoporous thin film system with alternating layers of Ag/indium tin oxide (ITO)/CoFeB/ITO/Ag, which was fabricated on a porous anodic aluminum oxide (AAO) substrate, was presented, so as to achieve the flexible tailoring of the Fabry-Pérot interference. The experimental results demonstrated that the amplitude of the Fabry-Pérot interference of this system, which had only an Ag layer deposited on the AAO substrate, was 12 times higher than that of pure AAO film, aside from the tunable oscillation periods. This was mainly due to the fact that the Ag mirror greatly improved the reflectivity of the air/AAO interface, rendering the intensities of light reflected from the air/AAO and AAO/Al interfaces comparable, thereby forming an effective interference enhancement. Furthermore, the existence of the ferromagnetic CoFeB layer was capable of significantly improving the absorbance in the ultraviolet and visible spectral ranges, and, in particularly, the oscillation ranges could be extended to the near-infrared spectral range (> 2,600 nm) by utilizing an ITO with lower conductivity as a spacer layer, due to its material dispersion which was approximately equal to zero. This new nanoporous thin film system represents a powerful tool for the future development of ultrasensitive optical devices based on the Fabry-Pérot interference and investigation of many interesting physical phenomena.