Based on highly ordered TiO2 nanotube arrays (NTAs), we successfully fabricated the Cu2O-TiO2 NTA heterojunction by a simple thermal decomposition process for the first time. The anodic TiO2 NTAs were functioned as both “nano-container” and “nano-reactors” to load and synthesize the narrow band Cu2O nanoparticles. The loaded Cu2O expanded absorption spectrum of the TiO2 NTAs from ultraviolent range to visible light range. We found that the Cu2O-TiO2 NTA heterojunction films had visible activity towards photocatalytic degrading methyl orange (MO). The photocatalytic abilities of the Cu2O-TiO2 NTA heterojunction films were found increased with the Cu2O content from 0.05 to 0.3 mol/L. This could be explained by more electron-hole pairs generated and less recombination, when the Cu2O-TiO2 heterojunction got formed. Here, we put forward this promising method, hoping it can facilitate the mass production and applications of Cu2O-TiO2 NTA heterojunction.

The Faraday rotation effect of both the La: yttrium iron garnet (YIG) film and the YIG metasurface were experimentally and numerically investigated in the terahertz (THz) region. A THz magneto-optic polarization measurement system was used to observe the transmission, resonance, and magneto-optical effect of the La:YIG film and YIG metasurface. The THz artificial chirality and resonance localization of the helical metasurface generate the superchiral THz field, which enhances the THz magneto-optical effect of the YIG film. The results show that the Faraday effect of the YIG metasurface is about three times that of the pure YIG film, whose differential rotation angle increases from 8° to over 24°. This work achieves more sensitively active polarization control of THz waves, which is of great significance for THz polarization conversion, sensing, and non-reciprocal transmission.

A compact and low-loss magnetically tunable bandpass filter (BPF) is presented in this letter. The yttrium iron garnet/gadolinium gallium garnet (YIG/GGG) film structure is regarded as a resonator excited by a stepped terminal short-circuited stripline, and additional metal rings are plated on the other side of the RO4350 substrate. Two YIG/GGG film structures placed in parallel are directly coupled. This structure enhances the RF magnetic field, reduces filter loss, and suppresses parasitic response. The filter design and geometrical parameter optimization are first carried out using CST Studio Suite. When the magnetic field changes from 1820 to 7420 Oe, the filter is tuned from 5 to 19 GHz, with a 3-dB bandwidth (BW) of 62–107 MHz, insertion loss (IL) of less than 2 dB, and parasitic response suppression of about 20 dB over the entire tuning range (TR).

In this paper, the Y₂Bi₁Fe₅O₁₂ films were grown on substituted gadolinium gallium garnet substrate by radio frequency magnetron sputtering and their magnetic properties were investigated. We found that the 20 nm-thick film had the best perpendicular magnetic anisotropy (PMA) under the combined effect of stress-induced anisotropy and surface roughness of the film; the applied magnetic field required for its out-of-plane magnetization saturation was 90 Oe, the remanence ratio was 0.8, the coercive force was 30 Oe, and the damping constant was 3.37 × 10⁻³. The PMA of the films was reduced due to the relaxation of the stress as the thickness of the film increased, and the easy magnetization axis became in-plane as the thickness reached 40 nm.

A new structure magnetically tunable bandpass filter with five stages was designed and realized in this article. Yttrium iron garnet/gadolinium gallium garnet/yttrium iron garnet (YIG/GGG/YIG) film multi-layer structure was set as the basic resonant unit, and the metal rectangular ring was added between the YIG/GGG/YIG film structures to improve the out-of-band suppression and adjust the bandwidth of the filter. Based on CST Studio Suite and experimental results, the parameters of the bandpass filter structure were determined. The filter center frequency can be tuned from 10 to 15 GHz as the bias magnetic field changing from 2850 to 5560 Oe, the out-of-band suppression was greater than 80 dBc, the insertion loss was less than 6.5 dB, and the bandwidth varied from 51 to 70 MHz in the whole working band range.