This letter presents a novel narrow-band bandpass spoof surface plasmon polarition (SSPP) filter, which has a controllable passband, good rejection, and a compact structure. It is composed of two end-extending SSPP transmission lines and a pair of L-shaped coupling branches. Both the bandwidth and the central frequency can be adjusted by changing the depth of the SSPP unit and the length of SSPP transmission line behind the coupling branches. The dispersion curves of the SSPP unit are analyzed, and the influences of some structural parameters are investigated. A SSPP band-pass filter is fabricated and measured based on the proposed method, showing a wide 3-dB fractional bandwidth of 11.2% centered at 6.25 GHz and an out-of-band rejection below -15 dB within 1-10 GHz. The measured result shows good agreement with the simulated one.

The authors have investigated various photonic processing for various energy devices on flexible substrates with nanoinks. For printable electronics, different conducting nanoinks are developed, including silver nanowires, silver nanoplates, Cu-Ag core-shell nanoparticles, graphene oxide, and graphene. The authors showed that these inks are enabling for direct writing of antenna on paper for radio frequency (RF) energy harvesting, potentially for wireless charging application. For curing printed nanoinks and nanopastes, the authors compared four kinds of methods: chemical activated self-sintering, thermal sintering, photonic sintering with flash light, and athermal sintering with ultrafast fiber laser irradiation. The authors also developed an innovative and facile approach to fabricate supercapacitors on flexible substrates with femtosecond laser writing and photonic reduction. Au-reduced graphene oxide nanocomposite is used for electrical electrodes and collectors. Unlike previous studies, collectors are fabricated through conventional photolithography gold electrodes is directly written by femtosecond laser reduction of Au ions. The authors found that gold nanoparticles can be well sintered on the surface of reduced graphene. The reduced graphene also work as glues to bridge the electrical interconnection. The measured conductivity of Au/reduced graphene reaches 10% of that of bulk gold. By optimizing an interdigital structure, the areal capacitor is achieved as 1.5 mF/cm2.

Laser-direct writing has become an alternative method to fabricate flexible electronics, whereas the resistive nature of laser-scribed conductors may distort the radio-frequency characteristics of circuits for high-frequency applications. We demonstrate that the transmission characteristics of microstrip lines are insensitive to the resistance of laser-scripted conductors when the sheet resistance is not above 0.32 Ω/□. On the other hand, the transmission and reflection characteristics of the MS lines can be simply modified through the accommodation of the resistance of the conductors, because a laser can trigger the sintering and melting of laser produced silver nanostructures. This could provide an alternative way to fabricate radio frequency (RF) resistors and promote their applications to flexible radio-frequency devices and systems.

Resonant integrated optical gyroscopes (RIOGs) can integrate discrete optical components as a promising candidate for high-performance micro-optical gyroscopes. However, the current RIOG still consists of discrete elements due to the difficulty and complexity of heterogeneous integration of resonator and modulators. This paper presents on-chip integration of optical functional components including modulator, resonator, beam splitter, and coupler for the organic-polymer-based RIOG. Simple integrated optical processes such as spin coating, lithography, and etching can realize RIOG chips with low cost, size, weight, and power (CSWaP) features. Thereinto, the electro-optic modulator (EOM) fabricated by self-synthesized electro-optic (EO) polymer (side chain bonded polyurethane imide) exhibits less than 2 V half-wave voltage, which is half of the lithium niobate (LiNbO₃) modulator. With respect to the resonator, a quality factor of approximately million was achieved using low-loss fluorinated polymer. In addition, the angular velocity sensing of RIOG was also investigated. By demonstrating the monolithic integration of the resonator and modulators, such an all-polymer RIOG chip prototype builds the technical foundation for the precision fully integrated optical gyroscope.