In this paper, a metal-dielectric-metal structure based on a Fabry–Perot cavity was proposed, which can provide near 100% perfect narrow-band absorption. The lossy ultrathin silver film was used as the top layer spaced by a lossless silicon oxide layer from the bottom silver mirror. We demonstrated a narrow bandwidth of 20 nm with 99.37% maximum absorption and the absorption peaks can be tuned by altering the thickness of the middle SiO₂ layer. In addition, we established a deep understanding of the physics mechanism, which provides a new perspective in designing such a narrow-band perfect absorber. The proposed absorber can be easily fabricated by the mature thin film technology independent of any nano structure, which make it an appropriate candidate for photodetectors, sensing, and spectroscopy.

Broadband antireflection (AR) coatings are essential elements for improving the photocurrent generation of photovoltaic modules or the enhancement of visibility in optical devices. In this paper, we report a hybrid nanostructured antireflection coating combination that is a clean and efficient method for fabricating a nanostructured antireflection coating (ARC). A multilayer thin-film was introduced between the ARC and substrate to solve the significant problem of preparing nanostructured ARCs on different substrates. In this way, we rebuilt a gradient refractive index structure and optimize the antireflective property by simply adjusting the moth-eye structure and multilayers. Subwavelength-structured cone arrays were directly patterned using a self-assembled single-layer polystyrene (PS) nanosphere array as an etching mask. Nanostructure coatings exhibited excellent broadband and wide-angle antireflective properties. The bottom-up preparation process and hybrid structural combination have the potential to significantly enhance the broadband and wide-angle antireflective properties for a number of optical systems that require high transparency, which is promising for reducing the manufacturing cost of nanostructured AR coatings.

The sealed neutron tube shell dissection process utilizing the traditional lathe turning method suffers from low efficiency and high cost due to the frequency of replacement of the diamond knife. In this study, a hybrid dissection method is introduced by combining the continuous-wave (CW) laser for efficient tangential groove production with an ultra-short pulse laser for delamination scanning removal. In this method, a high-power CW laser is firstly employed to make a tapered groove on the shell’s surface, and then a femtosecond pulse laser is used to micromachine the groove in order to obtain a cutting kerf. The thermal field was theoretically investigated in a finite element model. The simulation results show that the width of the area of temperature exceeding 100 °C is 1.9 mm and 0.4 mm with rotating speeds of 20 rad/s and 60 rad/s, respectively. In addition, a 2 mm deep slot in the 25 mm diameter tube was successfully produced in 1 min by a kilowatt fiber laser, and a 500-femtosecond pulse laser was employed to cut a plate with a material removal rate of 0.2 mm³/min. By using the hybrid method, the cutting efficiency was improved about 49 times compared to the femtosecond laser cutting. According to the simulation and experimental results, this method provides a high-efficiency and non-thermal cutting technique for reclaimed metallic neutron tube shells with millimeter-level thick walls, which has the advantages of non-contact, minimal thermal diffusion, and no effect of molten slag. It is indicated that the hybrid dissection method not only offers a new solution for thick neutron tube shell cutting but also extends the application of laser cutting techniques.