This PDF file contains the front matter associated with SPIE Proceedings Volume 13500, including the Title Page, Copyright information, Table of Contents, and Conference Committee information.

In the field of micro- and nanotechnology, the white light neutron Microchannel Plate (MCP) is a key component. It utilizes materials internally doped with nuclear-sensitive elements to capture neutrons and release converted electrons, triggering the electron multiplier process. In order to achieve high temporal resolution, high spatial resolution, and efficient detection of neutrons across a wider energy spectrum, the high uniformity of the microchannel plate is crucial. The corrosion step is crucial in the microchannel plate preparation process as it directly affects the formation and uniformity of the channels. To ensure consistent imaging quality, the corrosion level in each channel must be uniform. This paper focuses on the effect of various alkaline corrosion processes on the uniformity of microchannel plates doped with the neutron conversion material 10B . The results show that increasing the strength of alkaline treatments leads to poorer microchannel plate uniformity. This is because alkali metal oxides tend to reduce more alkali metal monomers during hydrogen reduction at high temperatures. This leads to an uneven distribution of alkali metals within each channel on the MCP surface, resulting in inconsistent gain and poorer uniformity. However, the uniformity of the microchannel plate can be effectively improved by controlling the concentration and duration of alkaline corrosion. Therefore, precise control of the alkaline corrosion process, especially the concentration and duration of alkaline corrosion, is expected to significantly enhance the performance of the microchannel plate and advance the development of white light neutron source resonance imaging technology.

The “mode-splitting” phenomenon based on whispering gallery mode (WGM) was observed in coupling resonators, which are composed of two size-mismatched microspheres. The wavelength separation and intensity of the two splitting peaks varied with changing sized discrepancy for coupling microspheres. As the size of the first microsphere was fixed and coupled with a tapered fiber, it’s shown that the wavelength separation of two splitting peaks increased firstly and then decreased with the increasing size of the size-varied microsphere coupled to the first. The maximal wavelength separation could be achieved for identical-sized microspheres, with a minimal difference for intensity also noted. This analysis could provide better application prospects in measurement for judging similar-sized microspheres and measuring the size of microspheres.

In this study, PbSe quantum dots (QDs) with subsequent characterization performed via X-ray diffraction (XRD) and transmission electron microscopy (TEM) were synthesized utilizing the thermal injection method. The absorption properties of the PbSe quantum dots were described using an ultraviolet-infrared spectrophotometer (UV-Vis), which shows that absorption in the range of 350 nm to 1600 nm, with an absorption typical peak near 1400 nm. Furthermore, the nonlinear optical properties of the quantum dots were systematically explored employing a femtosecond laser Z-scan system operating at a wavelength of 800 nm and a pulse width of 80 fs. As the incident laser power increasing, the nonlinear optical absorption behavior of the PbSe QDs underwent a discernible transition: from saturable absorption (SA） to reverse saturable absorption (RSA）. By fitting the experimental data, the corresponding nonlinear absorption coefficients were determined -3.538×10-8 and 1.362×10-8 respectively. The transition power of the two absorption states occurs at approximately ~3.4 mW. This nonlinear optical absorption phenomenon of PbSe QDs presents applying in optical limiting technology, laser modulation technology, and photodetectors.

In two-dimensional photonic crystals, the photonic bandgap can modulate electromagnetic waves with corresponding wavelengths. Photonic crystal surface-emitting laser (PCSEL) realizes the vertical emission of laser beam through the inplane resonance and optical feedback, and significantly overcomes typical problems of the traditional semiconductor laser, such as large divergence angle, elliptical beam and susceptibility to higher-order modes. Therefore, by designing the lattice structure and materials of photonic crystal appropriately, the photonic bandgap in different polarization states can be regulated to produce high performance laser beams. Therefore, to obtain a deeper understanding of the impact of photonic crystal structure on the output properties, we demonstrate that by simulating the energy band structure near the Γ2 point, mode B has a wavelength closer to the emission wavelength. Subsequently, we analyze the influence of lattice structure, number of air holes and symmetry degree on the photon energy band distribution of TE mode. At last, two types of lattice structures with different symmetry degrees, i.e., rhombic lattice and bullet-like lattice, respectively, were prepared using electron beam lithography. The full widths at half maximum (FWHMs) of photoluminescence spectra of these two photonic crystals were detected to be 73 nm and 53 nm, respectively, which verified that the reducing lattice symmetry is beneficial for decreasing the FWHM. In addition, the symmetry reduction is favorable to eliminate the photon energy band degeneracy, leading to a blueshift in wavelength. Our research provides theoretical design insights for achieving high-performance PCSEL lasers.

A four-band terahertz metamaterial absorber is proposed in this paper. The metamaterial absorber is based on a traditional "sandwich" structure, with structural units arranged in a honeycomb periodic arrangement in a plane. By using resonant structures of different sizes and selecting the appropriate array mode, the effect of multi-band absorption can be realized. This solves the limitation of poor frequency selectivity and low sensitivity of a single narrow-band absorption peak in terahertz detection applications. The electromagnetic properties of the metamaterial were calculated numerically by the finite element method, and four narrow-band perfect absorption peaks were obtained after parameter optimization. The results show that the absorption rates of the incident electromagnetic wave at 0.208 THz, 0.393 THz, 0.519 THz and 0.697 THz reach 97.27%, 96.69%, 99.37% and 99.33%, which has the characteristics of narrow absorption band and high absorption rate. According to the equivalent medium theory and the surface current mode analysis method, the physical mechanism of narrowband absorption is analyzed. The sensing performance of the metamaterial is significantly improved, with the figure of merit (FoM) reaching 4.55 and the Q value reaching 25. It has good polarization stability due to the high symmetry of the elements. And in the case of large incidence angle, it has good angular stability. Compared with the reported performance of metamaterial sensors, the sensing performance of the metamaterials proposed in this paper has been significantly improved, and it has potential application value in sensing, detection, etc.

The spectral sensitivity of conventional prism-based SPR sensors is numerically investigated and found to increase rapidly with the RI of the analyte. The sensitivity could be greatly enhanced by means of setting the x_component of the effective RI of the incident light a little larger than the RI of the analyte mainly on account of a large dielectric permittivity of the SPR active material which is essential in just mentioned approach in order to satisfy the coupling condition of SPR.

Brillouin scattering provides a unique approach in diverse applications ranging from sensing to signal processing and beyond. The recent advancement in Brillouin scattering research has been driven by the development of integrated photonic platforms. However, the realization of efficient Brillouin scattering with substantial gains at low pump powers within compact devices is still a challenge. We propose and demonstrate a chalcogenide metasurface as a promising candidate for facilitating spontaneous Brillouin scattering. By employing GeSbS materials with remarkable photoelastic properties and leveraging the capacity of metasurfaces to effectively confine light waves through quasi-bound states in the continuum, alongside their ability to confine acoustic waves via mechanical resonances, a substantial Brillouin gain of up to 21 dB is achieved at a low pump power of 9.12 mW within a metasurface of compact dimensions less than 0.03 cm. The superior performance of chalcogenide metasurfaces-based Brillouin scattering may hold profound potential to advance Brillouin scattering research and find wide applications.

The displacement measurement of the levitated particle is essential in optical tweezers in vacuum. However, crosstalk between the radial axes often occurs and will deteriorate the measurement precision. Common methods are proposed to align the coordinate systems of the motion and measurement, but few have considered the polarizations of the trapping beam and possible crosstalk control. Here single SiO2 particles with a diameter of 200nm are trapped in the single-beam optical tweezers in vacuum. Balanced detectors and D-shaped mirrors are used to measure the particle's displacements. As expected, the crosstalk coefficient can be periodically changed with the control of the linear polarization of the trapping beam. When the polarization direction is along Y axis, the crosstalk on the displacement x from the other radial axis can reach to infinity. When the polarization direction is along X axis, the crosstalk is eliminated. For comparison, crosstalk elimination is also achieved by an inserted Dove prism to rotate the beam along the propagation axis. The crosstalk elimination by polarization control is simpler, but it needs linear-polarized beam and will slightly change the particle’s resonant frequencies. The crosstalk elimination by beam rotations will need at least two Dove prisms, but it is adapted to most common conditions and does not change the resonant frequencies. The research is useful for the feedback cooling and the precise measurement of the physical quantities in future.

A photonic crystal fiber without any hole in the cladding is designed to achieve single-polarization single-mode (SPSM) operation. The core of PCF consists of alternating silicon nitride cylinders and air holes. Based on the full vector finite element method (FEM), characteristics of guiding modes are studied. The simulation results indicate that the proposed PCF offers an SPSM bandwidth of 241 nm (1.447~1.688 μm). At the center wavelength of 1.55 μm, the optimal structure realizes a high birefringence of 9.71×10^-3, a negative dispersion of -601.6 ps/(km·nm), an extremely low confinement loss of 7.77×10^-6 dB/km, and a high nonlinearity coefficient of 130.4 W^-1·km^-1. The proposed structure presents extensive application prospects in areas of polarization modulation, optical fiber sensing, ultra-short laser systems, etc.

A particle size measurement method based on micro-vision technology to improve the measuring precision is proposed in this paper. Firstly, the center point of the shape is determined by a single regular geometric boundary, and a corresponding spatial coordinate system is established. Secondly, by establishing a geometric shape size calibration model, the pixel size of basic parameters such as length, width, and cross-sectional area of the geometric shape is determined. Then, using autonomous motion calibration method, the pixel equivalent at the current image magnification is calibrated to reflect the correspondence between the pixel size of the image and the actual size, thereby expressing the actual size of the geometric shape. Finally, principal component analysis was used to compare, classify, and statistically analyze the measured geometric dimensions, eliminate duplicate values, reduce misidentification rates, and achieve accurate determination of geometric dimensions. In order to verify the validity of the method, repeat 5 times to measure the particle size of 100 nm, the experimental results show that the mean value ± standard deviation is consistent with the theoretical value. Therefore, this method reveals the possibility of high-precision measurement of particle size through computer micro-vision, and makes it be a much better option to be employed for further micro-nano structures analysis applications.

This study introduces a multidimensional structural color tuning method for a dual-layer rectangular prism structure composed of SiO₂-VO₂ and based on flexible materials. Using the phase transition characteristics of VO₂, specifically the meta-insulator phase transition and benefiting from the stretchability, high-temperature resilience, and low-temperature resistance of PDMS material, the metasurface structures exhibit stability in optical performance across a range of challenging temperature and deformation conditions, this study achieves flexible adjustment of structural color and modulation of solar spectrum reflectance by optimizing geometric parameters and controlling temperature. The results demonstrate substantial color changes in the structural color, shifting from the blue range to the green range when altering the period P from 280nm to 380nm, and exhibiting distinct color variations when transitioning VO₂ from insulating state to a metallic state upon temperature variation. The stimulation results demonstrate that the manipulation of key parameters such as side length W₁, side width W₂, and period P yields discernible alterations in both the structural color and reflection spectrum of the SiO₂-VO₂ structure. This work is simulated using Finite-Difference Time-Domain (FDTD) software. Therefore, the multidimensional structural color tuning method proposed in this study for the SiO₂-VO₂ dual-layer rectangular prism structure based on flexible materials showcases significant application potential in various fields such as smart color-changing materials, energy management, and information displays, enabling flexible control of structural color and switching of solar spectrum reflectance.