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S-bend waveguides with low-loss and downscaled footprints are indispensable devices in photonic integrated circuits (PICs). In this study, two low-loss 3D S-bend waveguides are designed. The simulation results for communication band (1530–1570 nm) reveal that two 3D S-bend waveguides with inner height of 2300/2400/2500 nm (1000/1100/1200 nm lower than the outer height of the transmission center) hold higher transmission efficiencies and lower crosstalk than planar S-bend waveguide of the same size. The S-bend waveguides were fabricated on the thick-silicon layer of silicon-on-insulator (SOI). For the 1550 nm, the measured transmission efficiencies of S-bend 1 (S-bend 2) with three different inner heights were 1.06/0.99/0.91 dB (1.19/1.21/1.26 dB) and 1.47/1.35/1.21 dB (1.81/1.79/1.74 dB) for TE and TM modes, respectively. 2.67/2.74/2.82 dB (2.54/2.52/2.47 dB) and 2.46/2.58/2.72 dB (2.12/2.14/2.19 dB) higher than those of the planar ones. This study provides a basis for the design and research of large-scale PICs. • Propose and design two innovative S-bend waveguides with 3D morphology for the photonic chip integration. • Calculate and exhibit the high optical transmission efficiency and low crosstalk of the two 3D S-bend waveguides by comparison. • Experimental results verify the higher transmission efficiency of the two 3D S-bend waveguides for both the TE and TM modes. • Pave a way for the design and research of large-scale PICs. [ABSTRACT FROM AUTHOR]

We report calculation to rebuild Raman frequencies detected in Raman scattering of high quality wurtzite-type AlN bulk single crystal. Then, we use this Raman verified mode and parameters to calculate mechanical constants and phonon pressure coefficients, which are all important parameters in Raman based stress detection. The relationship between the modes used in Raman rebuilding and constants calculation are discussed in detail. We have predicted for the first time 2 a ̃ + b ̃ under different pressures. We have oberserved a new trend that 2 a ̃ + b ̃ is decreasing slightly according to the pressure, oppose to a constant as assumed. This work is a good foundation for stress/strain analysis used in film and device reliability testing. [ABSTRACT FROM AUTHOR]

• A polarized laser-induced plasmonic welding method with high efficiency and low-damage was proposed. • Two Cu-Au heterogeneous nanojunctions were fabricated using polarized laser-induced plasmonic welding method. • The fabricated Cu-Au heterogeneous nanojunctions demonstrate good electrical properties and glucose detection accuracy. Cu nanomaterials have shown superior response speed and sensitivity to glucose sensors. Here, we demonstrate a polarized laser-induced plasmonic nanowelding technique to assemble Cu-Au heterogeneous nanojunction into glucose sensor. Our simulation results reveal that the localized surface plasmon resonance induced by laser with parallel polarization is located at the two ends of nanowire. Consequently, Cu nanowire assembled on Au pad pair is melted at the two ends and welded on two Au pads, thereby obtaining two Cu-Au heterogeneous nanojunctions. The current-voltage curves show that the plasmonic welded Cu-Au heterogeneous nanojunctions exhibit reliable ohmic contact with a contact resistance of about 100 Ω. In addition, the Cu nanowires did not suffer serious oxidative damage, because the oxidized Au-Cu heterogeneous nanojunctions form a Schottky contact. Experimental result shows that the plasmonic welded Cu-Au heterogeneous nanojunction has a high detection accuracy and response speed for glucose solutions. The minimum detection concentration and response speed are 1 × 10−6 mol/L and 0.8 s, respectively. [ABSTRACT FROM AUTHOR]

• A method to correct the defocus effect of ARS is proposed. • A polymer planar waveguide is employed to calibrate the incident angle at different defocus positions. • A defocus compensation function was derived based on the bare silicon wafer. Angle-Resolved Scatterometry (ARS) enables the acquisition of images at the back focal plane (BFP) of the objective lens. These images contain target geometry information, which is a function of the incident angle and azimuthal angle. This technique has recently exhibited significant potential in film measurement, owing to its advantages of being fast, accurate, low-cost, and non-contact for critical dimensions (CD) measurement. However, during on-line CD metrology, environmental vibrations or sample stage displacement errors can cause the measurement plane to deviate from the objective lens's focal plane. Consequently, the recorded defocused BFP images lack crucial large-angle information, exacerbating the discrepancy between experimental and simulated data. In this study, we propose a method to address the defocus effect in ARS. To calibrate the incident angle under varying defocus positions, a polymer planar waveguide is employed. By illuminating the waveguide with polarized light, surface plasmon resonances are excited at a specific incident angle. At this resonance angle, the reflectance becomes exceptionally low, resulting in the formation of a distinct dark ring at the BFP. Subsequently, we capture BFP images of the bare silicon under different defocus positions, which serve as a reference light source for reflectance normalization. This enables effective compensation for the corresponding spectral errors associated with defocus. The experimental results demonstrate that for the SiO 2 film with a reference thickness of 30.5 nm, the maximum measurement error reduces significantly (at −25 µm defocus position) from 8.4 nm to 2.4 nm. Across the entire defocus range, the measurement error is consistently controlled within 3.4 nm. [ABSTRACT FROM AUTHOR]

Highlights • Patterned SiO 2 was inserted between ITO and electrodes, serving as both CBL and passivation layer. • Patterned ITO underneath p-electrode was formed to improve LEE of LED. • The EQE of the fabricated LED was 13.8% higher than that of conventional LED. Abstract GaN-based blue light-emitting diodes (LEDs) with patterned SiO 2 current blocking layer (CBL) deposited on patterned indium-tin oxide (ITO) transparent conductive layer has been proposed and performed. The patterned SiO 2 layer was inserted between ITO and p-/n-electrodes, serving as both CBL and passivation layer. The results showed that the proposed single patterned SiO 2 CBL can significantly improve the current spreading and light emission intensity of the fabricated LEDs. Additionally, the ITO with periodic circular patterns underneath p-electrode was formed to enhance scattering events of light emanated from InGaN/GaN active emitting region, leading to a reduced light absorption by opaque p-electrode and improved light extraction efficiency (LEE). As a result, at 200 mA, the external quantum efficiency (EQE) of the LED with patterned SiO 2 CBL deposited on patterned ITO was 13.8% higher than that of conventional LED. [ABSTRACT FROM AUTHOR]

• A new concept has been proposed for designing miniaturized artificial compound eyes. • 3D lithography technology based on 4096-order electrically modulated laser for manufacturing more precise and complex ultrathin flat compound eye. • An ultrathin flat compound eye with a volume one order of magnitude lower than traditional artificial compound eyes can be directly integrated with planar photoelectric sensor. • Fast imaging of moving objects achieved through ultrathin flat compound eye. With a hemispherical surface, the compound eye cameras inspired by arthropod eyes provide a large field of view (FOV), low aberration, and a large depth of field. However, to match the hemisphere-imaging plane, the cameras require a hemisphere-photoelectric sensor instead of a standard planar complementary metal oxide semiconductor (CMOS) sensor. Additionally, the hemispheric shape of the imaging system restricts the miniaturization of high-performance compound eye cameras at the millimeter scale. Here, inspired by the working principle of the Fresnel lens, an ultrathin flat compound eye (UFCE) composed of an off-axis microlens array (OMLA) was developed. 3D lithography enabled the fabrication of the UFCE with a complex morphology. Compared to the traditional artificial compound eye (ACE), the thickness of the UFCE was greatly reduced. Meanwhile, a flat substrate and ultrathin structure allowed for direct integration of the UFCE into the surface of a CMOS. The resultant UFCE had a FOV of up to 110° and a resolution close to the diffraction limit and low dispersion. Furthermore, the UFCE allowed for fast imaging of mobile objects in any plane within the depth of field, which is the unique function of the UFCE. In brief, the fabricated UFCE based on OMLA reduces the complexity of constructing compound eye cameras while significantly optimizing the volume, suggesting an alternative method for creating high-performing optical elements with the possibility of simple integration and miniaturization. [ABSTRACT FROM AUTHOR]

• When irradiation duration exceeds 200 ms, increasing irradiation duration has little effect on promoting nanowelding. • Electrical property of Cu-Au nanojunction change from ohmic to Schottky contact due to excessive irradiation duration. • Excessive irradiation duration can cause the electrodes to fall off the insulation. Continuous wave (CW) laser-induced nanowelding holds great promise in micro-and nano-devices. However, because of the lengthy irradiation duration, the heat effect from CW laser irradiation may harm the manufactured devices. The simulation results show that an increase in irradiation duration will slightly improve the welding temperature but greatly expand the heat-affected area when the irradiation time exceeds 100 ms. Experimental results confirm that Cu nanowires irradiated for 20 ms are slightly oxidized. As the irradiation period is increased to 10,000 ms, the oxygen concentration in Cu nanowires significantly increases, and the color of Cu nanowires becomes first black, then green. The electrical property of the oxidized Cu-Au nanojunction shifts from ohmic contact to Schottky contact. Furthermore, the large heat-affected area will weaken the adhesion between the Au pad and the substrate due to the large difference in thermal expansion coefficient between the metal film and the insulating layer. Consequently, CW laser-induced thermal damage not only impairs the electrical properties of nanostructures but also their reliability. [ABSTRACT FROM AUTHOR]

The quality of optical storage is determined by several factors, especially diffraction limit, storage media, recording dimensions and readout schemes. To increase the storage density, more progressive strategies reaching high storage density need be explored, including excellent storage media, multiple recording dimensions and robust readout schemes. In this work, the three-dimensional hybrid nanostructures are proposed, which are composed by Si and Si 3 N 4. It can be fabricated with the three dimensional (3D) lithography technology, which is able to encode high density data information within multi-dimensions. To obtain robust information readout, spectra with a broad wavelength range and with a large angle range are combined for a high sensitivity. Meanwhile an artificial neural network is used to translate the spectra to the data sequences. For a 4-unit nanostructure, the 27 data sequences with 20% spectral noise, a 100% readout accuracy can be achieved. High readout speed is also demanded in optical storage. Therefore, we reduced the number of the selected wavelengths and angles in the spectra. It is demonstrated that when the number reduces to 1/50 of the original number, the reading accuracy is still 99.7% compared to the full range. Furthermore, the possibility of achieving higher storage densities is investigated for a further study. [ABSTRACT FROM AUTHOR]

Stress and strain in an AlN film grown on Si (111) substrate have been evaluated by measuring Raman frequency shifts. Mechanical properties and phonon deformation potentials of AlN are evaluated by first principles calculations. The calculation model is verified by comparing the calculated Raman frequencies and frequencies detected from a bulk single crystal. Results show that the two sets of frequencies agree very well with each other. Thus, with the same verified model and parameters, elastic constants and phonon deformation potentials are calculated. Additionally, we successfully develop a numerical model to verify the calculation above and the model itself is also useful to predict properties of crystal films. Finally, the stress, strain, and piezoelectric properties are analyzed and compared for films on different substrates. [ABSTRACT FROM AUTHOR]

• With the decrease of length, NW samples become stronger except the sample with 4 nm length and force on Ag end. • NWs with load on Ag end outperform the same NWs with load on Au end in terms of yield stress and elongation. • The analysis from the radial distribution functions of the Ag segment of NWs is used to explain above phenomenon The tensile process of nanowires (NWs), in which one end of a NW is fixed, and the load is applied to the other end, is investigated via molecular dynamics (MD). Here, we pay attention to length-dependent mechanical properties of heterostructured Au-Ag NWs under the above tensile form. It was discovered that all the samples became stronger except for the shortest one with the length of 4 nm and the load on the Ag end with the decrease of length. Meanwhile, we found that all samples with the load on Ag ends outperformed the same NWs with the load on Au ends in terms of yield strengths and elongations. Meanwhile, the NWs with the load on Ag ends may exhibit a better performance in terms of conductivity. A reasonable analysis from the perspective of radial distribution function has been developed to explain above phenomena. [ABSTRACT FROM AUTHOR]