Search Results (73)

Micro- and nanopatterning is crucial for advanced photonic, electronic, and sensing devices. Yet achieving large-area periodic nanostructures with a 75 nm half-pitch on low-cost laboratory systems remains difficult, because conventional near-ultraviolet laser interference lithography (LIL) suffers from Gaussian-beam non-uniformity and a narrow exposure latitude. Here, we report a cost-effective deep-ultraviolet (DUV) dual-beam LIL system based on a 266 nm laser and diffractive flat-top beam shaping, enabling large-area patterning of periodical nanostructures. At this wavelength, a moderate half-angle can be chosen to preserve a large beam-overlap region while still delivering 150 nm period (75 nm half-pitch) structures. By independently tuning the incident angle and beam uniformity, we pattern one-dimensional (1D) gratings and two-dimensional (2D) arrays over a Ø 1.0 cm field with critical-dimension variation < 5 nm (1σ), smooth edges, and near-vertical sidewalls. As a proof of concept, we transfer a 2D pattern into Si to create non-metal-coated nanodot arrays that serve as surface-enhanced Raman spectroscopy (SERS) substrates. The arrays deliver an average enhancement factor of ~1.12 × 10⁴ with 11% intensity relative standard deviation (RSD) over 65 sampling points, a performance near the upper limit of all-dielectric SERS substrates. The proposed method overcomes the uneven hotspot distribution and complex fabrication procedures in conventional SERS substrates, enabling reliable and large-area chemical sensing. Compared to electron-beam lithography, the flat-top DUV-LIL approach offers orders-of-magnitude higher throughput at a fraction of the cost, while its centimeter-scale uniformity can be scaled to full wafers with larger beam-shaping optics. These attributes position the method as a versatile and economical route to large-area photonic metasurfaces and sensing devices. Full article

This paper suggests a perspective-controlled solution for an integrated Infrared micro-/nanoplastic spectroscopy/photometry-based detection, from the diffraction up to the geometry etendue, with the aim of yielding a universal spectrometer/photometer. Spectrophotometry, unlike spectroscopy that shows the interaction between matter and radiated energy, is a specific form of photometry that measures light parameters in a particular range as a function of wavelength. The solution, meant for diffraction grating and geometry etendue of the display unit, is provided by a controller that tunes the grating pitch to accommodate any emitted/transmitted wavelength from a sample made of microplastics, their degraded forms and their potential retention, and ensures that all the diffracted wavelengths are concentrated on the required etendue. The purpose is not only to go below the current Infrared limit of $20\mathsf{\mu }\mathrm{m}$ microplastic size, or to suggest an Infrared spectrophotometry geometry capable of detecting micro- and nanoplastics in the range of ($1\mathrm{nm}$–$20\mathsf{\mu }\mathrm{m}$) for integrated nano- and micro-scales, but also to transform most of the pivotal components to be directly wavelength-independent. The related controlled geometry solutions, from the controlled grating slit-width up to the controlled display unit etendue functions, are suggested for a wider generic range integration. The results from image-size characterization show that the following charge-coupled devices, nanopixel CCDs, and/or micropixel CCDs of less than $100\mathrm{nm}$ are required on the display unit, justifying the Infrared micro- and nanoplastic-integrated spectrophotometry, and the investigation conducted with other electromagnetic spectrum ranges that suggests a possible universal spectrometer/photometer. Full article

To address the issues of decreased accuracy and poor stability in distributed transfer alignment caused by factors such as wing deflection and deformation in complex flight environments, this paper proposes a wing-distributed transfer alignment method based on Fiber Bragg Grating (FBG). This paper establishes a flexural deformation model based on FBGs, establishes a coupling angle model and a dynamic lever arm model, derives the motion parameter relationship model between the main and the sub-nodes, establishes the corresponding transfer alignment filter, and proposes a federated adaptive filter based on allocation coefficients and an updated federated adaptive filter. The results show that the federated adaptive filtering algorithm based on allocation coefficients improved the pitch angle accuracy of the Inertial Measurement Unit (IMU) by 66.38% and the position estimation accuracy by 75.67%, compared to traditional algorithms. The arm estimation accuracy was also improved in the east and sky directions. Compared with traditional algorithms, the updated federated adaptive filtering algorithm improved the pitch angle accuracy of the sub IMU by 76.72%, the position estimation accuracy by 63.51%, and the lever arm estimation accuracy. Full article

We propose a hybrid-integrated III–V-silicon optical-phased-array (OPA) based on passive alignment flip–chip bonding technology and provide new solutions for LiDAR. To achieve a large range of vertical beam steering in a hybrid-integrated OPA, a multi-lines OPA in a single chip is introduced. The system allows parallel hybrid integration of multiple dies onto a single wafer, achieving a multi-fold improvement in tuning efficiency. In order to increase the range of horizontal beam steering, we propose a half-wavelength pitch waveguide emitter with non-uniform width to reduce the crosstalk, which can remove the higher-order grating lobes in free space. In this work, we simulate OPA individually for four-lines and eight-lines. As a result, we simultaneously achieved a beam steering with nearly ±90° (horizontal) × 17.2° (vertical, when four-line OPA) or 39.6° (vertical, when eight-line OPA) field of view (FOV) and a high tuning efficiency with 1.13°/nm (when eight-line OPA). Full article

Silicon photonics is the leading platform in photonic integrated circuits (PICs), enabling dense integration and low-cost manufacturing for applications such as data communications, artificial intelligence, and quantum processing, to name a few. However, efficient and polarization-insensitive fiber-to-PIC coupling for multipoint wafer characterization remains a challenge due to the birefringence of silicon waveguides. Here, we address this issue by proposing polarization-insensitive grating couplers based on subwavelength dielectric metamaterials and metaheuristic optimization. Subwavelength periodic structures were engineered to act as uniaxial homogeneous linear (UHL) materials, enabling tailored anisotropy. On the other hand, particle swarm optimization (PSO) was employed to optimize the coupling efficiency, bandwidth, and polarization-dependent loss (PDL). Numerical simulations demonstrated that a pitch of 100 nm ensures UHL behavior while minimizing leaky waves. Optimized grating couplers achieved coupling efficiencies higher than −3 dB and a PDL of below 1 dB across the telecom C-band (1530–1565 nm). Three optimization strategies were explored, balancing efficiency, the bandwidth, and the PDL while considering the Pareto front. This work establishes a robust framework combining metamaterial engineering with computational optimization, paving the way for high-performance polarization-insensitive grating couplers with potential uses in advanced photonic applications. Full article

Silicon-on-Insulator (SOI) technology and optical resonators have significantly influenced the field of photonics for malignancy sensing. Cancer, a malignant disease, necessitates the precise and advanced diagnostic technique. This study introduces a novel approach for cancer detection utilizing a micro racetrack ring resonator (MRTRR) integrated with Subwavelength Gratings (SWGs). The grating pitch size (Λ) is 300 nm. The findings demonstrate that the SWG MRTRR achieves high Sensitivity (S) due to enhanced light matter interaction and weak mode confinement. The SWG MRTRR produces a spectral envelope as the transmission output, which eliminates the limitation of free spectral range (FSR). The ‘S’ values obtained for cervical cancer, breast cancer type-1, and breast cancer type-2 are 1825 nm/RIU, 1705.14 nm/RIU, and 1004.71 nm/RIU. The Q-factor and the intrinsic Limit of Detection (iLoD) values are 269.68, 280.78, 315.76, 3.28 × 10⁻³, 3.37 × 10⁻³, and 5.09 × 10⁻³, respectively. Full article

Piezoelectric composite materials, combining the advantages of both piezoelectric materials and polymers, have been extensively used in ultrasonic transducers. However, the pitch size of radial array ultrasonic transducers normally exceeds one wavelength, which limits their performance. In order to minimize grating lobes of current radial transducers and then increase their imaging resolution, a 2.5 MHz 1-3 composite radial array transducer with 64 elements and 600 μm pitch was designed and fabricated by combining flexible circuit board and using a bending-and-superposition method. All the array elements were connected and actuated via the customized circuit board which is thin and soft. The kerf size is set to be 1/3 wavelength. PZT-5H/epoxy 1-3 composite was used as an active material because it exhibits an ultrahigh electromechanical coupling coefficient (k_t = 0.74), a very low mechanical quality factor (Q_m = 11), and relatively low acoustic impedance (Z_c = 13.43 MRayls). The developed radial array transducer exhibited a center frequency of 2.72 MHz, an average −6 dB bandwidth of 36%, an insertion loss of 31.86 dB, and a crosstalk of −26.56 dB between the adjacent elements near the center frequency. These results indicate that the bending-and-superposition method is an effective way to fabricate radial array transducers by binding flexible circuit boards. Furthermore, the utilization of tailored flexible circuitry boards presents an effective approach for realizing reductions in crosstalk level (CTL). Full article

This paper presents a new type of phase-shifted Fiber Bragg Grating (FBG): the sliced-FBG (SFBG). The fabrication process involves cutting a standard FBG inside its grating region. As a result, the last grating pitch is shorter than the others. The optical output signal consists of the overlap between the FBG reflection and the reflection at the fiber-cleaved tip. This new fiber optic device has been studied as a vibration sensor, allowing for the characterization of this sensor in the frequency range of 150 Hz to 70 kHz. How the phase shift in the FBG can be controlled by changing the length of the last pitch is also shown. This device can be used as a filter and a sensing element. As a sensing element, we will demonstrate its application as a vibration sensor that can be utilized in various applications, particularly in monitoring mechanical structures. Full article

To eliminate the flow dead zone and homogenize the asymmetric flow field of a grate furnace, spirally twisted tape inserts (STTIs) with a pitch ratio of 1.5 were installed in the vertical flues of an SCL1000-13.5/450 grate boiler. The arrangement schemes found to be present inside the chosen 1000 t/d grate furnace, determined using the orthogonal experimental method, included separate installation in chamber II, separate placement in chamber III, and simultaneous arrangement in both chamber II and chamber III. The effects of row spacing H, column spacing W, and mounting angle φ were investigated by means of the practicable and feasible numerical simulation method. With a focus on the uniformity degree of the flue gas, the results showed that temperature distribution is directly correlated with the velocity field. When it comes to the uniformity of the flow field, the exclusive use of STTIs in chamber II was better than that in chamber III. Under the optimal combination scheme of STTIs in both chamber II and chamber III (scheme N3₂₃), the exhaust gas temperature reached the minimum value and the uniformity index of temperature increased to the range of 0.994~0.997. The findings in this work could provide a reference for the optimization of the flow field in a grate furnace. Full article

Large-scale diffraction gratings were fabricated in surface relief on azobenzene thin films and transferred to flexible PDMS substrates using soft lift-off lithography. The PDMS gratings were strained along the grating vector axis and the resulting surface topography was analyzed using diffraction angle measurements, AFM imagery and surface plasmon resonance (SPR) spectra. All measurement methods exhibited a linear response in strain indicating the useability of these sensors in real-world applications. For SPR-based strain sensing, an increasing pitch and a decreasing modulation depth were observed with increasing strain. The SPR peak shifted by ~1.0 nm wavelength and the SPR intensity decreased by ~0.3 a.u. per percentage of applied strain. The tested PDMS samples retained their integrity even after multiple cycles of stretching and relaxation, making them a suitable strain sensor. Full article

Controlling overlay in lithography is crucial for improving the yield of integrated circuit manufacturing. The process disturbances can cause undesirable morphology changes of overlay targets (such as asymmetric grating), which can significantly impact the accuracy of overlay metrology. It is essential to decouple the overlay target asymmetry from the wafer deformation, ensuring that the overlay metrology is free from the influence of process-induced asymmetry (e.g., grating asymmetry and grating imbalance). Herein, we use an asymmetric grating as a model and show that using high-diffraction-order light can mitigate the impact of asymmetric grating through the rigorous coupled-wave analysis (RCWA) method. In addition, we demonstrate the diffraction efficiency as a function of the diffraction order, wavelength, and pitch, which has guiding significance for improving the measurement accuracy of diffraction-based overlay (DBO) metrology. Full article

Three-dimensional passive acoustic mapping (PAM) with matrix arrays typically suffers from high demands on the receiving electronics and high computational load. In our study, we investigated, both numerically and experimentally, the influence of matrix array aperture size, element count, and beamforming approaches on defined image metrics. With a numerical Vokurka model, matrix array acquisitions of cavitation signals were simulated. In the experimental part, two 32 × 32 matrix arrays with different pitches and aperture sizes were used. After being reconstructed into 3D cavitation maps, defined metrics were calculated for a quantitative comparison of experimental and numerical data. The numerical results showed that the enlargement of the aperture from 5 to 40 mm resulted in an improvement of the full width at half maximum (FWHM) by factors of 6 and 13 (in lateral and axial dimension, respectively). A larger array sparsity influenced the point spread function (PSF) only slightly, while the grating lobe level (GLL) remained more than 12 dB below the main lobe. These results were successfully experimentally confirmed. To further reduce the GLL caused by array sparsity, we adapted a non-linear filter from optoacoustics for use in PAM. In combination with the delay, multiply, sum, and integrate (DMSAI) algorithm, the GLL was decreased by 20 dB for 64-element reconstructions, resulting in levels that were identical to the fully populated matrix reconstruction levels. Full article

In this paper, an ultracompact combined sensor for displacement and angle-synchronous measurement is proposed based on the self-imaging effect of optical microgratings. Using a two-grating structure, linear and angular displacement can be measured by detecting the change of phase and amplitude of the optical transmission, respectively, within one single structure in the meantime. The optically transmitted properties of the two-grating structure are investigated in both theory and simulation. Simulated results indicate that optical transmission changes in a sinusoidal relationship to the input linear displacement. Meanwhile, the amplitude of the curve decreases with an input pitch angle, indicating the ability for synchronous measurement within one single compact structure. The synchronous measurement of the linear displacement and the angle is also demonstrated experimentally. The results show a resolution down to 4 nm for linear displacement measurement and a maximum sensitivity of 0.26 mV/arcsec within a range of ±1° for angle measurement. Benefiting from a simple common-path structure without using optical components, including reflectors and polarizers, the sensor shows ultra-high compactness for multiple-degrees-of-freedom measuring, indicating the great potential for this sensor in fields such as integrated mechanical positioning and semiconductor fabrication. Full article

Concentric circular gratings are diffractive optical elements useful for polarization-independent applications in photonics and plasmonics. They are usually fabricated using a low-throughput and expensive electron beam lithography technique. In this paper, concentric circular gratings with selectable pitch values were successfully manufactured on thin films of azobenzene molecular glass using a novel laser interference lithography technique utilizing Bessel beams generated by a combined lens–axicon configuration. This innovative approach offers enhanced scalability and a simplified manufacturing process on larger surface areas compared to the previously reported techniques. Furthermore, the plasmonic characteristics of these concentric circular gratings were investigated using conventional spectrometric techniques after transferring the nanostructured patterns from azobenzene to transparent gold/epoxy thin films. In addition, the real-time imaging of surface plasmon resonance colors transmitted from the concentric circular gratings was obtained using a 45-megapixel digital camera. The results demonstrated a strong correlation between the real-time photographic technique and the spectroscopy measurements, validating the efficacy and accuracy of this approach for the colorimetric studying of surface plasmon resonance responses in thin film photonics. Full article

Biomass includes diverse raw materials of plant or animal origin that are biodegradable. It also constitutes a significant fraction of municipal waste burned in waste incineration plants. Grate technology is one of the more commonly used technologies in the thermal conversion of biomass. The mass transport of material on the grate is a complex issue. The article presents a model for determining selected mass flow parameters on the grate, primarily the distribution of residence time, degree of mixing, and dispersion. The model is a description of mechanical mass transport on the grates of thermal waste conversion devices and represents the kinetics of the processes occurring on the grate. It allows for the design of the details of the specific movement of the material particles on the grates depending on their size and density. In addition, experimental tests of flow parameters realized on a laboratory stand simulating the operation of the grate are presented. Tests were conducted on different types of grates and with selected types of biomass materials. They included variants of the operating parameters of the grates, such as the speed and pitch of the grates an their inclination, simultaneously with the fulfillment of the 1:1 scale condition of the size of the laboratory stand to the actual size of the industrial grate (its section). A general trend can be seen in the mean residence time of the material on the grate, which is higher in the case of a reciprocating grate. The degree of dispersion is mainly influenced for moving and reciprocating grates by the inclination angle of the grate. The analysis of the test results made it possible to clarify the mechanism of material mass transport on different types of grates. It is also proposed to use the results in modeling the process of biomass combustion in grate chambers as well as their design and operation. Full article