Linearized EUV mask optimization based on the adjoint method.

Mask optimization, a compensation method for the thick mask effect and the optical proximity effect in projection lithography, is essential for advanced EUV-enabled production nodes. However, owing to high computation costs and the absence of gradient calculations, it is challenging to optimize EUV masks under rigorous consideration of the thick mask effect. In this work, a linearized EUV mask optimization method based on the adjoint method is proposed to provide fast and effective optimizations. The adjoint method is introduced to calculate the gradient of the EUV mask model. Additionally, a linearized gradient is proposed to quickly compensate for wafer pattern distortion caused by the prominent thick mask effect. Two examples of the EUV mask optimization implemented with a two-step strategy were provided, from which it was observed that the linearized gradient can improve the efficiency by about 40% in the coarse optimization step. The proposed method is promising for accurate full-chip EUV mask optimization.

Ultra-simplified diffraction-based computational spectrometer.

Miniaturizing spectrometers for compact and cost-effective mobile platforms is a major challenge in current spectroscopy research, where conventional spectrometers are impractical due to their bulky footprint. Existing miniaturized designs primarily rely on precalibrated response functions of nanophotonic structures to encode spectral information captured in a snapshot by detector arrays. Accurate spectrum reconstruction is achieved through computational techniques, but this requires precise component design, high-precision fabrication, and calibration. We propose an ultra-simplified computational spectrometer that employs a one-to-broadband diffraction decomposition strategy facilitated by a numerical regularized transform that depends only on the spectrum of the diffracted radiation. The key feature of our design is the use of a simple, arbitrarily shaped pinhole as the partial disperser, eliminating the need for complex encoding designs and full spectrum calibration. Our spectrometer achieves a reconstructed spectral peak location accuracy of better than 1 nm over a 200 nm bandwidth and excellent resolution for peaks separated by 3 nm in a bimodal spectrum, all within a compact footprint of under half an inch. Notably, our approach also reveals a breakthrough in broadband coherent diffractive imaging without requiring any prior knowledge of the broadband illumination spectrum, assumptions of non-dispersive specimens, or correction for detector quantum efficiency.

Quantitatively Exploring Giant Optical Anisotropy of Quasi-One-Dimensional Ta2NiS5.

Optical anisotropy offers a heightened degree of flexibility in shaping optical properties and designing cutting-edge devices. Quasi-one-dimensional Ta2NiS5, with giant optical anisotropy, has been used in the development of new lasers and sensors. In this research endeavor, we successfully acquired the complete dielectric tensor of Ta2NiS5, utilizing the advanced technique of Mueller matrix spectroscopic ellipsometry, enabling a rigorous quantitative assessment of its optical anisotropy. The results indicate that Ta2NiS5 demonstrates giant birefringence and dichroism, with Δnmax = 1.54 and Δkmax = 1.80. This pursuit also delves into the fundamental underpinnings of this optical anisotropy, drawing upon a fusion of first-principles calculations and critical points analysis. The anisotropy of Ta2NiS5 arises from differences in optical transitions in different directions and is shown to be due to van Hove singularities without exciton effects. Its giant optical anisotropy is expected to be useful in the design of novel optical devices, and the revelation of the physical mechanism facilitates the modulation of its optical properties.

EUV mask model based on modified Born series.

Mask model is a critical part of computational lithography (CL). Owing to the significant 3D mask effects, it is challenging to accurately and efficiently calculate the near field of extreme ultraviolet (EUV) masks with complex patterns. Therefore, a method based on the modified Born series (MBS) was introduced for EUV mask modeling. With comparable accuracy, the MBS method was two orders of magnitude faster than the finite-difference time-domain method for the investigated examples. Furthermore, the time required for MBS was further reduced when the mask pattern was slightly changed. The proposed method shows great potential for constructing an accurate 3D mask model in EUV CL with high efficiency.

Investigations of Optical Functions and Optical Transitions of 2D Semiconductors by Spectroscopic Ellipsometry and DFT.

Optical functions and transitions are essential for a material to reveal the light-matter interactions and promote its applications. Here, we propose a quantitative strategy to systematically identify the critical point (CP) optical transitions of 2D semiconductors by combining the spectroscopic ellipsometry (SE) and DFT calculations. Optical functions and CPs are determined by SE, and connected to DFT band structure and projected density of states via equal-energy and equal-momentum lines. The combination of SE and DFT provides a powerful tool to investigate the CP optical transitions, including the transition energies and positions in Brillouin zone (BZ), and the involved energy bands and carries. As an example, the single-crystal monolayer WS2 is investigated by the proposed method. Results indicate that six excitonic-type CPs can be quantitatively distinguished in optical function of the monolayer WS2 over the spectral range of 245-1000 nm. These CPs are identified as direct optical transitions from three highest valence bands to three lowest conduction bands at high symmetry points in BZ contributed by electrons in S-3p and W-5d orbitals. Results and discussion on the monolayer WS2 demonstrate the effectiveness and advantages of the proposed method, which is general and can be easily extended to other materials.

Exosomal lncRNA HOTAIR promotes osteoclast differentiation by targeting TGF-ß/PTHrP/RANKL pathway.

Bone tissue is a common metastatic site of lung cancer, and bone metastasis is characterized by abnormal differentiation and malfunction of osteoclast, and the roles of exosomes derived from lung cancer have attracted much attention. In our study, we found that the level of HOTAIR expression in A549 and H1299 exosomes was higher than those of normal lung fibrocytes. Overexpression of HOTAIR in A549 and H1299 exosomes promoted osteoclast differentiation. Furthermore, A549-Exos and H1299-Exos targeted bone tissues, and bone formation was significantly inhibited in vivo. Mechanistically, exosomal lncRNA HOTAIR promoted bone resorption by targeting TGF-ß/PTHrP/RANKL pathway.

Multi-parameter and multi-objective optimization of stratified OLEDs over wide field-of-view considering thickness tolerance.

Poor wide field-of-view (FOV) performances and low production yields are major factors that restrict the application of organic light-emitting diodes (OLEDs) in large-size panels. In this paper, we propose an optimization and analysis method to improve optical performances of stratified OLEDs over wide FOV with consideration of the thickness tolerance in the practical production process. With key optical performance parameters defined using the angle-dependent luminescence spectra, including the external quantum efficiency (EQE), current efficiency (CE), just noticeable color difference (JNCD), and the color coordinates, the optimization of OLEDs over wide FOV is described as a multi-parameter and multi-objective optimization problem which is accomplished by the genetic algorithms (GAs). Further, the thickness tolerance is introduced to improve the structure stability considering thickness fluctuations in the practical production process. Appropriate thickness tolerances can be determined to achieve stable structures for the OLED device by defining and analyzing the distributions of preference regions of the GA output noninferior solutions and the correlation coefficients between the layer thicknesses. Based on the proposed methods, high-throughput simulations are carried out on a typical Green Bottom-emitting OLED (G-BOLED) to design a stable device structure with high-performances. Experimental results demonstrate that compared with the initial device, the performances of the optimized device have been significantly improved, with the CE improved by over 30% in the normal direction, the EQE improved by over 20%, and the JNCD reduced from 4.45 to 1.36 over the whole FOV of 0-60°. In addition, within the thickness fluctuation in the practical process, optimized devices can strictly satisfy the "Best" preferred region, indicating that the structure is more stable against thickness fluctuations in the practical production process. The proposed optimization method can simultaneously improve optical performances over wide FOV and provide a stable structure for stratified OLEDs, and it therefore can be expected to improve the production yields and promote the OLEDs applied to large-size panels.

Giant in-plane optical and electronic anisotropy of tellurene: a quantitative exploration.

Tellurene's giant in-plane optical anisotropy brings richer physics and an extra degree of freedom to regulate its optical properties for designing novel and unique polarization-sensitive devices. Here, we quantitatively evaluate the in-plane optical anisotropy of tellurene and further reveal its physical origins by combining imaging Mueller matrix spectroscopic ellipsometry (MMSE) and first-principles calculations. The anisotropic complex refractive indices and dielectric functions, as well as the derived giant birefringence (|Δn|max = 0.48) and dichroism (Δk > 0.4), are accurately determined by imaging MMSE to quantitatively evaluate the in-plane optical anisotropy of tellurene. With density functional theory (DFT), tellurene's optical anisotropy is connected to its low-symmetry lattice structure with electrical anisotropy (including the anisotropic effective mass, partial charge density, and carrier mobility), leading to anisotropic electric polarization and ultimately optical anisotropy. This work provides a general and quantitative way to explore the optical anisotropy and also helps to comprehend the connection between the lattice structure and the optical anisotropy of tellurene and even other emerging low-symmetry materials, which will further promote their polarization-sensitive optical applications.

Solasonine Inhibits Pancreatic Cancer Progression With Involvement of Ferroptosis Induction.

Pancreatic cancer is a highly fatal malignant tumor of the digestive system. It is characterized by early metastasis and high mortality rates. Solasonine, a steroidal alkaloid, is derived from Solanum nigrum L., a natural herb. Solasonine is associated with excellent anti-tumor effects, however, its effects on pancreatic cancer have not been fully established. Pancreatic cancer cells (PANC-1 and CFPAC-1) were used to verify the in vitro and in vivo effects of solasonine. Metabolomics were used to evaluate its underlying mechanisms. Solasonine promoted PANC-1 and CFPAC-1 cell apoptosis while inhibiting their proliferation, migration and invasion. Mouse xenograft models and metastasis models of ANC-1 and CFPAC-1 confirmed that solasonine blocked tumor formation and metastasis. Metabolomics confirmed the effects of solasonine on glutathione metabolism and SLC7A11-mediated ferroptosis. Furthermore, Co-Immunoprecipitation and Duolink® in situ PLA confirmed that OTUB1, a deubiquitylating enzyme, interacted with SLC7A11 and solasonine to enhance ubiquitinated degradation of SLC7A11 in PANC-1 and CFPAC-1 cells. Besides, molecular docking confirmed that solasonine directly bound TFAP2A and suppressed its protein levels. Bioinformatics and luciferase assays revealed that TFAP2A binds the OTUB1 promoter region, thereby promoting its transcription. In summary, solasonine inhibits the TFAP2A/OTUB1 SLC7A11 axis to activate ferroptosis and suppress pancreatic cancer cell progression.

Superachromatic polarization modulator for stable and complete polarization measurement over an ultra-wide spectral range.

The polarization measurement system deals with polarized light-matter interactions, and has been a kind of powerful optical metrology applied in wide fields of physics and material. In this paper, we address several general theoretical aspects related to the system model and optimization for linear polarization systems from a view of the matrix algebra. Based on these theories, we propose a new framework of superachromatic polarization modulator (PM) by combining a linear polarizer and a sequence of parallel linear retarders (LRs) for a typical kind of linear polarization system based on the rotating compensator (RC) principle. In the proposed PM, the LRs are made of quarter-wave plates and as a whole act as the RC. Compared with conventional achromatic/superachromatic composite waveplates, the LR sequence has general axis orientations and is optimized by the condition number of the instrument matrix of the PM, which thereby provide much more flexibility to achieve uniform, stable and complete polarization modulation over ultra-wide spectral range. The intrinsic mechanisms, including the working principle, optimization strategy and in-situ calibration method of the proposed PM, are presented and revealed mathematically by the matrix algebra. Results on several prototypes of the PM demonstrate the validity and capability of the proposed methods for applications in broadband polarization measurement systems. The fabricated PM is further applied to a home-made dual RC Mueller matrix ellipsometer, and the accuracy and precision in the full Mueller matrix measurement are better than 2‰ and 0.6‰ respectively over the ultra-wide spectral range of 200∼1000 nm. Compared with existing techniques, the proposed PM has advantages due to superachromatic performances over ultra-wide spectral ranges, stable and complete modulation of the polarized light, and convenience for adjustment and calibration.

Broadband and Incident-Angle-Modulation Near-Infrared Polarizers Based on Optically Anisotropic SnSe.

Optical anisotropy offers an extra degree of freedom to dynamically and reversibly regulate polarizing optical components, such as polarizers, without extra energy consumption and with high modulating efficiency. In this paper, we theoretically and numerically design broadband and incident-angle-modulation near-infrared polarizers, based on the SnSe, whose optical anisotropy is quantitatively evaluated by the complete dielectric tensor, complex refractive index tensor, and derived birefringence (~|Δn|max = 0.4) and dichroism (~|Δk|max = 0.4). The bandwidth of a broadband polarizer is 324 nm, from 1262 nm to 1586 nm, with an average extinction ratio above 23 dB. For the incident-angle-modulation near-infrared polarizer, the high incident angles dynamically and reversibly modulate its working wavelength with a maximum extinction ratio of 71 dB. Numerical simulations and theoretical calculations reveal that the considerable absorption for p light and continuously and relatively low absorption of s light lead to the broadband polarizer, while the incident-angle-modulation one mainly arises from the blue shift of corresponding wavelength of p light's minimum reflectance. The proposed novel design of polarizers based on SnSe are likely to be mass-produced and integrated into an on-chip system, which opens up a new thought to design polarizing optical components by utilizing other low-symmetry materials.

Optical Model and Optimization for Coherent-Incoherent Hybrid Organic Solar Cells with Nanostructures.

Embedding nanostructures in organic solar cells (OSCs) is a well-known method to improve the absorption efficiency of the device by introducing the plasma resonance and scattering effects without increasing the active layer thickness. The introduction of nanostructures imposes greater demands on the optical analysis method for OSCs. In this paper, the generalized rigorous coupled-wave analysis (GRCWA) is presented to analyze and optimize the performance of coherent-incoherent hybrid organic solar cells (OSCs) with nanostructures. Considering the multiple reflections of light scattered within the glass substrate by the device, the correction vector g is derived, then the modified expressions for the field and absorption distribution in OSCs are provided. The proposed method is validated by comparing the simulated results of various structures with results obtained by the generalized transfer matrix method (GTMM) and the "equispaced thickness method" (ETM). The results demonstrate that the proposed method can reduce the number of simulations by at least half compared to the ETM while maintaining accuracy. With the proposed method, we discussed the device performance depending on the geometrical parameters of nanostructures, and the optimization and analysis are accomplished for single and tandem OSCs. After optimization based on the proposed method, the performance of OSCs are significantly improved, which further demonstrates the practicality of the method.

Reconstruction of finite deep sub-wavelength nanostructures by Mueller-matrix scattered-field microscopy.

Computational super-resolution is a novel approach to break the diffraction limit. The Mueller matrix, which contains full-polarization information about the morphology and structure of a sample, can add super-resolution information and be a promising way to further enhance the resolution. Here we proposed a new approach called Mueller-matrix scattered-field microscopy (MSM) that relies on a computational reconstruction strategy to quantitatively determine the geometrical parameters of finite deep sub-wavelength nanostructures. The MSM adopts a high numerical-aperture objective lens to collect a broad range of spatial frequencies of the scattered field of a sample in terms of Mueller-matrix images. A rigorous forward scattering model is established for MSM, which takes into account the vectorial nature of the scattered field when passing through the imaging system and the effect of defocus in the measurement process. The experimental results performed on a series of isolated Si lines have demonstrated that MSM can resolve a feature size of λ/16 with a sub-7 nm accuracy. The MSM is fast and has a great measurement accuracy for nanostructures, which is expected to have a great potential application for future nanotechnology and nanoelectronics manufacturing.

Imaging Mueller matrix ellipsometry with sub-micron resolution based on back focal plane scanning.

The development of nanotechnology and nanomaterials has put forward higher requirements and challenges for precision measurement or nanometer measurement technology. In order to cope with this situation, a new type of imaging Mueller matrix ellipsometer (IMME) has been developed. A back focal plane scanning method is designed to make the IMME have the ability to measure multiple incident angles. A two-step calibration method is proposed to ensure the measurement accuracy of IMME. After calibration, the IMME can achieve measurement with wavelengths from 410 nm to 700 nm and incident angles from 0° to 65°. The lateral resolution of the IMME is demonstrated to be 0.8 µm over the entire measurement wavelength range. In addition, a Hadamard imaging mode is proposed to significantly improve the imaging contrast compared with the Mueller matrix imaging mode. Subsequently, the IMME is applied for the measurement of isotropic and anisotropic samples. Experimental results have demonstrated that the proposed IMME has the ability to characterize materials with complex features of lateral micron-distribution, vertical nano-thickness, optical anisotropy, etc., by virtue of its advantages of high lateral resolution and high precision ellipsometric measurement.

Strong Second- and Third-Harmonic Generation in 1D Chiral Hybrid Bismuth Halides.

Breaking the symmetry of a crystal structure can enable even-order nonlinear activities, including second-harmonic generation (SHG). The emerging chiral hybrid organic-inorganic metal halides feature unique optical and electronic properties and flexible crystal structures, making them a class of promising nonlinear optical materials. However, their nonlinear response performances are currently inferior to traditional nonlinear crystals, because of the lack of research on resonant enhancement and third-harmonic generation (THG). Herein, we designed chiral hybrid bismuth halides with naturally nonsymmetrical structure to enable SHG. Simultaneously, these chiral compounds preserve 1D crystal structures to create strong free exciton, broad self-trapped exciton (STE), and discrete band energy levels, which facilitate the resonant enhancement of SHG and THG susceptibilities. These new chiral films showcase superior effective SHG susceptibility (χ(2) ∼ 130.5 pm V-1 at an interesting wavelength of 1550 nm), exceeding that of the reference, a commercial LiNbO3 (χ(2) ∼ 83.4 pm V-1) single-crystal film. Furthermore, their THG intensities are even higher than their SHG intensities, with effective THG susceptibility (χ(3)) being ∼9.0 × 106 pm2 V-2 at 1550 nm (37 times that of the reference monolayer WS2). Their high SHG and THG performances indicate the promising future of these 1D chiral hybrid bismuth halides toward nonlinear optical applications.

Eigenvalue calibration method for dual rotating-compensator Mueller matrix polarimetry.

Dual rotating-compensator Mueller matrix polarimetry (DRC-MMP) has achieved wide spread applications in material characterization, nano-scale measurement, and biomedical diagnostics. However, the traditional calibration method for DRC-MMP relies on establishing an accurate system model, making its implementation cumbersome, especially in the presence of polarizing components that are to complex to be modeled. We propose a novel, to the best of our knowledge, eigenvalue calibration method for DRC-MMP without system modeling. Two specific basis vectors are introduced in order to transform the continuously modulated light intensity in DRC-MMP into a 5×5 projection matrix. Eigenvalue analysis is then performed based on the light intensity projection matrix to obtain the modulation matrix and the analysis matrix associated with the polarization state generator and the polarization state analyzer, respectively. The method is applied for DRC-MMP in both single-pass and double-pass setups. The experimental results have verified the proposed calibration method.

Birefringence and Dichroism in Quasi-1D Transition Metal Trichalcogenides: Direct Experimental Investigation.

Birefringence and dichroism are very important properties in optical anisotropy. Understanding the intrinsic birefringence and dichroism of a material can provide great help to utilize its optical anisotropy. But the direct experimental investigation of birefringence in nanoscale materials is rarely reported. As typical anisotropic transition metals trichalcogenides (TMTCs) materials with quasi-1D structure, TiS3 and ZrS3 have attracted extensive attention due to their special crystal structure and optical anisotropy characteristics. Here, the optical anisotropy properties such as birefringence and dichroism of two kinds of quasi-1D TMTCs, TiS3 and ZrS3 , are theoretically and experimentally studied. In experimental results, the anisotropic refraction and anisotropic reflection of TiS3 and ZrS3 are studied by polarization-resolved optical microscopy and azimuth-dependent reflectance difference microscopy, respectively. In addition, the birefringence and dichroism of ZrS3 nanoribbon in experiment are directly measured by spectrometric ellipsometry measurements, and a reasonable result is obtained. This work provides the basic optical anisotropy information of TiS3 and ZrS3 . It lays a foundation for the further study of the optical anisotropy of these two materials and provides a feasible method for the study of birefringence and dichroism of other nanomaterials in the future.

Multi-objective collaborative optimization strategy for efficiency and chromaticity of stratified OLEDs based on an optical simulation method and sensitivity analysis.

The low efficiency and dissatisfactory chromaticity remain as important challenges on the road to the OLED commercialization. In this paper, we propose a multi-objective collaborative optimization strategy to simultaneously improve the efficiency and ameliorate the chromaticity of the stratified OLED devices. Based on the formulations derived for the current efficiency and the chromaticity Commission International de L'Eclairage (CIE) of OLEDs, an optical sensitivity model is presented to quantitatively analyze the influence of the layer thickness on the current efficiency and the CIE. Subsequently, an evaluation function is defined to effectively balance the current efficiency as well as the CIE, and a collaborative optimization strategy is further proposed to simultaneously improve both of them. Simulations are comprehensively performed on a typical top-emitting blue OLED to demonstrate the necessity and the effectivity of the proposed strategy. The influences of the layer thickness incorporated in the blue OLED are ranked based on the sensitivity analysis method, and by optimizing the relative sensitive layer thicknesses in the optical views, a 16% improvement can be achieved for the current efficiency of the OLED with desired CIE meantime. Hence, the proposed multi-objective collaborative optimization strategy can be well applied to design high-performance OLED devices by improving the efficiency without chromaticity quality degradation.

High-speed Mueller matrix ellipsometer with microsecond temporal resolution.

A high-speed Mueller matrix ellipsometer (MME) based on photoelastic modulator (PEM) polarization modulation and division-of-amplitude polarization demodulation has been developed, with which a temporal resolution of 11 µs has been achieved for a Mueller matrix measurement. To ensure the accuracy and stability, a novel approach combining a fast Fourier transform algorithm and Bessel function expansion is proposed for the in-situ calibration of PEM. With the proposed calibration method, the peak retardance and static retardance of the PEM can be calibrated with high accuracy and sensitivity over an ultra large retardance variation range. Both static and dynamic measurement experiments have been carried out to show the high accuracy and stability of the developed MME, which can be expected to pave the way for in-situ and real-time monitoring for rapid reaction processes.

On the limits of low-numerical-aperture imaging scatterometry.

Although imaging scatterometry has been demonstrated to be a powerful technique for characterization of nano-gratings when high lateral resolution is required, some limits of this novel technique are still undisclosed yet, such as the constraint for the imaging numerical aperture (NA), the number of unit cells for accurate grating reconstruction, and the analyzability of image pixels associated with the grating region. To this end, we establish a vectorial image formation (VIF) model for imaging scatterometry based on the finite-difference time-domain (FDTD) method and vectorial diffraction theory. According to the established VIF model and the simulation results of a Si grating sample with finite numbers of unit cells, we find that accurate grating reconstruction by routine RCWA (rigorous coupled-wave analysis) -based data analysis requires an upper limit for the NA of the employed objective. And enough numbers of unit cells are also required to be covered in the illumination spot. Only in these conditions, the zeroth-order diffraction information of the grating under test can be exclusively and completely collected by the imaging system. Moreover, only the image pixels off the edge of the grating region are analyzable by routine RCWA-based data analysis due to the effect of edge scattering. The required number of grating unit cells and the size of the analyzable region are closely related with the imaging NA and the ratio between the illumination spot size and the size of the grating region D/L. Higher imaging NA or smaller D/L typically requires fewer grating unit cells and meanwhile allows a larger analyzable region. The investigation in this paper promises to provide valuable insights into the application of imaging scatterometry.