Optical Micro Research Articles

Two-dimensional optical micro displacement sensing and crosstalk elimination based on the self-imaging effect of a grating pair

This paper proposes a straightforward method for measuring micro-displacement synchronously along two orthogonal axes. A single structure consists of a pair of two-dimensional gratings and a quadrant detector aligned with a collimated laser is used to detect the micro-displacement. The crosstalk and the common-mode noise are eliminated through a two-step differential process. Experimental results demonstrate that the displacement measurement resolution can reach 40 nm with a sensitivity of 0.483 V/µm within the linear range. The accuracy obtained is 0.29% on the X-axis and 0.31% on the Y-axis within a 500 µm range. The signal-to-noise ratio is improved by 4.56 dB after differential. The simplicity and high compactness of this measurement structure make it suitable for fabrication and alignment using microfabrication processes, which show great potential in many applications such as gyroscopes, accelerators, and multi-dimensional displacement measurements.

High-harmonic spin-orbit angular momentum generation in crystalline solids preserving multiscale dynamical symmetry.

Symmetries essentially provide conservation rules in nonlinear light-matter interactions and facilitate control and understanding of photon conversion processes or electron dynamics. Since anisotropic solids have rich symmetries, they are strong candidates for controlling both optical micro- and macroscale structures, namely, spin angular momentum (circular polarization) and orbital angular momentum (spiral wavefront), respectively. Here, we show structured high-harmonic generation linked to the anisotropic symmetry of a solid. By strategically preserving a dynamical symmetry arising from the spin-orbit interaction of light, we generate multiple orbital angular momentum states in high-order harmonics. The experimental results exhibit the total angular momentum conservation rule of light even in the extreme nonlinear region, which is evidence that the mechanism originates from a dynamical symmetry. Our study provides a deeper understanding of multiscale nonlinear optical phenomena and a general guideline for using electronic structures to control structured light, such as through Floquet engineering.

Nano-optogenetics for Disease Therapies.

Optogenetic, known as the method of 21 centuries, combines optic and genetic engineering to precisely control photosensitive proteins for manipulation of a broad range of cellular functions, such as flux of ions, protein oligomerization and dissociation, cellular intercommunication, and so on. In this technique, light is conventionally delivered to targeted cells through optical fibers or micro light-emitting diodes, always suffering from high invasiveness, wide-field illumination facula, strong absorption, and scattering by nontargeted endogenous substance. Light-transducing nanomaterials with advantages of high spatiotemporal resolution, abundant wireless-excitation manners, and easy functionalization for recognition of specific cells, recently have been widely explored in the field of optogenetics; however, there remain a few challenges to restrain its clinical applications. This review summarized recent progress on light-responsive genetically encoded proteins and the myriad of activation strategies by use of light-transducing nanomaterials and their disease-treatment applications, which is expected for sparking helpful thought to push forward its preclinical and translational uses.

INOS is necessary for GBP-mediated T. gondii clearance in murine macrophages via vacuole nitration and intravacuolar network collapse

Toxoplasma gondii is an obligate intracellular parasite of rodents and humans. Interferon-inducible guanylate binding proteins (GBPs) are mediators of T. gondii clearance, however, this mechanism is incomplete. Here, using automated spatially targeted optical micro proteomics we demonstrate that inducible nitric oxide synthetase (iNOS) is highly enriched at GBP2+ parasitophorous vacuoles (PV) in murine macrophages. iNOS expression in macrophages is necessary to limit T. gondii load in vivo and in vitro. Although iNOS activity is dispensable for GBP2 recruitment and PV membrane ruffling; parasites can replicate, egress and shed GBP2 when iNOS is inhibited. T. gondii clearance by iNOS requires nitric oxide, leading to nitration of the PV and collapse of the intravacuolar network of membranes in a chromosome 3 GBP-dependent manner. We conclude that reactive nitrogen species generated by iNOS cooperate with GBPs to target distinct structures in the PV that are necessary for optimal parasite clearance in macrophages.

Triple Micro Optical Multiple Asymmetric Ring Resonator Performance Analysis as Optical Filter

The present article implements the modelling of triple asymmetrical optical micro ring resonator (TAOMRR) in z-domain and the waveguide spacing is designed using Finite Difference Time Domain (FDTD) methodology. The formulation of the transmission function is prepared in z-domain utilizing the delay line signal processing technique. The developed configuration is scrutinized by evaluating the frequency response analysis as well as various important characteristics that are dispersion, group delay, and finesse using MATLAB software. The efficacy of the proposed methodology is tested using OptiFDTD software and it is found that the results of both MATLAB and OptiFDTD are in very nearby settlement. The field analysis of propagated wave inside the microring resonator is shown. The specific gap for various optical directional couplers is also determined using OptiFDTD in this article. The proposed technique is very useful for modeling and analyzing of different configurations of micro optical asymmetric ring resonator which found great application in the field of optical filters as well as optical sensors.

Sub-wavelength focused light and optical trapping application based on two-mode interference from an optical micro-/nanofiber

The ability to focus light on a subwavelength scale is essential in modern photonics. Optical microfiber-based sub-wavelength focusing will allow a miniaturized, flexible and versatile tool for many applications such as biomedical imaging and optomechanics. For a separate mode exited from an optical micro-/nanofiber endface, the photons will experience significant diffraction into the free space. This situation can be changed by incorporating two-mode interference along with the specific spatial distributions of both <i> <b>E</b> </i>-field amplitude and phase. Herein we report a novel approach to realizing sub-wavelength focusing based on the two-mode interference exited from an optical microfiber endface. By utilizing specific distributions of <b><i>E</i></b> -field amplitude and phase of two interacting optical modes, interference field patterns with a single focus (e.g., via a two-mode set of HE<sub>11</sub> and HE<sub>12</sub>) or multiple foci (e.g., via a two-mode set of HE<sub>11</sub> and HE<sub>31</sub>) can be obtained. Then, it is proved that the constructed foci will readily facilitate and selective trapping of nanoparticles. Circular polarization of optical mode is utilized in order to bring in angular symmetry of sub-wavelength focusing patterns compared with linear polarized optical modes. Our simulation results show that the smallest focal spot produced from the EH<sub>11</sub> and HE<sub>12</sub> mode interference has a full width at half-maximum (FWHM) of ~ 348 nm (i.e. 0.65<i>λ</i>). Such a subwavelength focusing field is applied to the optical trapping of an 85 nm-diameter polystyrene nanosphere. Further calculation reveals that the stable trapping can be fulfilled with axial and transverse trap stiffness of 11.48 pN/(μm·W) and 64.98 pN/(μm·W), as well as axial and transverse potential well of 101 <i>k</i><sub>B</sub>T/W and 641 <i>k</i><sub>B</sub>T/W via two-mode interference of HE<sub>11</sub> and HE<sub>12</sub>. These values demonstrate the great improvement over conventional tapered fibers. Further investigations show that different foci, via a two-mode set of HE<sub>11</sub> and HE<sub>31</sub>, exhibit unlike trap stiffness and potential wells, justifying the potential for nanoparticle size sorting. Based on the flexible all-fiber device, this subwavelength focusing strategy by two-mode interference may find promising applications in optical manipulation, superresolution optical imaging, data storage and nanolithography.

Theoretical analysis and comparative study of assorted diaphragm primarily based Micro Electro Mechanical System (MEMS) optical pressure sensors

In general, micro pressure sensors use a diaphragm as the sensing element that converts the applied pressure into the required displacement. Displacement is employed to sense real physical phenomena, such as pressure, force with various conduction methods. The conduction is defined as capacitive, piezoresistive, piezoelectric or resonant. Understanding the behavior of structural elements prior to its design is very essential depends on conductive method. The main challenge of parameter optimization of the diaphragm is to attain unsurpassed device performance. Therefore, theoretical analysis of various structures of optical Micro Electro Mechanical System (MEMS) sensor is proposed in this manuscript. Here, diaphragm geometries, like square, rectangular and circular are considered to analyze the structures. The objective of this work is to analyze various structures of optical MEMS sensor measuring pressure theoretically. The displacements of the varied diaphragms are compared for different thicknesses and the graphs are analyzed against their displacements. The best suitable structure of diaphragm for pressure sensor design is obtained. The diaphragm with good characteristics is virtually fabricated using Intellifab. The parameters such as linearity and relationship between pressure and intensity are obtained for the best suited diaphragm.

Correlated-photon-pair generation via SFWM in tapered optical fibers with femtosecond laser pump

Spontaneous four-wave mixing (SFWM) in optical micro-/nanofibers is studied theoretically and experimentally. Joint spectral intensity of the biphoton field generated via SFWM under excitation of femtosecond laser pulses is measured and calculated considering self-phase modulation of the pump pulses and SFWM throughout the tapered fibers. In comparison with the previous study (Shukhin et al 2020 Phys. Rev. A 101 053822), replacing picosecond pump by a femtosecond one with the same average power makes it possible to increase the photon pair generation rate tenfold.

Automated spatially targeted optical micro proteomics identifies fibroblast- and macrophage-specific regulation of myocardial infarction scar maturation in rats

Myocardial infarction (MI) results from occlusion of blood supply to the heart muscle causing death of cardiac muscle cells. Following myocardial infarction (MI), extracellular matrix deposition and scar formation mechanically stabilize the injured heart as damaged myocytes undergo necrosis and removal. Fibroblasts and macrophages are key drivers of post-MI scar formation, maturation, and ongoing long-term remodelling; however, their individual contributions are difficult to assess from bulk analyses of infarct scar. Here, we employ state-of-the-art automated spatially targeted optical micro proteomics (autoSTOMP) to photochemically tag and isolate proteomes associated with subpopulations of fibroblasts (SMA+) and macrophages (CD68+) in the context of the native, MI tissue environment. Over a time course of 6-weeks post-MI, we captured dynamic changes in the whole-infarct proteome and determined that some of these protein composition signatures were differentially localized near SMA+ fibroblasts or CD68+ macrophages within the scar region. These results link specific cell populations to within-infarct protein remodelling and illustrate the distinct metabolic and structural processes underlying the observed physiology of each cell type.

Implementation of all-optical single qubit gates using Si3N4 based micro ring resonator

Quantum logic gates are the key element and basic brick for quantum computing and quantum communication process. This work intended a unique method to implement the Pauli single qubit X, Z, and Y quantum gates using the Si3N4 based optical micro ring resonators. The magnitude and phase encoding of the light signal has been done to get the desired result. To obtain the desired phase shifts of the light signal in the micro ring resonators, different pump power has been employed. The mathematical simulation results validated the proposed model for all-optical Pauli X, Z, and Y quantum gates. The key performance parameters of the proposed model like extinction ratio of 20.29 dB, Quality factor of 7750 and contrast ratio of 19.54 dB are obtained. The proposed model was evaluated and compared with the other reported work as shown better performance to them.

Comparison of the Effects Metal Inert Gas and Laser Beam Welding on Duplex Stainless Steel Properties

In this study, optimal characteristics for duplex stainless steels (2507DSS) are attained when austenite and ferrite are present in roughly equal amounts in the microstructure. Therefore, the purpose of this study is to compare how different metal inert gas (MIG) and laser welding (LBW) parameters affect the weld characters of joints that are butt welded joints of duplex stainless steel plate with thickness of 8mm, the speed is constant and changing beam power, with argon shielding gas. Conventional MIG welding parameters are ranges; current, voltage are constant with changing speed and using gas mixture Ar and CO2 with a filler metal, and a single V groove. Investigation of welded joints has been carried out using different methods visual inspection, optical micro structure, hardness measurements, energy dispersive X-ray (EDX) microanalysis and tensile test. The results achieved in this investigation disclosed that welding parameters obtaining satisfactory properties of welded joint; no visible welding flaws, porosity and incompetent penetration. The fusion zone's grain size is finer in LB than MIG welding. EDX microscopic analysis reveals a slightly different structure in MIG and LB welds of BM microstructure, with filler altering Fe element and C-carbone content, causing brittleness due to ferrite content. The hardness results showed that no appreciable differences between MIG and LB in the welding bool area zone were equalled (265- 289Hv) respectively. Tensile strength and ductility increased with MIG and LBW in HAZ, at the same time laser welded specimens showing the highest ductility and strength.

Optical Frequency Comb-Based Aerostatic Micro Pressure Sensor Aided by Machine Learning

Optical Frequency Comb-Based Aerostatic Micro Pressure Sensor Aided by Machine Learning

Acupotomy ameliorates subchondral bone absorption and mechanical properties in rabbits with knee osteoarthritis by regulating bone morphogenetic protein 2-Smad1 pathway.

To investigate the effects of acupotomy on the subchondral bone absorption and mechanical properties in rabbits with knee osteoarthritis (KOA). The rabbits were divided into blank control, model, acupotomy and electroacupuncture (EA) groups, with 12 rabbits in each. Modified Videman's method was used to prepare KOA model. The acupotomy and EA group were given indicated intervention for 3 weeks. The behavior of rabbits in each group was recorded. Subsequently, cartilage-subchondral bone units were obtained and morphological changes were observed by optical microscope and micro computed tomography. Compression test was used to detect the mechanical properties of subchondral bone, Western blot and real-time polymerase chain reaction (RT-PCR) were applied to detect the expression of bone morphogenetic protein 2-Smad1 (BMP2-Smad1) pathway in subchondral bone. Compared with the control group, rabbits in the KOA group showed lameness, knee pain, and cartilage degradation; the subchondral bone showed active resorption, the mechanical properties decreased significantly and the BMP2-Smad1 pathway downregulated significantly. Both acupotomy and EA intervention could increase the thickness of trabecular bone (Tb. Th), the bone volume fraction (BV/TV) and the thickness of subchondral bone plate, reduce the separation of trabecular bone (Tb. Sp), improve the maximum load and elastic modulus of subchondral bone, and effectively delay cartilage degeneration in KOA rabbits. This process may be achieved through upregulation the related proteins of BMP2-Smad1 pathway. The maximum load and elastic modulus of subchondral bone in the acupotomy group were slightly better than those in the EA group. Acupotomy could effectively protect cartilage by inhibiting abnormal bone resorption and improving mechanical properties of subchondral bone thorough the related proteins of BMP2-Smad1 pathway in KOA rabbits.

Optical micro mechanical accelerometer with double grating: design and simulation.

A double-grating-based optical micro mechanical accelerometer with differential detection structure is reported in order to enhance the optical scale factor. A theoretical model is established based on the multi-slits Fraunhofer diffraction model. According to the calculation and analysis, the normalized optical scale factor is improved from 5.491E6 with the single-side detection structure to 10.98E6 with the differential detection structure. Mechanical sensitivity with 4.04nm/g and natural frequency with 7756.8Hz of the optical accelerometer are shown by finite element simulation. The results of simulations show a novel scheme for an optical micro mechanical accelerometer with high resolution, to the best of our knowledge. Furthermore, micro-opto-electro-mechanical system fabrication flow is given in this work, which provides a reference for other kinds of optical sensors.

Nanoquartz in Late Cretaceous Deposits in the Lower Berezovskaya Subformation

The Lower Berezovskaya subformation in the Upper Cretaceous is a complex reservoir with unconventional reservoir rocks located in the north of Western Siberia. The clay–siliceous deposits in the Lower Berezovskaya subformation are represented by various types of silicites that have unique petrophysical and mineralogical characteristics that cause significant difficulties in the development of associated productive layers. The aim of the research is to study their mineral composition, the parameters of the void space structure, and the conditions of formation, as well as to determine the sources of silica and perform a detailed study on the structure of nanoquartz. To study the mineral composition, the structure of the void space, and the genesis, special methodological techniques were applied, and a comprehensive analysis of the results using a wide range of laboratory studies, including optical micro- and stereoscopy, scanning electron microscopy, X-ray diffraction analysis, and microtomography, was performed. Silicites in the Lower Berezovskaya subformation are caused by the complex structure of the void space, which includes a wide range of genetic types of voids ranging from micron and submicron dimensions to fractions of a millimeter (voids confined to the burrowing organisms, intraform voids, interform voids, lenticular voids, cellular voids, and voids confined to microstylolite seams). The most widespread type of void is the interaggregate (lenticular and cellular) void, which is formed by clay (montmorillonite) scales, on the surface of which numerous α-quartz nanocrystals ranging in size from 0.05 to 0.5 microns are noted. The content of such quartz reaches up to 80% of the total volume of the rock in individual samples. The source of siliceous material for nanoquartz crystals was most likely volcanic processes, since the revealed mineral paragenesis of montmorillonite, cristobalite, and zeolites indicates the active transformation of ash material that entered the basin from volcanic formations.

Effect of assisted heating on microstructure, material flow and intermetallic formation during friction stir welding of copper alloy and AA 6063

The friction stir welding (FSW) is a newly developed solid-state welding technique, which addresses a number of practical issues such as reducing melt related defects by reducing welding temperature. This provides an opportunity for dissimilar metal welding and provides high quality joints. In the present study friction stir welding was performed on AA6063 and copper alloys by conventional FSW method and with the aid of external flame heating during the FSW process. The concept behind the experimentation is to perform the welding at low RPM to improve the material mixing and joint properties. The microstructure, phase constituents and mechanical properties of FSW joints were studied through optical metallography, SEM, X-ray diffraction, micro hardness, and tensile tests. Al2Cu and Al4Cu9 intermetallic were formed during the conventional and assisted flame heating FSW process which were distributed in the nugget zone. Due to the flame heating, copper and aluminum alloys get softer and leads to distribution of intermetallic as lamellar structure. The values of tensile strength for conventional friction stir welding, and assisted flame heating FSW are 69 MPa, and 102 MPa respectively.

Wood Polymer Composite Based on a Styrene and Triethoxy(Vinylphenethyl)silane

Today obtaining environmentally friendly wood composite materials is one of the main tasks. The urea-, phenol-, and melamine-formaldehyde resins used today are harmful to the human body and have a long-lasting effect. Therefore, replacing these and other resins with safe binders is one of the major problems. The aim of the work was to obtain and research ecologically safe wood polymer composites-deckings based on a new environmentally safe binder and a reinforcing agent triethoxy(vinylphenethyl)silane and styrene (in-situ polymerization) with a pine sawdust filler and aluminum hydroxide as an antioxidant. On the basis of triethoxy(vinylphenethyl)silane, styrene, and sawdust, the wood polymer composites – deckings have been obtained by hot pressing method at different temperatures and ratios of used components in the presence of antioxidant. For deckings surface, a morphological examination using optical microscopy, scanning electron microscopic (SEM), and energy-dispersive X-ray roentgenographic microanalysis were performed. Water absorption, softening temperature (Vicat), strength on bending, and impact viscosity were determined. Besides, using sawdust as coupling and reinforcement agents, and aluminum hydroxide as an antioxidant, wood polymer composites (WPC) were obtained by hot pressing at different tempe¬ratures. For the obtained composites, the morphological study of the surface was carried out using optical micro¬scopy and scanning electron microscopy, energy disper¬sive X-ray microanalysis. Water absorption of compo¬sites, bending yield stress, impact strength, and softening temperature were determined by the Vicat method. The obtained composites were characterized by higher phy-sicomechanical properties and water absorption.

Temperature-Dependent Anisotropic Refractive Index in β-Ga2O3: Application in Interferometric Thermometers

An accurate knowledge of the optical properties of β-Ga2O3 is key to developing the full potential of this oxide for photonics applications. In particular, the dependence of these properties on temperature is still being studied. Optical micro- and nanocavities are promising for a wide range of applications. They can be created within microwires and nanowires via distributed Bragg reflectors (DBR), i.e., periodic patterns of the refractive index in dielectric materials, acting as tunable mirrors. In this work, the effect of temperature on the anisotropic refractive index of β-Ga2O3n(λ,T) was analyzed with ellipsometry in a bulk crystal, and temperature-dependent dispersion relations were obtained, with them being fitted to Sellmeier formalism in the visible range. Micro-photoluminescence (μ-PL) spectroscopy of microcavities that developed within Cr-doped β-Ga2O3 nanowires shows the characteristic thermal shift of red-infrared Fabry-Perot optical resonances when excited with different laser powers. The origin of this shift is mainly related to the variation in the temperature of the refractive index. A comparison of these two experimental results was performed by finite-difference time-domain (FDTD) simulations, considering the exact morphology of the wires and the temperature-dependent, anisotropic refractive index. The shifts caused by temperature variations observed by μ-PL are similar, though slightly larger than those obtained with FDTD when implementing the n(λ,T) obtained with ellipsometry. The thermo-optic coefficient was calculated.

Ultrafast Optomechanical Strain in Layered GeS

Strong coupling between light and mechanical strain forms the foundation for next-generation optical micro- and nano-electromechanical systems. Such optomechanical responses in two-dimensional materials present novel types of functionalities arising from the weak van der Waals bond between atomic layers. Here, by using structure-sensitive megaelectronvolt ultrafast electron diffraction, we report the experimental observation of optically driven ultrafast in-plane strain in the layered group IV monochalcogenide germanium sulfide (GeS). Surprisingly, the photoinduced structural deformation exhibits strain amplitudes of order 0.1% with a 10 ps fast response time and a significant in-plane anisotropy between zigzag and armchair crystallographic directions. Rather than arising due to heating, experimental and theoretical investigations suggest deformation potentials caused by electronic density redistribution and converse piezoelectric effects generated by photoinduced electric fields are the dominant contributors to the observed dynamic anisotropic strains. Our observations define new avenues for ultrafast optomechanical control and strain engineering within functional devices.

Image recovery from unknown network mechanisms for DNA sequencing-based microscopy.

Imaging-by-sequencing methods are an emerging alternative to conventional optical micro- or nanoscale imaging. In these methods, molecular networks form through proximity-dependent association between DNA molecules carrying random sequence identifiers. DNA strands record pairwise associations such that network structure may be recovered by sequencing which, in turn, reveals the underlying spatial relationships between molecules comprising the network. Determining the computational reconstruction strategy that makes the best use of the information (in terms of spatial localization accuracy, robustness to noise, and scalability) in these networks is an open problem. We present a graph-based technique for reconstructing a diversity of molecular network classes in 2 and 3 dimensions without prior knowledge of their fundamental generation mechanisms. The model achieves robustness by obtaining an unsupervised sampling of local and global network structure using random walks, making use of minimal prior assumptions. Images are recovered from networks in two stages of dimensionality reduction first with a structural discovery step followed by a manifold learning step. By breaking the process into stages, computational complexity could be reduced leading to fast and accurate performance. Our method represents a means by which diverse molecular network generation scenarios can be unified with a common reconstruction framework.