Beam Interference Research Articles

Design on constant coherent light intensity fringe locking system for scanning beam interference lithography

Design on constant coherent light intensity fringe locking system for scanning beam interference lithography

A hybrid method of phase shifting interferometry and optical tomographic techniques for determining the optical anisotropy of grafted nylon-6 fibres with PMMA polymer

A method combining the phase shifting interferometry PSI and optical tomographic techniques for detecting the optical properties of grafted nylon-6 fibres is introduced. The method is capable of detecting the optical anisotropy and morphological properties of the sample at same time for the same region of the tested sample. The effect of grafting of nylon-6 with poly(methyl methacrylate), PMMA, polymer on their optical and morphological properties was investigated. The two-beam Pluta polarising interference microscope attached to a fibre rotation device with the suggested method were used to produce both computed tomographic data for morphological characterisation of the grafted fibre and interferometric measurements of birefringence values along the fibre axis. A blank sample of nylon-6 fibre was used to confirm the impact of grafting process with the PMMA polymer on the optical and structural properties of the nylon-6 fibres. Two -beam interference patterns are included for illustration.

Radiation Path of Diurnal Internal Tides in the Northwestern Pacific Controlled by Refraction and Interference

AbstractThe diurnal internal tides contribute nearly a quarter of global baroclinic tidal energy. However, their roles in shaping the spatiotemporal inhomogeneity of the tidal energy field are not well known. Based on observation‐supported numerical simulation and theoretical analyses, we clarify the combined and relative contributions of β refraction, subtidal circulation refraction and multiwave interference to the long‐range radiation and dissipation maps of diurnal internal tides in the northwestern Pacific. The diurnal tidal beams primarily emanate from the Luzon Strait (LS) and Talaud‐Halmahera Passage (THP). The β refraction shifts the mean path of the LS tidal beam equatorward by ∼40° when it arrives at the deep basin. This is consistent with previous altimetric observations. A second refraction effect by subtidal circulation with seasonal variability deflects the mean beam path by ∼10°. Multiwave interference of the tidal beams from the LS and THP further enhances the inhomogeneous pattern. It enhances or reduces the energy fluxes of the tidal beams with distinct vertical structures in the western Mariana basin. A modified line‐source model and theoretical ray‐tracing analysis explain the effects of refraction and interference well. The internal tidal dissipation map in the deep basin coincides well with the inhomogeneous and spreading radiation paths. The characterization of the world's most energetic diurnal internal tides in the northwestern Pacific could improve our understanding of global baroclinic tidal energy redistribution and tidal mixing geography.

Combined DNA Damage Repair Interference and Ion Beam Therapy: Development, Benchmark, and Clinical Implications of a Mechanistic Biological Model

Our purpose was to develop a mechanistic model that describes and predicts radiation response after combined DNA damage repair interference (DDRi) and particle radiation therapy. The heterogeneous dose distributions of protons and 4He ions were implemented into the "UNIfied and VERSatile bio-response Engine" (UNIVERSE). Predictions for monoenergetic and mixed fields over clinically relevant dose and linear energy transfer range were compared with experimental in vitro survival data measured in this work as well as data available in the literature, including different cell lines and DDR interferences. Ultimately, UNIVERSE predictions were investigated in a patient plan. UNIVERSE accurately predicts survival of cell lines with and without DDRi in clinical settings of ion beam therapy based only on 3 parameters derived from photon data. With increasing dose or linear energy transfer, the radiosensitizing effect of DDRi decreases, resulting in diminished relative biological effect of ion beam radiation for cells subjected to DDRi in comparison to cells that are not. Similar trends were observed in patient plan recalculations; however, this analysis also suggests that DDRi+particle radiation therapy may better preserve the therapeutic window in comparison to DDRi+photon radiation therapy. The presented framework represents the first mechanistic model of combined DDRi and particle radiation therapy comprehensively benchmarked in clinically relevant scenarios and a step toward more personalized treatment. It reveals potential differences between DDRi+photon radiation therapy versus DDRi+particle radiation therapy, which have not been described so far. UNIVERSE could aid in appraising the clinical viability of combined administration of radiosensitizing drugs and charged particle therapy, as well as the identification of patients with known DDR deficiencies in the tumor who might benefit from therapy with light ions, freeing limited space at heavy ion therapy centers.

Active control technology of a diffraction grating wavefront by scanning beam interference lithography.

To fabricate plain holographic gratings with high wavefront quality and to obtain the wavefront required in varied line-space grating, an active control technology of a diffraction grating wavefront by modulating the phase distribution of the scanning-beam interference lithography system was proposed. Sinusoidal wavefront control is simulated, and the controlled wavefront being almost the same as the target wavefront. A photoresist grating was fabricated whose surface is uniform and the wavefront is ideally sinusoidal. The theoretical analysis and experimental results confirmed that the wavefront of the diffraction grating can be actively controlled by modulating the phase distribution of the scanning-beam interference lithography system.

Splitting, generation, and annihilation of phase singularities in non-coaxial interference of Bessel–Gaussian beams

Based on the non-coaxial interference of Bessel–Gaussian (BG) beams, a new complex-structured light field is formed. By varying the off-axis distance, phase difference, separation angle, and topological charges (TCs) of the component beams, we observed the splitting, generation, and annihilation of phase singularities. The net TCs of the composite light field is not always equal the sum of the TCs of the original beams. Different from the general single-ringed vortex beams, because BG beams have infinitely many rings, alternately positive and negative unit vortex chains arise in the interference region. Furthermore, the edge dislocations are unstable, by modulating the phase difference and separation angle, we observe controllable transitions between edge dislocations and vortex singularities. Beyond providing an effective method for studying composite vortex beam interference, our results are significant for laser calibration and complex particle manipulation.

Non-destructive evaluation of internal cracks in glass fiber-reinforced polymers using digital shearing interferometry

Shearography is one of the advanced methods of non-destructive techniques based on the interference of laser beams that have been reflected from the surface of the specimen. This method, which has high speed and accuracy, can evaluate the displacement derivative on the sample surface at once. In this paper, the possibility of sub-surface cracks detection with different lengths and angles in composite samples was investigated by shearography method and thermal stimulation system. For this purpose, in composite samples, controlled cracks were created with different lengths and angles. After calibration of the performance of the shearography setup, two heat sources of radiation were used to load samples. Loading quantity, the amount and direction of the shear, the cracks length, and their angles were chosen as the studied parameters. The results of this paper showed that the optimum loading amount plays a more critical role in the quality of the results than shear amount, and this value is related to the materials of the samples. To achieve the best results in crack detection on the selected specimens, optimum thermal loading was obtained between 12 and 15 seconds from in front of the specimen. Also, the optimum shear amount in the composite specimens was estimated at about 0.1 image width recorded by the camera. With the optimized values, all sub-surface cracks were identified.

The interference properties of single-photon vortex beams in Mach–Zehnder interferometer

Orbital angular momentum (OAM) is a unique degree of freedom for vortex beams. It is very important to study the interference of vortex beams carrying OAM in quantum information science. In this paper, we study the interference phenomenon of vortex beams based on a stable and adjustable Mach–Zehnder (MZ) interferometer using a laser and a single-photon as light sources. Furthermore, we also show the evolution of the different initial states in the MZ interferometer, and the interferograms of initial states vary with changing the interferometer phase. Our research not only helps us to understand the special phenomenon of OAM in the MZ interferometer but also provides some theoretical and experimental support for OAM as a quantum information carrier.

Analysis and design of fringe phase control system for scanning beam interference lithography

Scanning beam interference lithography (SBIL) is an advanced technology developed for manufacturing large-area diffraction grating at a nanometer-scale phase accuracy. To withstand environmental disturbances and maintain the interference fringes still relative to the substrate, SBIL requires high-precision phase control. We proposed a fringe phase control system with homodyne detection for SBIL. First, a homodyne detector is employed to achieve high-precision phase measurement, while ensuring the simplicity of the optics and high laser utilization. The time-varying nonlinear error in the measurement results is corrected by a dynamic ellipse fitting method. To reduce the latency effect, a lead controller is designed using the root locus method based on the model identification result. The lead controller considerably increases the control bandwidth while ensuring a sufficient phase margin, which further suppresses disturbances and stabilizes the interference fringes to within ∼1 / 60 of the fringe period. Wide-range phase tracking for perpendicular scanning with high accuracy is also verified through an experiment.

Design and analysis of all optical 2 × 4 decoder based on kerr effect and beams interference procedure

Design and analysis of all optical 2 × 4 decoder based on kerr effect and beams interference procedure

Manipulation of femtosecond laser multi-filament array by spatiotemporal phase modulation

Unstable random multi-filament distribution by free propagation of high power femtosecond laser in transparent medium is unfavorable to the filamentation applications and controllable regular multi-filament array is desired. Here, we present a novel method to modulate the spatial distribution of multi-filament by a phase plate-assisted interference of two delayable femtosecond laser pulses. The experimental results show that regular femtosecond laser multifilament array can be realized and the array can be conveniently converted from one patten to another with the varying of the delay of the two laser pulses. It is found that the spatiotemporal phase variation of the interference beam is responsible for this control process. This work provides a new way to regulate the spatial distribution of multi-filament by simply varying relative phase of the two laser beams and holds a great flexibility for a filament array in many applications.

Concise and efficient direct-view generation of arbitrary cylindrical vector beams by a vortex half-wave plate

A concise, efficient, and practical direct-view scheme is presented to generate arbitrary cylindrical vector (CV) beams, including CV beams, vortex beams, and cylindrical vector vortex (CVV) beams, by a vortex half-wave plate (VHP). Six kinds of first-order and other high-order CV beams, such as azimuthally polarized (AP) beams, antivortex radial polarization mode beams, and three-order AP beams, are formed by simply rotating a half-wave plate. The Stokes parameters and double-slit interference of multitype CV beams are investigated in detail. The polarization parameters, including degree of polarization, polarization azimuth, and ellipticity, are obtained, which demonstrates the efficient generation of CV beams. In addition, the double-slit interference experiment is introduced in the setup, and fringe misplacement and tilt appear for CVV beams, in which the misplacement number M is 2 P + 1 for P ≤ 2 and 2 P − 1 for P ≥ 3 , where P is the polarization order number, and the fringe tilt offset is positively related to the topological charge number l of CVV beams. In addition, new types of VHPs can be formed by cascading two or more VHPs when the types of available VHPs are limited, assisting in more flexible generation of multitype CV beams. It is experimentally demonstrated that arbitrary CV beams with high quality are effectively achieved by the proposed setup, and the double-slit interference method can be utilized to determine and analyze CV beams rapidly and concisely by practical performance, which shows the potential to be implemented as a commercial device.

A polarization-switch effect of silicon crystals under multiple-beam diffraction geometry

On the basis of rigorous dynamical-theory calculations, a complete X-ray polarization-switch effect of silicon crystals at the exact multiple-beam diffraction condition is demonstrated. The underlying physical mechanism of this unique phenomenon can be revealed using a simple multiple-wave propagation and interference model. The constructive and destructive interference of the multiple detoured-diffraction beams along the direction of the primary diffracted beam directly leads to the complete polarization switch. This phenomenon can be realized using both synchrotron and laboratory X-ray sources at many discrete wavelengths, and used to design a novel crystal-based polarizer to achieve a 90° polarization rotation.

A Design of Multi-element Anti-jamming GPS Antenna

Background: With the development of the application of GPS satellite, the requirement of anti-jamming and integration for navigation receiving terminal is gradually raised. In terms of anti-jamming performance, because the satellite signal arrives at the ground with weak intensity and is vulnerable to electromagnetic interference, the positioning results are not available. Objective: Therefore, in complex electromagnetic environment, the anti-jamming navigation receiving terminal is needed, and the interference nulling or beam pointing can be achieved by using multi- element antenna array with anti-jamming algorithm. Methods: Accordingly to requirements, the development trend of navigation receiving terminal is from single mode to multi-mode and miniaturization. A miniaturized 7-element anti-jamming antenna array is proposed. It mainly aims at GPS L1 and L2 frequency points. All elements adopt ceramic substrate microstrip antenna. The array elements adopt laminated design to effectively reduce the antenna aperture. The spacing between elements at two frequency points is not greater than half wavelength, which can ensure the back-end anti-jamming algorithm performance, and its performance and characteristics are verified through related experiments and simulations. Results: Anti-jamming algorithm performance, and its performance and characteristics are verified through related experiments and simulations. Conclusion: The designed multi-element antenna can be used in the anti-jamming application.

Method for exposure dose monitoring and control in scanning beam interference lithography.

To improve grating manufacturing process controllability in scanning beam interference lithography (SBIL), a novel method for exposure dose monitoring and control is proposed. Several zones in a narrow monitoring region are fabricated on a grating substrate by piecewise uniform scanning. Two monitoring modes are given based on the different widths of the monitoring region. The monitoring curve of the latent image diffraction efficiency to scanning velocity is calculated by rigorous coupled wave analysis. The calculation results show that the exposure dose in SBIL can be monitored by the shape change of the monitoring curve, and an optimized scanning velocity can be selected in the monitoring curve to control the exposure dose.

Two-atom interferometer

This Letter presents a nonclassical mechanism of two-atom interferometry. The two-atom interferometer introduces two different yet indistinguishable alternatives for randomly paired atoms to create a joint atom-detection event. The superposition of two-atom amplitudes yields two-atom interference with peculiar features which outshine the classic atom interferometer: (1) two-atom interference is still observable when the time delay of the interferometer is greater than the coherence time of the atom beam and (2) two-atom interference may eliminate phase noises, including background, variation, turbulence, and Raman laser induced phase noises, thereby allowing for higher sensitivity and stability sensing than is achievable by classic atom interferometers. These features are crucial in high sensitivity-accuracy acceleration and rotation measurements. The presented concept and mechanism of two-atom interference can be adapted to other matter-wave interferometers, such as two-neutron interferometer and two-electron interferometer.

Optimising backscatter from multiple beam interference.

Optical sensing applications are usually reliant on the intensity of the measured signal. For remote sensing applications where a target is probed with a laser beam, the sensitivity will be limited by the amount of backscattered light returned from the target to the detector. We demonstrate a method of increasing the signal returned to the detector by illuminating the target with a number of independently controlled beams, where both the position and phase are optimised. We show an improvement in the backscattered signal that is proportional to the number of beams used. The method is demonstrated within a laser microphone, measuring audio signal due to vibrations in surfaces, showing a significant improvement in the signal-to-noise of the measurement.

Radius of curvature of spherical wave measurement based on vortex beam interference

We proposed a new method for the radius of curvature (ROC) of spherical wave measurement based on vortex beam interference and Fermat's spiral fitting, which can not only provide a large measurement range but also have high precision. Theoretical analysis showed that the maximum distribution of the interference light intensity is in accordance with the Fermat's spiral, and the spiral coefficient is proportional to the ROC of spherical wave. For a concave spherical mirror with a ROC of 899.89mm and a convex spherical lens with a ROC of 59.99mm, the average measurement error of five measurements are 0.080% and 0.083%, respectively. Controlled experiments showed that, our proposed method has a higher measurement accuracy and a larger measurement range than Newton's rings method, it has almost equal measurement accuracy for large and small ROC. This research provides a theoretical basis for the development of a ROC measurement system with large measurement range and high precision.

Cylindrical Focused Laser Differential Interferometer

A novel configuration of focused laser differential interferometry (FLDI) was developed, simulated, and tested. The new configuration is referred to as cylindrical FLDI or CFLDI. Using cylindrical lenses in place of standard lenses changes the three-dimensional shape of the focusing beam from a cone shape for FLDI to a triangular sheet for CFLDI, allowing for probing of flat-plate boundary layers closer to the wall. The beam propagation and interference pattern were modeled to determine the transfer functions for one-dimensional sinusoidal disturbances of varying wavelength () and varying spanwise thickness () of the tested area. CFLDI was employed to measure the density perturbations in supersonic blowdown wind tunnel SBR-50 at the University of Notre Dame with the test section width of 0.076.2 m. It was determined that the CFLDI system sufficiently filtered the sidewall boundary layers to measure the spectra of density fluctuations in a plane wall boundary layer. However, accurate measurements of the density disturbances in the freestream flow must account for the contribution of the sidewall boundary layers. This serves as an initial validation of the CFLDI maintaining spatial filtering similar to a regular FLDI.

A design for an ultrafast all-optical full subtractor based on two-dimensional photonic crystals

A novel passive all-optical full subtractor device is realized using a two-dimensional (2-D) photonic crystal. The proposed structure is realized using the concept of beam interference in a sequence of T- and Y-shaped line-defective waveguide structures made of a linear material such as silicon with air as the background medium. The major advantage of this design approach is the avoidance of nonlinear materials and semiconductor optical amplifiers. In addition to the actual input ports, some reference input ports are also utilized to achieve the desired full subtractor functionality. The different input combinations to the full subtractor are given and optimized via several simulations. The full subtractor functionality is validated using the Opti-FDTD tool. The simulation results for the full subtractor are supported by the E-field distribution and power analysis at the output ports for different input logic values at a wavelength around 1550 nm. The proposed structure shows a fast response time of 0.16 ps, a bit rate of 6.25 Tbps, and a contrast ratio of 3.97 dB, and occupies an area of 465 µm2.