Measured Intensity Distribution Research Articles

Evaluation of the X-ray/EUV Nanolithography Facility at AS through wavefront propagation simulations.

Synchrotron light sources can provide the required spatial coherence, stability and control to support the development of advanced lithography at the extreme ultraviolet and soft X-ray wavelengths that are relevant to current and future fabricating technologies. Here an evaluation of the optical performance of thesoft X-ray (SXR) beamline of the Australian Synchrotron (AS) and its suitability for developing interference lithography using radiation in the 91.8 eV (13.5 nm) to 300 eV (4.13 nm) range are presented. A comprehensive physical optics model of the APPLE-II undulator source and SXR beamline was constructed to simulate the properties of the illumination at the proposed location of a photomask, as a function of photon energy, collimation and monochromator parameters. The model is validated using a combination of experimental measurements of the photon intensity distribution of the undulator harmonics. It is shown that the undulator harmonics intensity ratio can be accurately measured using an imaging detector and controlled using beamline optics. Finally, the photomask geometric constraints and achievable performance for the limiting case of fully spatially coherent illumination are evaluated.

A deconvolution method for estimating proton range from measured intensity distribution of prompt gamma rays

This study developed a technique for proton range verification based on measuring the intensity distribution of prompt gamma rays (PGs) along the beam path in a target and applying a deconvolution method for retrieving the corresponding distribution of PG emissions. The end-of-range Rret=dγp + Rres can be estimated according to the peak position dγp of the retrieved PG emission and the residual range Rres determined from the cross section of the relevant nuclear reaction. A 30-MeV, 1.5-nA proton beam irradiated polyethylene (PE) and polymethyl methacrylate (PMMA) targets, and spatial intensity distributions were obtained by measuring 4.4- and 6.13-MeV PGs from a depth of 0 mm to 10 mm; to this end, a collimator–detector arrangement comprising a 2-inch NaI(Tl) detector and a 2-mm-wide slit collimator was used. Simulations were conducted to identify the profile of PG emissions in a target and to determine the detector response; subsequently, the performance of the developed deconvolution algorithm was validated, and the limits of this approach were investigated. The data from the 30-MeV proton beam experiment were used, and the ranges Rret were estimated to be 7.85 mm for the PE target and 7.07 mm for the PMMA target; these were considerably close to the range at 80% dose fall-off level R80 achieved using Monte Carlo simulations. Our results demonstrated that a NaI(Tl)-based system with a millimeter-wide collimator can effectively resolve the spatial variation of PG emissions along a proton beam’s path. The proposed deconvolution method exhibited strong potential for verifying proton ranges with a sub-millimeter-level accuracy in a relatively simple and reliable manner.

Planar and ridge waveguides prepared by ion implantation and femtosecond laser ablation in Er3+-doped germanate glasses

The work reports the hydrogen-ion implantation and femtosecond laser ablation in the Er3+-doped germanate glass to make planar and ridge optical waveguides. The energy is 400 keV and the dose is 6 × 1016 ion/cm2 for the ion implantation. The pulse energy is 3 μJ and the scanning speed is 50 μm/s for the femtosecond laser ablation. A microscope is used to observe the cross-section morphologies of the planar and ridge waveguides. A measurement of the near-field intensity distribution at 632.8 nm is performed by the end-face coupling system. The effective refractive indices of the propagation modes are recorded by the m-line technique. It’s the first time that a ridge waveguide is fabricated in the Er3+-doped germanate glass by the proton implantation and femtosecond laser ablation, which is with potential application as new integrated optical devices.

Optical properties of the proton-implanted waveguide in the Dy3+-doped Y3Al5O12 transparent ceramic

The high-quality waveguide structure in the Dy[Formula: see text]-doped Y3Al5O[Formula: see text] transparent ceramic is of significance for the application of integrated micro-light elements. However, there have been no reports on the preparation of optical waveguides by ion implantation in the Dy[Formula: see text]-doped Y3Al5O[Formula: see text] transparent ceramic. The work reports on the formation of optical planar waveguides by using the proton implantation in the Dy[Formula: see text]-doped Y3Al5O[Formula: see text] transparent ceramic. The acceleration energy and the dose of the protons are 400[Formula: see text]keV and [Formula: see text] ions/cm2, respectively. The structure of the fabricated waveguide is captured with the high-res/mag images by a metallurgical microscope. The dark-mode spectrum and the refractive index distribution are gained by the prism coupling system and the RCM software, respectively. The measurement and simulation of the near-field intensity distribution indicate the propagation of light field in the waveguide. The results are of potential to the compact devices in the photonics.

The Sound Field Intensity Distribution in the Deep Sea in the “Depth—Angle–Time” Phase Space

The transition from the traditional representation of the wave field in the vertical section of an underwater sound channel as a function of depth and time to the distribution of this field in the 3D phase space “depth–angle–time” is considered. For this purpose, the method of coherent states developed in quantum theory is used. The meaning of the proposed transition is that the field intensity distribution in the specified phase space is less sensitive to sound velocity fluctuations than in the original 2D depth–time space. This fact can be used in solving inverse problems. As an example, we consider the reconstruction of the coordinates of a source in a waveguide from measurements of the field intensity distribution of this source in phase space.

Virtual Laboratory for the Full-Field Goniophotometer of Luminaires

In order to solve the problem that students have insufficient understanding of the full-field goniophotometer instrumentation due to the expensive equipment and the high requirements of the experimental environment, virtual reality technology is used to complete the virtual laboratory of a light intensity distribution measurement of the full-field goniophotometer through Unity 3D. The virtual laboratory is designed for near-field measurement, mid-field measurement, and far-field measurement of light intensity. It combines 3D MAX and C# to realize the model building of laboratory, luminaire and full-field goniophotometer, the dynamic drawing of light distribution curves, and the simulation system can also be run on mobile phones. The experimental process is mainly through the manipulation of the virtual experimenter and each module to generate collision detection, pop-up buttons, and click on the button triggers an event and the operation prompt page appears. The light distribution curve is generated dynamically by reading and processing the IES file data to generate 3D coordinates. This virtual simulation laboratory is demonstrated on multiple platforms. The results proved that the virtual simulation restored the experimental process vividly and can complete the experimental teaching remotely.

Active learning-assisted neutron spectroscopy with log-Gaussian processes

Neutron scattering experiments at three-axes spectrometers (TAS) investigate magnetic and lattice excitations by measuring intensity distributions to understand the origins of materials properties. The high demand and limited availability of beam time for TAS experiments however raise the natural question whether we can improve their efficiency and make better use of the experimenter’s time. In fact, there are a number of scientific problems that require searching for signals, which may be time consuming and inefficient if done manually due to measurements in uninformative regions. Here, we describe a probabilistic active learning approach that not only runs autonomously, i.e., without human interference, but can also directly provide locations for informative measurements in a mathematically sound and methodologically robust way by exploiting log-Gaussian processes. Ultimately, the resulting benefits can be demonstrated on a real TAS experiment and a benchmark including numerous different excitations.

New biosensors detect light deep inside the brain

In recent years, the field of biosensors has seen significant advances in the development of fluorescent sensors, including quantum dots,1 upconversion nanoparticles,2 and fluorescent proteins,3 to monitor the generation of information in living systems. The fluorescence of these sensors can be observed by shining a laser at them. However, conventional fluorescent sensors are limited in their ability to image signals in deep tissues because most of the light is absorbed or scattered as it penetrates the tissue. To address this challenge, a team led by Jasanoff developed a novel sensor that converts light into a magnetic signal that is unaffected by absorption or scattering. This allows the response of the light detector to be visualized using magnetic resonance imaging (MRI; Figure 1).4 The development of this sensor has significant potential to improve our understanding of information processing in deep tissues. Schematic illustration of mapping light distribution in tissues using MRI-detectable photosensitive liposomes. To fabricate the photosensitive MRI probe, magnetic particles were encapsulated in light-responsive azobenzene-conjugated liposomes (called Light-LisNRs).5 By adjusting the composition and proportion of the lipid bilayer molecules, these liposome nanoparticles can switch from being permeable to being impenetrable, depending on the type of light exposure. This property allowed modulation of the MRI contrast of the Light-LisNRs and facilitated the optimization of the switchable longitudinal relaxation time (T1). Specifically, upon exposure to ultraviolet (UV) light, the Light-LisNRs became more permeable to water, resulting in a strong interaction between the magnetic particles and water and thereby producing strong MRI signals. Conversely, exposure to blue light caused the Light-LisNRs to become impermeable to water, resulting in the lack of a detectable MRI signal. The optimized Light-LisNRs could potentially be used to map light distribution in live animals. When these nanoparticles were injected into the living rat brain, they effectively diffused through the brain by convection, as evidenced by changes in the magnetic resonance signal. The probes exhibited exceptional light sensitivity, which could be demonstrated by changes in magnetic relaxation under blue and UV irradiation. Relative to the initial baseline, the probes showed significant differences in the mean MRI signals in response to UV and blue light, and the temporal characteristics of the light response observed during repeated photoperiods were consistent. The steady performance of Light-LisNRs in the rat brain suggests that they are suitable for the quantitative measurement of the light intensity distribution in tissues. In addition, the researchers used a hybrid model consisting of a beam spreading function combined with a homogeneous photon diffusion term to fit the experimental data and produced a quantitative map of the distribution of light emitted by the optical fiber implanted near the brain's striatum. These results highlight the potential of the optimized Light-LisNRs in mapping the distribution of light in living animals. In summary, this study describes the design of a novel sensor and its application elucidating light propagation in optically opaque environments. The sensor exploits the photomodulation of liposomal permeability to enhance the contrast produced by contrast agent molecules, leading to improved visualization in MRI. The results of this work demonstrate the potential of Light-LisNRs as a versatile tool for photon detection and highlight opportunities for further optimization through adjustments to action spectra, absorption cross sections, and contrast agent packaging parameters. The sensing approach outlined here holds promise for the future development of MRI probes capable of detecting stimuli beyond light, such as neurochemicals or other molecular species in the brain. In addition, the sensor may serve as a valuable tool for monitoring patients undergoing light-based therapies, including photodynamic therapy, which uses lasers to ablate cancer cells. Lei Luo: Conceptualization, Visualization, Writing - Original draft; Dandan Yang: Writing - Reviewing & Editing; Yu Yang: Conceptualization, Funding Acquisition, Writing - Reviewing & Editing. The authors declare no conflicts of interest.

Regression of high-dimensional angular momentum states of light

The orbital angular momentum (OAM) of light is an infinite-dimensional degree of freedom of light with several applications in both classical and quantum optics. However, to fully take advantage of the potential of OAM states, reliable detection platforms to characterize generated states in experimental conditions are needed. Here, we present an approach to reconstruct input OAM states from measurements of the spatial intensity distributions they produce. To obviate issues arising from intrinsic symmetry of Laguerre-Gauss modes, we employ a pair of intensity profiles per state projecting it only on two distinct bases, showing how this allows to uniquely recover input states from the collected data. Our approach is based on a combined application of dimensionality reduction via principal component analysis, and linear regression, and thus has a low computational cost during both training and testing stages. We showcase our approach in a real photonic setup, generating up-to-four-dimensional OAM states through quantum walk dynamics. The high performance and versatility of the demonstrated approach make it an ideal tool to characterize high-dimensional states in quantum information protocols.

Periodic band formation of Fe(OH)3 precipitate through reaction–diffusion–reaction processes

This paper reports a new class of periodic banding of Fe(OH)3 precipitate through reaction–diffusion–reaction (RDR) processes in agarose gel sandwiched between two metal rods (Ti and Fe) with cyclic alternating voltages. In the RDR processes, electrochemical reactions at metal rods to generate reactant ions, diffusion of the ions influenced by the electric field in the gel, and reactions of the ions to form precipitates were coupled to generate periodic bands of Fe(OH)3 precipitates at the cathode side. The banding morphologies, spatial Fe distribution, and microscopic morphologies of the precipitates were investigated by visual inspection, Fe Kα intensity distribution measurements, and scanning electron microscopy observations. The periodic banding strongly depended on the applied voltages, the periods for voltage alternation, the cycle number (NC), and the length of the gel column. Periodic bands resembling Liesegang bands were most clearly observed with high reproducibility for 50 mm gel columns under the applied cyclic alternating voltages of 3 and 1 V for 1 and 4 h, respectively. The number of the periodic bands formed in this system was generally given by NC—NC1 + 1, where NC1 is the cycle number where the first band emerges. These periodic bands contained significant amounts of Fe atoms that were almost uniformly distributed in the agarose gel, strongly supporting the formation of gelatinous Fe(OH)3 precipitates in the bands.

Encoding arbitrary phase profiles to 2D diffraction orders with controllable polarization states

Abstract Generating 2D diffraction orders with uniform or tailored intensity distribution is highly desired for various applications including depth perception, parallel laser fabrication and optical tweezer. However, previous strategies lack the abilities to tailor multiple parameters of output light in different diffraction orders simultaneously. While such ability plays an important role in achieving various different functionalities parallelly. Here, we demonstrate a method for encoding arbitrary phase profiles to different diffraction orders with controllable polarization states by applying double-phase method into elaborately designed metasurface. Sixteen independent holograms that generated by GS algorithm are successfully encoded into 4 × 4 uniformly distributed diffraction orders. Hence, the predefined holographic images can be observed at the Fourier plane. Meanwhile, the corresponding polarization states of different orders are manipulated according to their Fourier coefficients. For verifying the polarization state of each holographic image, we calculate the Stokes parameter of each order from measured intensity distributions in the experiment. The proposed method provides an effective way to tailor multiple properties of output diffraction orders. Meanwhile, it may promote the realization of achieving various functionalities parallelly such as spectral-polarization imaging or phase-polarization detection and enhance the capabilities of optical communication systems.

Measurement of the radius of curvature of a spherical surface based on the transport-of-intensity equation

The transport-of-intensity equation provides a new non-interferometric and non-iterative access to quantitative information about the phase of a light wave by measuring intensity distributions. This equation can be used to implement a simple and accurate spatial phase measurement for optical testing of spherical surfaces. The method requires only a CMOS camera, which records transverse field intensity distributions in several planes. Processing of experimental measurements with specialized software allows one to reconstruct the value of the radius of curvature of the spherical surface under test with high accuracy. The method is compared with measurements made by an interferometer, showing the difference between the values of the surface radius of curvature to be 0.01 % or less and indicating good agreement of the results.

Distribution of the Fraunhofer Diffraction Intensity by a Rectangular Slit Using a Razor Blade

This research was conducted by making a rectangular slit using a razor blade as a narrow gap in the Fraunhofer diffraction experiment. The intensity distribution measurement on the resulting diffraction pattern uses a voltage divider circuit. This circuit takes advantage of the nature of the LDR, which changes resistance when exposed to light. Experiments show that a diffraction pattern screen when a 560 nm coherent light passes through a narrow rectangular slit made of razor cut. We measured the narrow gap using a tracker application with the resulting gap size (0.3564 x 0.4677) mm. The ratio of the intensity distribution of the x-axis bright pattern on the Fraunhofer diffraction by a rectangular slit with slit size height x width = (0.4677 x 0.3564) mm from b = -5p to 5p (maximum 4, maximum 3, maximum 2, maximum 1, central maximum, maximum 1, maximum 2, maximum 3, maximum 4) is 0.000873; 0.000763; 0.005395; 0.020583; 1; 0.039658; 0.008088; 0.002554; 0.001218. The ratio of the intensity distribution of the y-axis bright pattern on the Fraunhofer diffraction by a rectangular slit with slit size height x width = (0.4677 x 0.3564) mm from g = -5p to 5p (maximum 4, maximum 3, maximum 2, maximum 1, central maximum, maximum 1, maximum 2, maximum 3, maximum 4) is 0.001890; 0.001469; 0.002447; 0.040516; 1; 0.037141; 0.006482; 0.001690; 0.000440. This study indicates that diffraction experiments and the measurement of the diffraction pattern’s intensity can be carried out with simple materials and equipment and can be used in the correct experiment.

Theoretical and Observational Evidence for Coriolis Effects in Coronal Magnetic Fields via Direct Current Driven Flaring Events

Abstract All stars produce explosive surface events such as flares and coronal mass ejections. These events are driven by the release of energy stored in coronal magnetic fields, generated by the stellar dynamo. However, it remains unclear if the energy deposition in the magnetic fields is driven by direct or alternating currents. Recently, we presented observational measurements of the flare intensity distributions for a sample of ∼105 stars across the main sequence observed by TESS, all of which exhibited power-law distributions similar to those observed in the Sun, albeit with varying slopes. Here we investigate the mechanisms required to produce such a distribution of flaring events via direct current energy deposition, in which coronal magnetic fields braid, reconnect, and produce flares. We adopt a topological model for this process, which produces a power-law distribution of energetic flaring events. We expand this model to include the Coriolis effect, which we demonstrate produces a shallower distribution of flare energies in stars that rotate more rapidly (corresponding to a weaker decline in occurrence rates toward increasing flare energies). We present tentative evidence for the predicted rotation-power-law index correlation in the observations. We advocate for future observations of stellar flares that would improve our measurements of the power-law exponents, and yield key insights into the underlying dynamo mechanisms that underpin the self-similar flare intensity distributions.

Single-scan multiplane phase retrieval with a radiation of terahertz quantum cascade laser

Terahertz phase retrieval from a set of axially separated diffractive intensity distributions is a promising single-beam computational imaging technique that ensures the obtention of high spatial resolutions and phase wavefronts, but remains restricted by time-consuming data acquisition processes. In this work, we have adopted an approach, relying on the radiation of a quantum cascade laser and the implementation of an express single-scan measurement of intensity distributions through the continuous on-the-go displacement of a high-sensitivity antenna-coupled microbolometer sensor array. In addition to the simplicity of this practical implementation and the minimization of measurement times, such an approach overcomes the problem of preliminary optimal selections of transverse intensity distributions used in the iterative phase retrieval algorithm and guarantees the required data diversity for high-quality wavefront reconstruction.

Coherent modulation imaging realized by coaxial shift of an amplitude mask

As a lensless imaging technology, coherent modulation imaging (CMI) can reconstruct the complex amplitude of the object from the measured intensity distribution. In this paper, a new CMI scheme is proposed. A random binary amplitude mask is introduced between the light source and the object. The incident light is modulated by the mask and the speckle field is generated to illuminate the object. The object can then be accurately recovered with the iterative phase retrieval algorithm by means of moving the mask several times in the axial direction and recording the corresponding diffraction pattern. Compared to the existing CMI schemes, the experimental system of the proposed method is simple and compact. No spatial light modulator or phase plate is required. Both numerical simulations and experiments are performed to verify the feasibility of the method. The influence of moving times, moving interval and pixel size of the mask on the reconstruction accuracy are analyzed in detail. In addition, the image registration encountered in the experiment is discussed.

Accurately quantifying the superposition state of two different Laguerre\u2013Gaussian modes with single intensity distribution measurement

We develop a method to quantify the superposition state of two different Laguerre–Gaussian modes. By analyzing the characteristics of the intensity distribution obtained in a single measurement, including the petal number, the position and value of the extremum intensity, one can quantify the angular momentum index, the radial node index and the superposition coefficient simultaneously. Experimentally, we measure a series of superposition states, whose angular momentum index ranges from −47 to 53, radial node index from 0 to 3 and superposition weight from 0.1 to 0.9. The average trace distance and the mean fidelity of these states are lower than 0.053 ± 0.001 and higher than 0.982 ± 0.002, respectively. Our method can further obtain the superposition coefficient compared with previous mode verification ones and can reduce the number of measurement settings compared with the traditional quantum state tomography, thus more applicable in practice.

Generation of one-dimensional high-order Hermite-Gaussian laser beams with large mode volume

Hermite-Gaussian (HG) beams have many important applications in the optical frontier, and the limited output power of the high-purity HG beams is partly due to the small gain volume of the mode. The commonly used off-axis end-pumped scheme offers a narrow gain volume whose diameter is about a hundred microns. In this work, a new method of generating the HG beams based on a slab resonator that has a large mode volume is proposed and experimentally demonstrated. According to the optical resonator theory, the intra-cavity modes in thickness and width direction of the slab resonator are restricted by inserting two size-adjustable apertures, respectively. The one-dimensional HG beam generation is mainly guaranteed by the size of the aperture along the thickness direction of the slab, which matches the diameter of the fundamental mode. The different order one-dimensional HG beams are obtained by refined intra-cavity mode modulation. Since the higher-order modes are less sensitive to the misalignment of the cavity mirror than the lower-order modes, and the manipulation of the modes-loss at different orders is achieved by combining the tilt control of the coupled output mirror and the size control of intra-cavity apertures. By adjusting the optical gain and loss in the resonant cavity, the single mode wins the competition of laser modes. Therefore, high-purity one-dimensional HG beams with 0 to 9 orders (HG<sub>00</sub> to HG<sub>09</sub>) are generated. The pump module is comprised of a two-dimensional laser diode array which offers face-pumping to the large surface of the slab, therefore the width of the mode volume is extended to several millimeters. By further incorporating the 100mm-level long slab, the total gain volume is much larger than the counterpart in the off-axis pumping scheme. In this work, the output power of the highest order HG<sub>09</sub> mode increases up to 244 mW. Owing to the large gain volume and uniform gain distribution caused by the face-pumped slab, the purity of high order HG modes is quite good. The correlation coefficient <inline-formula><tex-math id="M3">\begin{document}$ \rho $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="1-20221422_M3.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="1-20221422_M3.png"/></alternatives></inline-formula> between the measured intensity distribution and the theoretical value is larger than 0.95. The beam quality factor <inline-formula><tex-math id="M4">\begin{document}$ {M}^{2} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="1-20221422_M4.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="1-20221422_M4.png"/></alternatives></inline-formula> is also in good agreement with the theoretical one. Finally, a conversion from Hermite-Gaussian beams to the donut-shaped Laguerre-Gaussian beams is realized by using an astigmatic mode converter. Hopefully, power scaling of the HG beam output is also expected by employing cascaded slab amplifiers, and the approach in this paper provides a novel solution for generation of high power HG beams.

Measurement and Analysis Method of Light Intensity Distribution for Street Lamps

In order to evaluate the actual illumination effect of high-pressure sodium lamp on the road, a high-pressure sodium lamp illuminance test system is developed in this paper. In the testing of sodium lamp illumination, light intensity distribution is the most important evaluation index. It is also one of the most difficult physical parameters to test due to its large amount of data and high accuracy requirements. This thesis investigates a fast and high-precision testing method for light intensity distribution of high-pressure sodium lamps, so as to improve the measurement of sodium lighting. The system performs light intensity distribution testing in the laboratory, studies the test method of light intensity illuminance distribution of high-pressure sodium lamps, uses Matlab to optically model high-pressure sodium lamps, uses various methods to model the data obtained from the experiments, and analyzes the resulting illuminance data, the system is able to quickly test and evaluate the illuminance of high-pressure sodium lamps after installation.

Laser intensity distribution measurement method based on tomographic imaging

The predecessor of China Optics was China Optics and Applied Optics Digest, which was founded in 1985. At that time, it was the only retrieval journal in the field of optics in China. At the end of 2008, China Optics and Applied Optics Digest was renamed