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Focusing properties of spirally polarized sinh Gaussian beam
摘要： The tight focusing properties of spirally polarized sinh-Gaussian beam is investigated numerically by vector diffraction theory. Results show that the optical intensity in focal region of spirally polarized sinh Gaussian beam can be altered considerably by the beam order, relative waist width and the spiral parameter that indicates the polarization spiral degree of the spirally polarized sinh Gaussian beam. Many novel focal patterns including flattop profile, focal hole axially separated focal spots and focal spot with long focal depth are evolved considerably for the suitable beam parameters. We expect such a tunable focal patterns are useful for optical manipulation of micro particles.
关键词： Vector diffraction theory,spirally polarized sinh Gaussian beam,Focusing property
更新于2025-09-23 15:21:01
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Feasibility Analysis of Nanostructured Planar Focusing Collectors for Concentrating Solar Power Applications
摘要： Concentrating solar power (CSP) technology is an attractive approach to harvesting solar energy. Unlike photovoltaic (PV) technology, thermal storage is used in lieu of batteries for electricity generation. However, the cost of current collection optics in a CSP plant hampers commercial competitiveness with PVs and natural gas. The use of a planar focusing collector (PFC) could help reduce cost of materials, installation, and maintenance. We present two candidate PFC designs, one based on metasurfaces and the other a Fresnel-like model. We feed each design through the entire system process—design, fabrication, scalability, and techno-economic feasibility—and discuss the challenges met at each stage. Two-photon and nanoimprint lithography are used to make PFC molds and replicas, respectively. We find that the annual optical efficiency for the Fresnel-based PFC is ~40%--higher than the current 30% target for natural gas, thereby suggesting potential economic advantages in the market of industrial process heat.
关键词： Metasurface,Two-Photon Lithography,Concentrating Solar Power (CSP),Planar Focusing Collector (PFC),Nanoimprint Lithography
更新于2025-09-23 15:21:01
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Spatial characteristics of the truncated circular Airyprime beam
摘要： The circular Airyprime (CiAiP) beam is introduced in this paper. The spatial proprieties are well discussed and compared to the first order radial Laguerre–Gaussian beam LG10. The width, the divergence and the beam propagation factor are calculated based on the second order moments method, the latter is equal to M2 = 3.08. The free propagating CiAiP beam exhibits an unexpected non-diffracting character, it doesn’t spread through propa- gation. The on-axis intensity of the focused circular Airyprime beam is also explored, it exhibits a dual focus corresponding to two on-axis intensity maxima, it could be modified under diffraction using a hard circular aperture. The latter presents a cheap beam shaper, it is shown that a hard aperture could transform an input circular Airyprime beam into per- fect ringed beam, a perfect Gaussian beam and a top hat beam. By combining the axial and the transversal behavior of a truncated circular Airyprime beam for a particular aperture diameter a perfect cylindrical optical bottle beam is obtained. The present work could be of big interest in the field of structured light.
关键词： Beam shaping,Propagation and focusing,Circular Airyprime beam
更新于2025-09-23 15:21:01
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FIBRE BRAGG GRATING SENSOR SYSTEM FOR TEMPERATURE APPLICATION
摘要： A practical pass-through type fibre Bragg grating (FBG) temperature sensor system have been designed and experimentally investigated. The performance of FBG was evaluated with the varying of focusing elements in harsh environments, under direct sunlight. The sensor head of FBG was designed to be focused with convex and hand lens. Results shows that the Bragg wavelength shift, ????? increase proportionally with the temperature for both systems. The sensitivities of FBG were recorded to be 0.0107 and 0.0122 nm °C-1 for the system where convex and hand lens applied to the FBG’s sensor head respectively.
关键词： focusing element,temperature sensor,Fibre Bragg grating,Bragg wavelength shift
更新于2025-09-23 15:21:01
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Universal Behavior of Modulationally Unstable Media
摘要： Evidence is presented of universal behavior in modulationally unstable media. An ensemble of nonlinear evolution equations, including three partial differential equations, an integro-differential equation, a nonlocal system, and a differential-difference equation, is studied analytically and numerically. Collectively, these systems arise in a variety of applications in the physical and mathematical sciences, including water waves, optics, acoustics, Bose--Einstein condensation, and more. All these models exhibit modulational instability, namely, the property that a constant background is unstable to long-wavelength perturbations. In this work, each of these systems is studied analytically and numerically for a number of different initial perturbations of the constant background, and it is shown that, for all systems and for all initial conditions considered, the dynamics gives rise to a remarkably similar structure comprised of two outer, quiescent sectors separated by a wedge-shaped central region characterized by modulated periodic oscillations. A heuristic criterion that allows one to compute some of the properties of the central oscillation region is also given.
关键词： nonlinear evolution equations,modulational instability,focusing media,nonlinear Schr\"odinger systems
更新于2025-09-23 15:21:01
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Quality improvement of acoustic-resolution photoacoustic imaging of skin vasculature based on practical synthetic-aperture focusing and bandpass filtering
摘要： We previously developed a compact acoustic-resolution photoacoustic (PA) imaging system with optical ?ber-based illumination, by which blood vessels in the rat skin were visualized in vivo. However, there were issues to be improved in the imaging characteristics: blurring in the out-of-focus region of the ultrasound sensor and degraded resolution due to low-frequency components in the PA signals. These are common limitations in acoustic-resolution PA imaging methods. In this study, we attempted to solve these problems by introducing signal processing methods based both on the synthetic-aperture focusing technique, which was applied only to signals in the detection zone of the sensor in the horizontal direction that was determined in advance in a phantom study, and on digital acoustic signal ?ltering with three speci?c frequency bands. Ex vivo and in vivo PA imaging of blood vessels in the rat skin and subcutaneous tissue showed the validity of the present signal processing methods.
关键词： photoacoustic imaging,bandpass ?ltering,skin vasculature,synthetic-aperture focusing
更新于2025-09-23 15:21:01
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A remote laser focusing system with spatial light modulator
摘要： This paper designs a remote laser focusing system (RLFS) based on spatial light modulator (SLM). In this system, the SLM serves as an active optical element that modulates the wavefront of the laser beam, causing variation in beam transmission. Theoretical analysis shows that a reflective SLM can compensate the residual aberrations at different operating distances, enabling the accurate focusing of targets without sacrificing the energy convergence. Based on optical design software, the geometrical parameters were optimized for the presented system through simulation. Finally, experimental demonstration and error analysis were carried out. The results show that the proposed RLFS-SLM is more stable and capable for controlling energy convergence than the traditional mechanical RLFS. Our system provides a desirable tool for high-energy laser applications.
关键词： Remote laser focusing (RLF),Wavefront modulation,Spatial light modulator (SLM),Mechanical focusing
更新于2025-09-23 15:19:57
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Polarization-enabled tunable focusing by visible-light metalenses with geometric and propagation phase
摘要： Flat metalenses with tunable focal length have wide applications in modern optical systems with high integration requirement. Here, by combining propagation phase and geometric phase, we numerically realize a metalens with a tunable focal length by controlling the polarization state of incident light. The tuning range can be as large as 15λ at the designer wavelength. Furthermore, the tunable performance can operate at the entire visible band with an ef?ciency over 35%. We believe that the proposed polarization-enabled tunable focusing metalens will ?nd signi?cant applications in imaging and sensing applications.
关键词： tunable focusing,metalens,polarization state,geometric phase
更新于2025-09-23 15:19:57
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[Laser Institute of America ICALEO?? 2017: 36th International Congress on Applications of Lasers & Electro-Optics - Atlanta, Georgia, USA (October 22a??26, 2017)] International Congress on Applications of Lasers & Electro-Optics - Laser direct writing lithography for rapid fabrication on non-planar surfaces
摘要： A modified laser direct writing lithography system with dynamic focusing is presented. This improved system can realize rapid fabrication on non-planar surfaces with large curvature and it offers new possibilities for fabricating micro-patterns on curved surfaces in an easy and fast way. A dynamic focusing lens group which is driven by a linear voice coil motor is introduced and it can rapidly control the laser spot to focus on the curved surface when processing in real-time. The focus range is almost 10 mm and it can be larger when working with the z-stage. The mathematic expression of dynamic focusing is deduced and the corresponding experiment results agree with the numerical analysis, which shows the practicability of the system. The effects of slopes with different tilted angles on exposure linewidth are studied. Finally, a concentric-circle grating is fabricated on a convex substrate with a diameter of 30 mm and a radius of curvature of 19.918 mm. The grating has homogeneous linewidth of 10 μm and line space of 20 μm, and the total processing time is within 40s. This technique can greatly improve the efficiency and has great potentials, such as rapid fabrication of diffractive optical elements (DOEs) or microelectromechanical systems (MEMS) on arbitrary 3D curved surfaces.
关键词： non-planar surfaces,dynamic focusing,micro-patterns,rapid fabrication,laser direct writing lithography
更新于2025-09-23 15:19:57
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Effect of obliquely external magnetic field on the intense laser pulse propagating in plasma medium
摘要： In this paper, self-focusing of intense laser pulse propagating along the obliquely external magnetic field on the collisional magnetoactive plasma by using the perturbation theory have been studied. The wave equation describing the interaction of intense laser pulse with collisional magnetoactive plasma is derived. In addition, employing source-dependent expansion (SDE) method, the analysis of the laser spot-size is discussed. It is shown that with increasing of the angle in obliquely external magnetic field, the spot-size of laser pulse decreases and as a result laser pulse becomes more focused. Furthermore, it is concluded that the self-focusing quality of the laser pulse has been enhanced due to the presence of obliquely external magnetic field in the collisional magnetoactive plasma. Besides, it is seen that with increasing of ν/?0, the laser spot-size reduces and subsequently the self-focusing of the laser pulse in plasma enhances. Moreover, it is found that changing the collision effect in the magnetoactive plasma leads to increases of self-focusing properties.
关键词： obliquely external magnetic field,Collisional magnetoactive plasma,source-dependent expansion method,laser spot-size,self-focusing
更新于2025-09-23 15:19:57