- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Máscara espectrográfica para registro digital de espectros de fontes brilhantes
摘要： In this work we present schematic diagrams for the construction of a spectrographic mask attachable to a camera objective in order to capture spectra using simple CD or DVD gratings. The mask is made of two parts: an adapter ring and elbow-shaped blockage for suitable registration of spectra in the lab and outdoors. By using a free software, we analyze and discuss the calibration of the wavelength scale of the solar spectrum, which allows us to identify many chemical elements in it. In the conclusion, we further discuss some interesting projects to be carried out by students using the idea.
关键词： Spectrum,Spectroscope,Image Processing,Diffraction Gratings,Optics
更新于2025-09-09 09:28:46
-
Extreme-ultraviolet refractive optics
摘要： Refraction is a well-known optical phenomenon that alters the direction of light waves propagating through matter. Microscopes, lenses and prisms based on refraction are indispensable tools for controlling light beams at visible, infrared, ultraviolet and X-ray wavelengths1. In the past few decades, a range of extreme- ultraviolet and soft-X-ray sources has been developed in laboratory environments2–4 and at large-scale facilities5,6. But the strong absorption of extreme-ultraviolet radiation in matter hinders the development of refractive lenses and prisms in this spectral region, for which reflective mirrors and diffractive Fresnel zone plates7 are instead used for focusing. Here we demonstrate control over the refraction of extreme- ultraviolet radiation by using a gas jet with a density gradient across the profile of the extreme-ultraviolet beam. We produce a gas- phase prism that leads to a frequency-dependent deflection of the beam. The strong deflection near to atomic resonances is further used to develop a deformable refractive lens for extreme-ultraviolet radiation, with low absorption and a focal length that can be tuned by varying the gas pressure. Our results open up a route towards the transfer of refraction-based techniques, which are well established in other spectral regions, to the extreme-ultraviolet domain.
关键词： lens,refractive optics,extreme-ultraviolet,prism,gas jet
更新于2025-09-09 09:28:46
-
Bessel beam expansion of linear focused ultrasound
摘要： Previous work on scattering by Bessel beams shows that expansion of incident sound fields in term of these beams has application to scattering [P. L. Marston, J. Acoust. Soc. Am. 122, 247–252 (2007)]. In this work, an expression for the expansion coefficients of propagating, axisymmetric, sound fields are derived. In this paper, this expression is applied to a linear focused axisymmetric sound field and is expanded in terms of Bessel beam components. This is done for focused beams radiated from a spherical cap source. A physical optics model is applied to sound propagation close to the source to facilitate the calculation of the Bessel beam expansion coefficients. This type of model is useful for focused scattering [P. L. Marston and D. S. Langley, J. Acoust. Soc. Am. 73, 1464–1475 (1983)]. Once the expansion coefficients are found, the sound field can be evaluated by superposition. The model agrees approximately with Chen, Schwarz, and Parker [J. Acoust. Soc. Am. 94, 2979–2991 (1993)] and O’Neil [J. Acoust. Soc. Am. 21, 516–526 (1949)] on axis and with direct integration of a Kirchhoff integral both on and off axis. This type of expansion will have applications to scattering problems. VC 2018 Acoustical Society of America. https://doi.org/10.1121/1.5080602
关键词： physical optics model,Kirchhoff integral,linear focused ultrasound,scattering,Bessel beam
更新于2025-09-09 09:28:46
-
Tailored long range forces on polarizable particles by collective scattering of broadband radiation
摘要： Collective coherent light scattering by polarizable particles creates surprisingly strong, long range inter-particle forces originating from interference of the light scattered by different particles. While for monochromatic laser beams this interaction decays with the inverse distance, we show here that in general the effective interaction range and geometry can be controlled by the illumination bandwidth and geometry. As generic example we study the modi?cations inter-particle forces within a 1D chain of atoms trapped in the ?eld of a con?ned optical nano?ber mode. For two particles we ?nd short range attraction as well as optical binding at multiple distances. The range of stable distances shrinks with increasing light bandwidth and for a very large bandwidth ?eld as e.g. blackbody radiation. We ?nd a strongly attractive potential up to a critical distance beyond which the force gets repulsive. Including multiple scattering can even lead to the appearance of a stable con?guration at a large distance. Such broadband scattering forces should be observable contributions in ultra-cold atom interferometers or atomic clocks setups. They could be studied in detail in 1D geometries with ultra-cold atoms trapped along or within an optical nano?ber. Broadband radiation force interactions might also contribute in astrophysical scenarios as illuminated cold dust clouds.
关键词： self-ordering,optical binding,fiber optics
更新于2025-09-09 09:28:46
-
Dependence of the saturation intensity with the dopant ion concentration: Application to the study of nonlinear optical properties in Nd-doped phosphate glass matrix
摘要： The effect of ion concentration on the saturation intensity, Is, was investigated and its effect on the evaluation of nonlinear optical properties was discussed. The suggested experimental approach points out a more accurate way to obtain Is. The value of Is in the limit of low concentration and low incident intensity was obtained as (266 ± 14) KW/cm2 at 514 nm. Through time resolved Z-scan the nonlinear refractive index, n2, of Nd-doped phosphate glass could be evaluated for different Nd concentrations. Finally, the n2 and Is values were used to determine the polarizability difference between ground and excited states as Δα = (2.6 ± 0.2) × 10?26 cm3, for Nd3+ ions in this glass matrix.
关键词： Nonlinear optics,Optical materials,Amorphous materials
更新于2025-09-09 09:28:46
-
Meta-optics and bound states in the continuum
摘要： We discuss the recent advances in meta-optics and nanophotonics associated with the physics of bound states in the continuum (BICs). Such resonant states appear due to a strong coupling between leaky modes in optical guiding structures being supported by subwavelength high-index dielectric Mie-resonant nanoantennas or all-dielectric metasurfaces. First, we review brie?y very recent developments in the BIC physics in application to isolated subwavelength particles. We pay a special attention to novel opportunities for nonlinear nanophotonics due to the large ?eld enhancement inside the particle volume creating the resonant states with high-quality (high-Q) factors, the so-called quasi-BIC, that can be supported by the subwavelength particles. Second, we discuss novel applications of the BIC physics to all-dielectric optical metasurfaces with broken-symmetry meta-atoms when tuning to the BIC conditions allows to enhance substantially the Q factor of the ?at-optics dielectric structures. We also present the original results on nonlinear high-Q metasurfaces and predict that the frequency conversion ef?ciency can be boosted dramatically by smart engineering of the asymmetry parameter of dielectric metasurfaces in the vicinity of the quasi-BIC regime.
关键词： bound states in the continuum,high-Q resonances,nanophotonics,nonlinear nanophotonics,BICs,dielectric metasurfaces,meta-optics
更新于2025-09-09 09:28:46
-
Human Retinal Pigment Epithelium: In Vivo Cell Morphometry, Multispectral Autofluorescence, and Relationship to Cone Mosaic
摘要： PURPOSE. To characterize in vivo morphometry and multispectral autofluorescence of the retinal pigment epithelial (RPE) cell mosaic and its relationship to cone cell topography across the macula. METHODS. RPE cell morphometrics were computed in regularly spaced regions of interest (ROIs) from contiguous short-wavelength autofluorescence (SWAF) and photoreceptor reflectance images collected across the macula in one eye of 10 normal participants (23–65 years) by using adaptive optics scanning light ophthalmoscopy (AOSLO). Infrared autofluorescence (IRAF) images of the RPE were collected with AOSLO in seven normal participants (22–65 years), with participant overlap, and compared to SWAF quantitatively and qualitatively. RESULTS. RPE cell statistics could be analyzed in 84% of SWAF ROIs. RPE cell density consistently decreased with eccentricity from the fovea (participant mean 6 SD: 6026 6 1590 cells/mm2 at fovea; 4552 6 1370 cells/mm2 and 3757 6 1290 cells/mm2 at 3.5 mm temporally and nasally, respectively). Mean cone-to-RPE cell ratio decreased rapidly from 16.6 at the foveal center to <5 by 1 mm. IRAF revealed cells in six of seven participants, in agreement with SWAF RPE cell size and location. Differences in cell fluorescent structure, contrast, and visibility beneath vasculature were observed between modalities. CONCLUSIONS. Improvements in AOSLO autofluorescence imaging permit efficient visualization of RPE cells with safe light exposures, allowing individual characterization of RPE cell morphometry that is variable between participants. The normative dataset and analysis of RPE cell IRAF and SWAF herein are essential for understanding microscopic characteristics of cell fluorescence and may assist in interpreting disease progression in RPE cells.
关键词： autofluorescence,retinal imaging,photoreceptors,retinal pigment epithelium,adaptive optics
更新于2025-09-09 09:28:46
-
Second harmonic spectroscopy of surface lattice resonances
摘要： Because of their large figures of merit, surface lattice resonances (SLRs) in metal nanoparticle arrays are very promising for chemical and biomolecular sensing, in both liquid and gas media. SLRs are sensitive to refractive index changes both near the surface of the nanoparticles (surface sensitivity) and in the volume between them (bulk sensitivity). Due to its intrinsic surface-sensitivity and a power-law dependence on electric fields, second harmonic generation (SHG) spectroscopy can improve upon both the surface and volume sensitivities of SLRs. In this report on SHG spectroscopy of plasmonic nanoparticles, we show that the SHG signal is greatly increased (up to 450 times) by the SLRs. We also demonstrate very narrow resonances in SHG intensity (~5 nm FWHM). We illustrate how the SHG resonances are highly sensitive to SLRs by varying the fundamental wavelength, angle of incidence, nanoparticle material and lattice constant of the arrays. Finally, we identify an SHG resonance (10 nm FWHM) that is electric dipole forbidden and can be attributed to higher-order multipoles, enhanced by the strong near-fields of SLRs. Our results open up new and very promising avenues for chemical and biomolecular sensing, based on SHG spectroscopy of SLRs.
关键词： Plasmonics,Quadrupoles,Nonlinear optics,Surface lattice resonance
更新于2025-09-09 09:28:46
-
Dynamically Configurable Nonlinear Optical Switching Based on Vertically Aligned Carbon Nanotubes
摘要： The modification of the third order nonlinear optical response exhibited by vertically aligned carbon nanotubes in two-wave mixing interactions was analyzed. All-optical switching effects were explored by using a vectorial optical Kerr gate with nanosecond pulses at 532 nm wavelength of excitation. The samples were prepared by a spray pyrolysis method. Morphological and structural characterization of the samples was conducted by Scanning Electron Microscopy, Transmission Electron Microscopy and Raman Spectroscopy studies. Important structural changes dependent on the temperature employed for the preparation of the carbon nanotubes were observed. It was highlighted a remarkable influence of nonlinear energy transference in spatially-resolved optical processes for designing ultrafast low-dimensional devices.
关键词： aligned carbon nanotubes,Nonlinear Optics,Two-wave mixing
更新于2025-09-09 09:28:46
-
X-ray photon pairs with highly suppressed background
摘要： We describe an experiment demonstrating the possibility to generate collinear indistinguishable x-ray photon pairs with a highly suppressed background. By choosing angles near 90 degrees between the detectors and the pump beam, where the pump polarization is in the scattering plane, we improve the signal-to-noise ratio by 2 orders of magnitude. We measure the pure coincidence spectrum without any energy discrimination with a bandwidth of 1.5 keV at the full width at half maximum.
关键词： background suppression,parametric down conversion,quantum optics,signal-to-noise ratio,x-ray photon pairs
更新于2025-09-09 09:28:46