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Journal ArticleDOI

Design of multifunctional diffractive optical elements

01 Feb 2015-Optical Engineering (International Society for Optics and Photonics)-Vol. 54, Iss: 2, pp 024104-024104
TL;DR: In this paper, a comparison of the beam generated by different beam generation and focused ion beam milling methods is presented. And in order to be able to compare methods, specific functions of ring generation and focusing have been added in all cases.
Abstract: Diffractive optics has traditionally been used to transform a parallel beam of light into a pattern with a desired phase and intensity distribution. One of the advantages of using diffractive optics is the fact that multiple functions can be integrated into one element. Although, in theory, several functions can be combined, the efficiency is reduced with each added function. Also, depending on the nature of each function, feature sizes could get finer. Optical lithography with its 1 μm limit becomes inadequate for fabrication and sophisticated tools such as e-beam lithography and focused ion beam milling are required. Two different techniques, namely, a modulo-2π phase addition technique and an analog technique for design and fabrication of composite elements are studied. A comparison of the beams generated in both cases is presented. In order to be able to compare methods, specific functions of ring generation and focusing have been added in all cases.
Citations
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Journal ArticleDOI
TL;DR: The CSFZP beam pattern was implemented in an optical trapping experiment and was found to possess particle trapping capabilities, with a strong central focal spot and twisted side lobes.
Abstract: In this study, we introduce what we believe is a novel holographic optical element called a chiral square Fresnel zone plate (CSFZP) The chirality is imposed on a square Fresnel zone plate (SFZP) using a nonclassical technique by rotating the half-period zones relative to one another The rotation of the half-period zones, in turn, twists the side lobes of the diffraction pattern without altering the focusing properties inherent to a SFZP As a consequence, the beam profile is hybrid, consisting of a strong central Gaussian focal spot with gradient force similar to that generated by a lens and twisted side lobes with orbital angular momentum The optical fields at the focal plane were calculated and found to possess a whirlpool-phase profile and a twisted intensity profile Analysis of the field variation along the direction of propagation revealed a spiraling phase and amplitude distribution Poynting vector plot of the fields revealed the presence of angular momentum in the regions of chiral side lobes The phase of the CSFZPs were displayed on a phase-only reflective spatial light modulator and illuminated using a laser The intensity patterns recorded in the experiment match the calculated ones, with a strong central focal spot and twisted side lobes The beam pattern was implemented in an optical trapping experiment and was found to possess particle trapping capabilities

24 citations

Journal ArticleDOI
TL;DR: In this article, generalized spiraling Bessel beams (GSBB) of arbitrary order are created by illuminating a curved fork-shaped hologram (CFH) by Laguerre-Gaussian beam (LGB).
Abstract: Generalized spiraling Bessel beams (GSBB) of arbitrary order are created by illuminating a curved fork-shaped hologram (CFH) by Laguerre–Gaussian beam (LGB). The analytical expressions of the diffracted wave field amplitudes and intensities are calculated and analyzed using the stationary phase method. The numerical results are given to understand the features of the GSBB by using CFH. Our finding provides the study of the LGB with null mode number n and azimuthal mode index l and the fundamental Gaussian beam through the considered optical system, which are as particular cases of the present investigation.

14 citations

Journal ArticleDOI
TL;DR: In this paper, a denoising deep learning neural network (DLNN) was trained using synthetic noisy images generated by the convolution of recorded point spread functions with the virtual object functions under a wide range of aberrations and noises.
Abstract: Coded aperture imaging (CAI) technology is a rapidly evolving indirect imaging method with extraordinary potential. In recent years, CAI based on chaotic optical waves have been shown to exhibit multidimensional, multispectral, and multimodal imaging capabilities with a signal to noise ratio approaching the range of lens based direct imagers. However, most of the earlier studies used only narrow band illumination. In this study, CAI based on chaotic optical waves is investigated for white light illumination. A numerical study was carried out using scalar diffraction formulation and correlation optics and the lateral and axial resolving power for different spectral width were compared. A binary diffractive quasi-random lens was fabricated using electron beam lithography and the lateral and axial point spread holograms are recorded for white light. Three-dimensional imaging was demonstrated using thick objects consisting of two planes. An integrated sequence of signal processing tools such as non-linear filter, low-pass filter, median filter and correlation filter were applied to reconstruct images with an improved signal to noise ratio. A denoising deep learning neural network (DLNN) was trained using synthetic noisy images generated by the convolution of recorded point spread functions with the virtual object functions under a wide range of aberrations and noises. The trained DLNN was found to reduce further the reconstruction noises.

14 citations

Journal ArticleDOI
TL;DR: In this article, a binary composite diffractive optical element with the functions of a spiral phase plate (SPP), an axicon, and a Fresnel zone lens (FZL) were designed with different topological charges.
Abstract: Binary composite diffractive optical elements with the functions of a spiral phase plate (SPP), an axicon, and a Fresnel zone lens (FZL) were designed with different topological charges. The element was designed in two steps. In the first step, the function of an SPP was combined with that of an axicon by spiraling the periods of the axicon with respect to the phase of the SPP followed by a modulo- 2π phase addition with the phase of an FZL in the second step. The higher-order Bessel beams generated by the binary phase spiral axicon are superposed at the FZL’s focal plane. Although location of the focal plane is wavelength dependent, the radius of the flower-like beams generated by the element was found to be independent of wavelength. The element was fabricated using electron-beam direct writing. The evaluation results matched well with the simulation results, generating flower-like beams at the focal plane of the FZL.

11 citations


Cites background or methods from "Design of multifunctional diffracti..."

  • ...The design parameters were selected to obtain a ring pattern with a diameter D 1⁄4 200 μm at the focal plane of the FZL.(31) The number of intensity maxima in the profile of the superposed higher-order Bessel beams is found to be twice that of the topological charge....

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  • ...2%.(31) Indium-tin-oxide (ITO) coated borosilicate glass substrates with a thickness of 1 mm were used....

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  • ...The design parameters were selected to obtain a ring pattern with a diameter D ¼ 200 μm at the focal plane of the FZL.31 The number of intensity maxima in the profile of the superposed higher-order Bessel beams is found to be twice that of the topological charge.20,28 The schematic of the optics configuration for generation of the flowershaped intensity profiles using DOE2 is shown in Fig....

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  • ...However, the modulo-2π phase addition indirectly masks 25% of the area of the device from participating in a decrease of intensity.(31) Hence, the decrease in efficiency when the wavelength changes is not as rapid as is the case when DOE1 and the FZL are independent components....

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  • ...1(a), the phase of the spiral element is combined with that of a binary axicon by spiraling the periods of axicon with respect to the phase of the SPP similar to spiraling the zones of FZL or axicon with respect to the phase of the SPP.23–25 The resulting element DOE1 can generate higher-order Bessel beams with opposite rotations.28 The element generated by combining SPP with an FZL25 by spiraling the periods of the FZL will generate a focused donut beam at the focal plane of the FZL....

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Journal ArticleDOI
18 Dec 2020
TL;DR: In this paper, a co-axial pump (optical)-probe (x-rays) experimental concept and show performance of the optical component are presented and different realisations of optical pump are discussed.
Abstract: We put forward a co-axial pump (optical)-probe (x-rays) experimental concept and show performance of the optical component. A Bessel beam generator with a central 100 µm diameter hole (on the optical axis) was fabricated using femtosecond (fs) laser structuring inside a silica plate. This flat-axicon optical element produces a needle-like axial intensity distribution which can be used for the optical pump pulse. The fs-x-ray free electron laser (X-FEL) beam of sub-1 µm diameter can be introduced through the central hole along the optical axis onto a target as a probe. Different realisations of optical pump are discussed. Such optical elements facilitate alignment of ultra-short fs-pulses in space and time and can be used in light–matter interaction experiments at extreme energy densities on the surface and in the volume of targets. Full advantage of ultra-short 10 fs-X-FEL probe pulses with fs-pump (optical) opens an unexplored temporal dimension of phase transitions and the fastest laser-induced rates of material heating and quenching. A wider field of applications of fs-laser-enabled structuring of materials and design of specific optical elements for astrophotonics is presented.

10 citations

References
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Journal ArticleDOI
TL;DR: Laser beams that contain phase singularities can be generated with computer-generated holograms, which in the simplest case have the form of spiral Fresnel zone plates.
Abstract: Laser beams that contain phase singularities can be generated with computer-generated holograms, which in the simplest case have the form of spiral Fresnel zone plates.

1,251 citations

Journal ArticleDOI
TL;DR: The Acri.Lisa 366D diffractive multifocal IOL gave good efficacy, predictability, and safety and excellent visual acuity at distance and near and an intraocular optical performance model showed good intraocular aberration, Strehl ratio, and MTF values.
Abstract: Purpose To evaluate clinical outcomes and intraocular optical performance of a diffractive multifocal intraocular lens (IOL), Acri.Lisa 366D (Acri.Tec). Setting Vissum-Instituto de Oftalmologico de Alicante, Alicante, Spain. Methods The study included 69 eyes (52 patients) with Acri.Lisa 366D IOLs. The intraocular optical quality in vivo was characterized by the difference between postoperative total and corneal optical aberrations. Visual and optical outcomes were evaluated 6 months postoperatively. The main outcomes measures were refractive defect, uncorrected and corrected distance acuities for far and near (40 cm), intraocular aberrations (root mean square [RMS]), modulation transfer function (MTF) values, point-spread function, and Strehl ratio. Results The mean spherical equivalent (SE) was +1.22 diopters (D) ± 3.62 (SD) preoperatively and +0.39 ± 0.51 D/D postoperatively; 69.32% of eyes were within ±0.50 and 86.36%, within ±1.00 D. The mean acuities were as follows: uncorrected distance, 0.75 ± 0.20; best corrected distance, 0.94 ± 0.11; best distance-corrected near, 0.90 ± 0.14. Near corrected acuity was J1 in 91.76% of eyes and J2 in 4.71%. The mean aberration values were total RMS, 1.45 ± 0.73 μm; spherical, 0.25 ± 0.10 μm; coma, 0.37± 0.21 μm. The mean Strehl ratio was 0.26 ± 0.05. The mean 0.5 MTF was 1.60 ± 0.63 cycles per degree (cpd) and the mean cutoff value, 50.25 ± 17.18 cpd. Conclusions The Acri.Lisa 366D diffractive multifocal IOL gave good efficacy, predictability, and safety and excellent visual acuity at distance and near. An intraocular optical performance model showed good intraocular aberration, Strehl ratio, and MTF values.

95 citations

MonographDOI
27 Oct 2009

85 citations

Journal ArticleDOI
TL;DR: Model simulations of isotropic etching of topographical features show good agreement with the measured shape evolution of the sampling grating profiles, and the simulations reveal the sensitivity of the final feature shape to its initial aspect ratio.
Abstract: We combined functionalities of two diffractive optics with almost 100× lateral and vertical scale-length difference onto a single fused-silica surface. Fine-scale (2-μm-period) gratings for beam sampling were printed in photoresist by interference lithography and transferred to the substrate by a hydrofluoric acid etch. Subsequently, 115-μm-linewidth stairstep gratings for color separation at focus were proximity printed and wet etched in a two-mask process. Line shapes of the lamellar sampling grating are remarkably preserved following etching of the much deeper color separation grating structures with this nominally isotropic etch process. Model simulations of isotropic etching of topographical features show good agreement with the measured shape evolution of the sampling grating profiles, and the simulations reveal the sensitivity of the final feature shape to its initial aspect ratio. As a rule of thumb, lamellar grating profiles can be etched approximately 0.08A-2 times their modulation depth, where A is their initial aspect ratio (height/width), before they evolve into a cusplike shape and begin to lose height.

24 citations

Journal ArticleDOI
TL;DR: A novel multifunctional double-layered diffractive optical element based on the fractional Talbot effect that can perform each of the multiple optical functions one by one by shifting the encoding layer.
Abstract: We propose a novel multifunctional double-layered diffractive optical element (DOE) based on the fractional Talbot effect. This DOE consists of two layers: one is the encoding layer, in which multiple sub-DOEs, i.e., multiple optical functions, are encoded; the other is the decoding layer, which is a properly designed Talbot illuminator. This DOE can perform each of the multiple optical functions one by one by shifting the encoding layer. Experimental results demonstrate that this method is efficient. This device should be highly interesting for integrated optics, optical interconnection, secure optical storage, and dynamic optical fiber communications.

23 citations