Optimizing the fabrication of diffractive optical elements using a focused ion beam system
TL;DR: In this article, a focused ion beam system (Nova Nanolab 600 from FEI) was used to write diffractive optical elements (DOEs) directly on a single mode fiber tip.
Abstract: In the past, UV lithography has been used extensively for the fabrication of diffractive optical elements (DOEs). The advantage of this technique is that the entire structure can be written at one time, however, the minimum feature size is limited to about 1 μm. Many 1-d and 2-d periodic grating structures may not need such fine details but it is essential for diffractive optics with circular structures. This is because the spacing between features typically decreases towards the edge of the element resulting in the smallest feature falling well below 1 μm. 1-d structures such as sub-wavelength gratings will also have smaller feature sizes throughout the structure. In such cases, advanced techniques such as Focused Ion Beam and Electron-beam Lithography are required for the fabrication of finer structures. In this paper, we present results of DOEs fabricated with a focused ion beam system (Nova Nanolab 600 from FEI) directly on a single mode fibre tip. The ability to write DOEs directly on fibre tip is of great importance in fields such as endoscopy and optical trapping. The DOE itself, transforms the laser beam to a phase and intensity profile that matches the requirement. Because it is located directly on the fibre, no extra alignment is required. In addition, the system becomes more compact, which is especially important for applications in the field of endoscopy. The main goal of the present work was to develop the most accurate method for creating the desired pattern (that is, the DOE structure) into an actually working element. Different exposure strategies for writing test structures directly with the ion beam on the fibre tip have been tested and carefully evaluated. The paper will present in detail the initial fabrication and optical test results for blazed and binary structures of 1-d and circularly symmetric Fresnel axicons on optical fibres.
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TL;DR: The realization of spiral phase optical elements on the cleaved end of an optical fiber by focused ion beam milling is presented and are expected to be promising candidates for all-fiber beam shaping and optical trapping applications.
Abstract: The realization of spiral phase optical elements on the cleaved end of an optical fiber by focused ion beam milling is presented. A focused Ga+ ion beam with an acceleration voltage of 30 keV is used to etch continuous spiral phase plates and fork gratings directly on the tip of the fiber. The phase characteristics of the output beam generated by the fabricated structures measured via an interference experiment confirmed the presence of phase singularity in the output beam. The devices are expected to be promising candidates for all-fiber beam shaping and optical trapping applications.
33 citations
TL;DR: In this article, two kinoform lenses made out of polycrystalline gold and nano-crystaline PdSi are successfully fabricated, thoroughly characterized and tested for their ultimate focusing performances at soft X-ray energies.
Abstract: A kinoform lens is a highly efficient photonic device capable of focusing a wide range of electromagnetic radiation. Unfortunately, its realization without the need of any approximation remained elusive for a very long time. A direct, simple and precise fabrication method was still missing. Here, an efficient preparation scheme is presented for the first time. Two kinoform lenses made out of polycrystalline gold and nano-crystalline PdSi, are successfully fabricated, thoroughly characterized and tested for their ultimate focusing performances at soft X-ray energies. The fabrication is made possible by means of gray-scale direct-write ion beam lithography. A first ever 2D imaging is carried out via scanning transmission X-ray microscopy achieving resolutions down to 60 nm. The diffraction efficiency is measured to be 77% to 89% of the theoretical value and is only limited by the strong absorption at the soft X-ray energy range. The impact of materials selection on the final quality of the lens is emphasized. The overall results enable the production of almost perfect kinoform profiles with high precision. This opens unprecedented perspectives for the focusing of soft and hard X-rays at very high efficiencies and paves the way toward new applications in a wider energy range.
28 citations
TL;DR: In this paper, the authors summarized the existing fabrication techniques to generate these lens structures, excluding molding, and discussed the strengths and future areas of research interest of the reviewed techniques.
18 citations
TL;DR: In this paper, double-sided hot embossing was used for the fabrication of lenses made out of multi-component oxide glasses by using doublesided hot-embossing to allow low-cost, low-volume replication of these lenses.
4 citations
01 Jan 2018
TL;DR: In this article, an optimization of focused ion beam (FIB) milling process for the fabrication of optical elements is presented, which can be used for fabrication of 3D elements and micro/nano-structures for various applications.
Abstract: This work presents an optimization of focused ion beam (FIB) milling process for the fabrication of optical elements. Focused ion beam is a nanofabrication tool involving ion–beam material interaction at atomic or molecular levels. The ion–solid interactions have been investigated for the fabrication of desired 3D geometries. Focused ion beam dwell time is an important parameter and determines the final geometry and accuracy of the fabrication. An algorithm has been developed to optimize the ion beam dwell time for the desired geometry fabrication maintaining high accuracy. Binary Fresnel zone plates (FZPs) have been fabricated using the optimized simulation results for demonstration. The algorithm can be used for fabrication of 3D elements and micro/nano-structures for various applications.
4 citations
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TL;DR: The application of focused ion beam (FIB) technology in microfabrication has become increasingly popular as discussed by the authors, and this can distinguish the FIB technology from the contemporary photolithography process and provide a vital alternative to it.
Abstract: The application of focused ion beam (FIB) technology in microfabrication has become increasingly popular. Its use in microfabrication has advantages over contemporary photolithography or other micromachining technologies, such as small feature resolution, the ability to process without masks and being accommodating for a variety of materials and geometries. An overview of the recent development in FIB microfabrication technology is given. The emphasis will be on direct milling, or maskless techniques, and this can distinguish the FIB technology from the contemporary photolithography process and provide a vital alternative to it. After an introduction to the technology and its FIB principles, the recent developments in using milling techniques for making various high-quality devices and high-precision components at the micrometer scale are examined and discussed. Finally, conclusions are presented to summarize the reviewed work and to suggest the areas for improving the FIB milling technology and for future research.
430 citations
TL;DR: Offering nanometer-scale spatial resolution and real-time reconfigurability, holographic optical traps provide unsurpassed access to the microscopic world and have found applications in fundamental research, manufacturing, and materials processing.
Abstract: Holographic optical tweezers use computer-generated holograms to create arbitrary three-dimensional configurations of single-beam optical traps that are useful for capturing, moving, and transforming mesoscopic objects. Through a combination of beam-splitting, mode-forming, and adaptive wavefront correction, holographic traps can exert precisely specified and characterized forces and torques on objects ranging in size from a few nanometers to hundreds of micrometers. Offering nanometer-scale spatial resolution and real-time reconfigurability, holographic optical traps provide unsurpassed access to the microscopic world and have found applications in fundamental research, manufacturing, and materials processing.
238 citations
"Optimizing the fabrication of diffr..." refers methods in this paper
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...Phase profiles of gratings and axicons with binary and blazed profiles were generated and analyzed using Fresnel’s diffraction formula shown in equation (1)....
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TL;DR: An improved iterative algorithm for designing diffractive phase elements for laser beam shaping in free space with mean-square errors of the amplitude and the intensity profile of the entire beam fitted to the corresponding parameters of the 12th-power super-Gaussian beam is presented.
Abstract: An improved iterative algorithm for designing diffractive phase elements for laser beam shaping in free space is presented. The algorithm begins with the Gerchberg–Saxton approach to obtain a stable solution. This is followed by several new iterations, in which modified constraining functions are imposed in the Fourier domain while the phase distribution of each iteration remains unchanged. For super-Gaussian beam shaping suitable for inertial confinement fusion applications the mean-square errors of the amplitude and the intensity profile of the entire beam fitted to the corresponding parameters of the 12th-power super-Gaussian beam are approximately 0.035 and 9.75×10-3, respectively. Approximately 97.4% of the incident energy is converged into the desired region.
145 citations
TL;DR: In this paper, the authors describe the efficient conversion of light from a laser diode into a Bessel beam whose axial intensity varies almost uniformly with distance using only a holographic optical element.
93 citations