Beam Pattern Generator Research Articles

Coherent beam combining – unlimited flexibility in laser material processing

AbstractCivan's unique beam shaping technology enables the generation of beam patterns with an arbitrary variation of the intensity distribution within the laser beam. In addition, it is possible to switch between these patterns at MHz frequencies. This offers great potential to influence and control laser material processes.

Contextual Learning-Based Wireless Power Transfer Beam Scheduling for IoT Devices

In this paper, we consider Internet of Things (IoT) systems in which IoT devices request power to a power beacon (PB) when their available power is deficient and the PB provides power to the IoT devices using switched beamforming. We study wireless power transfer (WPT) beam scheduling for the IoT systems under one-bit feedback which aims at maximizing the time-average number of the IoT devices whose power requests are satisfied. To achieve this, we propose a contextual learning-based WPT beam scheduling algorithm with one-bit feedback (CWBO) that learns the channel information using only one-bit feedback information and exploits it for the beam scheduling. Within CWBO, a beam pattern generation (BPG) problem should be solved in each time slot. To efficiently solve it, we develop a BPG algorithm based on monotonic optimization that can optimally solve the BPG problem. In addition, we also develop a heuristic BPG algorithm that has a lower computational complexity than the monotonic optimization-based BPG algorithm, while providing comparable performance. For CWBO in single-device WPT, we prove an analytical performance bound, which shows its optimality in terms of the long-term average performance even with one-bit feedback. In addition, through the simulation results, we show that our algorithms achieve performances close to that of the optimal beam scheduling policy in multidevice WPT as well. This demonstrates that our algorithms can be used for WPT IoT systems with IoT devices having only limited capabilities for feedback and estimation of the channel information due to their limited power.

A Dual-Layer Planar Leaky-Wave Antenna Designed for Linear Scanning Through Broadside

A low-cost planar leaky-wave antenna (LWA) offering directive antenna beam patterns as well as linear beam scanning through broadside is proposed. The design is based on a one-sided annular slot grating placed on a dual-layer grounded dielectric slab with an integrated TM $_0$ antenna feed system in the bottom ground plane. By appropriate selection of the width and the period of the top radiating annular slots, as well as the substrates, the structure is optimized to excite and perturb the dominant TM mode for the generation of directive beam patterns that can scan with frequency in the far field. In particular, the antenna parameters are chosen to obtain a narrow open stopband frequency range at broadside as well as control the dispersive scanning behavior. A method-of-moments dispersion analysis has also been developed to assist in the design and fully characterize the proposed antenna. These results are complemented by full-wave simulations and measurements of a LWA prototype offering realized gain values in excess of 14 dBi with scanning through broadside at 23.5 GHz.

Near ultraviolet-visible radial wire grid polarizer for tight focusing applications

Abstract. A circular wire grid polarizer (WGP) as a device to produce high quality radially polarized light at nearUV wavelength range (in particular at the wavelength of λ ¼ 405 nm) is presented starting from design modelingfollowed by fabrication and performance analysis. The wire grid consists of concentric subwavelength metalliccylinders covering a high quality glass substrate and fabricated using an electron beam pattern generator andetchingtechniques.Thetheoreticalmodelingusingtherigorousfinite-elementmethodandmeasurementsofthetransmittedlightthroughthemaskhavebeenevaluated.AnanalysisonadjustmentsofthegeometryoftheWGPto produce the optimum focused spot of the longitudinal component of the electric field, its implementation, andqualitative testing are also presented. © 2015 Society of Photo-Optical Instrumentation Engineers (SPIE) [DOI: 10.1117/1.OE.54.10.104101] Keywords: wire grid polarizer; radially polarized light; metallic grating; finite-element method; near ultraviolet wavelength range;physical optics; diffractive optics.Paper 150862 received Jun. 24, 2015; accepted for publication Aug. 31, 2015; published online Oct. 6, 2015.

Transformation of a LG10 beam into an optical bottle beam

We have demonstrated that a simple diaphragm can play the role of a very cheap reconfigurable diffractive optical element allowing the generation of interesting laser beam patterns. For instance, a truncated Laguerre–Gauss LG10 beam (one peak surrounded by one ring) can be transformed in the focal plane of a lens into an optical bottle beam (OBB) which consists to a dark (or minimal intensity) region surrounded by higher intensity light in the three principal directions. Depending on the beam truncation, one can also observe a flat-top intensity profile.

LCD와 가시광선 LED를 사용한 전사방식의 Scanbeam-SLA 개발

In Projection Stereolithography Apparatus (PSLA), Digital Micromirror Device (DMD) and Liquid Crystal Display (LCD) are used as a beam pattern generator. The DMD shows high resolution, but it is mostly applied in micro stereolithography due to high cost and fabricable area. In LCD, the size of pattern beam is freely controlled due to various panel sizes. The LCD, however, has some limitations such as short life time by the high power light source, non-uniform light intensity of pattern beam and low transmittance of UV-light. To solve these problems in LCD-based PSLA, a Scanbeam-SLA with LCD of 19 inches and visible LED-array is developed. In this system, the light module works like a scanner for uniform illumination. The system configuration, working principle and fabrication examples are addressed in this study.

Process control for 32 nm imprint masks using variable shape beam pattern generators

Step and Flash Imprint Lithography (S-FIL ®) is a unique method that has been designed from the beginning to enable precise overlay for creating multi-level devices. However, since the technology is 1X, it is critical to address the infrastructure associated with the fabrication of templates (imprint masks). For device manufacturing, one of the major technical challenges remains the fabrication of full-field 1X templates with commercially viable write times. Recent progress in the writing of sub-40 nm patterns using commercial variable shape e-beam tools and non-chemically amplified resists has demonstrated a very promising route to realizing these objectives, and in doing so, has considerably strengthened imprint lithography as a competitive manufacturing technology for the sub-32 nm node. Here we report the critical dimension (CD) uniformity and process latitude of dense 32 nm patterns from templates written with variable shape beam pattern generators. Uniformity on the template and in the imprinted field was 3.22 and 3.45 nm, 3 σ. Process latitude during the writing of the template was improved by increasing both feature bias and exposure dose. As an example, the slopes for the 36 and 32 nm features are approximately 0.30 and 0.25 nm/μC/cm 2, respectively, indicating a substantial process window for exposure dose.

A Novel Wideband Subarray Technique for Shaped Pattern Generation and Adaptively Interference Rejection

In this article, a simple and efficient technique for the wideband shaped beam and sector beam pattern generation with their adaptive interference rejection is proposed. A microcontroller controlled and time delay based beam forming network for simultaneously generating multiple beams, shaped beam and sector beam is conceptualized. The antenna patterns considered here is formed by linear array of isotropic elements grouped as subarray. The shaped and sector beam synthesis procedure is practically simplified by simultaneous adding the constituents beams from the subarrays, was theoretically established by Woodward and Lawson (Proc. IEE. 95(1):362–370, 1948). Apart from the shaped beam generation a technique for adaptive interference rejection in shaped patterns using combination of time delay and phase shifter is discussed. This topic promises good prospect for wideband pattern generation and interference rejection.

Describing thin-film imaging with a Gaussian beam as potential flow

It is shown that patterning with a Gaussian beam on thin films is congruent to a diffusion process. In particular, the acuity of the image patterned is tied to a steady state (Laplace equation). For a small spot size, pattern acuity improves locally when the Laplacian approaches zero at the said region. However, when the spot size (blur) of the patterning beams is of the order of the critical dimensions of the geometry, the diffusion equation gives rise to a global steady state. As a corollary, a conformal mapping of the type w=z2 is applied, transforming a 45∘ rotated cross into a contact hole. We discuss the relevance of conformal mapping to corner rounding seen on raster beam pattern generators.

The new electron beam test facility JUDITH II for high heat flux experiments on plasma facing components

With the installation of a new electron beam (EB) test facility JUDITH II, the parameter range of high heat flux simulations is extended and the urgent need of additional testing capacity is addressed. A nominal power of 200 kW combined with a beam scanning angle of ±14° enables to test larger components of up to 0.5 m × 1 m surface area. A relatively low acceleration voltage (30–60 kV) reduces volumetric heating for the benefit of a more plasma like surface heating. Due to a very flexible and individual programmable system for electron beam pattern generation, very homogeneous load distributions can be achieved during static load tests and highly realistic simulations of ITER relevant transient heat loads become possible. Furthermore, static and transient loads can be combined in one single experiment. Improved diagnostics, such as IR-analyses, a spectrometer in the visible range, a photodiode array and acoustic emission shall finally contribute to a better understanding of the effects caused by extreme thermal shock loads.

Picometer resolution measurement of the frequency spectrum of a periodic structure written by a MEBES electron beam pattern generator

A differential diffractive interferometric technique allows the high resolution retrieval of the spatial frequency profile along a long grating of supposedly constant period from the measurement of the phase of the two interference products detected by a double read head sensor upon its fly over the grating under test. The application of the technique to a 100 mm long grating written by a fifth generation MEBES e-beam writer reveals a maximum deviation of 2 pm from a nominal period of 1.070442 μm.

Study of active antenna receivers and calibration method for digital beamforming

AbstractIn next‐generation high speed wireless communications, the development of digital beamforming (DBF) is indispensable for the creation of base stations and terminal antennas with high functionality, low cost. and small size. On the other hand, active antennas that combine a passive antenna and active devices are advantageous for use in DBF, because the feed line can be shortened and phase and amplitude imbalance among the array branch elements can be reduced. Further, if technologies to reduce the number of active devices, such as the direct conversion and Low IF schemes, are combined, it is possible to attempt miniaturization and reduction of individual differences. In this paper, a receiver of small size for DBF is proposed and experimentally studied by using an active integrated antenna containing an amplifier and a Low IF scheme. A calibration circuit for amplitude and phase corrections is discussed in which the error factors in the characteristics between the devices are taken into account. Further, experimental results on beam pattern generation by the test system in an anechoic chamber are presented. © 2003 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 86(11): 20–29, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.10119

Fabrication of Bragg Grating Structures in Silicon

A fabrication process to realise very short period grating structures in silicon has been developed. The period of a first order Bragg grating operating at a wavelength of 1.55 μm is 230 nm. The grating structures have been directly written to PMMA resist using an electron beam pattern generator. The grating pattern in PMMA is transferred into a silicon dioxide masking layer using plasma etching and into silicon using an inductively coupled plasma etching. An etch depth of 0.6 μm has been achieved. The integration of the grating structure with a large core size silicon-on-insulator rib waveguide is presented.

A continuous phase plate for non-uniform illumination beam shaping using the inverse phase contrast method

This paper describes an algorithm for calculating the transmission function of a phase plate (PP) using the inverse phase contrast method. With this algorithm, calculations of a continuous PP that is less sensitive to wavelength variation can be made. A design of a continuous PP for beam shaping using the algorithm is simulated. The continuous PP can be used for beam shaping, pattern generation and light projection with a moderate bandwidth light source.

Raster shaped beam pattern generation

We propose a new approach to electron-beam (e-beam) pattern generation, in which the best attributes of raster scan writing are combined with beam shaping. The maximum dimension of the variable shaped flash is equal to the minimum feature size required in the pattern. The limited shaping range allows the use of very high speed, limited-resolution, digital-to-analog conversion circuits and amplifiers to form the shapes, and also allows thermal field emission cathode and optics to be used effectively, providing a very high current density. The system should support a sustained flash rate of at least 100 MHz, which is much higher than that found in conventional variable shaped beam architectures. The throughput is pattern independent and attractive for photomask fabrication at the 130 and 100 nm wafer technology nodes.

Apodized annular-aperture diffractive axicons fabricated by continuous-path-control electron beam lithography

Binary diffractive axicons, designed to generate a uniform axial line focus over a specified interval, are fabricated by electron beam lithography. Continuous-path-control mode and dynamic beam expansion of a low-voltage electron beam pattern generator are employed to avoid quantization errors in the patterning of the circular zones. Apodization by local control of diffraction efficiency is shown to be an effective method to reduce axial intensity oscillations along the focal line. A novel split-groove apodization method is introduced to suppress second-order interference.

Scan density and resolution in a laser beam pattern generator

The influence of the line scan density on the resulting profile of an exposed resist pattern is described for a pattern written by a laser beam pattern generator (LBPG). It is shown that employing a wide band optical modulator in conjunction with appropriate oversampling is beneficial for the modulation depth and the steepness of critical features in the pattern. The relationship between the modulation depth and the rate of oversampling is given.

Coulomb interactions in a shaped ion beam pattern generator

The statistical Coulomb interactions between the particles of a focused ion beam can severely reduce the quality of a system. The interactions in the source region of a liquid metal ion source have been studied extensively and lead to the well-known virtual source diameter of 50 nm and energy width of 5 eV in a Ga source. In this report, the interactions are described in the rest of the column of the Delft ion beam pattern generator, a system using a shaped beam with Köhler illumination. The simulations have been done with the Interac and Montec programs developed by Jansen [G. H. Jansen, Coulomb Interactions in Particle Beams (Academic, San Diego, 1990), Suppl. 22; G. H. Jansen, Montec, and Interac Programs, information obtainable from, Particle Optics Foundation, Lorentzweg 1, 2628 CJ Delft, The Netherlands]. The results show that the Coulomb interactions are a limiting factor for the beam quality, not only in the source region but also in the rest of the column. In particular, long segments with small opening angles cause deterioration of the beam. In these segments, the beam can even tend to thermodynamic relaxation. For the case of a square shape with size 100 nm and edge sharpness 25 nm, for which the normal probe current should be about 1 nA, interactions cause the edge sharpness to deteriorate by a factor of two at 100 pA while for more than 200 pA the square shape is not recognizable anymore.

Possibilities and limits of high speed e-beam submicron lithography

Abstract Theory shows that the speed of electron beam pattern generators (EBPG's) can be improved considerably. Above that the availability of high resolution - high sensitive resists will make writing speeds in principle possible for 0.2 μm lithography - which exceed the speed of todays 1.0 μm optical steppers. The concept of 1:1 photo- or MIM cathode electron steppers is more promising as can be derived from the research effort put into it.

Definition of geometries with complicated, curved boundaries for electron beam pattern generation

To facilitate the design of complicated, curved structures, we have added some new tools to a commercial IC layout system. These tools are used to approximate such structures by a large number of abutting polygons with up to 200 vertices each. Vector scan electron beam lithography systems are well suited for pattern generation of these structures, and we have created a lot of complicated structures this way.