Broadband, high-efficiency, arbitrary focusing lens by a holographic dielectric meta-reflectarray

Femtosecond laser is now widely used in micro holes drilling because of its unique advantages, such as high efficiency, high precision and non-contact. Femtosecond laser is the best choice to fabricate micro holes. This paper makes a systematic study of the influence of laser power and number of pulses on diameter and depth of micro holes on S136 die steel through the focusing lens with focal length of 35 cm. A series of high-precision micro holes with different diameter and depth are fabricated. The relationship between the dimension of fabricated micro holes and the process parameters is determined.

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Helmholtz‐Resonator Metasurface Based High‐Efficiency Acoustic Focusing Lens

Annalen der Physik ◽

10.1002/andp.202100218 ◽

2021 ◽

pp. 2100218

Author(s):

Hongjun Liu ◽

Ying Zheng ◽

Yu Lu ◽

Qianlong Kang ◽

Kai Guo ◽

...

Keyword(s):

High Efficiency ◽

Helmholtz Resonator ◽

Acoustic Focusing ◽

Focusing Lens

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Compact Double-Layer FR4-Based Focusing Lens Using High-Efficiency Huygens’ Metasurface Unit Cells

Sensors ◽

10.3390/s20216142 ◽

2020 ◽

Vol 20 (21) ◽

pp. 6142

Author(s):

Kd M. Raziul Islam ◽

Sangjo Choi

Keyword(s):

Double Layer ◽

Printed Circuit Board ◽

High Efficiency ◽

Transmission Loss ◽

High Gain ◽

Unit Cell ◽

Circuit Board ◽

Magnetic Current ◽

Unit Cells ◽

Focusing Lens

High transmission efficiency metasurface unit cells have been designed based on surface electric and magnetic impedances derived from Huygens’ principle. However, unit cells for low transmission loss (<1 dB) over a wide transmission phase range require at least three metallic layers, which complicates the unit cell design process. In this paper, we introduce high-efficiency Huygens’ metasurface unit cell topologies in double-layer FR4 printed circuit board (PCB) by implementing surface electric and magnetic current using the top and bottom metallic patterns and via drills. Eleven unit cells were optimized for wide phase coverage (−150° to 150°) with a low average transmission loss of −0.82 dB at 10 GHz. To demonstrate the high-efficiency of the designed unit cells, we designed and fabricated two focusing lenses with dimensions of near 150 × 150 mm (5λ × 5λ) to focus a spherical beam radiated from short focal distances (f = 100 and 60 mm). The fabricated focusing lens showed 12.87 and 13.58 dB focusing gain for f = 100 and 60 mm at 10 GHz, respectively, with a 1 dB fractional gain bandwidth of near 10%. We expect that the proposed focusing lens based on high-efficiency double-layer metasurface unit cells can help realize compact and high-gain focusing lens-integrated antenna systems.

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Design of Multifunctional Janus Metasurface Based on Subwavelength Grating

Nanomaterials ◽

10.3390/nano11041034 ◽

2021 ◽

Vol 11 (4) ◽

pp. 1034

Author(s):

Ruonan Ji ◽

Chuan Jin ◽

Kun Song ◽

Shao-Wei Wang ◽

Xiaopeng Zhao

Keyword(s):

High Efficiency ◽

Structural Parameters ◽

Extinction Ratio ◽

Bottom Layer ◽

Subwavelength Grating ◽

Operational Mechanism ◽

Metal Insulator Metal ◽

Linearly Polarized ◽

Selection Property ◽

Focusing Lens

In this paper, a Janus metasurface is designed by breaking the structural symmetry based on the polarization selection property of subwavelength grating. The structure comprises three layers: a top layer having a metallic nanostructure, a dielectric spacer, and a bottom layer having subwavelength grating. For a forward incidence, the metal-insulator-metal (MIM) structure operates as a gap plasmonic cavity if the linearly polarized (LP) component is parallel to the grating wires. It also acts as a high-efficiency dual-layer grating polarizer for the orthogonal LP component. For the backward incidence, the high reflectance of the grating blocks the function of the gap plasmonic cavity, leading to its pure functioning as a polarizer. A bifunctional Janus metasurface for 45 degrees beam deflector and polarizer, with a transmission of 0.87 and extinction ratio of 3840, is designed at 1.55 μm and is investigated to prove the validity of the proposed strategy. Moreover, the proposed metasurface can be cascaded to achieve more flexible functions since these functions are independent in terms of operational mechanism and structural parameters. A trifunctional Janus metasurface that acts as a focusing lens, as a reflector, and as a polarizer is designed based on this strategy. The proposed metasurface and the design strategy provide convenience and flexibility in the design of multifunctional, miniaturized, and integrated optical components for polarization-related analysis and for detection systems.

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Microcalorimeters for X-Ray Spectroscopy

International Astronomical Union Colloquium ◽

10.1017/s0252921100107365 ◽

1988 ◽

Vol 102 ◽

pp. 41

Author(s):

E. Silver ◽

C. Hailey ◽

S. Labov ◽

N. Madden ◽

D. Landis ◽

...

Keyword(s):

High Resolution ◽

High Efficiency ◽

Thermal Response ◽

Low Noise ◽

High Resolution Spectroscopy ◽

Superconducting Transition ◽

Sapphire Substrates ◽

Laboratory Plasmas ◽

Adiabatic Demagnetization ◽

Theoretical Predictions

The merits of microcalorimetry below 1°K for high resolution spectroscopy has become widely recognized on theoretical grounds. By combining the high efficiency, broadband spectral sensitivity of traditional photoelectric detectors with the high resolution capabilities characteristic of dispersive spectrometers, the microcalorimeter could potentially revolutionize spectroscopic measurements of astrophysical and laboratory plasmas. In actuality, however, the performance of prototype instruments has fallen short of theoretical predictions and practical detectors are still unavailable for use as laboratory and space-based instruments. These issues are currently being addressed by the new collaborative initiative between LLNL, LBL, U.C.I., U.C.B., and U.C.D.. Microcalorimeters of various types are being developed and tested at temperatures of 1.4, 0.3, and 0.1°K. These include monolithic devices made from NTD Germanium and composite configurations using sapphire substrates with temperature sensors fabricated from NTD Germanium, evaporative films of Germanium-Gold alloy, or material with superconducting transition edges. A new approache to low noise pulse counting electronics has been developed that allows the ultimate speed of the device to be determined solely by the detector thermal response and geometry. Our laboratory studies of the thermal and resistive properties of these and other candidate materials should enable us to characterize the pulse shape and subsequently predict the ultimate performance. We are building a compact adiabatic demagnetization refrigerator for conveniently reaching 0.1°K in the laboratory and for use in future satellite-borne missions. A description of this instrument together with results from our most recent experiments will be presented.

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UHV-TEM studies of laser-induced damage

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100087471 ◽

1991 ◽

Vol 49 ◽

pp. 632-633

Author(s):

T.S. Savage ◽

R. Ai ◽

D. Dunn ◽

L.D. Marks

Keyword(s):

Surface Science ◽

Rapid Heating ◽

Local Heating ◽

Routine Practice ◽

Transmission Electron ◽

Northwestern University ◽

Laser Induced Damage ◽

Set Up ◽

Focusing Lens ◽

Diffusion Of Impurities

The use of lasers for surface annealing, heating and/or damage has become a routine practice in the study of materials. Lasers have been closely looked at as an annealing technique for silicon and other semiconductors. They allow for local heating from a beam which can be focused and tuned to different wavelengths for specific tasks. Pulsed dye lasers allow for short, quick bursts which can allow the sample to be rapidly heated and quenched. This short, rapid heating period may be important for cases where diffusion of impurities or dopants may not be desirable.At Northwestern University, a Candela SLL - 250 pulsed dye laser, with a maximum power of 1 Joule/pulse over 350 - 400 nanoseconds, has been set up in conjunction with a Hitachi UHV-H9000 transmission electron microscope. The laser beam is introduced into the surface science chamber through a series of mirrors, a focusing lens and a six inch quartz window.

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Imaging and diffraction modes in Scanning Transmission Electron Microscopy

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100144814 ◽

1986 ◽

Vol 44 ◽

pp. 684-687

Author(s):

J. M. Cowley ◽

R. Glaisher ◽

J. A. Lin ◽

H.-J. Ou

Keyword(s):

Scanning Transmission Electron Microscopy ◽

High Efficiency ◽

Fiber Optic ◽

Image Intensifier ◽

Detector System ◽

Detector Plane ◽

Secondary Electrons ◽

Transmission Electron ◽

Scanning Transmission ◽

Special Detector

Some of the most important applications of STEM depend on the variety of imaging and diffraction made possible by the versatility of the detector system and the serial nature, of the image acquisition. A special detector system, previously described, has been added to our STEM instrument to allow us to take full advantage of this versatility. In this, the diffraction pattern in the detector plane may be formed on either of two phosphor screens, one with P47 (very fast) phosphor and the other with P20 (high efficiency) phosphor. The light from the phosphor is conveyed through a fiber-optic rod to an image intensifier and TV system and may be photographed, recorded on videotape, or stored digitally on a frame store. The P47 screen has a hole through it to allow electrons to enter a Gatan EELS spectrometer. Recently a modified SEM detector has been added so that high resolution (10Å) imaging with secondary electrons may be used in conjunction with other modes.

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Influence of MBE Growth Conditions on Dislocation Densities of GaAs/Ge Epilayers Grown on Silicon Substrates

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100118692 ◽

1985 ◽

Vol 43 ◽

pp. 364-365

Author(s):

K.M. Hones ◽

P. Sheldon ◽

B.G. Yacobi ◽

A. Mason

Keyword(s):

High Efficiency ◽

Lattice Mismatch ◽

Low Cost ◽

Growth Conditions ◽

Nonradiative Recombination ◽

Device Structure ◽

Si Substrates ◽

Transmission Electron ◽

Dislocation Densities ◽

Dislocation Type

There is increasing interest in growing epitaxial GaAs on Si substrates. Such a device structure would allow low-cost substrates to be used for high-efficiency cascade- junction solar cells. However, high-defect densities may result from the large lattice mismatch (∼4%) between the GaAs epilayer and the silicon substrate. These defects can act as nonradiative recombination centers that can degrade the optical and electrical properties of the epitaxially grown GaAs. For this reason, it is important to optimize epilayer growth conditions in order to minimize resulting dislocation densities. The purpose of this paper is to provide an indication of the quality of the epitaxially grown GaAs layers by using transmission electron microscopy (TEM) to examine dislocation type and density as a function of various growth conditions. In this study an intermediate Ge layer was used to avoid nucleation difficulties observed for GaAs growth directly on Si substrates. GaAs/Ge epilayers were grown by molecular beam epitaxy (MBE) on Si substrates in a manner similar to that described previously.

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The use of high-resolution FESEM to study solid-state phase transformations and reactions

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100172875 ◽

1994 ◽

Vol 52 ◽

pp. 1028-1029

Author(s):

P. G. Kotula ◽

D. D. Erickson ◽

C. B. Carter

Keyword(s):

Solid State ◽

High Resolution ◽

Phase Transformations ◽

High Efficiency ◽

Sol Gel ◽

Quantitative Information ◽

Solid State Reactions ◽

Critical Dimensions ◽

Backscattered Electrons ◽

Backscattered Electron

High-resolution field-emission-gun scanning electron microscopy (FESEM) has recently emerged as an extremely powerful method for characterizing the micro- or nanostructure of materials. The development of high efficiency backscattered-electron detectors has increased the resolution attainable with backscattered-electrons to almost that attainable with secondary-electrons. This increased resolution allows backscattered-electron imaging to be utilized to study materials once possible only by TEM. In addition to providing quantitative information, such as critical dimensions, SEM is more statistically representative. That is, the amount of material that can be sampled with SEM for a given measurement is many orders of magnitude greater than that with TEM.In the present work, a Hitachi S-900 FESEM (operating at 5kV) equipped with a high-resolution backscattered electron detector, has been used to study the α-Fe2O3 enhanced or seeded solid-state phase transformations of sol-gel alumina and solid-state reactions in the NiO/α-Al2O3 system. In both cases, a thin-film cross-section approach has been developed to facilitate the investigation. Specifically, the FESEM allows transformed- or reaction-layer thicknesses along interfaces that are millimeters in length to be measured with a resolution of better than 10nm.

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Interlayer confinement synthesis of Ir nanodots/dual carbon as an electrocatalyst for overall water splitting

Journal of Materials Chemistry A ◽

10.1039/d0ta09358k ◽

2020 ◽

Author(s):

Yaru Li ◽

Yu-Quan Zhu ◽

Weili Xin ◽

Song Hong ◽

Xiaoying Zhao ◽

...

Keyword(s):

Water Splitting ◽

Noble Metal ◽

High Efficiency ◽

Overall Water Splitting ◽

Highly Dispersed

Rationally designing low-content and high-efficiency noble metal nanodots offers opportunities to enhance electrocatalytic performances for water splitting. However, the preparation of highly dispersed nanodots electrocatalysts remains a challenge. Herein, we...

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