scholarly journals Polarization-insensitive GaN metalenses at visible wavelengths

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Meng-Hsin Chen ◽  
Cheng-Wei Yen ◽  
Chia-Chun Guo ◽  
Vin-Cent Su ◽  
Chieh-Hsiung Kuan ◽  
...  
Keyword(s):  
High Performance ◽  
Numerical Aperture ◽  
Light Output ◽  
Optical Microscope ◽  
Vacuum System ◽  
Patterned Substrates ◽  
Patterned Structures ◽  
Polarization Insensitive ◽  
Wide Bandgap Materials ◽  
Visible Wavelengths

AbstractThe growth of wide-bandgap materials on patterned substrates has revolutionized the means with which we can improve the light output power of gallium nitride (GaN) light-emitting diodes (LEDs). Conventional patterned structure inspection usually relies on an expensive vacuum-system-required scanning electron microscope (SEM) or optical microscope (OM) with bulky objectives. On the other hand, ultra-thin metasurfaces have been widely used in widespread applications, especially for converging lenses. In this study, we propose newly developed, highly efficient hexagon-resonated elements (HREs) combined with gingerly selected subwavelength periods of the elements for the construction of polarization-insensitive metalenses of high performance. Also, the well-developed fabrication techniques have been employed to realize the high-aspect-ratio metalenses working at three distinct wavelengths of 405, 532, and 633 nm with respective diffraction-limited focusing efficiencies of 93%, 86%, and 92%. The 1951 United States Air Force (USAF) test chart has been chosen to characterize the imaging capability. All of the images formed by the 405-nm-designed metalens show exceptional clear line features, and the smallest resolvable features are lines with widths of 870 nm. To perform the inspection capacity for patterned substrates, for the proof of concept, a commercially available patterned sapphire substrate (PSS) for the growth of the GaN LEDs has been opted and carefully examined by the high-resolution SEM system. With the appropriately chosen metalenses at the desired wavelength, the summits of structures in the PSS can be clearly observed in the images. The PSS imaging qualities taken by the ultra-thin and light-weight metalenses with a numerical aperture (NA) of 0.3 are comparable to those seen by an objective with the NA of 0.4. This work can pioneer semiconductor manufacturing to choose the polarization-insensitive GaN metalenses to inspect the patterned structures instead of using the SEM or the bulky and heavy conventional objectives.

scholarly journals Nanograting-Enhanced Optical Fibers for Visible and Infrared Light Collection at Large Input Angles

Photonics ◽  
2021 ◽  
Vol 8 (8) ◽  
pp. 295
Author(s):  
Ning Wang ◽  
Matthias Zeisberger ◽  
Uwe Hübner ◽  
Markus A. Schmidt
Keyword(s):  
Optical Fibers ◽  
High Performance ◽  
Large Angle ◽  
Coupling Efficiency ◽  
Numerical Aperture ◽  
Infrared Light ◽  
Light Collection ◽  
High Performance Fiber ◽  
Visible Wavelengths ◽  
Quantum Technology

The efficient incoupling of light into particular fibers at large angles is essential for a multitude of applications; however, this is difficult to achieve with commonly used fibers due to low numerical aperture. Here, we demonstrate that commonly used optical fibers functionalized with arrays of metallic nanodots show substantially improved large-angle light-collection performances at multiple wavelengths. In particular, we show that at visible wavelengths, higher diffraction orders contribute significantly to the light-coupling efficiency, independent of the incident polarization, with a dominant excitation of the fundamental mode. The experimental observation is confirmed by an analytical model, which directly suggests further improvement in incoupling efficiency through the use of powerful nanostructures such as metasurface or dielectric gratings. Therefore, our concept paves the way for high-performance fiber-based optical devices and is particularly relevant within the context of endoscopic-type applications in life science and light collection within quantum technology.

scholarly journals Broadband high-efficiency dielectric metasurfaces for the visible spectrum

2016 ◽  
Vol 113 (38) ◽  
pp. 10473-10478 ◽  
Author(s):  
Robert C. Devlin ◽  
Mohammadreza Khorasaninejad ◽  
Wei Ting Chen ◽  
Jaewon Oh ◽  
Federico Capasso
Keyword(s):  
High Performance ◽  
High Efficiency ◽  
Numerical Aperture ◽  
Optical Loss ◽  
Visible Spectrum ◽  
Optical Element ◽  
Atomic Layer ◽  
Optical Elements ◽  
Layer Deposition ◽  
Visible Wavelengths

Metasurfaces are planar optical elements that hold promise for overcoming the limitations of refractive and conventional diffractive optics. Original dielectric metasurfaces are limited to transparency windows at infrared wavelengths because of significant optical absorption and loss at visible wavelengths. Thus, it is critical that new materials and nanofabrication techniques be developed to extend dielectric metasurfaces across the visible spectrum and to enable applications such as high numerical aperture lenses, color holograms, and wearable optics. Here, we demonstrate high performance dielectric metasurfaces in the form of holograms for red, green, and blue wavelengths with record absolute efficiency (>78%). We use atomic layer deposition of amorphous titanium dioxide with surface roughness less than 1 nm and negligible optical loss. We use a process for fabricating dielectric metasurfaces that allows us to produce anisotropic, subwavelength-spaced dielectric nanostructures with shape birefringence. This process is capable of realizing any high-efficiency metasurface optical element, e.g., metalenses and axicons.

Vacuum System to Minimize the Specimen Contamination of High-Performance EM

1977 ◽  
Vol 35 ◽  
pp. 68-69
Author(s):  
N. Yoshimura ◽  
K. Shirota ◽  
T. Etoh
Keyword(s):  
Electron Microscope ◽  
High Speed ◽  
High Performance ◽  
High Vacuum ◽  
Vacuum System ◽  
Pump System ◽  
Pumping System ◽  
Diffusion Pump ◽  
Almost All ◽  
Cascade Type

One of the most important requirements for a high-performance EM, especially an analytical EM using a fine beam probe, is to prevent specimen contamination by providing a clean high vacuum in the vicinity of the specimen. However, in almost all commercial EMs, the pressure in the vicinity of the specimen under observation is usually more than ten times higher than the pressure measured at the punping line. The EM column inevitably requires the use of greased Viton O-rings for fine movement, and specimens and films need to be exchanged frequently and several attachments may also be exchanged. For these reasons, a high speed pumping system, as well as a clean vacuum system, is now required. A newly developed electron microscope, the JEM-100CX features clean high vacuum in the vicinity of the specimen, realized by the use of a CASCADE type diffusion pump system which has been essentially improved over its predeces- sorD employed on the JEM-100C.

On resolving fine periodic microstructures in the optical microscope

1989 ◽  
Vol 47 ◽  
pp. 364-365
Author(s):  
W.S. Putnam ◽  
C. Viney
Keyword(s):  
Liquid Crystalline ◽  
Numerical Aperture ◽  
Polarized Light ◽  
Normal Incidence ◽  
Optical Microscope ◽  
Angle Of Incidence ◽  
Resolution Limit ◽  
Crystalline Materials ◽  
Periodic Microstructures ◽  
Liquid Crystalline Materials

Many sheared liquid crystalline materials (fibers, films and moldings) exhibit a fine banded microstructure when observed in the polarized light microscope. In some cases, for example Kevlar® fiber, the periodicity is close to the resolution limit of even the highest numerical aperture objectives. The periodic microstructure reflects a non-uniform alignment of the constituent molecules, and consequently is an indication that the mechanical properties will be less than optimal. Thus it is necessary to obtain quality micrographs for characterization, which in turn requires that fine detail should contribute significantly to image formation.It is textbook knowledge that the resolution achievable with a given microscope objective (numerical aperture NA) and a given wavelength of light (λ) increases as the angle of incidence of light at the specimen surface is increased. Stated in terms of the Abbe resolution criterion, resolution improves from λ/NA to λ/2NA with increasing departure from normal incidence.

scholarly journals Polarization-Insensitive Metalenses at Visible Wavelengths

Nano Letters ◽  
2016 ◽  
Vol 16 (11) ◽  
pp. 7229-7234 ◽  
Author(s):  
M. Khorasaninejad ◽  
A. Y. Zhu ◽  
C. Roques-Carmes ◽  
W. T. Chen ◽  
J. Oh ◽  
...  
Keyword(s):  
Polarization Insensitive ◽  
Visible Wavelengths

scholarly journals Metalenses Based on Symmetric Slab Waveguide and c-TiO2: Efficient Polarization-Insensitive Focusing at Visible Wavelengths

Nanomaterials ◽  
2018 ◽  
Vol 8 (9) ◽  
pp. 699 ◽  
Author(s):  
Yaoyao Liang ◽  
Zhongchao Wei ◽  
Jianping Guo ◽  
Faqiang Wang ◽  
Hongyun Meng ◽  
...  
Keyword(s):  
Berry Phase ◽  
Incident Light ◽  
Visible Spectrum ◽  
Slab Waveguide ◽  
Optical Elements ◽  
Polarization Insensitive ◽  
Wavefront Shaping ◽  
Visible Wavelengths ◽  
532 Nm ◽  
Good Agreement

A key goal of metalens research is to achieve wavefront shaping of light using optical elements with thicknesses on the order of the wavelength. Here we demonstrate ultrathin highly efficient crystalline titanium dioxide metalenses at blue, green, and red wavelengths (λ0 = 453 nm, 532 nm, and 633 nm, respectively) based on symmetric slab waveguide theory. These metalenses are less than 488 nm-thick and capable of focusing incident light into very symmetric diffraction-limited spots with strehl ratio and efficiency as high as 0.96 and 83%, respectively. Further quantitative characterizations about metalenses’ peak focusing intensities and focal spot sizes show good agreement with theoretical calculation. Besides, the metalenses suffer only about 10% chromatic deviation from the ideal spots in visible spectrum. In contrast with Pancharatnam–Berry phase mechanism, which limit their incident light at circular polarization, the proposed method enables metalenses polarization-insensitive to incident light.

Comparative studies of energy saving polymers and fabrication of high performance transparent polymer by solvent bonding

2018 ◽  
Vol 39 (1) ◽  
pp. 68-75
Author(s):  
S.P. Aadhy ◽  
T. Hema Sinega ◽  
C. Karthikeyan ◽  
S. Akshay ◽  
Mohan Kumar Pitchan ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Energy Saving ◽  
High Performance ◽  
Solvent Mixture ◽  
Heat Transfer Analysis ◽  
Compression Moulding ◽  
Lap Shear ◽  
Visible Wavelengths ◽  
Pass Through ◽  
Solvent Bonding

Abstract This work investigates the possibility of using polyetherimide (PEI) as an energy saving alternative to glass, polymethylmethacrylate (PMMA) and polycarbonate (PC) by carrying out heat transfer analysis and suggests vaporized solvent bonding as a viable bonding technique for the fabrication of PEI. By heat transfer analysis using building energy simulation, it is observed that less energy is expended for space-conditioning of a building with windows made of PEI when compared to glass, PMMA and PC. The compression moulding technique is used to mould PEI and fabrication is done using a solvent mixture of dimethyl sulfoxide and tetrahydrofuran in 1:1 ratio. The optical properties of the bonded specimen are studied using UV-visible spectrophotometry and it is found that PEI does not allow UV wavelength radiation to pass through while transmitting visible wavelengths. The mechanical strength of the bond is tested using lap shear tensile strength test and the type of failure is observed to be cohesive from the structure. This is indicative of the fact that using this particular solvent to bond PEI results in the maximum possible strength.

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