A Far-Field Implementation of Near-Field Phase-Shift Lithography Using Diffractive Optical Elements

Abstract A great deal of research focuses on how the mesoscale environment influences convective storms, but relatively little is known about how supercells modify the nearby environment. Soundings from three field experiments are used to investigate differences in the near and far inflow of supercell thunderstorms. Close-range soundings in the near inflow of supercells are compared to near-simultaneous soundings released farther away (but still within inflow). Several soundings from the second field phase of the Verification of the Origins of Rotation in Tornadoes Experiment (VORTEX2) supplement the Mesoscale Predictability Experiment (MPEX/MiniMPEX) dataset, resulting in 28 near–far inflow pairs from a wide variety of tornadic and nontornadic supercells. The focus of this study is on a comparison of a subset of 12 near–far inflow pairs taken near tornadic supercells and 16 near–far inflow pairs taken near nontornadic supercells. Similar values of 0–1-km storm-relative helicity (SRH01) are found in the far field of the tornadic and nontornadic supercells, possibly as a result of a difference in mean diurnal timing. However, SRH01 is found to increase substantially in the near field of the tornadic supercells, but not the nontornadic supercells. Differences in the thermodynamic environment include greater moisture above the ground in the far field of the tornadic supercells (despite similar near-ground moisture in both the tornadic and nontornadic subsets) and a subtle increase in static stability near the surface in the nontornadic near inflow.

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Near-field phase profile and far-field contrast modulation for micro-lens arrays at the refraction limit

SN Applied Sciences ◽

10.1007/s42452-020-03759-y ◽

2020 ◽

Vol 2 (12) ◽

Author(s):

M. Yousefi ◽

D. Nečesal ◽

T. Scharf ◽

M. Rossi

Keyword(s):

Plane Wave ◽

Point Source ◽

Gaussian Beam ◽

Near Field ◽

Field Pattern ◽

Far Field ◽

High Contrast ◽

Field Phase ◽

Far Field Pattern ◽

Micro Lens

Abstract We investigate the far-field pattern generation for a micro-lens array (MLA) illuminated under different conditions. Plane wave and Gaussian beam illumination are considered for an MLA with a small diameter of 27 microns and 30 microns period. At these dimensions, the optical effects are governed by diffraction and refraction and sometimes the regime is called the refraction limit. For Gaussian beam illumination, a high contrast dot pattern can be obtained in the far field according to the self-imaging theory for point source illumination and it is investigated in the simulation part. Also, we designed an interference microscopy setup to record both the phase and intensity in near field behind the MLA and also in the far field. The new instrument allows us to change illumination conditions from plane wave to point source. We then experimentally compare the near-field phase modulation and resulting far-field intensity for different conditions. For plane wave illumination, a high contrast pattern is observed in the far field. For the Gaussian beam illumination, the contrast of the far-field pattern depends on the distance of the source and MLA resulting in high contrast and a larger field of view only for particular distances depending on the interference of the Gaussian beam curved phase front and the MLA.

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Printing polarization and phase at the optical diffraction limit: near- and far-field optical encryption

Nanophotonics ◽

10.1515/nanoph-2020-0352 ◽

2020 ◽

Vol 10 (1) ◽

pp. 697-704

Author(s):

Qinghua Song ◽

Samira Khadir ◽

Stéphane Vézian ◽

Benjamin Damilano ◽

Philippe de Mierry ◽

...

Keyword(s):

Near Field ◽

Diffraction Limit ◽

Optical Data Storage ◽

Optical Diffraction ◽

Optical Data ◽

Orthogonal Polarization ◽

Security Level ◽

Far Field ◽

Field Phase ◽

Optical Encryption

AbstractSecuring optical information to avoid counterfeiting and manipulation by unauthorized persons and agencies requires innovation and enhancement of security beyond basic intensity encryption. In this paper, we present a new method for polarization-dependent optical encryption that relies on extremely high-resolution near-field phase encoding at metasurfaces, down to the diffraction limit. Unlike previous intensity or color printing methods, which are detectable by the human eye, analog phase decoding requires specific decryption setup to achieve a higher security level. In this work, quadriwave lateral shearing interferometry is used as a phase decryption method, decrypting binary quick response (QR) phase codes and thus forming phase-contrast images, with phase values as low as 15°. Combining near-field phase imaging and far-field holographic imaging under orthogonal polarization illumination, we enhanced the security level for potential applications in the area of biometric recognition, secure ID cards, secure optical data storage, steganography, and communications.

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