Fabrication of a concentric-circular focusing grating coupler by a conic-wave-front interference method and light-convergence experiments using the coupler

Nishiwaki, Seiji; Asada, Jun-ichi; Ohshima, Kiyoko; Kitagawa, Tetsuo

doi:10.1364/ao.34.007372

Cited by 3 publications

(3 citation statements)

References 6 publications

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“…More complicated holographic techniques have been used to make circular structures such as Fresnel zone plates 3 and concentric circular ring patterns with constant periods. 4 Refractive lenses with high precision and quality are needed in this holographic method to obtain the wave fronts. Moreover, the periodicity of the patterns produced is limited to the radial direction since it would be difficult if not impossible to produce a wave with continuous phase variation along the azimuthal direction using refractive optics.…”

Section: Introductionmentioning

confidence: 99%

Patterning of circular structure arrays with interference lithography

Solak

Dávid

2003

Journal of Vacuum Science &Amp; Technology B: Microelectronics and Nanometer Structures Processing, Measurement, and Phenomena

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We have developed an interference lithography method that enables the production of circular periodic patterns. The range of accessible patterns includes concentric circular rings, spiral-and spoke-like patterns, and dots positioned periodically on concentric circular tracks. The method is based on the use of transmission diffraction gratings to create circular beams with wave fronts that are not accessible with reflective or refractive optics. Diffraction gratings with equally spaced concentric circles are used to obtain diverging or converging conical waves with radial phase variation and spiral-like gratings are used to obtain waves with the phase varying in both radial and azimuthal directions. We have experimentally demonstrated the method with electron-beam written diffraction gratings, which we illuminated with a coherent laser beam to form the interference patterns. Many different designs are possible that bring two, three, or more beams together to form a desired interference pattern. The technique should in general be useful in applications requiring circular periodic patterns, which may include production of patterned magnetic media, spoke patterns for angular encoders, and photonic crystals with circular symmetry.

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Section: Introductionmentioning

confidence: 99%

Patterning of circular structure arrays with interference lithography

Solak

Dávid

2003

Journal of Vacuum Science &Amp; Technology B: Microelectronics and Nanometer Structures Processing, Measurement, and Phenomena

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“…To provide a robust answer to these challenges, we devised a novel structure (named CGC-LIDAR) using an LC (liquid crystal) and demonstrated the light-scanning principle over a 360-degree sweeping range.Structure and operational principle of a CGC-LIDAR. Figure 1a,b are a perspective and cross-sectional illustration of a CGC-LIDAR that includes concentric grating couplers (CGCs) [24][25][26] . Light of wavelength λ = 0.94 µm emitted from a laser diode is collimated to parallel light by a collimator and is reflected to a polarizing beam splitter (PBS).…”

mentioning

confidence: 99%

“…Structure and operational principle of a CGC-LIDAR. Figure 1a,b are a perspective and cross-sectional illustration of a CGC-LIDAR that includes concentric grating couplers (CGCs) [24][25][26] . Light of wavelength λ = 0.94 µm emitted from a laser diode is collimated to parallel light by a collimator and is reflected to a polarizing beam splitter (PBS).…”

mentioning

confidence: 99%

Biaxial 360-degree scanning LIDAR using a liquid crystal control

Nishiwaki

2021

Sci Rep

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Sophisticated non-mechanical technology for LIDARs is needed to realize safe autonomous cars. We have confirmed the operating principle of a non-mechanical LIDAR by combining concentric circular-grating couplers (CGCs) with a coaxially aligned rod lens. Laser light incident vertically on the center of the inner CGC along the center axis of the lens is radiated from the outer CGC and passes through the side surface of the lens. It is converted to a parallel beam that scans in two axes by applying voltages to two area-segmented electrode layers sandwiching the CGCs and a liquid crystal layer formed on the CGCs. We have demonstrated scanning whose motion ranges were 360 degrees horizontally and 10° vertically. A beam with a spread angle of 0.3° × 0.8° at a minimum swept vertically up to a frequency of 100 Hz and ten equally spaced beams scanned rotationally with a 6-degree cycle variation of spread of between 0.8° and 3.5°.

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Design of a high-efficiency volume grating coupler for line focusing

1998

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A volume grating for outcoupling and line focusing of waveguided infrared light is designed and optimized. A local grating vector approach is used in combination with the rigorous coupled-wave analysis. By design, this volume grating coupler is holographically constructed on top of a waveguide by the interference of two coherent 364-nm ultraviolet waves formed with two aberration-optimized cylindrical lenses. This focusing coupler exhibits preferential-order coupling (92.9%) into the cover as well as very low focal intensity side lobes. This is accomplished through a chirped, slanted-fringe volume grating with a designed spatial variation in the attenuation coefficient (describing the outcoupling of the guided mode) along the length of the grating. This is achieved by a specific variation in the grating slant angle along the grating length. By design, the 1000-mum-length coupler focuses an 850-nm infrared guided wave to a line with an intensity FWHM of 3.32 mum and a 90% power width of 5.53 mum at a focal distance of 4 mm directly above the grating. Its performance is compared with that of a corresponding electron-beam-written surface-relief coupler design.

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Fabrication of a concentric-circular focusing grating coupler by a conic-wave-front interference method and light-convergence experiments using the coupler

Cited by 3 publications

References 6 publications

Patterning of circular structure arrays with interference lithography

Patterning of circular structure arrays with interference lithography

Biaxial 360-degree scanning LIDAR using a liquid crystal control

Design of a high-efficiency volume grating coupler for line focusing

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