Recent years have seen the emergence of efficient, general-purpose terahertz photonic-crystal waveguides etched from high-resistivity silicon. Systems founded upon this platform will require antennas in order to interface with free-space fields. Multi-beam antennas are desirable to this end, as they are capable of interacting with a number of distinct directions simultaneously. Such functionality can be provided by Luneburg lenses, which we aim to incorporate with the terahertz photonic crystal waveguide. A Luneburg lens requires a precisely defined gradient-index, which we realize using effective medium techniques that are implemented with micro-scale etching of silicon. Thus, the photonic crystal waveguides can be integrated directly with the Luneburg lens and fabricated together from the same silicon wafer. In this way, we develop a planar Luneburg-lens antenna with a diameter of 17 mm and seven evenly spaced ports that cover a 120° field of view. Numerical and experimental characterization confirm that the antenna functions as intended over its operation bandwidth, which spans from 320 to 390 GHz. The Luneburg-lens antenna is subsequently deployed in a demonstration of terahertz communications over a short distance. The device may therefore find applications in terahertz communications, where multiple point-to-point links can be sustained by a given transceiver node. This form of terahertz beam control may also be useful for short-range radar that monitors several directions simultaneously.

Terahertz multi-beam antenna using photonic crystal waveguide and Luneburg lens

The performance of additive manufactured (AM) RF circuits and antennas is continuously improving, and in some cases these AM components are comparable to state-of-the-art circuits made with traditional manufacturing techniques. Medium to high-power waveguides made with AM methods such as copper-plated plastics, selective laser melting (SLM), and copper additive manufacturing (3-D CAM) have shown good performance up to terahertz frequencies. In this paper, binder jetting (BJ) metal printing is characterized using electron beam microscopy [scanning electron microscopy (SEM)] and energy dispersive spectroscopy. The RF performance of the 3-D-printed circuits is benchmarked with Ka-band cavity resonators, waveguide sections, and a filter. An unloaded resonator $Q$ of 616 is achieved, and the average attenuation of the WR-28 waveguide section is 4.3 dB/m. The BJ technology is tested with a meshed parabolic reflector antenna, where the illuminating horn, waveguide feed, and a filter are printed in a single piece. The antenna shows a peak gain of 24.56 dBi at 35 GHz.

Ka-Band Characterization of Binder Jetting for 3-D Printing of Metallic Rectangular Waveguide Circuits and Antennas

A practical approach to realize substrateless, unclad, micro-scale intrinsic silicon waveguides for the terahertz range is presented. The waveguides are monolithically integrated within a supporting silicon frame, with which they are fabricated together from the same silicon wafer in a single-mask etching process. This establishes an integration platform to house many diverse components and facilitates packaging. Effective medium techniques are deployed to prevent the frame from interfering with the waveguide's functionality. Straight waveguides of this sort are experimentally found to be efficient and broadband. Elementary components including Y-junctions and evanescent couplers are developed, and deployed in demonstrations of applications for terahertz waves including sensing and communications. This is a promising pathway to realize future microphotonic devices for diverse applications of terahertz waves.

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Unclad Microphotonics for Terahertz Waveguides and Systems

Design, Fabrication, and Modulation of THz Bandpass Metamaterials

Three‐dimensional printing technologies for terahertz applications: A review

For the first time, 3D printed metal-pipe rectangular waveguides (MPRWGs) have been demonstrated in the WM-380 (500-750 GHz) and WM-250 (750 GHz-1.1 THz) waveguide bands. The ultra-high spatial resolution offered by the new RECILS additive manufacturing technology enables the precision fabrication of these prototype MPRWGs at such high frequencies. This enabling technology avoids the need for access to expensive microfabrication resources and, thus, opens up the terahertz spectrum to the low-cost manufacture of passive components.

3D printed 1.1 THz waveguides

The regression characteristics of axial-injection end-burning hybrid rocket were experimentally investigated using a laboratory-scale motor. The axial-injection end-burning type fuel grains were ma...

Fuel Regression Characteristics of a Novel Axial-Injection End-Burning Hybrid Rocket

The authors have previously proposed the concept of end-burning-type hybrid rockets, which would use cylindrical fuel grains consisting of an array of many small ports running in the axial directio...

https://eprints.lib.hokudai.ac.jp/dspace/bitstream/2115/67715/1/2016-06-B36359_source%20file.pdf

Hiroyuki Yasukochi

Papers

3D printed 1.1 THz waveguides

Fuel Regression Characteristics of a Novel Axial-Injection End-Burning Hybrid Rocket

Verification Firings of End-Burning Type Hybrid Rockets

Verification firings of end-burning type hybrid rockets

Investigation of Throttling Response Characteristics of Axial-Injection End-Burning Hybrid Rockets