Three-dimensional stereolithography for millimeter wave and terahertz applications

Abstract: Metal-coated polymers shaped by 3D stereolithography are introduced as a new manufacturing method for passive components for millimeter to terahertz electromagnetic waves. This concept offers increased design capabilities and flexibilities while shortening the manufacturing process of complex shapes, e. g., corrugated horns, mirrors, etc. Tests at 92.5, 140, and 170 GHz are reported. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.3701738

Monolithic Metal-Coated Plastic Components for mm-Wave Applications

A stereolithography-based manufacturing process for monolithic high aspect ratio components for mm-wave and sub-mm-wave applications is demonstrated. A 25mm long straight waveguide and a diagonal horn antenna, both for the WR-3.4 band (220–330 GHz), are manufactured and characterized. The waveguide is found to exhibit transmission losses close to the theoretical minimum for Cu, and the performance of the diagonal antenna in terms of cross-polarization and directivity matches closely a metallic split-block reference antenna. These results confirm the high surface quality and mechanical accuracy of the employed 3D printing and plating techniques and thus validate the process for rapid manufacturing of monolithic components up to 330 GHz

Stacked rings for terahertz wave-guiding

We demonstrate the construction of corrugated waveguides using stacked rings to propagate terahertz frequencies. The waveguide allows propagation of the same fundamental mode as an optical-fiber, namely, the H E11 mode. This simple concept opens the way for corrugated wave-guides up to several terahertz, maintaining beam characteristics as for terahertz applications

Experimental study from linear to chaotic regimes on a terahertz-frequency gyrotron oscillator

Basic wave-particle interaction dynamics from linear to chaotic regimes is experimentally studied on a frequency tunable gyrotron generating THz radiation in continuous mode (200W) at 263GHz which will be used for dynamic nuclear polarization nuclear magnetic resonance spectroscopy applications. In the studied system, the nonlinear dynamics associated to the waveparticle interaction is dominated by longitudinal mode competition of a given transverse TEm;p cavity-mode. This study covers a wide range of control parameter from gyro-traveling wave tube (gyro-TWT) to gyro-backward wave oscillator (gyro-BWO) like interactions for which extensive theoretical studies have been performed in the past on a simplified system. Besides the common route to chaos characterized by period doubling, other routes have been identified among which some are characterized by line-width frequency-broadening on the side-bands. The complex nonlinear dynamics is in good agreement with the theory and the experimental results are discussed on the basis of the prediction obtained with the nonlinear time-dependent selfconsistent codes TWANG and EURIDICE both based on a slow-time scale formulation of the self-consistent equations governing the wave-particle dynamics. V

Terahertz passive components for Dynamic Nuclear Polarization Nuclear Magnetic Resonance applications

Terahertz radiation, THz = 1012 Hz, refers to electromagnetic signals with frequencies in the range of 0.3 to 3 THz, and wavelengths between 1 and 0.1 mm. This part of the electromagnetic spectrum is located in between millimeter waves at lower frequencies, and far-infrared at higher frequencies. THz is one of the last underemployed portions of the electromagnetic spectrum, despite the interest it raises for research and applications. One application that makes use of THz signals is Dynamic Nuclear Polarization - Nuclear Magnetic Resonance (DNP-NMR). It allows for a dramatic increase in signal sensitivity over conventional NMR. The latter is a widespread technique used from Chemistry to Material Science. First commercial DNP-NMR spectrometers appeared on the market in 2008. However, the application can still benefit from developments in its THz components. This thesis reports on the development of THz wave guiding-components for DNP-NMR. In particular, Corrugated wave-guiding components are studied, in view of their low propagation losses. A new manufacturing technique for those Corrugated wave-guiding components is presented: the Stacked Rings technology. This technology circumvents the limitations in achievable mechanical precisions with conventional machining, and allows for the scaling of Corrugated wave-guiding components through the THz spectrum. Corrugated waveguides made by Stacked Rings are presented at 263 GHz, and are successfully integrated in commercial DNP-NMR spectrometers. A transmission line made by Stacked Rings at 140 GHz for a Dissolution DNP pre-polarizer is also presented. The pre-polarizer uses DNP to generate contrast agents for Magnetic Resonance Imaging. An increase in the pre-polarizer’s DNP performances is demonstrated. Finally, the Stacked Rings technology is used to demonstrate the performances of a modular set of Corrugated wave-guiding components between 500 and 750 GHz for test and measurement applications. All components are characterized at THz frequencies with two experimental platforms and associated methodologies developed in the framework of this thesis. A crucial THz component for DNP-NMR applications is the probe. It couples the THz signal to the sample under study, while also integrating features necessary for NMR. A chapter of this thesis reports on an experimental and simulation study of the THz field distributions in this complex environment with dimensions larger than the THz wavelength. Probe chambers of commercial DNP-NMR probes are studied, complex field distributions are put into evidence, and key parameters influencing these field distributions are identified for future optimizations

Over-moded resonant cavity for magnetic resonance based on a photonic band gap stucture

The present invention relates to a probe for multiple irradiation magnetic resonance techniques like, for instance, dynamic nuclear polarization (DNP) or ENDOR. The probe comprises an overmoded resonant cavity based on a Photonic Band Gap (PBG) structure for the excitation and/or detection of electron paramagnetic resonance in the millimeter or sub-millimeter wave region and an NMR coil for the excitation and/or detection of nuclear magnetic resonance at RF frequencies. The sample, the sample holder and the NMR coil may form part of the PBG resonant structure, possibly contributing to the defects that give rise to the trapping of electromagnetic modes with millimeter or sub-millimeter wavelengths

Passive components for millimeter, submillimeter and terahertz electromagnetic waves made by piling up successive layers of material

The passive component for the transmission and manipulation of electromagnetic signals having frequencies from 30 GHz to 100 THz, comprises a corrugated or smooth wall unit alone or an assembly of at least one corrugated or smooth wall unit in a hollow guiding rod. The external shape of said unit(s) corresponds to the internal shape of the hollow guiding rod, and said units or the entire assembly may be metal plated to form the component. The manufacturing method of such components includes building units or sub units by piling up successive layers of material using 3D printing, 3D microfabrication based on 2-photon photopolymerisation, stereolithography, selective laser sintering (SLS), electron beam melting (EBM). The units or sub units are later possibly metal plated on selective or all surfaces

TERAHERTZ : New Opportunities for Industry

The purpose of this wiki is to collect information on terahertz technologies, and to foster collaborations among researchers in industry and academia worldwide