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Evaluation of Micro Laser Sintering Metal 3D-Printing Technology for the Development of Waveguide Passive Devices up to 325 GHz
... In addition, 3D printing could be more cost-effective than traditional methods such as CNC and microfabrication. A range of 3D-printed RF components has been demonstrated across frequency bands from 20 to 400 GHz [6][7][8][9][10][11]. Among the various aspects of 3D-metal-printed structures, surface quality plays a critical role in determining electrical performance. ...
... It is important to note that skin depth is inversely proportional to the square of the frequency. While several studies [1,6,9,12] have assessed surface roughness in terms of Ra or RMS (root mean square), additional research may be needed to improve modeling accuracy. Furthermore, the effect of skin depth may differ depending on the type of RF component. ...
To investigate the effect of the surface roughness of 3D-metal-printed sub-THz components, the WR-10 3-inch-long waveguide and 24 dBi rectangular horn antenna were 3D-metal-printed using a titanium alloy powder and a high-resolution 3D metal printer. The characterized surface roughness of the printed components was 17.27 µm in RMS from a 3D optical surface profiler, and a nodule ratio of 7.89 µm and surface ratio of 1.52 for Huray model from the analyzed SEM images. The measured results of the 3D-metal-printed waveguide and rectangular horn antenna were compared with the ones of commercial waveguide and horn antenna having the same shapes. The 3D-metal-printed waveguide has 4.02 dB higher loss than the commercial waveguide, which may be caused by an ohmic loss of 0.85 dB and a surface roughness loss of 2.81 dB. The 3D-metal-printed horn antenna has 2 dB higher loss then the commercial horn antenna, which may be caused by an ohmic loss of 0.2 dB, surface roughness of 0.1 dB and fabrication tolerance loss of 1.7 dB. The loss separation was done from the EM simulation by changing the conductor material and surface roughness.
... With metal 3D printing technology such as micro laser sintering (MLS) and selective laser melting (SLM) technology, waveguides achieved an insertion loss of 0.09°dB/mm in WR-5.1 and WR-3.4 band. In comparison, metal printed waveguides have higher loss per unit length than plastic ones, and it can be attributed to the higher surface roughness of the metal printed waveguides, whereas the plastic waveguides can be electroplated to achieve a smoother metal surface [10,11]. ...
... step E 500-750 0.05-0.07 [14] UV-LIGA E 220-325 ∼ 0.096 [9] SLA No 220-325 ∼ 0.014 [10] MLS No 140-220 ∼ 0.09 [11] SLM ...
This paper reports the design, fabrication and measurement techniques for a set of low-loss slotted waveguides. The waveguides are fabricated based on a micro metal additive manufacturing technology. They were fabricated layer by layer in one piece without the need of post-fabrication assembly. As examples, straight waveguides in WR-3.4 (220-330°GHz) and WR-2.2 (330-500°GHz) bands were fabricated and tested. Measurement results show the insertion loss per unit length is 0.0615-0.122°dB/mm and 0.116-0.281°dB/mm, respectively.
... (<2 μm) compared to BJ technology with 4 μm. However, for frequencies higher than 200 GHz, more aggressive surface roughness is needed (<1 μm), leading to metal-coated dielectric 3D printed devices using stereolithography apparatus or metal 3D printed devices relying on micro laser sintering technology [21] to achieve promising performances. ...
This paper proposes an innovative hybrid package integration strategy compatible with silicon-based technologies. It is evaluated beyond 200 GHz by the integration of a WR3 back-to-back waveguide-to-suspended stripline transition designed in BiCMOS technology, relying on metallic split-block package and organic laminate substrate. Simulated insertion loss below 3 dB is observed in the 220–320 GHz frequency band, competing with reported traditional solutions using III–V substrates. The achieved performances lead to promising perspectives for low-cost silicon packaging solutions beyond 200 GHz.
... This increased carrier density, potentially caused by processing conditions or material defects, leads to enhanced absorption of light within the modulator structure. Additionally, scattering losses at the contact regions between the ITO and other layers might play a role in the higher measured IL. [14][15][16] Furthermore, the influence of deposited layer roughnesses and intrinsic material defects, such as surface states and oxygen vacancies, cannot be entirely ruled out. These imperfections can introduce additional scattering centers and energy traps, further contributing to the observed increase in IL. ...
A silicon-integrated Schottky metal-insulator-semiconductor plasmonic modulator with remarkable optical loss performance is demonstrated. The proposed device architecture is realized through the heterogeneous integration of amorphous aluminum, silica, and indium tin oxide, forming a metal-insulator-semiconductor plasmonic stack housed on an SOI substrate. The device exhibited extinction ratio and insertion loss levels of 1 dB/μm and 0.128 dB/μm, respectively for a 10 μm-long waveguide. By taking advantage of the absence of diffraction limits in plasmonic structures, strong modal confinement proved possible as evidenced by simulation results, paving the way for improved optical processes and miniaturized photonic circuits.
... The higher experimental IL level is attributed to the additional free carrier absorption caused by elevated ITO carrier density and scattering losses from the contact region. Effects from deposited layer roughnesses and various intrinsic defects, such as surface states and oxygen vacancies, could have played an additional role in this higher measured IL level [75][76][77] . Nonetheless, IL and CE values exhibit low variations between nm and 1600 nm, indicating a potential broadband modulator operation. ...
By taking advantage of the absence of diffraction limit restrictions in plasmonic structures, strong modal confinement is made possible, paving the way for improved optical processes and miniaturized photonic circuit integration. Indium tin oxide (ITO) has emerged as a promising plasmonic material that serves as a relatively low-carrier density Drude metal by its electro-optic tunability and versatility as an integrative oxide. We herein demonstrate the facile integration of SiO2/ITO heterointerfaces into metal–insulator–semiconductor (MIS) electrooptic structures. The first MIS device employs a SiO2/ITO heterostructure grown on thin polycrystalline titanium nitride (poly-TiN) and capped at the ITO side with thin aluminum (Al) film contact electrode. The TiN interlayer acts as a bottom electrode, forming a metal–insulator–semiconductor-metal (MISM) heterojunction device, and grows directly on (100)-oriented silicon (Si). This MISM device enables one to examine the electrical properties of semiconductive ITO layers. The second MIS device incorporates a semiconductive ITO layer with a SiO2 dielectric spacer implemented on a silicon-on-insulator (SOI) platform, forming a graded-index coupled hybrid plasmonic waveguide (CHPW) modulator. This device architecture represents a crucial step towards realizing plasmonic modulation using oxide materials. The CHPW device performance presented herein provides a proof-of-concept that demonstrates the advantages offered by such device topology to perform optical modulation via charge carrier dispersion. The graded-index CHPW can be dynamically reconfigured for amplitude, phase, or 4-quadrature amplitude modulation utilizing a triode-like biasing strategy. It exhibited extinction ratio (ER) and insertion loss (IL) levels of around 1 dB/µm and 0.128 dB/µm, respectively, for a 10 µm waveguide length.
Feynman's statement, “There is plenty of room at the bottom”, underscores vast potential at the atomic scale, envisioning microscopic machines. Today, this vision extends into 3D space, where thousands of atoms and molecules are volumetrically patterned to create light‐driven technologies. To fully harness their potential, 3D designs must incorporate high‐refractive‐index elements with exceptional mechanical and chemical resilience. The frontier, however, lies in creating spatially patterned micro‐optical architectures in glass and ceramic materials of dissimilar compositions. This multi‐material capability enables novel ways of shaping light, leveraging the interaction between diverse interfaced chemical compositions to push optical boundaries. Specifically, it encompasses both multi‐material integration within the same architectures and the use of different materials for distinct architectural features in an optical system. Integrating fluid handling systems with two‐photon lithography (TPL) provides a promising approach for rapidly prototyping such complex components. This review examines single and multi‐material TPL processes, discussing photoresin customization, essential physico‐chemical conditions, and the need for cross‐scale characterization to assess optical quality. It reflects on challenges in characterizing multi‐scale architectures and outlines advancements in TPL for both single and spatially patterned multi‐material structures. The roadmap provides a bridge between research and industry, emphasizing collaboration and contributions to advancing micro‐optics.
This work presents two manufacturing approaches for waveguide diplexers applicable to separating two of the G-band, 140-220 GHz, channels used in space borne radiometry of the Earth’s atmosphere. Waveguide diplexing is a lower volume alternative to a quasi-optical, i.e., frequency selective surface based, system. The two channels considered are 164-167 GHz and 175-191 GHz. The diplexer comprises a Y junction with two waveguide-cavity filters. Two high-precision fabrication technologies have been utilized: computer numerical control (CNC) machining and 3D printing. Two units were CNC machined as brass split-blocks and a third was 3D printed monolithically in stainless steel by a micro laser sintering process. The latter is an innovative structure that incorporates the diplexer with the waveguide flanges. All devices were gold coated to reduce loss. Measured insertion losses in the two channels were 0.6 and 0.34 dB for the CNC-machined diplexers and 1.8 and 0.8 dB for the 3D printed diplexer. The maximum frequency shifts from design were 0.695 GHz in the CNC-diplexers and 1.55 GHz in the 3D printed diplexer.
This article presents a comprehensive evaluation of 3-D-printed monolithic waveguide components fabricated by a high-precision micro laser sintering (MLS) process. The investigated devices are two 180-GHz bandpass filters and a straight
G
-band (140–220 GHz) waveguide section. All were made of stainless steel, which was later gold coated using an electroless process. One of the filter samples was characterized using micro X-ray computed tomography (XCT) to inspect the printing quality as well as measure the internal dimensions. The sample was then sectioned to allow measurement of the surface roughness of the inner surfaces and inspect the gold coating quality. The as-manufactured stainless steel components showed high insertion losses: over 3 dB in the filter passbands and between 4.7 and 7 dB for the waveguide section, increasing with frequency over the
G
-band. This loss is due to the electrical conductivity of stainless steel as well as the surface roughness. Gold plating significantly reduced the insertion losses to 0.5 dB for the filters and to between 0.6 and 1 dB for the waveguide section. The investigative study showed the high-dimensional accuracy and good printing quality achieved by MLS, demonstrating the value of the technique in producing monolithic metal waveguide components with fine geometrics.
This article presents a waveguide with a pair of
E
-plane bends and two waveguide bandpass filters (BPFs) which operate in WR-3.4 band (220–330 GHz). These devices are fabricated by a micro metal additive manufacturing (M-MAM) technology on copper in one piece. Both filters are fifth order and operate at a center frequency of 280 GHz with a bandwidth of 8 GHz. Cylindrical resonators are employed for filter design. The standard feed waveguides are designed in bend structures, facilitating the measurements. The M-MAM technology is a layer-by-layer additive manufacturing process constructing the waveguide devices in five layers. Since the layout of the devices has a strong impact on the electrostatic field distributions and hence the electroforming quality, both full-wave electromagnetic (EM) simulations and electrostatic analysis are simultaneously considered in the device design. It eases the subsequent electroforming and polishing processes, effectively improving the performance of the devices. The insertion losses and return losses of the measured filters are lower than 1.65 dB and better than 15 dB. The center frequency shifts are less than 0.3%. The excellent results attribute to the delicate co-design method between EM and electrostatic analyses encountered both in the filter design and in the additive manufacturing process.
We report a
D
-band waveguide diplexer, with two passbands of 130–134 and 151.5–155.5 GHz, fabricated using micro laser sintering (MLS) additive manufacturing with stainless steel. This is the first demonstration of metal 3-D printing technology for multiport filtering devices at a sub-terahertz (THz) frequency. For comparison, the same diplexer design has also been implemented using computer numerical controlled (CNC) milling. The diplexer, designed using coupling matrix theory, employs an all-resonator and
E
-plane split-block structure. The two channels are folded for compactness. A staircase coupled structure is used in one channel to increase the isolation performance. The printed waveguide flanges are modified to adapt to the limited printing volume from the MLS. Effects of fabrication tolerance on the diplexer are investigated. An effective and unconventional electroless plating process is developed. The measured average insertion losses of the gold-coated diplexer are 1.31 and 1.37 dB, respectively. The respective frequency shifts from design values are 0.92% and 1.1%, and bandwidth variations are 4% and 15%. From a comprehensive treatment of the end-to-end manufacturing process, the work demonstrates MLS to be a promising fabrication technique for complex waveguide devices at a sub-THz frequency range.
This paper presents a fifth-order W-band waveguide bandpass filter with a Chebyshev response, operating at center frequency of 90 GHz and having fractional bandwidth of 11%. The filter is fabricated by micro laser sintering process which is a powder bed based additive manufacturing technology. Use of this technology allows the filter to be made accurately with high resolution and good surface quality in one piece. This results in better performance in term of insertion loss and reproducibility. For the purpose of comparison, two similar filters are presented in this paper with the same structure and specification, one made from stainless steel and the other made from stainless steel coated with copper. Both filters are tested and have excellent agreement between measurements and simulations.
This paper explores the potential of metallic 3-D printing technology for millimeter-wave (mmWave) applications. It uses the selective laser melting (SLM) technology to melt the Cu-15Sn powder layer by layer to build up rectangular waveguides at E- (60-90 GHz), D- (110-170 GHz), and H-band (220-325 GHz). Different from nonmetallic 3-D printed waveguides, SLM Cu-15Sn waveguides are printed once in a whole piece. Postelectroplating and assembling are not necessary. Besides, the SLM waveguide also outperforms the nonmetallic 3-D printed waveguide in mechanical robustness. Compared with nonmetallic 3-D printed and commercial metallic waveguides, SLM waveguides demonstrate comparable performance at E-band with averaged dissipative attenuation 7.51 dB/m and 7.76 dB/m for 50- and 100-mm waveguides, respectively. The attenuation of SLM waveguides is acceptable up to D-band. We prove the potential of the SLM technology for mmWave applications in both prototyping and mass production.
Integration of a 140-GHz packaged low-temperature cofired ceramic (LTCC) antenna with a power detector is demonstrated under the concept of antenna-in-package. The detector is designed on an indium phosphide (InP) process. A grid array antenna in LTCC is designed to provide package for the detector. Coplanar ground–signal–ground (GSG) bond wires are used to connect the detector and the antenna. Parallel plate mode is observed in the InP substrate and absorbed by the LTCC substrate. The comparison between the measured responsivity of the power detector with and without the antenna indicates the acceptable insertion loss of the coplanar GSG bond wires transition. It shows a feasible solution for the D-band front-end integration and packaging.
It is difficult to package and interconnect components and devices at millimeter-waves (mm-waves) due to excessive losses experiences at these frequencies using traditional techniques. The problem is multiplied manifold at terahertz (THz) frequencies. In this article, we review the current state of THz packaging and describe several novel techniques. As we will show, micromachined packaging is emerging as one of the best choices for developing advanced THz systems.
The 200 and 320 GHz frequency band constitutes an interesting window with approximately constant attenuation, which could potentially have applications in the area of ultra-high-capacity wireless links. The user's demand of data for future 5G mobile systems will require backhaul systems to be able to provide several dozens of GHz in order to satisfy those demands. Furthermore, additive manufacturing techniques stand as an interesting way of reducing costs without sacrificing performance. In this work, a choke horn antenna, designed at a central frequency of 240 GHz and manufactured by 3D-printing technology is presented. This antenna is thought to serve as the feed of a compact parabolic reflector. The antenna has been measured by Near-and Far-Field techniques and these measurements show an adequate agreement with simulation results. Additionally, the measurement setup included a novel dynamic time-domain, software-controlled gating that readjusts itself for every measured point.
This paper presents a study to use the metallic three dimensional (3-D) printing technology for antenna implementations up to 325 GHz. Two different printing technologies and materials are used, namely binder jetting/sintering on 316L stainless steel and selective laser melting (SLM) on Cu–15Sn. Phases, microstructure, and surface roughness are investigated on different materials. Balancing between the cost and performance, the manually polished Cu–15Sn is selected to develop a series of conical horn antennas at the E-(60–90 GHz), D- (110–170 GHz), and H-band (220–325 GHz). Good agreement is observed between the simulated and measured antenna performance. The antennas’ impedance bandwidth ([Formula: see text]) cover the whole operational band, with in-band gain of >22.5, >22, and >21.5 dBi for the E-, D-, and H-band antennas, respectively. Compared with the traditional injection molding and micromachining for metallic horn antenna implementation, the 3-D printed metallic horn antenna features environmental friendliness, low cost, and short turn-around time. Compared with the nonmetallic 3-D printed antennas, they feature process simplicity and mechanical robustness. It proves great potential of the metallic 3-D printing technology for both industrial mass production and prototyping.
A stereolithography-based manufacturing process for monolithic high aspect ratio components for mm-wave and sub-mm-wave applications is demonstrated. A 25 mm 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.
Aero-WAVE is a scientific payload that operates in W-band. It will be embarked onboard a stratospheric platform or high altitude platform (HAP) in order to perform a first test of the channel behavior at an altitude of about 20 km. The stratospheric platform is a high altitude aircraft known as the M-55 Geophysica, a Russian aircraft well known in the atmospheric research environment and the European scientific community since 1996. The M-55 Geophysica will be equipped with the payload instrumentation to carry out the measurements. These measurements and the resulting data provided throughout the Aero-WAVE mission will give good indications of the channel behavior at different weather conditions and at different locations within the GEO-WAVE coverage
This letter presents the design and characterization of a 220 GHz microstrip monolithic microwave integrated circuit single-ended resistive mixer in a 0.1 GaAs mHEMT technology. A conversion loss as low as 8.7 dB is obtained, limited by the available local oscillator (LO) power (1.5 dBm) in the measurement setup. The radio frequency (RF) bandwidth is also limited by the measurement setup, but the mixer demonstrates a flat response over the measured 200 to 220 GHz frequency range. Furthermore, measured intermediate frequency bandwidth, 1-dB input compression point, LO-to-RF isolation, and reflection coefficients are presented and discussed.
Advanced Schottky Diode Receiver Front-Ends for Terahertz Applications
- P Sobis