image: Figure | Next-Generation Terahertz Systems via 3D Printing. a, Concept of an integrated terahertz system, comprising an optoelectronic THz signal source connected to an amplifier via a 3D-printed "bridge" (THz interconnect, TIC), and an elevated THz antenna (TA) that efficiently emits the signal into free space. The top portion illustrates a custom 3D-printed probe (THz probe, TP) used for testing such microscopic circuits. b, THz interconnect: A microscope image of a 3D-printed "bridge" seamlessly connecting THz transmission lines across separate chips. c, THz probe: A microscope image of a 3D-printed testing probe. The structure is shown upside down for better visibility. d, THz antenna: A microscope image of the 3D-printed antenna. By elevating the structure above the underlying substrate, the antenna can radiate signals much more efficiently.
Credit: Christian Koos et al.
The terahertz (THz) and millimeter-wave (mmW) frequency range holds immense potential for ultra-high-speed wireless communications, advanced sensing, and ultra-broadband signal processing. Leveraging this potential, however, requires advanced THz devices that combine highly conductive metal elements with low-loss dielectrics in precisely defined three-dimensional (3D) freeform geometries. Manufacturing such structures is a challenge that conventional techniques struggle to meet, typically requiring complex manual assembly or falling short of providing the bulk-like electrical conductivity and sub-micrometer precision needed for high-performance THz devices.
In a new paper published in Light: Advanced Manufacturing, a team of scientists at Karlsruhe Institute of Technology (KIT), Germany, led by Professor Christian Koos and co-workers, have developed a transformative approach to overcome these fabrication hurdles. Their technique relies on so-called "metal-coated freeform structures" (MCFS), manufactured by a scalable method that uniquely combines the essentially unlimited 3D design freedom of direct-write multi-photon lithography with highly directive metal deposition techniques. Based on this technique, the team successfully demonstrated a series of high-performance THz components that are directly integrated on chips with sub-micrometer precision. The researchers achieved ultra-broadband chip-to-chip connections, cost-effective probe tips, and suspended on-chip antennas operating at frequencies of up to 0.3 THz.
The scientists summarize the operational principle of their method: “Our concept exploits in-situ printed polymer support structures, that are selectively coated through highly directive metal deposition techniques exploiting precisely aligned 3D-printed shadowing structures”. They emphasize that the resulting structures “offer high surface quality in combination with conductivities comparable to bulk material values of the respective metal and do not require any manual assembly steps”. By enabling the seamless integration of highly conductive elements with microscopic precision, the MCFS approach drastically reduces the cost and complexity of producing THz systems while maintaining sub-micrometer accuracy. "We believe that our approach offers disruptive potential in the field of mmW and THz technology and may unlock an entirely new application field for laser-based 3D manufacturing," the scientists forecast. This breakthrough will open new avenues for ultra-fast communications, advanced sensing, and chiplet-based THz systems.
Journal
Light: Advanced Manufacturing
Article Title
Freeform terahertz structures fabricated by multi-photon lithography and metal coating