The University of Osaka · Engineering
Professor Ratmalgre Koala's research lab specializes in advancing integrated terahertz photonics, focusing on all-silicon dielectric waveguides, low-loss waveguide components, and photonic integrated circuits for high-data-rate wireless communications and short-reach interconnects. The lab pioneers ultra-broadband, compact, and low-loss THz devices such as Y-junctions, gradient-index antennas, and photonic crystal waveguides, enabling applications in 6G wireless systems and high-speed data links. By leveraging monolithic integration and advanced silicon processing techniques, the lab drives innovation in compact, efficient, and scalable THz systems for next-generation communication and sensing technologies.
Figures are computed from collected data and may differ slightly.
Recent advances in silicon (Si) microphotonics have enabled novel devices for the terahertz (THz) range based on dielectric waveguides. In the past couple of years, dielectric waveguides have become commonplace for THz systems to mitigate issues in efficiency, size, and cost of integration and packaging using metal-based waveguides. Therefore, THz systems have progressively evolved from cumbersome collections of discreet components to THz-wave integrated circuits. This gradual transition of THz
This study presents ultra-low-loss and broadband all-silicon dielectric waveguides for the WR-1 band (0.75–1.1 THz). The waveguides are built in high-resistivity silicon (10 kΩ-cm) and integrated with supportive frames fabricated from the same silicon wafer in a single etch process to achieve a compact design. We pursued low-loss, broadband, substrateless, unclad and effective medium waveguides. Smaller propagation losses of 0.3 dB/cm and 0.1 dB/cm were achieved for the unclad and effective medi
The terahertz range has significant potential for high data rate wireless communications, due to large, underutilized spectral bandwidth. The exploitation of that potential is being enhanced by novel devices implemented using all-silicon micro-scale photonic techniques. Here, we show the design of a dielectric rod array antenna that employs integrated gradient-index optics to enhance antenna gain in 300-GHz band. The antenna is fed with a monolithically integrated, specialized broadband photonic
Nascent data-intensive emerging technologies are mandating low-loss, short-range interconnects, whereas existing interconnects suffer from high losses and low aggregate data throughput owing to a lack of efficient interfaces. Here, we report an efficient 22-Gbit/s terahertz fiber link using a tapered silicon interface that serves as a coupler between the dielectric waveguide and hollow core fiber. We investigated the fundamental optical properties of hollow-core fibers by considering fibers with
Abstract The authors studied the transmission performance for orthogonal polarization fundamental modes in a dielectric silicon terahertz waveguide for doubling the data rate. The maximum data rate of practical error‐free condition (bit‐error rate < 10 −11 ) for both polarizations is comparable over 20 Gbit/s under on‐off keying modulation at 0.3‐THz band.
The incorporation of active components to micro scale photonic devices is beneficial to building fully integrated systems in the terahertz region. In this work we introduce a center-fed slot-antenna resonant tunneling diode (RTD) chip that is backside-coupled to a photonic crystal waveguide. Experiments revealed stable oscillation at 346 GHz and efficient coupling.
Hollow metallic waveguides have long been employed as interconnects in terahertz (THz) systems. However, these waveguides are associated with increased ohmic loss at higher frequencies. Herein, we propose a 50-mm-long, compact, packaged low-loss waveguide module using a silicon unclad waveguide with an input/output interface compatible with a standard WR-1 waveguide flange. The superiority of this module was experimentally validated. The results revealed an average total loss of 2 dB across the
This paper presents both an innovative monopole plasma antenna and a traditional metal based monopole antenna suitable for mobile communications and wireless communications related applications ranging from 550MHz to 650MHZ. Monopole antenna is one of the most commonly used antennas. As the interest for plasma antenna is rising among engineers and developers of telecommunications, navigation and radar related fields, a thorough analysis of plasma to prove the efficiency of plasma based antenna c
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