6 research outputs found
Monolithically integrated mode converter from terahertz substrateless silicon guide to conductive slotline
No full textAlthough substrateless micro-scale silicon waveguides are a useful and versatile platform for terahertz waves, the fact that modal fields occupy the volume of the core limits the potential to dynamically manipulate guided waves. To address this, we introduce an aperiodic lattice structure to enable the monolithic co-integration of a Vivaldi antenna-like mode converter with a substrateless silicon waveguide. This broadband transition is experimentally confirmed to exhibit ∼2.5 dB average loss for two couplers, from 220 GHz to 330 GHz, and enables a photoexcited variable attenuator as proof-of-concept demonstration. This is an important enabling step to incorporate general-purpose dynamic reconfigurability, sensing, and modulation functionality into terahertz-range silicon-based integrated circuits, which are currently limited to primarily all-passive structures.Daniel Headland, Panisa Dechwechprasit, and Withawat Withayachumnanku
Terahertz disk resonator on a substrateless dielectric waveguide platform
No full textPublished 31 August 2023Abstract not availablePanisa Dechwechprasit, Rajour Tanyi Ako, Sharath Sriram, Christophe Fumeaux, and Withawat Withayachumnanku
Tunable Terahertz Components on Substrateless Silicon Platform
No full textThe integration and portability of terahertz systems is vital for practical applications in sensing and communications. In recent years, a substrateless silicon platform based on effective-medium-cladded waveguides has emerged as a promising pathway for realising diverse active and passive components monolithically combined for terahertz integrated systems. This platform is realised using high-resistivity silicon that has exceptionally low loss to terahertz waves. On the basis of the effective medium concept, a subwavelength hole array created into such a silicon slab results in a homogeneous material with a refractive index lower than that of solid silicon. As a consequence, controlling the array configuration yields a high contrast of refractive indices between a solid silicon waveguide core and cladding made of effective medium, while entailing design flexibility for various components. Inheriting characteristics from its constituting high-resistivity silicon, the platform has demonstrated remarkably low attenuation in broad bandwidth. Within this platform, diverse passive components can be created, such as filters, waveguide crossings, 2D horn antennas, or frequency- and polarisationdivision multiplexers. However, this platform is yet still constrained by the absence of tunable components, thereby limiting its potential for a broader range of applications. This thesis focuses on the development of efficient tunable terahertz components on the substrateless silicon platform for applications requiring sensing, switching, and modulation. One contribution involves, a series of disk resonators that are integrated onto the substrateless silicon platform to achieve a high-Q factor. Photoexcitation of selected areas of the silicon-based platform populates free carriers, resulting in the switchability of the resonance. Leveraging this photoexcitation effect, integrated disk resonators are employed to introduce switching functionality. The proposed switch achieves low insertion loss and directional switching capabilities. Moreover, the switch is monolithically integrated with a Luneburg lens on the same platform to function as a beam switching antenna. In terahertz communications, achieving efficient control over the modulator of terahertz waves is beneficial. We have proposed the integration of a photonic crystal cavity and a dipole resonator into the substrateless silicon platform to create an optically tunable terahertz modulator. This modulator has shown enhanced modulation depth with high efficiency and low required optical power. The proposed tunable components on the substrateless silicon platform showcase the potential to serve various functions, including sensing, switching, wave routing, and modulation. This contributes to a promising pathway for the development of future terahertz integrated systems.Thesis (Ph.D.) -- University of Adelaide, School of Electrical and Mechanical Engineering, 202
Resonant cavities based on substrateless dielectric waveguide platform for terahertz integrated systems
No full textIn the past two decades, terahertz technology has been steadily improved with a wide range of scientific studies to develop terahertz applications. Recently, a substrateless dielec-tric waveguide platform based on effective medium has been proposed. Waveguiding on this silicon-based platform can be realized with low loss and low dispersion. One important series of components for this platform includes resonant cavities of different characteristics that are crucial for terahertz integrated systems. In this article, we present one design of a disk resonator, and one design of a photonic crystal cavity based on this sub-strateless dielectric waveguide platform. These cavities operate within the frequency range of 220–330 GHz. The simulation and measurement results of these resonant cavities show a strong resonant behavior, with a resonance Q-factor that can be tuned. These cavities can be employed in various terahertz applications including sensing, switching, and modulation.Panisa Dechwechprasit, Christophe Fumeaux, Withawat Withayachumnanku
