Projects:2020s2-7153 High-efficiency planar waveguides for terahertz waves
Abstract
Terahertz integrated systems are still in its infancy in terms of its technology. However, it has shown a great number of potential uses in communication, radar, imaging and sensing. This project aims to continue the study of waveguide by examining the dispersion, cross-polarization and crosstalk, along with the characteristics of bends and crossings over the 220 to 330 GHz (WR-3 band) operating frequency range. The waveguides are substrate-less effective medium with a subwavelength arrays of hole while supporting Ex11 and Ey11 modes with low loss and low dispersion. As a step to reduce significant absorption in metals and dielectrics at terahertz frequencies, the self-supporting structures are built by using a single silicon wafer.
Introduction
With a substantially growing proportion of the world's population accessing online services, data traffic has grown significantly. Most terahertz (THz) sources, however, are inaccessible, so designing efficient THz waveguides for versatile broadband THz radiation delivery is an important step towards terahertz techniques for practical applications. The terahertz spectrum that covers the frequency range from 0.1 to 10THz is an appropriate option for the support of the high-speed wireless sight transmission line by convergence electronics and optics. When used to connect the numerous THz point devices, such as sources, filters, sensor cells and detectors, THz waveguides can be very beneficial on system integration stage.
Project team
Project students
- Mahmoud Alshnqiti
- Muhammad Zulhisyam Mohd Hosni
- Muhammad Hairie Mohd Hamdan
Supervisors
- Dr. Withawat Withayachumnankul
- Dr. Wendy Lee
- Weijie Gao
Objectives
The principle objective of this project to enhance the effective-medium-clad waveguides which is a promising candidate for terahertz integrated circuits. Accordingly, we are enhancing the compactness of the platform by proposing a new bend design with smaller footprint. However, the main challenge is to decrease the footprint while maintaining high transmission, physical structure strength, and adhering the fabrication limitation.
Background
Terahertz background
The term terahertz (THz) is a prefix which refer to 1012. However, the terahertz domain typically defined as the frequencies from 100 GHz to 10 THz. The terahertz domain falls between the electronics and the photonics domains. The terahertz has special characteristics as it can penetrate plastic and fabric (e.g. dry clothes) and it's suitable for non-destructive imaging.
Effective medium cladding
Silicon has a high refractive contrast of n = 3.418 , allowing for high degree of confinement in the core via total internal reflections. By perforating cylindrical holes in a silicon wafer, with a small period compared to the wavelength, we could achieve an effective medium that has a refractive index between silicon and air.
https://www.youtube.com/watch?v=NtyunEEIOR4
Method
Similar to most RF related projects, the feedback of the quality of solutions proposed in this project are evaluated using a full-time software simulation package. Namely, CST software. In addition, after a satisfactory design simulations results, the design is sent oversees for fabrication. The process of fabrication is called deep reactive ion-etching (DRIE). The DRIE consitsts of a laser with high resolution that can make perforations into a slab of silicon with a diameter greater than 20μm.
Bend designs E-field plots
Bend designs transmission coefficients before normalization
Bend designs transmission coefficients after normalization
Results
Project outcomes:
- Successfully decreased the bend design footprint by almost a factor of 3.
- The proposed bend design maintained high efficiency transmission in both fundamental modes EX11 and EY11.
- We proposed equations that can be used for designing waveguides bends universally.
More importantly, the principle outcome of this project is that we proposed a novel bend design that can achieve high transmissions and is simple to implement in which we anticipate to be greatly beatifical for researchers in photonics.
Conclusion
In conclusion, the effective-medium-clad waveguides has a potential to be a platform for terahertz integrated circuits. In this project, we successfully decreased the footprint of the bend waveguide by almost a factor of 3. However, the bend is core component in integrated terahertz circuits and therefore, we improved the compactness of the effective-medium-clad waveguides. In addition, we proposed a new approach for designing bend with loss-low and simplicity which we anticipate will be of great interest fro researchers in photonics. The new design method and the equations were not mentioned in this wiki page, since it's prepared to be published in scientific journals in the upcoming times.
