Projects:2021s1-13153 Free-space optics for terahertz camera

==Project blurb== 

The project presents two passive optics structures operating at terahertz frequencies. One is a Wollaston prism the other is a broadband terahertz waveplates. Both structures rely on birefringence, where the propagation speeds of two polarisations is different. The prism separates two polarisations into different directions. For the broadband waveplate, the designs include half- and quarter- waveplates, which are designed and optimised via genetic algorithm. The operating frequency range is from 220GHz to 330GHz. Both structures are fabricated via 3D printing of cyclic olefin copolymer.

Acknowladge

Initially, thanks to our two supervisors, we did such a poor job in the project, and they still did not give up on us. Then, the team would like to thank Mr. Harrison Noel Lees for his kindness suggestions and assistance to produce the measurement. In addition, the team would like to thank Terahertz Laboratory for providing a platform for sample testing. Eventually, the sample is fabricated by 3D printing with the help of Mr. Hayden Westell.

Team members

Hanwen Liu, Shenghao Gu

Supervisors

Assoc. Prof. Withawat Withayachumnankul, Dr. Xiaolong You

Motivations

As passive optical elements, prism and broadband waveplate have very high research value in the field of wireless communications. In addition, based on 3D printing, the production cost and production cycle can be well controlled.

The terahertz wave

The terahertz frequency range span from 0.1 THz to 10 THz. In the electromagnetic spectrum, it falls between microwave radiation and infrared radiation. Hence it shares some properties with each of these.

Refractive indices measurement

Since ultra-low loss cyclic copolymer (COC) is not a birefringent material, it is necessary to mix it with air. The team used Thorlabs RB13P1/M to measure the refractive indices of the sample and the calculation results are as follow.