Oral thesis defence examination
ขอแสดงความยินดีกับ นางสาวณัฐสิมา ศักดา นักศึกษาจากกลุ่มวิจัยทัศนศาสตร์ประยุกต์และกลุ่มวิจัยฟิสิกส์ศึกษา ภาควิชาฟิสิกส์ คณะวิทยาศาสตร์ มหาวิทยาลัยมหิดล ผ่านการสอบ “Oral thesis defence examination” เพื่อสำเร็จการศึกษาในหลักสูตร ปรัชญาดุษฎีบัณฑิต สาขาวิชาฟิสิกส์ (หลักสูตรนานาชาติ) โดยได้ทำจิจัยและได้นำเสนอผลงานในชื่อ “THE NOVEL DESIGN OF RECONFIGURABLE PHASE CHANGE METASURFACE FOR THE THZ REFLECTOR”
ABSTRACT
Over a couple of decades, the radiation locating in the gap between infrared and microwave called “Terahertz Radiation” has been utilized increasingly. The spectral range of the T-rays spread over the range of 0.3-3.0 THz. This frequency has been under scrutiny according to their unique properties including: (i) non-ionizing to biological cells, (ii) strongly sensitive to water molecules, and (iii) frequency matching to the mode vibrations of biomolecular bonding. As a result, appropriate THz applications regarding the properties has been sought after by researchers worldwide. However, the challenge is found as the shortage of the terahertz devices since the THz bandgap is not commonly found in available devices. Fortunately, the emerging of metamaterials, defined as “the engineered periodic structure came to a rescue because they can be designed to provide the required electromagnetic response from their specially designed unit cell structure rather than the constituent material.” The metamaterials have become the potential device in order to operate in the terahertz regime. Nevertheless, those fascinating properties is generally fixed after the fabrication process has been done. For a better flexibility in the usage, the property of the metamaterials such as the switchability can be enhanced by introducing the phase change material (PCM). PCM responses significantly different to the electromagnetic wave when operating between two states by using optical or electrical pulses to induce. In this research, the hexagonal metasurface was designed and showed the reflection property of the dual-band at 1.72 and 2.70 THz. In addition, the volatile phase change material known as GST was integrated to the designed metasurface obtain the switchable property. The numerical results reveal that the first mode resonance (1.72 THz) has a consistent level of reflectivity during the phase transition, while the second resonance (2.70 THz) achieves the switchability with a contrasts value around 80% when the phase change from amorphous to crystalline states. The geometrical parameters, including periodicity, sidelength, dielectric thickness, and GST thickness, were also investigated to optimize the performances of the reflector evaluated by using two key parameters: insertion loss (IL) and extinction ratio (ER). Finally, the incident angle and polarization were also examined.
ภาพกิจกรรม
ผู้สนใจในงานด้านนี้สามารถติดตามเพิ่มเติมได้ที่นี่
- Sakda N, Chitaree R, Rahman BMA. Reflective Terahertz Metasurfaces Based on Non-Volatile Phase Change Material for Switchable Manipulation. Photonics. 2022; 9(8):508.
- Natsima Sakda, Souvik Ghosh, Ratchapak Chitaree, and B. M. Azizur Rahman, “Performance optimization of a metasurface incorporating non-volatile phase change material,” Opt. Express 30, 12982-12994 (2022)