ENGINEERING THE DYNAMICS OF LIGHT WITH DIELECTRIC META-LATTICE SYSTEM

• Main Author: Dwi Isro, Suhandoko
• Format: Dissertations
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/71445
• Institution: Institut Teknologi Bandung

Optical sciences play a very important role in the development of modern technology. Various ways for controlling the dynamics of light, especially those involving scattering phenomena, are demanded for improving the functionality of those technologies. Among the most popular ways used by the scientists to achieve that goal is by using metamaterials. Various phenomena have been discovered from the research of metamaterials and their potential applications have been developed. Lately, the research of metamaterial is facing a new challenge, that is, the quest of structure with tunability. A number of method has been proposed, unfortunately, with a rather non-user-friendly mechanisms when applied for daily usage. This research is dediated to developing a tunable metamaterial system with simple construction that can be adopted immediately in the industry of optics In particular, in this research, a metamaterial system will be developed based on a periodic arrangement of cylindrical particles. The research will be conducted analytically, that is, by deriving the electromagnetic field solution in the system which will then be implemented into a computer program. In the initial stage of the research a benchmark will be carried out to make sure that method of research can yield results that are mutual with previous reports. On the other hand, the initial stage of the research is also conducted as a survey to determine the kind of material that is more preferable for developing a metamaterial system with high performance. Afterwards, the geometry and optical parameters of the system will be optimized to obtain a desirable caharacteristics. The initial stage of the research shows that a nanotube structure having a construction of dielectric core covered with a silver shell can provide multiple resonance in the extinction spectra. The emergence of those resonances is in a well agreement with the well-known plasmon hybridization theory. Further, the shifting of the core position results in additional resonance in the extinction spectra. This also agrees with the theory of multipolar-mixing. Interestingly, the non-coaxial nanotube will generate a directional scattering and the intensity depends on the angle of the incident light. This dependency has never been reported previously. This discovery implies that the aforementioned structure can be useful for the detection of light direction. It is also found that the detection mechanism can work in a different wavelength region by changing the permittivity of the core material. Unfortunately, this mechanism can work well only in the proximity of the structure and thus unpreferable for far-field application. For this reason, the research is then continued by using dielectric material. The following research with cylindrical dielectric particle shows that multiple resonances emerge in the cross-section spectra due to the excitation of Mie resonance modes. This phenomenon has now become well-known in the field of meta-optics. However, the effect of incident light angle on the pattern and the polarization of the scattered waves has never been studied in detail previously. The research discovers that for light incident at an angle approaching grazing angle, for incident light with transverse-electric polarization, a quadrupole scattering pattern will be formed. Interestingly, by decomposing the polarization of the scattered waves, it is found that the quadrupole actually is a combination of two orthogonal dipole, namely, the electric dipole and the magnetic dipole. This means that one may convert the polarization of light from pure transverse-electric into half transverse magnetic. Having seen the potential of cylindrical dielectric particle, the research is then continued to the development of tunable metasurface by arranging those particles into a system of meta-lattice. It is found that the meta-lattice system can be tuned between the transparrent or reflective states by controlling the optical periodicity of the system. Such a mechanism has never been reported previously and it is simpler compared to other methods such as mechanical stressing, thermal heating, or electrical induction. Further, it is found that the switching mechanism in the meta-lattice system can be achieved by using materials with relatively low refractive index. The research unveils that, even by using low index material, the phenomenon may occur if the scattered waves in the system are in phase and thus result in a strong polarizing field. The phase condition of those waves can also be controlled from the optical periodicity of the system. Such a discovery has never been reported previously. In particular, the aforementioned phenomenon will be useful for the development of a transflective-liquid-crystal-display (TLCD). This is important considering that the development of TLCD has lately been hindered since the majority of transflectors have the working principle similar to that of a half mirror. Besides, no research on metasurface has ever been conducted for the development of TLCD.