پایان‌نامه: کنترل نانوذرات به کمک میدان‌های پلاسمونی ناشی از نوارهای گرافنی بایاسِ غیریکنواخت
استاد راهنما: دکتر مصطفی قربان‌زاده

پایان‌نامه: طراحی و شبیه‌سازی یک سلول خورشیدی با قابلیت ردیابی حداکثر توان توسطMATLAB
استاد راهنما: دکتر محمدحسین مقامی

Realizing tunable high intensified and localized multiple hot spots are crucial for developing integrated optical tweezers in lab-on-a-chip devices to study interparticle interactions, routing and delivering nanoparticles. In this work, we utilize from a wedge-shaped Si structure to create and guide an extremely localized optical wedge mode and also as a non-uniform gate to non-uniformly control the chemical potential of topped graphene strips. Using three-dimensional finite-difference time-domain numerical method, we show that the wedge mode can excite localized surface plasmon (LSP) modes on the surface of each graphene strips with two distinct hot spots (trapping sites). The position of the trapping sites can be electrically manipulated continuously along the length of each graphene strip and discretely along the direction of propagation of the wedge mode by tuning the gate voltage. The calculated plasmonic forces by Maxwell stress tensor (MST) method reveals that 7 V change in the gate voltage leads to displacement of trapped particles by ∼ 49 nm. Moreover, we show that in the proposed structure by smoothly varying the gate voltage of graphene strips, active plasmonic focusing and defocusing lenses can be realized. We believe the proposed system can be implemented in lab-on-a-chip devices for electrically manipulating multiple nanoparticles without the need to use large scale expensive optical instruments.

Optical tweezers provide the possibility of contactless moving and trapping of micro and nanoparticles. The optical trapping mechanism is based on the momentum exchange between the trapped particle and the trapping beam using a scattering process. Using optical tweezers, small cell or biological particles can be optically trapped and moved. If there is a balance between linear diffraction and nonlinear self-focusing, spatial soliton will be created. Spatial solitons are beams that propagate through a medium without spatial diffraction. In this article, a brief review of optical tweezers and spatial solitons have been done. Considering the interesting properties of solitons, it seems that it is possible to design optical tweezers based on spatial solitons that have higher efficiency and better performance than other optical tweezers. Optical tweezers can help us manipulate particles of a wide range of sizes, from atoms that exhibit quantum behavior to cells that exhibit classical behavior. For this, optical tweezers have emerged as an effective tool that allows us to explore and clarify the boundary between the classical world and the quantum world. In this regard, our expectations for the years to come are also great.

This work presents the design and simulation of AlGaN/GaN based UV-A LED on a sapphire substrate. We used periodic layers as multiple-quantum-well to reach better optoelectronic properties and used EBLs to reduce the leakage current in modern multi-quantum-well. We deposited ITO as a top layer and Ni/Au to form ohmic contacts to p-type GaN and approach higher frequency response. We performed simulation by “SILVACO Software” and followed the fabrication process based on “ATHENA” rules and techniques.

HEMT transistors are field-effect transistors formed from the combination of two semiconductors with different energy gaps. Presented here is a simulation of an AlGaN/GaN-based high electron mobility transistor (HEMT) on a sapphire substrate, which was conducted in this work. We used the "SILVACO Software" to simulate the manufacturing process, which was based on "ATLAS" principles and procedures, and we were able to generate the ID-VG, ID-VD, power gain, current gain, polarization charge, transconductance (Gm), conduction band energy, and valence band energy curves as a result.