Browsing by Author "Naz, Ehsan Saei Ghareh"
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- ItemHighly Symmetric and Extremely Compact Multiple Winding Microtubes by a Dry Rolling Mechanism(Weinheim : Wiley-VCH, 2020) Moradi, Somayeh; Naz, Ehsan Saei Ghareh; Li, Guodong; Bandari, Nooshin; Bandari, Vineeth Kumar; Zhu, Feng; Wendrock, Horst; Schmidt, Oliver G.Rolled-up nanotechnology has received significant attention to self-assemble planar nanomembranes into 3D micro and nanotubular architectures. These tubular structures have been well recognized as novel building blocks in a variety of applications ranging from microelectronics and nanophotonics to microbatteries and microrobotics. However, fabrication of multiwinding microtubes with precise control over the winding interfaces, which is crucial for many complex applications, is not easy to achieve by existing materials and technologies. Here, a dry rolling approach is introduced to tackle this challenge and create tight windings in compact and highly symmetric cylindrical microstructures. This technique exploits hydrophobicity of fluorocarbon polymers and the thermal expansion mismatch of polymers and inorganic films upon thermal treatment. Quality parameters for rolled-up microtubes, against which different fabrication technologies can be benchmarked are defined. The technique offers to fabricate long freestanding multiwinding microtubes as well as hierarchical architectures incorporating rolled-up wrinkled nanomembranes. This work presents an important step forward toward the fabrication of more complex but well-controlled microtubes for advanced high-quality device architectures. © 2020 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
- ItemSelective Out‐of‐Plane Optical Coupling between Vertical and Planar Microrings in a 3D Configuration(Hoboken, NJ : Wiley, 2020) Valligatla, Sreeramulu; Wang, Jiawei; Madani, Abbas; Naz, Ehsan Saei Ghareh; Hao, Qi; Saggau, Christian Niclaas; Yin, Yin; Ma, Libo; Schmidt, Oliver G.3D photonic integrated circuits are expected to play a key role in future optoelectronics with efficient signal transfer between photonic layers. Here, the optical coupling of tubular microcavities, supporting resonances in a vertical plane, with planar microrings, accommodating in‐plane resonances, is explored. In such a 3D coupled composite system with largely mismatched cavity sizes, periodic mode splitting and resonant mode shifts are observed due to mode‐selective interactions. The axial direction of the microtube cavity provides additional design freedom for selective mode coupling, which is achieved by carefully adjusting the axial displacement between the microtube and the microring. The spectral anticrossing behavior is caused by strong coupling in this composite optical system and is excellently reproduced by numerical modeling. Interfacing tubular microcavities with planar microrings is a promising approach toward interlayer light transfer with added optical functionality in 3D photonic systems.