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.

2020, Wang, Jiawei, Tang, Min, Yang, Yue-De, Yin, Yin, Chen, Yan, Saggau, Christian Niclaas, Zhu, Minshen, Yuan, Xiaobo, Karnaushenko, Dmitriy, Huang, Yong-Zhen, Ma, Libo, Schmidt, Oliver G.

Dielectric optical microcavities have been explored as an excellent platform to manipulate the light flow and investigate non‐Hermitian physics in open optical systems. For whispering gallery mode optical microcavities, modifying the rotational symmetry is highly desirable for intriguing phenomena such as degenerated chiral modes and directional light emission. However, for the state‐of‐the‐art approaches, namely deforming the cavity geometry by precision lithography or introducing local scatterers near the cavity boundary via micromanipulation, there is a lack of flexibility in fine‐adjusting of chiral symmetry and far‐field emission direction. Here, precise engineering of cavity boundary using electron‐beam‐induced deposition is reported based on rolled‐up nanomembrane‐enabled spiral‐shaped microcavities. The deformation of outer boundary results in delicate tailoring of asymmetric backscattering between the outer and inner rolling edges, and hence deterministically strong mode chirality. Besides, the crescent‐shaped high‐index nanocap leads to modified light tunneling channels and inflected far‐field emission angle. It is envisioned that such a localized deposition‐assisted technique for adjusting the structural deformation of 3D optical microcavities will be highly useful for understanding rich insights in non‐Hermitian photonics and unfolding exotic properties on lasing, sensing, and cavity quantum electrodynamics.

2020, Wang, Jiawei, Medina Sanchez, Mariana, Yin, Yin, Herzer, Raffael, Ma, Libo, Schmidt, Oliver G.

By virtue of the well-developed micro- and nanofabrication technologies and rapidly progressing surface functionalization strategies, silicon-based devices have been widely recognized as a highly promising platform for the next-generation lab-on-a-chip bioanalytical systems with a great potential for point-of-care medical diagnostics. Herein, an overview of the latest advances in silicon-based integrated optofluidic label-free biosensing technologies relying on the efficient interactions between the evanescent light field at the functionalized surface and specifically bound analytes is presented. State-of-the-art technologies demonstrating label-free evanescent wave-based biomarker detection mainly encompass three device configurations, including on-chip waveguide-based interferometers, microring resonators, and photonic-crystal-based cavities. Moreover, up-to-date strategies for elevating the sensitivities and also simplifying the sensing processes are discussed. Emerging laboratory prototypes with advanced integration and packaging schemes incorporating automatic microfluidic components or on-chip optoelectronic devices lead to one significant step forward in real applications of decentralized diagnostics. Besides, particular attention is paid to currently commercialized label-free optical bioanalytical models on the market. Finally, the prospects are elaborated with several research routes toward chip-scale, low-cost, highly sensitive, multi-functional, and user-friendly bioanalytical systems benefiting to global healthcare. © 2020 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim