@unpublished{SteglichRabusSadaetal.2021, author = {Steglich, Patrick and Rabus, Dominik G. and Sada, Cinzia and Paul, Martin and Weller, Michael G. and Mai, Christian and Mai, Andreas}, title = {Silicon Photonic Micro-Ring Resonators for Chemical and Biological Sensing: A Tutorial}, series = {TechRxiv}, journal = {TechRxiv}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-16840}, year = {2021}, abstract = {Silicon photonic micro-ring resonators (MRR) developed on the silicon-on-insulator (SOI) platform, owing to their high sensitivity and small footprint, show great potential for many chemical and biological sensing applications such as label-free detection in environmental monitoring, biomedical engineering, and food analysis. In this tutorial, we provide the theoretical background and give design guidelines for SOI-based MRR as well as examples of surface functionalization procedures for label-free detection of molecules. After introducing the advantages and perspectives of MRR, fundamentals of MRR are described in detail, followed by an introduction to the fabrication methods, which are based on a complementary metal-oxide semiconductor (CMOS) technology. Optimization of MRR for chemical and biological sensing is provided, with special emphasis on the optimization of waveguide geometry. At this point, the difference between chemical bulk sensing and label-free surface sensing is explained, and definitions like waveguide sensitivity, ring sensitivity, overall sensitivity as well as the limit of detection (LoD) of MRR are introduced. Further, we show and explain chemical bulk sensing of sodium chloride (NaCl) in water and provide a recipe for label-free surface sensing.}, language = {en} } @article{SteglichBondarenkoMaietal.2020, author = {Steglich, Patrick and Bondarenko, Siegfried and Mai, Christian and Paul, Martin and Weller, Michael G. and Mai, Andreas}, title = {CMOS-Compatible Silicon Photonic Sensor for Refractive Index Sensing Using Local Back-Side Release}, series = {IEEE Photonics Technology Letters}, volume = {32}, journal = {IEEE Photonics Technology Letters}, number = {19}, issn = {1941-0174}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-13649}, pages = {1241 -- 1244}, year = {2020}, abstract = {Silicon photonic sensors are promising candidates for lab-on-a-chip solutions with versatile applications and scalable production prospects using complementary metal-oxide semiconductor (CMOS) fabrication methods. However, the widespread use has been hindered because the sensing area adjoins optical and electrical components making packaging and sensor handling challenging. In this work, a local back-side release of the photonic sensor is employed, enabling a separation of the sensing area from the rest of the chip. This approach allows preserving the compatibility of photonic integrated circuits in the front-end of line and metal interconnects in the back-end of line. The sensor is based on a micro-ring resonator and is fabricated on wafer-level using a CMOS technology. We revealed a ring resonator sensitivity for homogeneous sensing of 106 nm/RIU.}, language = {en} } @inproceedings{SteglichPaulMaietal.2021, author = {Steglich, Patrick and Paul, Martin and Mai, Christian and B{\"o}hme, Andrea and Bondarenko, Siegfried and Weller, Michael G. and Mai, Andreas}, title = {A monolithically integrated micro fluidic channel in a silicon-based photonic-integrated-circuit technology for biochemical sensing}, series = {Proc. SPIE 11772, Optical Sensors 2021}, booktitle = {Proc. SPIE 11772, Optical Sensors 2021}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-13925}, year = {2021}, abstract = {In this work, a cost-effective optofluidic system is propossed and preliminary experimental results are presented. A microfluidic channel monolithically integrated into a photonic integrated circuit technology is used in conjunc- tion with a cyclo-olefin copolymer (COC) substrate to provide fluidic in- and output ports. We report on initial experimental results as well as on the simple and cost-effective fabrication of this optofluidic system by means of micro-milling.}, language = {en} } @inproceedings{FuenningPeczekKrohetal.2025, author = {F{\"u}nning, Tabea and Peczek, Anna and Kroh, Aleksandra and Mai, Christian and Paul, Martin and Thomsen, Florian and Tannenberg, Robert and Schumann, Christoph and Weller, Michael G. and Mai, Andreas and Steglich, Patrick}, title = {Optimization of local backside released micro-ring resonators for sensing applications using silicon photonic integrated circuits in a SOI technology}, series = {Proceedings of SPIE : Optical Sensors 2025}, volume = {13527}, booktitle = {Proceedings of SPIE : Optical Sensors 2025}, editor = {Baldini, Francesco and Homola, Jiri and Lieberman, Robert A.}, publisher = {SPIE}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-20449}, year = {2025}, abstract = {Photonic micro-ring resonators (MRR) are widely studied for their high sensitivity across applications like environmental monitoring, healthcare, and chemical analysis. Their evanescent field sensing requires partially unembedded waveguides compatible with CMOS processing. Our approach uses local backside etching with an additional buried oxide (BOX) etch to release waveguides while preserving the back-end of line (BEOL) structure, enabling spatial separation of the sensing area and electronics. The BOX etch critically affects sensor performance, as waveguide surface roughness can alter MRR properties and coupling. We analyzed MRR design variations, comparing wet and dry etching techniques for their effects on optical performance across rib and strip waveguides in quasi-TE and quasi-TM modes. Wafer-level measurements show that backside-released MRR achieve high extinction ratios with slightly reduced quality factors, advancing high-sensitivity photonic sensors.}, language = {en} }