Abstract
The concept of point of darkness has received much attention for biosensing based on phase-sensitive detection and perfect absorption of light. The maximum phase change is possible at the point of darkness where the reflection is almost zero. To date, this has been experimentally realized using different material systems through the concept of topological darkness. However, complex nanopatterning techniques are required to realize topological darkness. Here, we report an approach to realize perfect absorption and extreme phase singularity using a simple metal-dielectric multilayer thin-film stack. The multilayer stack works on the principle of an asymmetric Fabry–Perot cavity and shows an abrupt phase change at the reflectionless point due to the presence of a highly absorbing ultrathin film of germanium in the stack. In the proof-of-concept phase-sensitive biosensing experiments, we functionalize the film surface with an ultrathin layer of biotin-thiol to capture streptavidin at a low concentration of 1 pM.
Highlights
The concept of point of darkness has received much attention for biosensing based on phasesensitive detection and perfect absorption of light
Thin films of Ag and Ge were deposited by thermal evaporation, and a layer of methyl methacrylate (MMA) was spin-coated on the samples (Methods)
Field-emission scanning electron microscopy (FE-SEM) images of the Ge surface are shown in Supplementary Fig. 2 and indicate that the thermally evaporated 10 nm thick Ge film has a uniform surface texture and morphology
Summary
The concept of point of darkness has received much attention for biosensing based on phasesensitive detection and perfect absorption of light. The maximum phase change is possible at the point of darkness where the reflection is almost zero To date, this has been experimentally realized using different material systems through the concept of topological darkness. In the proof-of-concept phase-sensitive biosensing experiments, we functionalize the film surface with an ultrathin layer of biotin-thiol to capture streptavidin at a low concentration of 1 pM It is well-known that enhancement of light absorption in optical structures is only possible when the total combined reflection and transmission are decreased. The close to zero reflection condition is sufficient for sensing applications By exploiting this concept, an areal mass sensitivity at a level of fgmm−1 with single-molecule sensitivity has been achieved using plasmonic gold nanoarray metamaterial[11]; such sensitivity is much higher than the sensitivity of plasmonic sensors based on spectroscopic techniques. The proposed system does not require nanopatterning to achieve phase singularity, thereby enabling cost-effective large-area multi-channel sensing
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
