On-chip terahertz (THz) biosensors have enormous potential in advancing the development of integrable devices for real-time, label-free, and noninvasive detection of proteins, DNA, and cancerous tissue. However, high absorption of THz waves by water necessitates evanescent field-based biosensing. The conventional on-chip THz biosensors with small mode confinement volumes and scaling sensitivity to defects severely limit the interaction of analyte with the electromagnetic field. Here, we reveal a topological waveguide cavity system with topologically protected propagating interfacial modes, exhibiting evanescent waves with an out-of-plane field extent of , where is the wavelength corresponding to the cavity resonance frequency. Our experiments involving biomolecule detection and leaf-hydration monitoring show that the near-field of high-Q topological cavity resonances accurately detects minute frequency shifts over extended periods, facilitating real-time sensing and monitoring of biological matter. Implementation of topologically protected evanescent fields in waveguide-cavity systems will enhance on-chip THz biosensing.
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17 July 2023
Research Article|
July 18 2023
On-chip topological THz biosensors

Nikhil Navaratna
;
Nikhil Navaratna
(Conceptualization, Data curation, Formal analysis, Investigation, Software, Validation, Writing – original draft, Writing – review & editing)
1
Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University
, Singapore
6373712
Centre for Disruptive Photonic Technologies, The Photonics Institute, Nanyang Technological University
, Singapore
639798
Search for other works by this author on:
Yi Ji Tan
;
Yi Ji Tan
(Formal analysis, Software, Writing – review & editing)
1
Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University
, Singapore
6373712
Centre for Disruptive Photonic Technologies, The Photonics Institute, Nanyang Technological University
, Singapore
639798
Search for other works by this author on:
Abhishek Kumar
;
Abhishek Kumar
(Software, Writing – review & editing)
1
Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University
, Singapore
6373712
Centre for Disruptive Photonic Technologies, The Photonics Institute, Nanyang Technological University
, Singapore
639798
Search for other works by this author on:
Manoj Gupta
;
Manoj Gupta
(Software, Writing – review & editing)
1
Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University
, Singapore
6373712
Centre for Disruptive Photonic Technologies, The Photonics Institute, Nanyang Technological University
, Singapore
639798
Search for other works by this author on:
Ranjan Singh
Ranjan Singh
a)
(Conceptualization, Funding acquisition, Supervision, Writing – review & editing)
1
Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University
, Singapore
6373712
Centre for Disruptive Photonic Technologies, The Photonics Institute, Nanyang Technological University
, Singapore
639798 a)Author to whom correspondence should be addressed: [email protected]
Search for other works by this author on:
Nikhil Navaratna
1,2
Yi Ji Tan
1,2
Abhishek Kumar
1,2
Manoj Gupta
1,2
Ranjan Singh
1,2,a)
1
Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University
, Singapore
637371
2
Centre for Disruptive Photonic Technologies, The Photonics Institute, Nanyang Technological University
, Singapore
639798
a)Author to whom correspondence should be addressed: [email protected]
Appl. Phys. Lett. 123, 033705 (2023)
Article history
Received:
May 07 2023
Accepted:
June 03 2023
Connected Content
A companion article has been published:
Building a better platform paradigm for terahertz biosensing
Citation
Nikhil Navaratna, Yi Ji Tan, Abhishek Kumar, Manoj Gupta, Ranjan Singh; On-chip topological THz biosensors. Appl. Phys. Lett. 17 July 2023; 123 (3): 033705. https://doi.org/10.1063/5.0157357
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