Comparison of Physical and System Factors Impacting Hydration Sensing in Leaves Using Terahertz Time-Domain and Quantum Cascade Laser Feedback Interferometry Imaging
Khushboo Singh,
Aparajita Bandyopadhyay,
Karl Bertling,
Yah Leng Lim,
Tim Gillespie,
Dragan Indjin,
Lianhe Li,
Edmund H. Linfield,
A. Giles Davies,
Paul Dean,
Aleksandar D. Rakić,
Amartya Sengupta
Affiliations
Khushboo Singh
Department of Physics, Indian Institute of Technology Delhi, New Delhi 110016, India
Aparajita Bandyopadhyay
DRDO-Industry-Academia Center of Excellence, Indian Institute of Technology Delhi, New Delhi 110016, India
Karl Bertling
School of Information Technology & Electrical Engineering, The University of Queensland, Brisbane, QLD 4072, Australia
Yah Leng Lim
School of Information Technology & Electrical Engineering, The University of Queensland, Brisbane, QLD 4072, Australia
Tim Gillespie
School of Information Technology & Electrical Engineering, The University of Queensland, Brisbane, QLD 4072, Australia
Dragan Indjin
School of Electronic and Electrical Engineering, University of Leeds, Leeds LS2 9JT, UK
Lianhe Li
School of Electronic and Electrical Engineering, University of Leeds, Leeds LS2 9JT, UK
Edmund H. Linfield
School of Electronic and Electrical Engineering, University of Leeds, Leeds LS2 9JT, UK
A. Giles Davies
School of Electronic and Electrical Engineering, University of Leeds, Leeds LS2 9JT, UK
Paul Dean
School of Electronic and Electrical Engineering, University of Leeds, Leeds LS2 9JT, UK
Aleksandar D. Rakić
School of Information Technology & Electrical Engineering, The University of Queensland, Brisbane, QLD 4072, Australia
Amartya Sengupta
Department of Physics, Indian Institute of Technology Delhi, New Delhi 110016, India
To reduce the water footprint in agriculture, the recent push toward precision irrigation management has initiated a sharp rise in photonics-based hydration sensing in plants in a non-contact, non-invasive manner. Here, this aspect of sensing was employed in the terahertz (THz) range for mapping liquid water in the plucked leaves of Bambusa vulgaris and Celtis sinensis. Two complementary techniques, broadband THz time-domain spectroscopic imaging and THz quantum cascade laser-based imaging, were utilized. The resulting hydration maps capture the spatial variations within the leaves as well as the hydration dynamics in various time scales. Although both techniques employed raster scanning to acquire the THz image, the results provide very distinct and different information. Terahertz time-domain spectroscopy provides rich spectral and phase information detailing the dehydration effects on the leaf structure, while THz quantum cascade laser-based laser feedback interferometry gives insight into the fast dynamic variation in dehydration patterns.
