Subtleties of nanophotonic lithium niobate waveguides for on-chip evanescent wave sensing

Creators: Harper, Nathan A.¹; Hwang, Emily Y.¹; Kocheril, Philip A.¹; Lam, Tze King; Cushing, Scott Kevin¹

1. California Institute of Technology

Abstract

Thin-film lithium niobate (TFLN) is promising for optical sensing due to its high nonlinearities, but its material properties present unique design challenges. We compare the sensing performance of the fundamental modes on a TFLN waveguide with a fluorescent dye sample. The TM mode has better overlap with the sample, with a 1.4 × greater sample absorption rate versus the TE mode. However, the TM mode also scatters at a 1.4 × greater rate, yielding less fluorescence overall. The TE mode is, therefore, more appropriate for sensing. Our findings have important implications for TFLN-based sensor designs.

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Funding

U.S. Department of Energy (DE-SC0022089).

Acknowledgement

The authors gratefully acknowledge the critical support and infrastructure provided for this work by The Kavli Nanoscience Institute (KNI) and the Beckman Biological Imaging Facility at Caltech. This work was additionally supported by the KNI-Wheatley Scholar in Nanoscience and the Rothenberg Innovation Initiative. The authors thank Ryoto Sekine and Alireza Marandi for providing the TFLN dies and Giada Spigolon for her helpful discussions in fluorescence imaging. N.A.H. was supported by the Department of Defense (DoD) through the National Defense Science and Engineering Graduate (NDSEG) Fellowship Program. E.Y.H. and P.A.K. were supported by the National Science Foundation Graduate Research Fellowship Program under Grant no. DGE-1745301. P.A.K. is grateful for financial support from a Hertz Fellowship. Any opinion, findings, and conclusions or recommendations expressed in this material are those of the authors(s) and do not necessarily reflect the views of the National Science Foundation.

Data Availability

Data underlying the results presented in this paper are not publicly available at this time but may be obtained from the authors upon reasonable request.

Additional Information

See Supplement 1 for supporting content. This supplementary document provides additional information and raw data for the image analysis, mode calculations, and system parameters.

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