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Creating terahertz pulses from titanium-doped lithium niobate-based strip waveguides with 1.55 μm light

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Abstract

We demonstrate that terahertz radiation can be generated from titanium-diffused magnesium oxide-doped lithium niobate optical strip waveguides when pumped by a single laser source with a wavelength of 1.55 μm. Titanium-in-diffusion was performed on a magnesium oxide-doped lithium niobate substrate by the deposition of titanium in a 40-µm wide strip pattern and then annealing in a vacuum furnace. Prism-coupled Cherenkov-phase matching was utilized to extract the terahertz emission from the waveguide. The contrast between the emission from the waveguide against the bulk crystal when the sample was moved along its crystal facet was also recorded, where an improvement of ~ 18.0% in the time-domain peak signal of the waveguide was observed. The waveguide’s performance was also measured against that of a commercial terahertz emitter, a photoconductive antenna, where it was found that the time-domain signals of the two were comparable. The terahertz power spectra also revealed that the lithium niobate-based waveguides have a broader bandwidth by more than 1 THz, with a similar signal-to-noise ratio. As an effect, the waveguides gave a better signal at higher frequencies and, at times, reaching as high a difference of 20 dB. These results indicate the possibility of using titanium-in-diffusion to generate intense terahertz emission from titanium-doped lithium niobate waveguides and that these strip waveguides are viable alternatives to commercial terahertz emitters, especially at high frequencies. It is expected that much better output can be obtained from an optimized waveguide design and with more appropriate optics.

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Authors and Affiliations

  1. Research Center for Development of Far-Infrared Region, University of Fukui, Fukui, 910-8507, Japan

    Joselito E. Muldera, Takashi Furuya, Hideaki Kitahara & Masahiko Tani

  2. Faculty of Pure and Applied Sciences, University of Tsukuba, Tsukuba, 305-8573, Japan

    Jessica Pauline C. Afalla

  3. National Institute of Physics, University of the Philippines, Diliman, 1101, Quezon City, Philippines

    Elmer S. Estacio

  4. Department of Electrical and Electronic Engineering, Synchrotron Light Application Center, Saga University, 1 Honjo, Saga, 840-8502, Japan

    Katsuhiko Saito & Qixin Guo

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  1. Joselito E. Muldera
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Muldera, J.E., Afalla, J.P.C., Furuya, T. et al. Creating terahertz pulses from titanium-doped lithium niobate-based strip waveguides with 1.55 μm light. J Mater Sci: Mater Electron 32, 23164–23173 (2021). https://doi.org/10.1007/s10854-021-06802-9

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