Long-period gratings on lithium-niobate waveguides: phase-matching turning points for ultra-broadband mode conversion

Chenxu Lu; Wei Jin; Kin Seng Chiang

doi:10.1364/OL.467588

Author(s)

Chenxu Lu
Wei Jin
Kin Seng Chiang

Related Research Unit(s)

Department of Electrical Engineering

Detail(s)

Original language	English
Pages (from-to)	3984-3987
Journal / Publication	Optics Letters
Volume	47
Issue number	16
Online published	2 Aug 2022
Publication status	Published - 15 Aug 2022

Link(s)

DOI	DOI https://doi.org/10.1364/OL.467588 Final Published version
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Attachment(s)	Documents 112834457.pdf Post-print, 1.03 MB, PDF Publisher's Copyright Statement © 2022 Optica Publishing Group. One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modifications of the content of this paper are prohibited.
Link to Scopus	https://www.scopus.com/record/display.uri?eid=2-s2.0-85135439468&origin=recordpage
Permanent Link	https://scholars.cityu.edu.hk/en/publications/publication(7686e4e8-06da-4528-bad9-6a71e1b2a677).html

Abstract

We analyze a polymer long-period grating (LPG) formed on the surface of a z-cut lithium-niobate (LN) few-mode waveguide for TM₀₀-TM₁₀ mode conversion. We identify and explore the turning points along the phase-matching curves of the LPGs for the achievement of ultra-broadband mode conversion. We fabricate a number of gratings with annealed proton-exchanged LN waveguides and our experimental results agree well with the theoretical results. A typical fabricated grating operating near the turning point provides a mode extinction ratio larger than 20 dB from 1550nm to a wavelength longer than 1700 nm, and another one provides a mode extinction ratio larger than 10 dB from 1464nm to a wavelength longer than 1700 nm. Our gratings show good thermal stability. The structure of the LPG on LN waveguide could be applied to the realization of ultrabroadband high-speed mode switches for mode-multiplexing applications.