Open AccessUltra-compact, broadband adiabatic passage optical couplers in thin-film lithium niobate on insulator waveguides
Author(s) -
Yi Lin,
Mohammadreza Younesi,
Hung-Pin Chung,
Hua Kung Chiu,
Reinhard Geiß,
Q. H. Tseng,
Frank Setzpfandt,
Thomas Pertsch,
Yen-Hung Chen
Publication year - 2021
Publication title -
optics express
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.394
H-Index - 271
ISSN - 1094-4087
DOI - 10.1364/oe.435633
Subject(s) - lithium niobate , adiabatic process , power dividers and directional couplers , optics , materials science , waveguide , stimulated raman adiabatic passage , optoelectronics , photonics , broadband , hybrid coupler , photonic integrated circuit , physics , laser , thermodynamics
We report the first demonstration of broadband adiabatic directional couplers in thin-film lithium niobate on insulator (LNOI) waveguides. A three LN-waveguide configuration with each waveguide having a ridge cross section of less than 1 square micron, built atop a layer of SiO 2 based on a 500-µm-thick Si substrate, has been designed and constructed to optically emulate a three-state stimulated Raman adiabatic passage system, with which a unique counterintuitive adiabatic light transfer phenomenon in a high coupling efficiency of >97% (corresponding to a >15 dB splitting ratio) spanning telecom S, C, and L bands for both TE and TM polarization modes has been observed for a 2-mm long coupler length. An even broader operating bandwidth of >800 nm of the device can be found from the simulation fitting of the experimental data. The footprint of the realized LNOI adiabatic coupler has been reduced by >99% compared to its bulk counterparts. Such an ultra-compact, broadband LNOI adiabatic coupler can be further used to implement or integrate with various photonic elements, a potential building block for realizing large-scale integrated photonic (quantum) circuits in LN.