High coupling efficiency waveguide grating couplers on lithium niobate.
Opt Lett
; 48(12): 3267-3270, 2023 Jun 15.
Article
em En
| MEDLINE
| ID: mdl-37319078
ABSTRACT
We propose and validate a new, to the best of our knowledge, approach for high coupling efficiency (CE) grating couplers (GCs) in the lithium niobate on insulator photonic integration platform. Enhanced CE is achieved by increasing the grating strength using a high refractive index polysilicon layer on the GC. Due to the high refractive index of the polysilicon layer, the light in the lithium niobate waveguide is pulled up to the grating region. The optical cavity formed in the vertical direction enhances the CE of the waveguide GC. With this novel structure, simulations predicted the CE to be -1.40â
dB, while the experimentally measured CE was -2.20â
dB with a 3-dB bandwidth of 81â
nm from 1592â
nm to 1673â
nm. The high CE GC is achieved without using bottom metal reflectors or requiring the etching of the lithium niobate material.
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2023
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