Open AccessVertically tapered waveguide spot size converters fabricated via a linewidth controlled grey tone lithography for InP-based photonic integrated circuits
Author(s) -
O. Salehzadeh,
Martin Vachon,
Nicaulas Sabourin,
Siegfried Janz,
A. J. SpringThorpe
Publication year - 2020
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.397489
Subject(s) - materials science , coupling loss , optics , laser linewidth , photonic integrated circuit , tapering , photolithography , electronic circuit , photonics , optoelectronics , fabrication , lithography , waveguide , optical fiber , laser , physics , medicine , computer graphics (images) , alternative medicine , pathology , quantum mechanics , computer science
We report a novel and simple fabrication process to realize vertically tapered spot size converters (SSC) on InP photonic integrated circuits. The vertical tapering was achieved via a linewidth controlled local optical dose variation, leading to a grey tone photoresist profile. The fabricated SSCs are compact, polarization insensitive and demonstrate a very high mode conversion efficiency of 95%. Integrated SSCs improved the overall loss by 5 dB giving a coupling loss as low as 1.3 dB/facet, for a lensed fibre with a mode field diameter of 3.0 µm. A good agreement was found between the fibre-to-fibre optical loss measurements and those predicted from simulations.