Weak One-Dimensional Field Confinement Silica Waveguides

Chenming Zhao,Lei Xu,Lin Chen,Liying Liu

doi:10.1109/jphot.2020.3007721

Abstract

A novel weak one-dimensional field confinement silica waveguide (WCSW) with a large horizontal and vertical aspect ratio and low refractive index difference is proposed and fabricated via sol-gel technique. This new type of waveguide exhibits properties of high lithography tolerance, low polarization dependence, low propagation loss and low coupling loss with a single-mode fiber. More importantly, WCSW can provide extremely large evanescent field in vertical direction. The measured propagation loss and coupling loss are as low as 0.81 dB/cm and 0.71 dB/facet, respectively. In addition, high efficiency vertical coupling with a 1.9 μm gap between a WCSW bus waveguide and a WCSW based high Q (5.4 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sup> ) ring resonator is achieved, which demonstrates that vertical integration of WCSW is potentially applicable.

Highlights

Large evanescent field is of great importance in integrated photonics devices because it enables high sensitivity sensing [1], [2], high efficiency coupling [3]
The core layer, silica doped with Zr4+, was prepared on the silica layer by dip-coating and rapid thermal annealing (DC-RTA) from a sol composed of methacryloxypropyl trimethoxysilane (MAPTMS), zirconium n-propoxide (ZPO) and methacrylic acid (MAA)
The silica doped with Zr4+ has a higher refractive index, which related to the proportion of ZPO

Summary

Introduction

Large evanescent field is of great importance in integrated photonics devices because it enables high sensitivity sensing [1], [2], high efficiency coupling [3] It can be realized both in high and low refractive index contrast waveguides near cutoff waveguide thickness. For a low refractive index material such as silica, waveguide width can be as large as several micrometers but still provides large evanescent field as well, high efficiency coupling with single-mode fiber is feasible without using additional mode converters. The simulation results show that WCSW has low polarization dependence with effective refractive index difference of 2.7 × 10−4, the coupling loss with single-mode fiber is as low as 0.5 dB/facet, and vertical coupling can be achieved with 100% efficiency.

Modelling and Simulations

Experimental Results and Discussions

Conclusion