Photonic nanowires and waveguides for spectral shaping with Sagnac loop
reflectors
Abstract
We propose and theoretically investigate integrated photonic filters
based on two coupled Sagnac loop reflectors (SLRs) formed by a
self-coupled optical waveguide. Recently we investigated integrated
photonic filters based on cascaded SLRs and coupled SLRs. Here, we
advance this field by presenting a unique approach of using coupled SLRs
formed by a self-coupled optical waveguide. This enables us to achieve
high performance filter functions including Fano-like resonances and
wavelength interleaving with a simpler design and a higher fabrication
tolerance by tailoring coherent mode interference in the device. Our
design takes into account the device fabrication issues as well as the
requirements for practical applications. As a guide for practical device
fabrication, an analysis of the impact of the structural parameters and
fabrication tolerance on each filter function is also provided. The
Fano-like resonances show a low insertion loss (IL) of 1.1 dB, a high
extinction ratio of 30.2 dB, and a high slope rate (SR) of 747.64 dB/nm.
The combination of low IL and high SR promises this device for Fano
resonance applications. Our device also can achieve wavelength
de-interleaving function with high fabrication tolerance which is
attractive for optical interleavers that need a flat-top symmetric
filter shape. Optical interleavers and de-interleavers are core elements
for signal multiplexing and demultiplexing in wavelength division
multiplexing optical communication systems. Versatile spectral responses
with a simple design, compact device footprint, and high fabrication
tolerance make this approach highly promising for flexible response
shaping in a wide variety of applications.