Silicon photonic filters with high rejection of both TE and TM modes for on-chip four wave mixing applications.

Giuseppe Cantarella,Michael J Strain,Marc Sorel,Charalambos Klitis

doi:10.1364/oe.25.019711

Giuseppe Cantarella, Michael J Strain + Show 2 more

Open Access

https://doi.org/10.1364/oe.25.019711

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Abstract

Wavelength selective filters represent one of the key elements for photonic integrated circuits (PIC) and many of their applications in linear and non-linear optics. In devices optimised for single polarisation operation, cross-polarisation scattering can significantly limit the achievable filter rejection. An on-chip filter consisting of elements to filter both TE and TM polarisations is demonstrated, based on a cascaded ring resonator geometry, which exhibits a high total optical rejection of over 60 dB. Monolithic integration of a cascaded ring filter with a four-wave mixing micro-ring device is also experimentally demonstrated with a FWM efficiency of -22dB and pump filter extinction of 62dB.

Highlights

Silicon on insulator (SOI) is one of the most mature and well developed photonic integration platforms [1,2,3,4,5], benefiting from the availability of CMOS fabrication technology, where it is possible to use electronics fabrication facilities to make photonic circuitry [6]
Devices optimised for TE mode filtering do not inherently suppress light propagating in the orthogonal TM polarisation. This becomes a significant issue in silicon photonics where scattering between the TE and TM modes has been shown to be non-negligible in typical SOI waveguides (220nm × 500nm) fabricated by reactive ion etching, limiting polarisation extinction to ≈ 20 dB [27]
In both coupledresonator optical waveguide (CROW) and cascade geometries, the number of resonators can be increased in order to increase the filter rejection but, given the sensitivity of the optical spectrum analyser (OSA) detection system and the substrate light noise, described in section 5, the number of the rings used in this work has been limited to three

Summary

Introduction

Silicon on insulator (SOI) is one of the most mature and well developed photonic integration platforms [1,2,3,4,5], benefiting from the availability of CMOS fabrication technology, where it is possible to use electronics fabrication facilities to make photonic circuitry [6]. Devices optimised for TE mode filtering do not inherently suppress light propagating in the orthogonal TM polarisation This becomes a significant issue in silicon photonics where scattering between the TE and TM modes has been shown to be non-negligible in typical SOI waveguides (220nm × 500nm) fabricated by reactive ion etching, limiting polarisation extinction to ≈ 20 dB [27]. This effect leads to the potential for a significant amount of light to be scattered from the TE to the TM mode in access waveguides transmitted through the TE mode filter. Fiber to polymer inverse taper losses were measured at 2.5 dB per facet

Polarisation effects in ring resonator filters

Plasmonic TM mode attenuator

SiO2 1

Monolithic device for FWM and on-chip pump filtering

Conclusion