Tunable Bandpass Filter With Serially Coupled Ring Resonators Assisted MZI

Niharika Kohli,Bruno Sang,Frederic Nabki,Michael Menard

doi:10.1109/jphot.2021.3103142

Niharika Kohli, Bruno Sang + Show 2 more

Open Access

https://doi.org/10.1109/jphot.2021.3103142

Copy DOI

Abstract

We present the analytical modelling and experimental characterization of a new design of silicon nitride tunable bandpass filter based on serially coupled ring resonators assisted Mach-Zehnder interferometer (SR-MZI). SR-MZI filters provide an additional degree of freedom to independently control the bandwidth and shape of the passband as compared to previous ring-assisted MZI filters. It is possible to tune the bandwidth, shape and side-band rejection of the response by adjusting the coupling in the filters, providing a scope for fully reconfigurable performance. The fabrication of the filters is CMOS compatible and supports mass production. Preliminary results for thermal controllability are presented.

Highlights

I NTEGRATED optical filters are among the most widely used components in photonic circuits
The serially coupled ring resonators assisted Mach-Zehnder interferometer (SR-Mach-Zehnder Interferometer (MZI)) filter designs were implemented using trapezoidal Silicon Nitride (SiN) strip waveguides with a side-wall angle of 86°
The fabrication process started with a TEOS Low-Pressure Chemical Vapor Deposition (LPCVD) of a 3.2 μm thick SiO2 layer on the silicon wafer

Summary

INTRODUCTION

I NTEGRATED optical filters are among the most widely used components in photonic circuits. To be useful in EONs, the filter should be dynamic such that it is able to adapt to the ongoing traffic requirements These filters should have low insertion loss, a box-like response, and a high extinction ratio and side-band rejection. One promising approach to implement a tunable BPF is the Ring Assisted Mach-Zehnder interferometer (RA-MZI) with one or more ring resonators (RRs) embedded in one or both of its arms [16], [20], [23], [24] This configuration offers a more box-like passband response compared to cascaded RRs without the MZI [19], [21], [22]. The effect of the coupling coefficients between the two RRs and between the RRs and MZI is shown on the pole-zero plots and transmission responses. The effect of the transmission coefficients on the pole-zero plot of such a filter is presented

Theoretical filter responses

EXPERIMENTAL RESULTS

Experimental results for different coupling gaps

Experimental results with thermal tuning

CONCLUSION