Tunable large free spectral range microring resonators in lithium niobate on insulator

Inna Krasnokutska,Alberto Peruzzo,Jean-Luc J. Tambasco

doi:10.1038/s41598-019-47231-3

Inna Krasnokutska, Alberto Peruzzo + Show 1 more

Open Access

https://doi.org/10.1038/s41598-019-47231-3

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Abstract

Microring resonators are critical photonic components used in filtering, sensing and nonlinear applications. To date, the development of high performance microring resonators in LNOI has been limited by the sidewall angle, roughness and etch depth of fabricated rib waveguides. We present large free spectral range microring resonators patterned via electron beam lithography in high-index contrast Z-cut LNOI. Our microring resonators achieve an FSR greater than 5 nm for ring radius of 30 μm and a large 3 dB resonance bandwidth. We demonstrate 3 pm/V electro-optic tuning of a 70 μm-radius ring. This work will enable efficient on-chip filtering in LNOI and precede future, more complex, microring resonator networks and nonlinear field enhancement applications.

Highlights

Microring resonators are fundamental components in any high-index contrast photonic platform[1,2]
We demonstrate the versatility of our fabrication process, etching down to 300 nm trenches in Lithium Niobate On Insulator wafers (LNOI), critical for advanced photonic components
In order to confirm that the photonic components are not limited by the propagation loss, loss measurements were performed prior to the characterization of the microrings, using the Fabry-Perot loss measurement technique[37]

Summary

Introduction

Microring resonators are fundamental components in any high-index contrast photonic platform[1,2] They are a highly sought after cavity component, as they enable on-chip field enhancement as well as spectral filtering and fast modulation of optical signals[1,3,4,5,6]. To achieve a large free spectral range (FSR) for telecommunication applications and sensing, small, single-mode high-index contrast waveguides are required. Multimode waveguide rings have been reported in LNOI, but suffered from high propagation loss due to fabrication imperfection[24,25]. We present a detailed study of all-pass microring resonators fabricated monolithically in Z-cut LNOI from small, low-loss, high-index contrast and single mode C-band waveguides. We expect the microring resonators in this work to pave the way towards on-chip filtering in LNOI with ring networks, as well as field enhancement applications such as switching and nonlinear photon generation

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