Michelson interferometer modulator based on hybrid silicon and lithium niobate platform

Mengyue Xu,Jian Xu,Ziliang Ruan,Xinlun Cai,Wenjun Chen,Liu Liu,Lifeng Chen,Mingbo He,Siyuan Yu,Xueqin Wen

doi:10.1063/1.5115136

Abstract

We propose and demonstrate a hybrid silicon and lithium niobate Michelson interferometer modulator (MIM) with a reduced half-wave voltage-length product compared to a Mach-Zehnder modulator. The modulator is based on seamless integration of a high-contrast waveguide based on lithium niobate—a widely used modulator material—with compact, low-loss silicon circuitry. The present device demonstrates a half-wave voltage-length product as low as 1.2 V cm and a low insertion loss of 3.3 dB. The 3 dB electro-optic bandwidth is approximately 17.5 GHz. The high-speed modulations are demonstrated at 32 Gbit/s and 40 Gbit/s with the extinction ratio of 8 dB and 6.6 dB, respectively. The present device avoids absorption loss and nonlinearity in conventional silicon modulators and demonstrates the lowest half-wave voltage-length product in lithium niobate modulators. The hybrid MIM demonstrates high-speed data modulation showing potential in future optical interconnects.

Highlights

We demonstrate a heterogeneous silicon and LN Michelson interferometer modulator (MIM) in compact footprint (0.1 mm2) with half of Vπ ⋅ L compared to a Mach-Zehnder modulator (MZM)
In the on-off keying (OOK) eye diagram measurement, we have shown open optical eye diagram data rates up to 40 Gbit/s with 6.6 dB extinction ratio, which is comparative to that of silicon modulators
The present device in this work is the only one in which low insertion loss and competitive performance of data modulation are demonstrated simultaneously. This hybrid platform can avoid some disadvantages in conventional silicon modulators, such as absorption loss and nonlinearity

Summary

INTRODUCTION

Silicon photonics on the silicon-on-insulator (SOI) platform has emerged as the leading technology for optical interconnect due to the possibility of low-cost and high-volume production of photonic integrated circuits (PICs) in CMOS foundries. optical modulations in the silicon material mainly rely on freecarrier plasma dispersion effect, which leads to inevitable absorption losses, nonlinear voltage response, and temperature sensitivity. Lithium niobate (LiNbO3, LN) shows potential for realizing high performance electro-optic (EO) modulators due to its physical properties: large EO coefficient (30 pm/V), strong Pockels effect, wide bandgap (wide transparency window), and good temperature stability. commercial bulk LN modulators based on the indiffused or proton-exchange waveguide are suffering with a low refractive index contrast, large half-wave voltage-length product (Vπ ⋅ L, typically >10 V cm), and difficult to integrate. Commercial bulk LN modulators based on the indiffused or proton-exchange waveguide are suffering with a low refractive index contrast, large half-wave voltage-length product (Vπ ⋅ L, typically >10 V cm), and difficult to integrate. The LNOI-based modulator allows for a good overlap between optical and electrical fields and reduced Vπ ⋅ L. (MZM) based on the heterogeneous silicon/LN platform with low loss and large modulation bandwidth.. We propose and demonstrate a Michelson interferometer modulator (MIM) based on the heterogeneous silicon/LN platform [Fig. 1(a)]. The bottom SOI circuit supports all other passive functions, consisting of a 3 dB multimode interference (MMI) coupler that splits and combines the optical power, two loop mirrors that serve as broadband reflectors, and two grating couplers for off-chip coupling. The RF signal is applied to ground-signal-ground (GSG) electrodes, and modulated light is detected at another grating coupler

DEVICE DESIGN AND FABRICATION

Vπ π 2

DEVICE CHARACTERIZATION

CONCLUSION