High-channel-count 20 GHz passively mode-locked quantum dot laser directly grown on Si with 41 Tbit/s transmission capacity

Songtao Liu,M J Kennedy,John E Bowers,Xinru Wu,Daehwan Jung,Hon K Tsang,Justin C Norman,Arthur C Gossard

doi:10.1364/optica.6.000128

Abstract

Low cost, small footprint, highly efficient and mass producible on-chip wavelength-division-multiplexing (WDM) light sources are key components in future silicon electronic and photonic integrated circuits (EPICs) which can fulfill the rapidly increasing bandwidth and lower energy per bit requirements. We present here, for the first time, a low noise high-channel-count 20 GHz passively mode-locked quantum dot laser grown on complementary metal-oxide-semiconductor compatible on-axis (001) silicon substrate. The laser demonstrates a wide mode-locking regime in the O-band. A record low timing jitter value of 82.7 fs (4 - 80 MHz) and a narrow RF 3-dB linewidth of 1.8 kHz are measured. The 3 dB optical bandwidth of the comb is 6.1 nm (containing 58 lines, with 80 lines within the 10 dB bandwidth). The integrated average relative intensity noise values of the whole spectrum and a single wavelength channel are - 152 dB/Hz and - 133 dB/Hz in the frequency range from 10 MHz to 10 GHz, respectively. Utilizing 64 channels, an aggregate total transmission capacity of 4.1 terabits per second is realized by employing a 32 Gbaud Nyquist four-level pulse amplitude modulation format. The demonstrated performance makes the laser a compelling on-chip WDM source for multi-terabit/s optical interconnects in future large-scale silicon EPICs.

Highlights

Driven by the huge demand for high-performance computing and large-scale data centers, photonic interconnects employing wavelength division multiplexing (WDM) are evolving fast as it is a feasible technology to meet the high-bandwidth and low energy consumption requirements required for data centers [1,2,3,4]
We demonstrate the first 20 GHz passively mode locked quantum dot laser (QD-mode locked lasers (MLLs)) that is directly grown on on-axis (001) CMOS compatible silicon substrate
The demonstrated performance suggests the Si-based QDMLL is a strong WDM light source candidate that can be integrated in future large-scale silicon electronic and photonic integrated circuits (EPICs) to boost the system capacity and efficiency

Summary

INTRODUCTION

Driven by the huge demand for high-performance computing and large-scale data centers, photonic interconnects employing wavelength division multiplexing (WDM) are evolving fast as it is a feasible technology to meet the high-bandwidth and low energy consumption requirements required for data centers [1,2,3,4]. Record high performance Fabry-Perot (FP) QD lasers with a lowest lasing threshold and longest lifetime of more than a million hours [14] have been demonstrated recently due to the significant reduction in threading dislocation density (TDD) in the GaAs buffer layers [15]. It is, attractive to realize QD on-chip WDM sources for future large scale silicon EPICs to fulfill the bandwidth and power consumption requirements. The demonstrated performance suggests the Si-based QDMLL is a strong WDM light source candidate that can be integrated in future large-scale silicon EPICs to boost the system capacity and efficiency

DEVICE DESIGN AND FABRICATION

CHARACTERIZATION AND DISCUSSION

PASSIVE MODE LOCKING PERFORMANCE

DATA TRANMISSION PERFORMANCE

Findings

CONCLUSIONS