Ultra-stable 10 GHz Optical Clocks Based on Injection Mode-Locked Semiconductor Lasers

Al-Rubaiee, M., Ye, S. , Yuan, B., Fan, Y., Marsh, J. H. and Hou, L. (2023) Ultra-stable 10 GHz Optical Clocks Based on Injection Mode-Locked Semiconductor Lasers. 46th European Semiconductor Laser Workshop ESLW 2023, University of Glasgow, 30 September 2023.

Abstract

In the field of high-speed digital systems, there is a critical need to distribute fast and stable clock signals. This work demonstrates an ultra-stable 10 GHz optical clock based on a 1550 nm two-section passive semiconductor mode-locked laser (SMLL), which is injection-locked to a 10 GHz actively mode-locked fibre laser (Pritel). The passive SMLL is based on AlGaInAs/InP material with a three-quantum-well (3QW) active layer on a semi-insulating InP substrate. Using only 3 QWs reduces the optical overlap with the QWs leading to a reduction in self-phase modulation (SPM) effects in the gain section. A 160 nm thick 1.1 Q far-field reduction layer (FRL) was inserted in the lower n-cladding layer to increase the spot size, reduce the internal loss of the cavity and further reduce optical overlap with QWs while suppressing higher transverse mode lasing. Passive mode-locking (ML) was achieved by applying a forward current to the gain section and a reverse voltage to the saturable absorber (SA) section. Sech2 pulses of 1.8 ps duration were generated at a repetition rate of 10 GHz. Compared with a free-running SMLL, the RF linewidth of injected SMLLs was reduced from 46.5 kHz to subhertz. The FRL reduced the divergence angle from 34.7° × 35.1° to 18.3°×31.1°, which doubles the coupling efficiency to a flat cleaved single-mode fibre (SMF). The significant reduction in RF linewidth and timing jitter in our device proves injection locking is a promising technique for distributing ultra-stable optical clocks.

• Item Type: Conference or Workshop Item
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Yuan, Bocheng and Hou, Dr Lianping and FAN, YIZHE and Marsh, Professor John and Al Rubaiee, Mohanad Jamal Abbas and Ye, Dr Shengwei
• Authors: Al-Rubaiee, M., Ye, S., Yuan, B., Fan, Y., Marsh, J. H., and Hou, L.
• College/School: College of Science and Engineering > School of Engineering; College of Science and Engineering > School of Engineering > Electronics and Nanoscale Engineering

Related URLs

• Organisation