Passively mode-locked semiconductor quantum dot on silicon laser with 400 Hz RF line width

Area of Science:

• Optoelectronics
• Materials Science
• Telecommunications

Background:

• Mode-locked semiconductor lasers are crucial for high-speed optical communications.
• Quantum dot (QD) lasers offer unique properties for generating optical frequency combs.
• Integration of optoelectronic devices on silicon substrates is a key challenge.

Purpose of the Study:

• To demonstrate stable optical pulse train generation using monolithic passively mode-locked InAs/InGaAs quantum dot lasers.
• To investigate the performance of these lasers for high-capacity communication applications.
• To achieve high-quality optical frequency combs on a silicon platform.

Main Methods:

• Fabrication of a monolithic, passively mode-locked, edge-emitting, two-section quantum dot laser.
• Utilizing a five-stack InAs/InGaAs dots-in-a-well structure grown on an on-axis (001) silicon substrate via solid-source molecular beam epitaxy.
• Characterization of optical pulse width, repetition rate, timing jitter, amplitude jitter, and comb width.

Main Results:

• Stable optical pulse trains with pulse widths as short as 1.7 picoseconds (ps) were achieved.
• A pulse repetition rate of 9.4 gigahertz (GHz) was obtained with a minimum pulse-to-pulse timing jitter of 9 femtoseconds (fs).
• Optical frequency combs exhibited low amplitude jitter and comb widths exceeding 5.5 nanometers (nm) (-3 dB), containing over 100 comb carriers.

Conclusions:

• Monolithic InAs/InGaAs quantum dot lasers grown on silicon are promising for high-speed and high-capacity communication systems.
• The demonstrated low timing jitter and wide comb width indicate excellent performance for optical frequency comb generation.
• Direct growth on silicon substrates paves the way for scalable and cost-effective photonic integrated circuits.