Frequency comb generation by CW laser injection into a quantum-dot mode-locked laser.

Area of Science:

• Optoelectronics
• Quantum Optics
• Laser Physics

Background:

• Quantum-dot lasers offer unique properties for light generation.
• Hybridly mode-locked quantum-dot lasers (HMLQDL) are explored for advanced applications.
• Frequency combs are crucial for precise measurements and high-speed communications.

Purpose of the Study:

• To demonstrate frequency comb generation at 1.5 μm using a hybridly mode-locked InAs/InP quantum-dot laser.
• To characterize the properties of the generated frequency comb.
• To assess the coherence and potential applications of the comb.

Main Methods:

• Injection of a continuous-wave (CW) laser into a two-section HMLQDL.
• Utilizing InAs/InP quantum-dot material for laser fabrication.
• Characterizing comb properties including mode count, spacing, spectral width, and signal-to-background ratio.

Main Results:

• Generation of a frequency comb with over 60 modes spaced by approximately 4.5 GHz.
• Observed a -20 dBc spectral width exceeding 100 GHz (23 modes).
• Achieved a signal-to-background ratio greater than 30 dB.
• Demonstrated comb generation even when the CW laser was detuned significantly from the HMLQDL spectrum.
• Confirmed full coherence between the generated comb, the injected CW laser, and the RF driving frequency.

Conclusions:

• The HMLQDL is an effective platform for generating wide, coherent frequency combs at 1.5 μm.
• This technique enables the creation of compact and robust frequency combs.
• Potential applications include optical frequency metrology, high-frequency RF generation (>100 GHz), and telecommunications.