Phase noise characterization of a QD-based diode laser frequency comb

Area of Science:

• Quantum optics
• Semiconductor lasers
• Frequency comb technology

Background:

• Quantum dot laser frequency combs (QDLFCs) offer potential for precise optical frequency generation.
• Characterizing phase noise in QDLFCs is crucial for their application in metrology and spectroscopy.
• Simultaneous phase measurement is needed to distinguish different noise sources.

Purpose of the Study:

• To simultaneously measure the phases of multiple comb lines from a passively mode-locked InAs/InP QDLFC.
• To separate common-mode and differential-mode phase noise.
• To determine the intrinsic differential-mode phase (IDMP) between adjacent subcarriers.

Main Methods:

• Utilized multi-heterodyne coherent detection to compare QDLFC lines against a stable reference comb.
• Employed simultaneous phase measurement to enable noise separation.
• Analyzed phase data to calculate IDMP standard deviation.

Main Results:

• Common-mode and differential phases were found to be uncorrelated.
• For the first time in a QDLFC, the IDMP between adjacent subcarriers was measured to be substantially constant across all pairs.
• The standard deviation of IDMP was determined to be 4.4 ps over a 200 µs interval.

Conclusions:

• The consistent IDMP supports a stable phase relationship between adjacent comb lines in QDLFCs.
• This finding is significant for understanding and improving the phase stability of QDLFCs.
• The results provide a benchmark for phase noise characterization in quantum dot laser frequency combs.