Injection locking of an actively mode-locked semiconductor laser

Area of Science:

• Optics and Photonics
• Semiconductor Lasers
• Laser Physics

Background:

• Actively mode-locked lasers are crucial for generating ultrashort optical pulses.
• Injection locking is a technique used to synchronize and stabilize laser outputs.
• Extended cavity semiconductor lasers offer tunability but require precise control.

Purpose of the Study:

• To report the first observation of synchronous coherent injection locking of an actively mode-locked extended cavity semiconductor laser.
• To investigate the effects of injection locking on the temporal and spectral characteristics of the laser output.
• To theoretically verify experimental observations of pulse narrowing and spectral filtering.

Main Methods:

• Experimental setup involving an actively mode-locked extended cavity semiconductor laser.
• Injection of an external light pulse train to achieve synchronous coherent locking.
• Temporal and spectral measurements of the laser output using appropriate diagnostic tools.
• Theoretical modeling to validate experimental findings.

Main Results:

• Observed significant narrowing of the output pulse in the temporal domain.
• Demonstrated narrowing of the output optical spectrum in the spectral domain.
• Experimentally verified rejection of spectral components outside the locking pulse's spectral band.
• Measured locking ranges of approximately 200 ps in the time domain and 5 nm in the frequency domain.

Conclusions:

• Synchronous coherent injection locking is effectively demonstrated in actively mode-locked extended cavity semiconductor lasers.
• The technique leads to improved temporal pulse characteristics (narrower pulses).
• The method provides spectral control by filtering unwanted spectral components, enhancing spectral purity.