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Mode-locking via delayed orthogonal-polarization reinjection in semiconductor VCSELs
Optics Letters
|August 2, 2025
Summary
Researchers achieved harmonic mode-locking in semiconductor vertical-cavity surface-emitting lasers (VCSELs) by controlling polarization feedback. This method precisely tunes pulse rates and multiplicity for ultrafast pulse engineering.
Area of Science:
- Laser Physics
- Optoelectronics
- Nonlinear Dynamics
Background:
- Vertical-cavity surface-emitting lasers (VCSELs) are crucial optoelectronic devices.
- Mode-locking in VCSELs is essential for generating ultrafast optical pulses.
- Controlling pulse characteristics in VCSELs remains a key challenge.
Purpose of the Study:
- To demonstrate harmonic mode-locking in a semiconductor VCSEL.
- To investigate the use of polarization-controlled delayed feedback for pulse control.
- To explore the underlying polarization-mediated nonlinear dynamics.
Main Methods:
- Utilized a semiconductor VCSEL with an external cavity.
- Integrated a rotatable half-wave plate (λ/2-plate) for polarization control.
- Employed polarization-resolved measurements and cross-correlation analyses.
Main Results:
- Achieved stable fundamental and harmonic dual-pulse mode-locking in TE and TM modes.
- Demonstrated precise control over pulse multiplicity and repetition rates by adjusting the λ/2-plate angle.
- Observed coherent pulse alignment at half the cavity roundtrip time.
Conclusions:
- Polarization-controlled delayed feedback is an effective method for harmonic mode-locking in VCSELs.
- This technique enables precise engineering of ultrafast optical pulses.
- The study advances the understanding of polarization-mediated nonlinear dynamics in laser systems.
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