Simple method for measuring the linewidth enhancement factor of semiconductor lasers by optical injection locking

Area of Science:

• Optics
• Semiconductor Physics
• Laser Technology

Background:

• The linewidth enhancement factor (alpha) is a critical parameter in semiconductor lasers, influencing their modulation characteristics and spectral properties.
• Accurate measurement of alpha is essential for laser design and performance optimization.
• Existing methods often require complex setups or knowledge of parameters like detuning and injection power.

Purpose of the Study:

• To present a simplified optical method for measuring the linewidth enhancement factor (alpha) in semiconductor lasers.
• To demonstrate that alpha can be determined solely from optical power changes during stable optical injection locking.
• To assess the measurement error associated with the proposed technique.

Main Methods:

• Utilizing optical injection locking of a semiconductor laser.
• Monitoring changes in optical power within the stable injection-locking regime.
• Calculating the linewidth enhancement factor (alpha) without prior knowledge of absolute detuning or injection levels.

Main Results:

• A simple and effective method for measuring the linewidth enhancement factor (alpha) was successfully developed.
• The linewidth enhancement factor (alpha) of a 0.83-microm channeled substrate planar laser was determined to be 2.65 +/- 0.2.
• The measurement error and its contributing factors were analyzed.

Conclusions:

• The proposed optical injection locking method offers a straightforward approach to quantify the linewidth enhancement factor (alpha) in semiconductor lasers.
• This technique eliminates the need for precise detuning and injection power measurements, simplifying experimental procedures.
• The evaluated alpha value provides crucial data for understanding and improving the performance of channeled substrate planar lasers.