Mode locking of a broad-area semiconductor laser with a multiple-quantum-well saturable absorber.

Area of Science:

• Optics and Photonics
• Semiconductor Lasers
• Materials Science

Background:

• Broad-area semiconductor lasers are crucial for high-power applications but suffer from poor beam quality and mode instability.
• Mode locking is essential for generating ultrashort laser pulses, but achieving it in broad-area devices is challenging.
• Saturable absorbers are commonly used for mode locking, but their integration with broad-area lasers requires effective mode control strategies.

Purpose of the Study:

• To demonstrate hybrid mode locking in a broad-area semiconductor laser.
• To present a novel method for controlling the modes of a broad-area laser.
• To achieve ultrashort pulse generation with high peak power from a semiconductor laser.

Main Methods:

• Utilized a hybrid mode-locking technique combining an external cavity with a semiconductor laser.
• Employed a multiple-quantum-well (MQW) saturable absorber integrated into the laser system.
• Developed a novel mode control method by patterning the MQW saturable absorber into a microdot mirror structure.

Main Results:

• Successfully achieved hybrid mode locking in the broad-area semiconductor laser.
• Generated ultrashort pulses with a duration as short as 15 picoseconds (ps).
• Obtained a high repetition rate of 593 MHz, an average power of 9 milliwatts (mW), and a peak power of 1 watt (W).

Conclusions:

• The microdot mirror patterning of the MQW saturable absorber provides effective mode control for broad-area lasers.
• Hybrid mode locking is a viable technique for generating high-quality, ultrashort pulses from broad-area semiconductor lasers.
• This work offers a promising approach for developing advanced semiconductor laser sources for various applications.