Short pulse generation using a passively mode locked single InGaAsP/InP quantum well laser

Area of Science:

• Optoelectronics
• Semiconductor Lasers
• Quantum Well Technology

Background:

• Passively mode-locked lasers (MLL) are crucial for generating ultrashort optical pulses.
• Quantum well active layers are widely used in MLLs, but achieving narrow linewidths remains a challenge.
• Low optical confinement structures can influence laser performance and pulse characteristics.

Purpose of the Study:

• To demonstrate subpicosecond pulse generation using a novel InGaAsP/InP single quantum well active layer.
• To investigate the performance characteristics of two-section MLLs with low optical confinement.
• To achieve and report the narrowest radio-frequency linewidth for a quantum well device at 21 GHz.

Main Methods:

• Fabrication of passively mode-locked lasers (MLL) utilizing a single InGaAsP/InP quantum well active layer grown in one epitaxial step.
• Employing a two-section laser design for mode-locking operation.
• Systematic investigation and characterization of laser performance, including pulse width, repetition rate, peak power, time-bandwidth product, and radio-frequency linewidth.

Main Results:

• Achieved subpicosecond pulse generation with a pulse width of 860 fs at a repetition rate of 21.31 GHz.
• Demonstrated a peak power of approximately 500 mW and a time-bandwidth product of 0.57.
• Recorded a radio-frequency linewidth of 30 kHz at 21 GHz, the lowest reported for a quantum well device.

Conclusions:

• The developed low optical confinement single InGaAsP/InP quantum well active layer enables efficient subpicosecond pulse generation.
• The two-section MLL design demonstrates excellent performance, including high peak power and a narrow time-bandwidth product.
• The achieved 30 kHz linewidth represents a significant advancement for quantum well-based laser devices in high-frequency applications.