High power, low linewidth enhancement factor gain chip based on the second conduction subband transition

Area of Science:

• Semiconductor physics
• Optoelectronics
• Materials science

Background:

• Quantum well (QW) lasers are crucial for optoelectronic devices.
• High-power operation and narrow linewidth are key performance metrics.
• Linewidth enhancement factor (α-factor) impacts laser stability and spectral purity.

Purpose of the Study:

• To demonstrate a high-power InGaAs/GaAs quantum well gain chip with a suppressed α-factor.
• To investigate the use of the second conduction subband (E2) transition for improved laser performance.
• To achieve high-power, single-mode operation with enhanced stability.

Main Methods:

• Utilized an asymmetric epitaxial waveguide and a J-shaped ridge structure for single-mode operation.
• Leveraged the second conduction subband (E2) transition in InGaAs/GaAs quantum wells.
• Analyzed the device performance under high current injection, comparing E1 and E2 transitions.

Main Results:

• Achieved a fundamental transverse-mode output of 180.01 mW at 990 nm (E2 transition).
• Demonstrated a sixfold reduction in α-factor compared to the first conduction subband (E1) transition.
• Observed higher gain for the E2 transition and lower sensitivity to carrier fluctuations.

Conclusions:

• E2-transition engineering is an effective strategy for high-performance narrow-linewidth light sources.
• The developed gain chip shows significant potential for high-power scaling.
• The low α-factor and high gain of the E2 transition are beneficial for advanced optoelectronic applications.