Coupled distributed feedback laser system at 820 nm for THz beat-frequency generation

Area of Science:

• Semiconductor Physics
• Optoelectronics
• Photonics

Background:

• Distributed feedback (DFB) lasers are crucial for wavelength-specific light generation.
• Dual-mode operation in DFB lasers allows for beat frequency generation, useful in sensing and communications.
• AlGaAs/GaAs heterostructures are widely used in high-performance semiconductor devices.

Purpose of the Study:

• To present a novel coupled DFB laser system capable of simultaneous dual-mode operation.
• To demonstrate dual-mode lasing with specific wavelength spacing and beat frequency.
• To highlight the advantages of the new design, including simplified fabrication and potential tunability.

Main Methods:

• Epitaxial growth of AlGaAs/GaAs compound semiconductor.
• Design of a DFB laser system supporting two lateral modes sharing a Bragg grating.
• Characterization of electroluminescence, lasing modes, wavelength spacing, beat frequency, and output power.

Main Results:

• Achieved electroluminescence near 820 nm.
• Demonstrated simultaneous dual-mode lasing operation.
• Recorded a 4.2 nm wavelength spacing, corresponding to a 1.86 THz beat frequency.
• Obtained an output power of 14.7 mW at 195 mA injection current.

Conclusions:

• The presented coupled DFB laser system successfully achieves dual-mode operation.
• The design offers simplified fabrication compared to previous dual-mode DFB lasers.
• The system shows potential for beat frequency tunability and compatibility with LT-GaAs photodetectors.