Dual-wavelength distributed feedback laser array based on four-phase-shifted sampled Bragg grating for terahertz...

Area of Science:

• Photonics and Optoelectronics
• Semiconductor Lasers
• Integrated Optics

Background:

• Distributed feedback (DFB) lasers are crucial for optical communications and sensing.
• Achieving stable dual-wavelength operation and high output power in DFB lasers presents significant challenges.
• Sampled Bragg gratings offer a method to enhance grating properties but require precise fabrication.

Purpose of the Study:

• To propose and demonstrate a novel dual-wavelength DFB laser array.
• To enhance the coupling coefficient and stability of dual-mode lasing.
• To enable efficient generation of terahertz (THz) signals.

Main Methods:

• Utilizing a four-phase-shifted sampled Bragg grating to enhance coupling coefficient.
• Introducing π-phase shifts for stable dual-mode lasing.
• Fabricating the laser array with a single lithography step for ridge waveguide and gratings.
• Integrating with semiconductor optical amplifiers and photoconductive antennas.

Main Results:

• Achieved an enhanced coupling coefficient ~2.83 times greater than conventional sampled Bragg gratings.
• Demonstrated stable dual-mode lasing with frequency spacings up to 1 THz.
• Obtained a maximum output power of 23.6 mW when integrated with semiconductor optical amplifiers.
• Generated THz signals with a measured power of 12.8 µW via photomixing.

Conclusions:

• The proposed dual-wavelength DFB laser array offers a promising platform for THz signal generation.
• The use of a four-phase-shifted sampled Bragg grating significantly improves device performance.
• The simplified fabrication process and stable dual-mode operation make this design highly scalable and practical.