Laterally coupled dual-grating distributed feedback lasers for generating mode-beat terahertz signals

Area of Science:

• Optoelectronics
• Semiconductor Lasers
• Photonics

Background:

• Distributed Feedback (DFB) lasers are crucial for optical communications.
• Generating multiple wavelengths from a single laser cavity is desirable for advanced applications.
• Stabilizing frequency beating signals is essential for reliable signal transmission.

Purpose of the Study:

• To develop a single-cavity, dual-wavelength AlGaInAs/InP DFB laser.
• To achieve simultaneous emission of two longitudinal modes at distinct wavelengths (1.56/1.57-μm).
• To stabilize the terahertz (THz) frequency beating signal between the two emitted modes.

Main Methods:

• Fabrication of a laterally coupled DFB laser with two different grating periods on each sidewall.
• Monolithic integration of an electro-absorption modulator (EAM) within the resonant cavity.
• Utilizing nonlinear four-wave mixing within the EAM to stabilize the beating signal.

Main Results:

• Simultaneous emission of two longitudinal modes at 1.56-μm and 1.57-μm was achieved.
• A frequency separation of 0.82 THz between the two modes was obtained.
• A stable 0.82 THz beating signal was observed across a broad range of drive currents and bias parameters for the DFB and EAM sections.

Conclusions:

• The developed dual-wavelength DFB laser successfully generates two distinct frequencies.
• Nonlinear four-wave mixing in the integrated EAM effectively stabilizes the THz beating signal.
• This device offers a stable and tunable THz beat source for potential optical communication applications.