Monolithically integrated tunable DFB laser array for the generation of wide-range continuously tunable THz signals

Area of Science:

• Photonics
• Terahertz Technology
• Integrated Optics

Background:

• Terahertz (THz) applications require broadband tunable signal sources.
• Conventional THz sources often lack tunability, compactness, or broad frequency coverage.
• Monolithic integration of photonic devices is key for scalable THz systems.

Purpose of the Study:

• To develop a monolithically integrated photonic chip for generating continuously tunable optical beat-note signals.
• To achieve a broad THz frequency range using an electrically controlled platform.
• To enable compact and scalable broadband heterodyne sources for THz applications.

Main Methods:

• Integration of four independently current-controlled distributed feedback (DFB) lasers on a single chip.
• Utilizing thermal wavelength tuning of DFB lasers for continuous frequency spacing.
• Employing an on-chip semiconductor optical amplifier for power equalization.
• Characterization of optical beat signals in spectral and temporal domains.

Main Results:

• Achieved continuous wavelength spacing from 0.46 nm to 40 nm, corresponding to beat frequencies from 60 GHz to 4.96 THz.
• DFB lasers demonstrated stable single-mode operation with ~5 MHz linewidths and >50 dB side-mode suppression ratios.
• Consistent beat-note intensity across the tuning range due to on-chip power equalization.
• High coherence and stability of optical beat signals confirmed over the entire tuning range.

Conclusions:

• The developed photonic chip provides a fully electrically controlled, compact, and scalable solution for broadband heterodyne THz signal generation.
• The device eliminates the need for external tuning components, simplifying system integration.
• Enables advancements in THz sensing, spectroscopy, and communication systems.