Planarized THz quantum cascade lasers for broadband coherent photonics

Area of Science:

• Integrated photonics
• Terahertz (THz) technology
• Quantum cascade lasers

Background:

• Growing interest in integrated THz photonics for communications, spectroscopy, and sensing.
• Need for advanced platforms enabling broadband THz signal generation and control.

Purpose of the Study:

• To present a new integrated photonic platform for THz applications.
• To demonstrate the co-integration of active and passive THz photonic components.
• To achieve broadband THz signal generation and mode-locking.

Main Methods:

• Development of a double-metal, high-confinement waveguide platform planarized with low-loss polymer.
• Utilizing a homogeneous quantum-cascade active core for THz emission.
• Employing extended top metallization for improved waveguide properties.
• External radio frequency (RF) drive for active mode-locking.

Main Results:

• Observation of free-running quantum cascade laser combs spanning 800 GHz.
• Generation of harmonic states with over 1.1 THz bandwidth.
• Achieved RF-injected broadband incoherent states spanning nearly 1.6 THz.
• Demonstrated actively mode-locked pulses as short as 4.4 ps.
• Fabrication of low insertion loss passive waveguides for cavity tuning.

Conclusions:

• The presented integrated THz photonic platform successfully integrates active and passive elements.
• The platform enables broadband THz signal generation, including mode-locked pulses.
• This technology holds promise for advancing THz communications, spectroscopy, and sensing.