Ultrabroadband Heterogeneous THz Quantum Cascade Laser.

Area of Science:

• Physics
• Electrical Engineering
• Materials Science

Background:

• Broadband terahertz (THz) emission is crucial for spectroscopy and white light sources.
• Terahertz quantum cascade lasers (TQCLs) offer high output power and wavelength tunability via bandstructure engineering.
• Combining multiple active regions in a single TQCL can achieve broadband emission.

Purpose of the Study:

• To develop a single-device TQCL capable of broadband THz emission.
• To demonstrate a heterogeneous TQCL design integrating multiple active regions.
• To investigate the performance of a novel three-well active region design for high-temperature operation.

Main Methods:

• Fabrication of a heterogeneous TQCL comprising five distinct active regions.
• Utilizing a three-well, LO-phonon depopulation design for active regions.
• Characterization of laser performance in pulsed and continuous-wave (CW) operation.

Main Results:

• The heterogeneous TQCL successfully lased in both pulsed and CW modes.
• Broadband emission was achieved across a spectral range of 1.9 to 4.5 THz (1.37 octaves).
• The device demonstrated a maximum operating temperature of 143 K in pulsed mode.

Conclusions:

• Heterogeneous TQCLs are a viable technology for generating broadband THz radiation.
• The three-well active region design facilitates high-temperature operation.
• This technology advances compact, high-power THz sources for diverse applications.