Temperature-insensitive long-wavelength (λ ≈14 µm) Quantum Cascade lasers with low threshold

Area of Science:

• Semiconductor Lasers
• Quantum Cascade Lasers
• Mid-Infrared Photonics

Background:

• Quantum Cascade (QC) lasers are semiconductor devices emitting in the mid-infrared to terahertz range.
• Achieving high performance, particularly at room temperature and long wavelengths, remains a key challenge.
• Efficient population inversion and lower laser level depopulation are critical for device efficiency.

Purpose of the Study:

• To demonstrate high-performance, long-wavelength (≈14 µm) Quantum Cascade lasers.
• To implement and validate a "two-phonon-continuum" depletion scheme for enhanced laser operation.
• To characterize the performance metrics of these novel QC lasers at room temperature.

Main Methods:

• Fabrication of Quantum Cascade lasers utilizing a diagonal optical transition.
• Implementation of a "two-phonon-continuum" population depletion scheme.
• Experimental characterization of threshold current density, output power, slope efficiency, and characteristic temperature (T0).

Main Results:

• Demonstrated a 2.8 mm long QC laser with a low threshold current density of 2.0 kA/cm² at 300 K.
• Achieved a peak output power of approximately 336 mW and a slope efficiency of 375 mW/A at 300 K.
• Observed a high characteristic temperature (T0) of ~310 K over a broad temperature range (240 K to 390 K).

Conclusions:

• The "two-phonon-continuum" depletion scheme effectively enables high-performance operation of long-wavelength QC lasers.
• The demonstrated QC lasers exhibit excellent power, efficiency, and temperature stability at room temperature.
• This work paves the way for advanced mid-infrared applications requiring compact and efficient light sources.