Room temperature continuous wave quantum dot cascade laser emitting at 7.2 μm.

Area of Science:

• Semiconductor Lasers
• Quantum Dot Technology
• Mid-Infrared Photonics

Background:

• Quantum cascade lasers (QCLs) are crucial for mid-infrared applications.
• Improving QCL performance, especially at room temperature, remains a key challenge.
• Quantum dots offer unique electronic and optical properties for advanced laser designs.

Purpose of the Study:

• To demonstrate a novel quantum cascade laser (QCL) utilizing Indium Arsenide (InAs) quantum dots.
• To achieve efficient continuous wave (CW) room temperature lasing at a 7.2 μm wavelength.
• To investigate the underlying physics responsible for performance enhancements.

Main Methods:

• Fabrication of a QCL with active regions comprising InAs quantum dots on Gallium Arsenide (GaAs) buffer layers.
• Integration of these quantum dots within Indium Gallium Arsenide (InGaAs) wells and Indium Aluminum Arsenide (InAlAs) barriers.
• Characterization of laser performance under continuous wave (CW) and pulsed operational modes at various temperatures.

Main Results:

• Demonstrated CW room temperature lasing at 7.2 μm.
• Achieved a low threshold current density of 1.89 kA/cm².
• Observed lasing up to 110 °C in pulsed mode.
• Formulated a theory attributing performance gains to weak localization of states.

Conclusions:

• The InAs quantum dot-based QCL design significantly enhances mid-infrared laser performance.
• Weak localization of states is identified as a key factor for improved efficiency and operating temperature.
• This work paves the way for next-generation mid-infrared semiconductor lasers.