Ultra-broad gain quantum cascade lasers tunable from 6.5 to 10.4 μm.

Area of Science:

• Optics and Photonics
• Semiconductor Devices
• Quantum Electronics

Background:

• Quantum cascade lasers (QCLs) are essential for mid-infrared applications.
• Achieving ultra-broad gain profiles in QCLs is crucial for tunable laser systems.

Purpose of the Study:

• To design and demonstrate a novel quantum cascade laser structure with an ultra-broad gain profile.
• To achieve wide continuous tuning and single-wavelength lasing across the mid-infrared spectrum.

Main Methods:

• Fabrication of a quantum cascade laser structure with an ultra-broad gain profile.
• Integration into a grating-tuned external cavity for continuous wave (CW) tuning.
• Development of distributed feedback (DFB) QCL arrays with varied grating periods.

Main Results:

• Demonstrated an ultra-broad gain profile covering 6.5 to 10.4 μm.
• Achieved continuous tuning from 1027 to 1492 cm⁻¹ (9.6 to 6.7 μm) in an external cavity.
• Realized single-wavelength lasing from 962 to 1542 cm⁻¹ (10.4 to 6.5 μm) in DFB QCL arrays.
• Achieved a relative frequency coverage of 46%.

Conclusions:

• The novel QCL design enables unprecedented spectral coverage and tunability in the mid-infrared.
• This broad gain QCL technology is suitable for various applications requiring wide spectral access, such as spectroscopy and sensing.
• The DFB QCL arrays provide versatile single-wavelength sources across the demonstrated spectral range.