Terahertz ambipolar dual-wavelength quantum cascade laser

Area of Science:

• Physics
• Electrical Engineering
• Materials Science

Background:

• Terahertz frequency quantum cascade lasers (THz QCLs) are compact solid-state sources of terahertz radiation.
• THz QCLs have diverse applications in gas sensing, non-destructive testing, security, and medical imaging.
• Molecular fingerprint spectra in the terahertz range are crucial for identification.

Purpose of the Study:

• To demonstrate an electrically-switchable dual-wavelength THz QCL.
• To enable spectroscopic information acquisition within THz QCL-based imaging systems.
• To utilize a single active region for dual-wavelength emission.

Main Methods:

• Fabrication of a quantum cascade laser device.
• Electrical biasing of the device in forward and reverse directions.
• Characterization of laser emission wavelengths, threshold current densities, and operating temperatures.

Main Results:

• The device emits at 2.3 THz in forward bias and 4 THz in reverse bias.
• Threshold current densities were measured as 490 A/cm² (2.3 THz) and 330 A/cm² (4 THz).
• Maximum operating temperatures were 98 K (2.3 THz) and 120 K (4 THz).

Conclusions:

• An electrically-switchable dual-wavelength THz QCL was successfully demonstrated.
• The device integrates two emission wavelengths within a single active region.
• This technology advances THz imaging systems by enabling spectroscopic analysis.