Quantum Cascade Lasers are mid-infrared light sources covering the mid-infrared (4 to 20 µm) and terahertz waves (1 to 6 THz).

Unlike the standard bipolar laser diodes, the wavelength emitted by QCL depends on the geometry of a heterostructure and not on band structure properties of the semiconductor material. This allows a precise tailoring of the wavelength emitted by the design of the band structure.


In interband transitions (top), the wavelength of the emitted photons depend on the properties of the material used. Quantum Cascade Lasers use intersubband transitions (bottom) which allow a tailoring of the emitted wavelength through design of the structure, while always using the same material.

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