Terahertz quantum cascade laser

Lytid’s core technology is the terahertz quantum cascade laser or THz QCL. QCLs are electrically pumped unipolar semiconductor lasers. Their operation mechanism differs fundamentally from standard semiconductor diodes as they exploit intersubband transitions in cascaded quantum well structures to generate terahertz radiation between 2 to 5 THz or 150 to 60 μm in wavelength.

Unlike standard diode lasers where the emission frequency is determined by the energy bandgap difference between the materials used, QCL emission frequency is determined by the engineered band structure — the size and width of the quantum wells — and is independent of the materials used. The cascaded structure, hence the name quantum cascade laser, allows for quantum efficiencies greater than unity. Each electron that goes through the structure will emit N THz photon, where N is the number of periods in the laser. Typically, the value of N is around 100.

Quantum cascade laser operation principle

Standard semiconductor laser diode using interband transitions to generate radiation between 300 and 1000 nm (left). This range is limited by the energy bandgap difference of the materials used. Schematic (right) of a single QCL period exploiting an intersubband transition between two adjacent coupled quantum wells to generate directly THz radiation between 60 and 150 μm (2 to 5 THz).

  • Direct generation of terahertz photons
  • High output power
  • Stability and reliability of semiconductor lasers
  • Cryogenic operating temperature

Turning state-of-the-art quantum devices into user-friendly tools

Several challenges had to be tackled before turning this quantum technology into a tool suitable for science and industry. Among them was developing compact laser drivers designed for the specific needs of THz QCLs and integrating a high performance, highly reliable cryogen-free cooling system.

Cryogen-free cooling

To achieve cryogen-free cooling in our TeraCascade 1000 series, we use highly reliable Stirling engines developped for space programs. These cooler are rated for more than 200.000 hours of MTBF, the equivalent of 23 years of 24/24H operation. The typical operating temperature of our quantum cascade laser chips is about 50K. The compactness of these engines allow the TeraCascade 1000 series system to be the size of about two shoe boxes.

Custom QCL drivers

We have developed a custom quantum cascade laser driver that fits into the palm of your hand. It’s compact size allow us to integrated it directly into the box of our TeraCascade 1000 series. This driver meets the specific requirements of THz QCL chips for both continuous wave (CW) operation as well as quasi continuous wave (QCW or pulsed) operation.

Read more about terahertz quantum cascade lasers :

Terahertz quantum-cascade lasers (Nature Photonics 2007)


Phase-locking of a 2.7-THz quantum cascade laser to a mode-locked erbium-doped fibre laser (Nature Photonics 2010)


Coherent sampling of active mode-locked terahertz quantum cascade lasers and frequency synthesis (Nature Photonics 2011)


Wave engineering with THz quantum cascade lasers (Nature Photonics 2013)