Source: Quantum Optoelectronics Group – ETH Zürich

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Quantum Cascade Lasers

Introduction

A quantum cascade laser is a unique type of semiconductor laser that emits mid-infrared light. Unlike traditional lasers, it operates on intersubband transitions within a semiconductor structure, allowing for a wide range of operating wavelengths.

Operation

A quantum cascade laser consists of multiple quantum wells arranged in a cascade structure. When an electron is injected into the gain region, it undergoes intersubband transitions within each quantum well, leading to the emission of multiple photons per electron. This design results in higher optical gain but requires a higher operating voltage compared to conventional laser diodes.

Design Flexibility

One of the key advantages of quantum cascade lasers is their design flexibility. By adjusting the layer thickness values of quantum wells, these lasers can be tailored to emit light at wavelengths ranging from a few microns to well above 10 μm, including the terahertz region.

Properties

Quantum cascade lasers typically emit mid-infrared light, making them ideal for applications such as laser absorption spectroscopy of trace gases. They offer moderate to high output power levels, with some devices achieving power conversion efficiencies of around 50%. Additionally, these lasers exhibit narrow linewidths and high modulation bandwidths, making them suitable for various applications.

Applications

Quantum cascade lasers have diverse applications, including trace gas analysis, terahertz imaging, free-space communications, and infrared countermeasures. Their ability to operate at room temperature and generate high-power terahertz radiation has opened up new possibilities in fields such as spectroscopy, imaging, and defense.

Conclusion

Quantum cascade lasers represent a significant advancement in laser technology, offering unique capabilities for a wide range of applications. With ongoing research and development, these lasers are poised to play a crucial role in various industries, from environmental monitoring to telecommunications.

Source: Phys.org
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