The Quantum Cascade Laser: Will it Be the Mid and Far Infrared
Laser of the Future?
by Yisa Rumala
Contents
- Introduction
- The meaning of the word Laser
- Applications of the Mid and Far Infrared portion of the Spectrum
- Importance of Gas Sensing
- Advantages of Quantum Cascade (QC) Lasers
- A single laser can be tuned from one wavelength to the other externally.
- Quantum Cascade Lasers have higher optical power than other types of mid and far infrared lasers.
- Quantum Cascade Lasers can operate in continuous wave mode at room temperature.
- Quantum Cascade Lasers are small compared to other types of mid and far infrared lasers.
- Quantum Cascade Lasers produce Laser light in the terahertz portion of the spectrum.
- Conclusion
- References
Abstract
Quantum Cascade lasers are small semiconductor lasers that emit light in the mid and far infrared portion of the spectrum. They have many advantages over other types of semiconductor lasers such as Lead Salt Diode lasers or Diode lasers. Some of the advantages include precise tuning from one wavelength to another, higher optical power, continuous wave operation and the ability to produce light in the terahertz range of the spectrum. This paper explores the advantages of Quantum Cascade lasers over other types of lasers that produce light in the mid infrared portion of the spectrum. During the exploration of these advantages, some applications of infrared light and Quantum Cascade lasers will be discussed.
Introduction
In 1917, Albert Einstein, a brilliant physicist, announced the possibility of producing light with certain key characteristics. It was not until the 1960s that the realization of this phenomenon was seen with the invention of the first laser. Since then, there have been continued breakthroughs in the development of new lasers that can perform tasks beyond previously established records. The Quantum Cascade laser, which was invented in 1994 and is currently being developed, is another example of a technological breakthrough that illustrates the ever-growing scientific innovations of man.
Quantum Cascade (QC) lasers are novel semiconductor devices that have a wide range of applications. Some of their applications include remote and point sensing of chemical vapors [1, 2] (such as Carbonyl sulfide, Carbon monoxide, Nitrogen monoxide etc), free space optical communication [3, 4], infrared counter measures, metal detection and astronomical applications. These applications are as a result of its ability to be tuned from one wavelength (a single color of light) to another, and the fact that it emits light in the mid and far infrared portion of the spectrum (these wave lengths are between 3.5 -24 micrometers and between 57 - 150 micrometers, respectively). This part of the spectrum is not visible to the human eyes. Figure 1 shows the location of the infrared portion of the spectrum compared to the visible portion of the spectrum. In addition, QC lasers are small compared to other lasers that produce light in that region of the spectrum. Nevertheless, there are other contending lasers such as lead salt diode lasers that emit light in that portion of the spectrum and also have a wide range of applications. In this paper, Quantum Cascade lasers (QC) will be compared to Lead Salt Diode (LSD) lasers or Diode lasers. In making this comparison, a brief overview of the properties of laser light will be given. Second, the importance of the mid and far infrared region of the spectrum will be discussed. And third, the characteristics of QC lasers which make them unique as opposed to LSD lasers will be explained.
Figure 1: This picture shows the infrared portion of the spectrum with respect to the visible portion of the spectrum. The far infrared or terahertz wavelengths are close to the microwave wavelengths (Picture from Teacher Background Information website) [6].