|Welcome to the International Quantum Cascade Lasers School and Workshop 2012 held in Baden near Vienna, Austria|
Quantum Cascade lasers (QCL's) are unipolar semiconductor devices based on intersubband transitions in quantum wells. The different physical principles, which markedly differentiate them from the more traditional diode lasers, enable the realization of optical sources in previously underdeveloped regions of the optical spectrum, such as the mid- and far-infrared. The field of QCL's has been continuously expanding since their first demonstration in 1994 and the performances of these devices have reached today a level of maturity that allows the realisation of commercial optical systems. The operating wavelengths cover a very wide spectral range spanning from 3 - 300µm. Room-temperature continuous wave (CW) operation is routinely achieved and devices are commercially available, opening the door to a wealth of industrial and military applications, particularly in the arenas of chemical and remote sensing, analytical imaging and security.
Yet, there is scope for improvement and many exciting areas need more investigations to push farther QCL performance such as operating temperatures, wavelength coverage, linewidth control and output power. To this end it is essential to combine technological and fundamental aspects, to find the synergy between device fabrication and growth with the basic understanding of electronic transport and quantum design. Moreover, new QCL architectures based on electronic and photonic engineering or on multi-terminal device may offer new opportunities for applications.