Mid- and far-infrared diode laser sources have been used in spectroscopic applications for a number of years. Historically, however, the application of these devices has been hindered by low output power and the need for cryogenic refrigeration. The quantum cascade laser, being an unipolar device, does not suffer from the same non-radiative mechanisms that have limited most mid- and far-infrared laser sources. Despite some intrinsic inefficiency due to a shorter carrier lifetime and higher optical losses than near-infrared bipolar diodes, this technology is now capable of both room temperature and high power operation over a significant portion of the mid- and far-infrared spectral region. With potential for multiwatt arrays, many more, especially remote, applications have started to become feasible. This talk will go through some of the development cycle at the Center for Quantum Devices that has led to the demonstration of high-power, continuous-wave quantum cascade laser diodes. While the focus will be mostly on continuous operation, quasi-cw operation will also be given as an alternative for even higher average power delivery. In conclusion, the current limitations to diode performance will be discussed, as well as possible near- and long-term solutions.
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