Recent advances in QCL for optoelectronics

The quantum cascade laser based on intersubband transitions in quantum wells is now maturing as a technological device for both physics and applications. It allows design of lasers of widely different wavelengths from the same heterostructure material. Recently, a strong improvement of the laser operating performances has enabled the room temperature operation of continuous wave, single mode, lasers around a wavelength of 5.4 m. These distributed feedback lasers operate with 3-5 mW of output power and a currents well below 1 A. An other fascinating new development has been the realization of terahertz QC lasers. Devices based based on GaAs have reached now operating temperatures higher than 100 K. However, devices based on InGaAs/AlInAs lattice-matched on InP should have the advantage of a stronger optical matrix element and a lower optical phonon scattering rate and therefore should enable operation at higher temperatures.