Coherent nonlinear optics with quantum cascade structures

Abstract

We discuss several coherent nonlinear optical phenomena that occur in active quantum-cascade (QC) structures that support both laser action and, at the same time, nonlinear self-conversion of laser light into coherent radiation at other frequencies. In other words, the laser field serves as an intracavity optical pump for a desired nonlinear optical process. In such systems, resonant absorption of the pump field is overcome by laser gain, and giant resonant nonlinearities of the intersubband transitions can be fully exploited. The proposed approach holds promise to extend the operating wavelength of QC lasers to the spectral regions where they become less efficient, constrained by material limitations, or operate only at cryogenic temperatures. It may also lead to the development of new broadly tunable injection-pumped sources. We review recent development in this research direction including the demonstration of the Raman injection laser.