Intracavity generation of infrared and terahertz radiation in heterolasers
On the basis of the ideas proposed and developed at IAP, coherent radiation at the difference and summation frequencies in two- and multi-frequency diode lasers on the basis of specially designed GaAs/InGaAs/InGaP heterostructures have been achieved for the first time in the world. Such structures contain various quantum holes and ensure intracavity mixing of the different-frequency modes due to quadratic nonlinearity of a semiconductor at room temperature. In particular, even the simplest, so-called two-ship version of such lasers produces a difference-frequency radiation with a power of up to 1 μW for a laser mode power of ~1 W in the mid-IR wavelength range (8 μm for wavelengths of laser generation modes being 0.99 μm and 1.13 μm). This work was performed jointly with the Institute of Physics of Microstructures of RAS and R&D Physical-Technical Institute of the Nizhny Novgorod State University. Experimental and theoretical analysis of several designed and manufactured two-frequency lasers, first of all, inter-band cascade tunneling lasers and two-chip heterolasers with the combined cavities, which ensure stable two-colour generation, led to the development of the ways, which allow one to bring their difference-frequency radiation up to the milliwatt power level and shift it to the far IR range at room temperature.
IAP researchers have developed the original schemes of the two-frequency lasers with intracavity nonlinear mixing of two close-frequency modes of the optical or near IR wavelength range, which were designed to ensure an efficient diffraction output of the difference-frequency radiation through the surface or the substrate which are equipped with the dielectric and/or metal diffraction gratings. The above-described schemes of the emission of the difference-frequency radiation allow one to almost completely prevent its absorption by free carriers, narrow the radiation pattern by many times, increase significantly the overlapping integral of three nonlinearly interacting modes, solve the problem of their phase matching, and raise significantly the intensity of the produced radiation and efficiency of the whole process of the nonlinear intracavity mode mixing (A. V. Andrianov, V. V. Kocharovsky, Vl. V. Kocharovsky).