Fig. 1. Conduction band energy diagram for one active region between two injector regions. The significant energy levels inside the active region are labeled 1 to 5. The thicknesses in nanometers of the InGaAs QW’s and AlInAs barriers of one period of injector and active region are from right to left: 3.7/2.1/3.0/2.1/3.5/2.1/3.4/3.6/3.1/1.2/6.4/1.3/4.7/2.6, the barriers are indicated in bold font and the underlined layers are doped to n_Si=2.5×10¹⁶ cm^-3. The yellow bars indicate the levels involved in THG; the red bars and arrow indicates the laser transition.

Fig. 2. Emission spectra of a QC laser with integrated third-order nonlinear oscillator in the active region. Part (A) shows the spectrum of the fundamental light emission at a wavelength of 11.1 µm. The spectrum was taken with a MCT detector. Part (B) shows the SHG and THG light emission from the same device. The SHG and THG are at wavelengths of 5.4 µm and 3.7 µm, respectively. The spectra were taken with an InSb detector.