Low Threshold Quantum Cascade Lasers: From Laboratory to Industrialization
演讲课题：Low Threshold Quantum Cascade Lasers: From Laboratory to Industrialization
Quantum cascade lasers (QCLs) are semiconductor laser sources based on electron transitions between intersubbands of multiple well systems. Their unique operating principle and good performance have established themselves as the leading coherent semiconductor source in the infrared spectrum regimes, which is expected to find a variety of applications such as gas sensing, free-space communication and high-resolution spectroscopy. These applications require QCL with single-mode, low threshold and room-temperature continuous-wave (CW) operation. Here, we report some results on design, grown, fabrication and application of mid-infrared QCLs in the Institute of Semiconductors, Chinese Academy of Sciences. Room-temperature CW operation of QCLs emitting at 4.2-11 μm is presented. Two-phonon resonance, excited-state injection and bound-to-continuum in active region design combined with strain-compensation for material growth using molecular beam epitaxy (MBE) promise low threshold current density. Threshold current densities as low as 0.56, 0.5, 1.1 and 0.95 kA/cm2 for distributed feedback (DFB) QCLs emitting at 4.6, 4.9, 5.2 and 7.2 μm respectively in CW operation at 293 K were achieved for this state-of-the-art QCL [1-6]. The threshold power consumptions of DFB-QCLs can be reduced to 0.72 and 0.4 W at emitting wavelengths of λ ~ 4.9 and 5.2 μm respectively [5, 7]. The first quantum dot cascade laser operated at room temperature in CW mode with wavelength of 7.15 μm was achieved for improving the wall plug efficiency of QCL from the basic principle . These fabricated devices have been widely used in automobile exhaust remote measurement, carbon dioxide isotope detection and other aspects.