Application of step-scan FTIR to the research of quantum cascade lasers

Fourier transform infrared (FTIR) spectroscopy has moreadvantages over many other techniques for high resolu-tion studies in the mid-infrared and far-infrared spectralranges. In addition to the high frequency resolution, itexhibits a high signal-to-noise ratio (SNR), high through-put, and broad band range. There are two ways forthe spectrometer to implement the scan process, i.e.,the rapid-scan (continuous-scan) mode and the step-scan mode. Although many relatively simple rapid-scanFTIRs h…     

Terahertz Quantum Cascade Laser Operating at 2.94THz

The development of quantum cascade laser at 2.94 THz is reported. The laser structure is based on a bound-to-continuum active region and a semi-insulating surface-plasmon waveguide. Lasing is observed up to a heat-sink temperature of 70 K in pulsed mode with light power of 4.75 mW at 10 K and 1 mW at 70 K. A threshold current density of 296.5 A/cm2 and an internal quantum efficiency of 1.57 × 10-2 per cascade period are also observed at 10 K. The characteristic temperature of this laser is extracted to be T0 = 57.5 K.     

High-Duty-Cycle Operation of GaAs/AlGaAs Quantum Cascade Laser above Liquid Nitrogen Temperature

We present a detailed study of λ- 9.75 μm GaAs/AlGaAs quantum cascade lasers. For a coated 2-rmm-long and 40-μm-wide laser, an optical power of 85 μ W is observed at 95% duty cycle at 80K. At a moderate driving pulse （1 kHz and 1% duty cycle）,the device presents a peak power more than 20mW even at 120K. At 80K, the fitted result of threshold current densities shows evidence of potential cw operation.     

High-Power and Low-Threshold-Current-Density GaAs/AlGaAs Quantum Cascade Lasers

We report on the realization of GaAs/AlGaAs quantum cascade lasers with an emission wavelength of 9.1 μm above the liquid nitrogen temperature. With optimal current injection window and ridge width of 24 and 60μm respectively, a peak output power more than 500mW is achieved in pulsed mode operation. A low threshold current density Jth = 2.6 kA/cm^2 gives the devices good lasing characteristics. In a drive frequency of i kHz, the laser operates up to 20% duty cycle.     

High Temperature Operation of 5.5μm Strain-Compensated Quantum Cascaded Lasers

We develop 5.5-μm InxGa1-xAs/InyAl1-yAs strain-compensated quantum cascade lasers with lnP and InGaAs cladding layers by using solid-source molecular-beam epitaxy. Pulse operation has been achieved up to 323K （50℃） for uncoated 20-μm-wide and 2-mm-long devices. These devices display an output power of 36mW with a duty cycle of 1% at room temperature. In continuous wave operation a record peak optical power of 10mW per facet has been measured at 83K.