27 April 2016 Low-threshold external-cavity quantum cascade laser around 7.2 μm
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Optical Engineering, 55(4), 046116 (2016). doi:10.1117/1.OE.55.4.046116
Room-temperature continuous wave (CW) operation of a tunable external-cavity quantum cascade laser (EC-QCL) at center wavelength around 7.2 μm is presented. The EC-QCL was implemented in a Littrow configuration. The gain chip is based on a diagonal bound-to-continuum design with a high-reflection coating on the back facet. A two-layer antireflection (AR) coating consisting of Al2O3 and ZnSe was designed and deposited on the front facet of the chip to suppress the Fabry–Pérot modes. With this AR coating, single-mode tuning range of 128  cm−1 was achieved, from 1346.7 to 1475.3  cm−1 (6.78 to 7.43 μm). High side-mode suppression ratio over 30 dB was achieved near the center gain region. A very low-threshold current density of 0.89  kA/cm2 and a high output power of 50 mW were obtained when the EC-QCL was operated in CW mode at 20°C.
© 2016 Society of Photo-Optical Instrumentation Engineers (SPIE)
Zhibin Zhao, Lijun Wang, Zhiwei Jia, Jinchuan Zhang, Fengqi Liu, Ning Zhuo, Shenqiang Zhai, Junqi Liu, Zhanguo Wang, "Low-threshold external-cavity quantum cascade laser around 7.2 μm," Optical Engineering 55(4), 046116 (27 April 2016). https://doi.org/10.1117/1.OE.55.4.046116


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