High order sideband generation in terahertz quantum cascade lasers
High order sideband generation in terahertz quantum cascade lasers
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DOI：
10.1063/1.4808385
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发表时间：
2013-06-03
影响因子：
4
通讯作者：
Dhillon, S. S.
中科院分区：
文献类型：
--
作者：
Cavalie, P.;Freeman, J.;Dhillon, S. S.
我们演示了在太赫兹量子级联激光器（QCL）中，在近红外（NIR）光载波上产生高阶太赫兹（THz）频率边带（高达3阶）。NIR载波与构成QCL的量子威尔斯的带间跃迁共振，允许非线性增强并导致频率混合。利用双金属腔的声子减布居QCL来提高腔内功率密度和显示高阶边带。一阶边带强度与单个太赫兹光子对应的太赫兹功率呈线性关系，而二阶边带强度与两个太赫兹光子相互作用呈二次关系，因此具有三阶极化率。将这些测量结果与光致发光和QCL能带结构进行比较，以确定所涉及的状态，最低导带状态对边带强度的贡献最大。我们还表明，二阶边带的相互作用对应于类似于7 × 10（-16）（m/V）（2）的增强的直接三阶极化率chi（（3）），比体值大两个数量级。(C)2013 AIP Publishing LLC.
We demonstrate the generation of high order terahertz (THz) frequency sidebands (up to 3rd order) on a near infrared (NIR) optical carrier within a THz quantum cascade laser (QCL). The NIR carrier is resonant with the interband transition of the quantum wells composing the QCL, allowing the nonlinearity to be enhanced and leading to frequency mixing. A phonon depopulation based QCL with a double metal cavity was used to enhance the intracavity power density and to demonstrate the higher order sidebands. The 1st order sideband intensity shows a linear dependence with THz power corresponding to a single THz photon, while the second order sideband has a quadratic dependence implying a two THz photon interaction and hence a third order susceptibility. These measurements are compared to the photoluminescence and the QCL bandstructure to identify the states involved, with the lowest conduction band states contributing the most to the sideband intensity. We also show that the interaction for the second order sideband corresponds to an enhanced direct third order susceptibility chi((3)) of similar to 7 x 10(-16) (m/V)(2), two orders of magnitude greater than the bulk value. (C) 2013 AIP Publishing LLC.