Realization of High-Performance and Farinfrared/Teraherz Quantum Cascade Lasers through Electron-Scattering Control

电子散射的控制是实现高性能远红外/太赫兹量子级联激光器（QCL）的关键，QCL有望成为适用于环境气体监测和生命科学的光源。通过对QCL谱线增强因子α和相对强度噪声（RIN）的研究，可以获得电子散射的信息。α的测量为我们提供了导带子带的非抛物性和布洛赫增益的知识。通过测量RIN随光输出功率和温度的变化关系，可以获得无辐射弛豫时间的信息。我们还分析了实现远红外/太赫兹QCL的对角过渡微带结构。由于电子-电子散射与四次方成正比，光学跃迁与波函数重叠的平方成正比，因此可以通过使用对角跃迁来减少电子-电子散射。

Control of electron scattering is a key to achieve high-performance and farinfrared/terahertz quantum cascade lasers (QCLs) which are expected as light sources applicable to environmental gas monitoring and life science. Information on the electron scattering can be obtained by investigating the line enhancement factor α and relative intensity noise (RIN) of QCLs. Measurement of α provided us the knowledge of the non parabolicity of subbands in the conduction band and the Bloch gain. We could gain information on nonradiative relaxation time through the measurement of RIN dependence on optical output power and temperatures. We also analyzed a diagonal transition miniband structure for realizing farinfrared/terahertz QCLs. Since electron-electron scattering is proportional to the fourth power and optical transition the square of the overlap of wave functions, it is possible to reduce electron-electron scattering by using the diagonal transition.