Comment on Highly temperature insensitive quantum cascade lasers
Comment on Highly temperature insensitive quantum cascade lasers
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高温度不敏感量子级联激光器评述
DOI：
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发表时间：
2011
期刊：
影响因子：
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通讯作者：
D. Boteza
中科院分区：
文献类型：
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作者：
D. Boteza
在Bai等人最近的一封信中，在讨论低激光能级单声子共振SPR消居方案的高度温度不敏感量子级联激光器QCL的器件设计时，作者写道：“假设玻尔兹曼分布，平均散射时间34与exp E43−LO /kT成正比，其中LO为LO声子能量”，其中T为晶格温度。鉴于该信参考文献8的错误，Bai等人给出的载流子与晶格处于热平衡时散射时间34与之成正比的指数量的表达式是不正确的。由于勘误表是在Bai等人的稿件被接受发表前三周发布的，我们意识到它可能被忽视了，因此希望提供正确的表达。采用修正后的非弹性散射率公式，表达式为exp E43 /kT。另一个问题是作者假设的有效性，即对于发射5.0 m的量子晶体，载流子与晶格温度处于平衡状态。在4.8 m发射应变补偿qcl Ref. 4上的实验测量表明，注入器基态Teg的电子温度明显高于晶格的电子温度；也就是说，注入器中的电子是热的。反过来，由于上激光能级、状态ul和注入器基态g之间的强耦合，该状态Teul的电子温度基本等于Teg；在考虑4.6-4.8 m发光qcl的Teul Teg时，我们得到的计算T0值与实验T0值之间的良好一致性证实了这一事实。那么，利用文献3中修正后的Eq. 4，从能态ul到下一个更高的有源区能态ul+1的非弹性散射率可表示为：
In a recent letter by Bai et al., when discussing the device design for a highly temperature insensitive quantum cascade laser QCL of single-phonon-resonance SPR depopulation scheme of the lower laser level, the authors write the following: “Assuming Boltzmann distribution, the averaged scattering time 34 is proportional to exp E43 − LO /kT , where LO is the LO-phonon energy,” where T is taken to be the lattice temperature. In view of the erratum to Ref. 8 of that letter, the expression provided by Bai et al. for the exponential quantity to which the scattering time 34 is proportional to if carriers are in thermal equilibrium with the lattice is incorrect. While the erratum was published three weeks before the Bai et al. manuscript was accepted for publication, we realize that it might have been overlooked, and thus would like to provide the correct expression. By using the corrected inelastic scattering-rate formula, the expression becomes, exp E43 /kT . Another issue is the validity of the authors’ assumption that for 5.0 m emitting QCLs the carriers are in equilibrium with the lattice temperature. Experimental measurements on 4.8 m emitting, strain-compensated QCLs Ref. 4 have revealed that the electronic temperature of the injector ground state Teg is significantly higher than that of the lattice; that is, the electrons in the injector are hot. In turn, due to the strong coupling between the upper laser level, state ul, and the injector ground state g, the electronic temperature of that state Teul is basically equal to Teg; a fact confirmed by the good agreement we obtained between calculated and experimental T0 values when considering that Teul Teg for 4.6–4.8 m emitting QCLs. Then, by using the corrected Eq. 4 of Ref. 3, the inelastic-scattering rate from the energy state ul to the next higher active-region energy state ul+1 can be written as follows: