Background: One of the main challenges in photonics is to achieve a laser technology that is fully compatible with the silicon part of industrial manufacturing processes. Basically, silicon and germanium, which are the main group IV elements, are penalized for light emission due to the indirect nature of their electronic band structure. Alloying germanium with tin (GeSn) has been shown to achieve direct band structure alignment and first experimental demonstrations of lasing with these materials were carried out in 2015. It is also possible to combine the tensile stress with the alloy to allow even more degrees of freedom for more efficient emitters, with continuous-wave (cw) lasing achieved [1]. These alloys are being exploited to obtain an increasingly robust lasing effect for integration into an application environment for the detection of chemical elements in the infrared. At C2N, in collaboration with the CEA, we have, for example, demonstrated for the first time a lasing effect at room temperature under optical pumping [2].
Challenges of the postdoc: One of the challenges is to realize more compact laser devices operating under electrical injection. This requires specific design developments of the devices as well as knowledge of the transport properties and fine modelling of the optical gain. It will be necessary to describe the phenomena of charge scattering, by alloy potentials for example, and intersubband valence absorption. The use of quantum heterostructures is also envisaged to improve the gain properties and the efficiency of the lasers. In order to design the optimal structure it is necessary to model their electronic band structure and optical gain. This requires a good knowledge of parameters such as band discontinuities at the interfaces between GeSn and different barrier materials (such as SiGeSn), and such as strain potentials.
During the project, the candidate will be involved in the design, fabrication in the C2N clean room and electro-optical analysis of GeSnOI (GeSn-on-Insulator) based photonic layers recently developed in the group [3] in order to experimentally extract material parameters. He (she) will interact with the researchers of the team who calculate the electronic structure of materials using DFT (Density-Functional Theory) methods combined with multibands k.p. modelling. It will be appreciated if he/she is also involved in the electromagnetic modelling of resonant cavities for lasers and in their experimental analysis.
Key words: laser sources, GeSnOI, silicon photonic
References:
[1] Elbaz, A., Buca, D., von den Driesch, N. et al. Ultra-low-threshold continuous-wave and pulsed lasing in tensile-strained GeSn alloys. Nat. Photonics 14, 375–382 (2020). https://doi.org/10.1038/s41566-020-0601-5
[2] A. Bjelajac, M. Gromovyi, E. Sakat, B. Wang, G. Patriarche, N. Pauc, V. Calvo, P. Boucaud, F. Boeuf, A. Chelnokov, V. Reboud, M. Frauenrath, J.-M. Hartmann, and M. El Kurdi, Up to 300 K lasing with GeSn-On-Insulator microdisk resonators, Opt. Express 30, 3954-3961 (2022)
[3] B. Wang, E. Sakat, E. Herth, M. Gromovyi, A. Bjelajac, J. Chaste, G. Patriarche, P. Boucaud, F. Boeuf, N. N. Pauc, V. Calvo, J. Chrétien, M. Frauenrath, A. Chelnokov, V. Reboud, J.-M. Hartmann, M. El Kurdi, GeSnOI mid-infrared laser technology. Light Sci Appl. 10, 232 (2021). https://doi.org/10.1038/s41377-021-00675-7
Contact: moustafa.el-kurdi@c2n.upsaclay.fr
