PHOTO : Devices - VCSEL lasers
Integrated VCSEL / modulator
The goal of this research topic is to develop low cost and energy-efficient laser sources for short optical links at very high data rates. To do so, it is essential to outperform the actual current-modulated VCSEL performances. The main objective is to realize a new device design enabling to reach optical transmission data rates up to 100 Gb/s per channel, and fullfilling the real-world operating and environmental conditions such as in data centers. Our approach is based on the monolithic integration of an electro-absorption modulator within the vertical structure of the VCSEL. The performances at ultra-high frequencies will be improved by decoupling the electrical and optical properties of the modulator and the laser. This type of vertically-integrated multifunctional device leans on the mature VCSEL technology, with the objective to widely extend the performances and application domains for the next generations of optical links.
Schematics of an integrated VCSEL/modulator
MOST Team, TONA-VUB Bruxelles, TU Berlin
PhD co-supervised by VUB Bruxelles /UPS Toulouse (2014-2018), ANR project EAM-VCSEL (2020-2023)
Related publications :
Marigo-Lombart, L., et al. "High frequency operation of an integrated electro-absorption modulator onto a vertical-cavity surface-emitting laser." Journal of Physics: Photonics 1, 02LT01, 2019. Marigo-Lombart, L., et al. "Vertical electro-absorption modulator design and its integration in a VCSEL." Journal of Physics D: Applied Physics 51, 145101, 2018. Marigo-Lombart, L., et al. "Single lithography-step self-aligned fabrication process for Vertical-Cavity Surface-Emitting Lasers." Materials Science in Semiconductor Processing 61, 35-38, 2017. Marigo-Lombart, L., et al. "Oxide-confined VCSELs fabricated with a simple self-aligned process flow." Semiconductor Science and Technology 32, 125004, 2017. Chusseau, L., Almuneau, G., Coldren, L. A., Huntington, A., and Gasquet, D. "Coupled-cavity vertical-emitting semiconductor laser for continuous-wave terahertz emission." IEEE Proceedings-Optoelectronics 149(3), 88-92, 2002.
Until now, the lateral confinement by Al-III-V based oxide has led to the best performances with near-infrared VCSELs, enabling their wide industrialization for multiple applications. Similarly, our objective is to apply this efficient lateral oxide confinement scheme to mid-infrared VCSELs (MIR-VCSEL). The MIR-VCSELs are indeed compact laser sources with ideal properties for the gas detection applications in this spectral region. We proposed an original solution based on the lateral oxidation of a GaAs/AlGaAs/GaAs stack which is combined to epitaxial layers grown on GaSb substrate, by means of metamorphic molecular beam epitaxial (MBE) growth. This project is based on a close collaboration with the IES/University of Montpellier lab.
We have succesfully oxidized AlGaAs metamorphic layers grown onto GaSb in very similar conditions as for lattice-matched films on GaAs. Then, it is possible to realize a lateral confinement by selective oxidation onto GaSb-based epitaxial structures ; which is a very attractive approach for the mid-infrared laser domain. This lateral confinement technique, very simple to implement compared to its counterpart epitaxial regrowth techniques, is straightforwardly applicable to MIR-VCSEL devices. We have successfully used this type of oxide confinement in RCLED and VCSEL emitting in the 2-3 µm range, as well as for the fabrication of GaAs/AlOx sub-diffractive mirrors (HCG).
SEM images of a RC-LED with HCG mirrors based on GaSb technology
IES/University of Montpellier, FOTON INSA Rennes, Supélec Metz
ANR Marsupilami (2009-2013), ANR MIMIC-SEL (2017-2019)
Related publications :
Laaroussi, Y., et al. "Oxide confinement and high contrast grating mirrors for Mid-infrared VCSELs." Optical Materials Express 3, 1576-1585, 2013. Laaroussi, Y., et al. "Method for improving the electrical insulating properties of wet thermal oxide of AlAsSb on GaSb substrates." Applied Physics Letters 103, 101911, 2013. Laaroussi, Y., et al. "Oxide-confined mid-infrared VCSELs." Electronics Letters 48(25), 1616-1618, 2012. Almuneau, G., et al. "High reflectivity monolithic sub-wavelength diffraction grating with GaAs/AlOx stack." Journal of Optics 13, 015505, 2010.