Silicon photonics continues to progress tremendously, both in near-infrared datacom/telecoms and in mid-IR optical sensing, despite the fact a monolithically integrated group IV semiconductor laser is still missing. GeSn alloys are one of the most promising candidate materials to realize such devices, as robust lasing under optical pumping was demonstrated by several groups up to mild cryogenic temperatures. Ideally, the integrated lasers should be tunable by design over a wide spectral range, offering a versatility that is required for optical sensing devices. We present here an innovative approach, taking advantage of local strain management in the semiconductor laser’s active zone. Arrays of differently strained Fabry-Pérot GeSn microlasers were fabricated side-by-side on the very same chip after blanket epitaxy on a Ge-buffered silicon-on-insulator substrate. Thanks to the local strain design, laser emission over a very large wavelength range under optical pumping, with laser lines peaking from 3.1 up to 4.6 μm at 25 K and with thresholds lower than 10 kW·cm–2. Laser operation persists up to 273 K, that is, very close to room temperature. This strategy, implemented on group IV semiconductors, opens up a new route to control the emission properties of microlasers integrated on a chip over significant photon energy windows representing a significant step forward in the integration and miniaturization of light sources emitting at a process-defined wavelength.
GeSn alloys are nowadays considered as the most promising materials to build Group IV laser sources on silicon (Si) in a full complementary metal oxide semiconductorcompatible approach. Recent GeSn laser developments rely on increasing the band structure directness, by increasing the Sn content in thick GeSn layers grown on germanium (Ge) virtual substrates (VS) on Si. These lasers nonetheless suffer from a lack 1 of defect management and from high threshold densities. In this work we examine the lasing characteristics of GeSn alloys with Sn contents ranging from 7 % to 10.5 %. The GeSn layers were patterned into suspended microdisk cavities with different diameters in the 4-8 µm range. We evidence direct band gap in GeSn with 7 % of Sn and lasing at 2-2.3 µm wavelength under optical injection with reproducible lasing thresholds around 10 kW cm −2 , lower by one order of magnitude as compared to the literature. These results were obtained after the removal of the dense array of misfit dislocations in the active region of the GeSn microdisk cavities. The results offer new perspectives for future designs of GeSn-based laser sources.
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