In this wavelength range, Kiani and coworkers were able to develop a compact chip-scale laser that is monolithically integrated on a low-loss Si3N4 platform. As an active material, their device exploits thulium-doped tellurium oxide (TeO2) that is used as an upper cladding of a Si3N4 microring resonator with a quality factor of 4.8×105. The high refractive index of TeO2 enables a high confinement in the active region for both pump and laser radiation. With a resonant pumping at 1610 nm, emission at any wavelength from 1815 nm to 1895 nm can be achieved by controlling the coupling between the microring laser cavity and the input waveguide. This microlaser exhibits on-chip output powers with up to 4.5 mW with a threshold as low as 11 mW and a slope efficiency as high as 17%.
Also, this time, we can conclude that the transparency wavelength range of Si3N4 and TeO2 may offer the possibility to extend even more the spectral range of chip-scale laser sources, going to longer and longer wavelengths. We just have to wait, probably not so long. So… who’s next?
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