supported by the National Key Basic Research Program of China(Grant Nos.2012CB921804 and 2011CBA00205);the National Natural Science Foundation of China(Grant Nos.61435007 and 11321063)
We demonstrate ultralow-threshold thulium-doped, as well as thulium-holmium-codoped, microtoroid lasers on silicon chips, operating at the wavelength of around 2 ?m. High quality factor whispering gallery mode(WGM) mi...