Demonstration of an erbium-doped microdisk laser on a silicon chip

An erbium-doped microlaser is demonstrated utilizing $\mathrm{Si}{\mathrm{O}}_2$ microdisk resonators on a silicon chip. Passive microdisk resonators exhibit whispering-gallery-type modes (WGM’s) with intrinsic optical quality factors of up to $6\times {10}^7$ and were doped with trivalent erbium ions (peak concentration $\sim 3.8\times {10}^{20}{\mathrm{cm}}^{-3}$) using MeV ion implantation. Coupling to the fundamental WGM of the microdisk resonator was achieved by using a tapered optical fiber. Upon pumping of the ${}^{4}I_{15∕2}\to {}^{4}I_{13∕2}$ erbium transition at $1450\mathrm{nm}$, a gradual transition from spontaneous to stimulated emission was observed in the $1550\text{−}\mathrm{nm}$ band. Analysis of the pump-output power relation yielded a pump threshold of $43\mu \mathrm{W}$ and allowed measuring the spontaneous emission coupling factor: $\beta \approx 1\times {10}^{-3}$.