InGaAsP-InP nanoscale waveguide-coupled microring lasers with submilliampere threshold current using Cl2--N2-based high-density plasma etching

We demonstrate InGaAsP-InP nanoscale waveguide-coupled microring lasers fabricated with inductively coupled plasma (ICP) using Cl₂--N₂-based gas mixtures. To fabricate optical waveguides, the requirement of anisotropic profiles and sidewall smoothness is stringent. In particular, for strongly lateral confined nanoscale waveguides used for microring resonators, the degree of anisotropy and sidewall smoothness is critical in determining the device performance. For optoelectronic devices such as microcylinder and microring lasers, the requirement of low active-layer damage further adds to the stringency. We show that the excellent etching property of high-density plasma using Cl₂--N₂-based gas mixtures satisfies the requirements. The good etching results are demonstrated by using the etching method to realize room-temperature operations of the InGaAsP-InP waveguide-coupled microring lasers. For the waveguide-coupled microring lasers with a diameter of 10 μm, we obtained submilliampere threshold current.