Population inversion and low cooperative upconversion in Er-doped silicon-rich silicon nitride waveguide

Single-mode, strip-loaded silicon-rich silicon nitride (SRSN) waveguide with 11 at.% excess Si and 1.7×10(20) cm(-3) Er was fabricated and characterized. By using a 350 nm thick SRSN:Er core layer and a 850 nm wide SiO2 strip, a high core-mode overlap of 0.85 and low transmission loss of 2.9 dB/cm is achieved. Population inversion of 0.73-0.75, close to the theoretical maximum, is estimated to have been achieved via 1480 nm resonant pumping, indicating that nearly all doped Er in SRSN are optically active. Analysis of the pump power dependence of Er3+ luminescence intensity and lifetime indicate that the Er cooperative upconversion coefficient in SRSN:Er is as low as 2.1×10(-18) cm3/sec.