Optical gain at 1.53 μm in Er³⁺-Yb³⁺ co-doped porous silicon waveguides

Erbium-ytterbium (Er-Yb)-co-doped porous silicon planar waveguides were prepared from P⁺-type (1 0 0) oriented silicon wafer. Erbium and ytterbium ions were electrochemically introduced into the porous structure of the waveguide core. The doping profiles of erbium and ytterbium ions were determined by EDX analysis performed on sample cross-section. The mean concentration in the guiding layer is of about 1 × 10²⁰ cm^-3. The refractive indices were measured from co-doped porous silicon and undoped waveguides after the thermal treatments. The photoluminescence (PL) peak of optically activated erbium ions at 1.53 μm was recorded. The PL enhancement is the result of the energy transfer from the excited state of Yb to the state of Er. Optical losses at 1.55 μm were measured on these waveguides and were of about 2 dB/cm. An internal gain at 1.53 μm of 5.8 dB/cm has been measured with a pump power of 65 mW at 980 nm.