Optical gain in a-SiNx:H〈Nd〉

Abstract We report optical gain measurements in neodymium-doped amorphous hydrogenated silicon sub-nitride (a-SiNx:H〈Nd〉) planar waveguides. Samples (1.5 μm thick) were prepared by reactive rf-sputtering from a silicon target partially covered by metallic neodymium platelets using an Ar + N2 + H2 atmosphere. The substrates are oxidized 〈1 0 0〉 silicon wafers that are cleaved to define highly parallel flat waveguide faces. At low temperatures, the photoluminescence spectrum measured at the waveguide edge shows an increased and narrowed peak at 1130 nm when compared with the spectrum taken in the direction of the guide top surface. The guided signal presents supralinear intensity dependence. An optical gain of 270 ± 10 cm−1 was determined using the variable slit method exciting with a CW multiline Ar+ laser at 8 kW/cm2. The photon energy of the Ar+ laser lines is not resonant with any of the Nd3+ transitions, indicating that the excitation is efficiently transferred from the host to the rare earth ions. This result indicates that a-SiNx:H〈Nd〉 can be used as an active optical medium.