Lead sulfide quantum-dot-doped glass passively modelocks Cr:forsterite laser
Semiconductor quantum dots in glass can be used as saturable absorbers for solid-state lasers, providing a less-expensive alternative to epitaxially grown semiconductors. As an intracavity saturable absorber, lead sulfide (PbS) quantum-dot-doped glass produces passive CW modelocking in a Cr:forsterite laser over a tunable range from 1207 to 1307 nm, according to a grou¥from the Optical Sciences Center of the University of Arizona (Tucson, AZ) and the Technology Grou¥of Corning Inc. (Corning, NY). The 6.6-nm-diameter PbS quantum dots were obtained by thermal treatment of an oxide glass. Polishing the PbS-doped glass plate to a thickness of about 150 µm allowed the researchers to reduce intracavity losses and obtain a reasonable output power when the plate was aligned with a 19-mm-long Cr:forsterite crystal. With a Nd:YAG laser providing 7.2 W of linearly polarized 1064-nm output, modelocking produced nearly transform-limited 4.6-ps pulses at a repetition rate of 110 MHz, with an average power u¥to 74 mW. Spectral width of the pulses was 0.4 nm. Varying the size of the quantum dots changed the absorption of the doped glass--currently the researchers are exploring the use of PbS quantum-dot-doped glasses as saturable absorbers in other near-infrared lasers.