Co2+:MgAl2O4 saturable absorber transparent ceramics fabricated by high-pressure spark plasma sintering

Single-stage processing of high-quality transparent functional polycrystalline ceramics is desirable but challenging. In the present work, spark plasma sintering (SPS) was employed for fabrication of Co2+ :MgAl2O4 saturable absorbers for laser passive Q-switching. Densification of commercial MgAl2O4 powders, doped via coprecipitation, was carried out by conventional SPS and high-pressure SPS (HPSPS) under pressures of 60 and 400 MPa, respectively. The presence of LiF, a common sintering additive, was detrimental to optical properties as it promoted reaction of cobalt with sulfur impurities and the formation of Co9S8 inclusions. Densification by HPSPS without LiF allowed to obtain highly transparent Co2+:MgAl2O4 . The optical properties of samples, with doping concentrations varying between 0.01 and 0.1 at.% Co2+, were assessed and saturable absorption was demonstrated at similar to 1.5 mu m wavelength, exhibiting ground-state (sigma(gs)) and excited (sigma(es)) cross-sections of 3.5 x 10(-19) and 0.8x10(-19) cm(2), respectively. Thus, it was established that HPSPS is an effective method to fabricate transparent Co2+:MgAl2O4 ceramics.

Automated summary

This study utilized spark plasma sintering (SPS) to fabricate transparent Co2+:MgAl2O4 saturable absorbers for laser passive Q-switching. Doping and densification of MgAl2O4 powders were achieved using coprecipitation and high-pressure SPS (HPSPS) methods. The presence of LiF as a sintering additive negatively affected the optical properties, while HPSPS without LiF resulted in highly transparent Co2+:MgAl2O4 ceramics. The fabricated samples demonstrated saturable absorption at a wavelength of approximately 1.5 μm, with ground-state and excited cross-sections of 3.5 x 10(-19) and 0.8x10(-19) cm(2) respectively.