Silver gallium selenide (AgGaSe2, AGSe) is an optically negative uniaxial crystal with a reasonable transmittance over roughly 0,7 μm - 18 μm region. AGSe crystals have proven to be used in nonlinear parametric downconversion (difference frequency generation, DGF) in the Mid-IR range by tandem with commercially available synchronously-pumped optical parametric oscillators (SPOPOs) in the femtosecond and picosecond regime. AGSe crystal has one of the highest figure of merits (~70 pm2/V2) from commercially available mid-IR nonlinear crystals, which is six times larger than counterpart AGS. For some particular reasons AGSe is also a better choice over other mid-IR crystals. For example, even though GaSe has higher nonlinearity and comparable transparency region, AGSe has lower spatial walk-off and availability to be processed for particular application (growth and cut direction, dielectric thin-film coatings). ZGP has higher figure of merit, but its transparency region (~2-12 μm) is no match to AGSe.
Main features
Excellent properties across the transmission range from 0,73 to 18 µm
Low optical absorption and scattering
High FOM (figure of merit) for non-linear interactions in NIR and MIR
Application examples
Frequency mixing in the IR region from 4,0 to 18,3 µm
Second harmonic generation and up-conversion for CO2 lasers
Tunable OPO for solid-state lasers with efficiency up to 10%