AgGaSe2 crystals
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%
- Description
- Properties
- Standard specifications
- References
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.
| Physical and optical properties | |
|---|---|
| Chemical formula | AgGaSe2 |
| Crystal structure | Tetragonal, 42m |
| Lattice parameters | a= 5,9920 Å, c= 10,8803 Å |
| Optical symmetry | Negative uniaxial (no > ne, λ < 804 nm ne > no) |
| Density | 5,7 g/cm3 |
| Mohs hardness | 3-3,5 |
| Transparency range | 0,71 - 19 µm @“0“ transmittance level |
| Sellmeier equations @T=293 K (λ in μm) | no2=6,8507 + 0,4297/(λ2 - 0,1584) - 0,00125 λ2; ne2= 6,6792 + 0,4598/(λ2 - 0,2122) - 0,00126 λ2 |
| Refractive indices | no = 2,5917; ne = 2,5585 @10,5 µm |
| Thermal conductivity @T = 293 K | 1 (||c) Wm-1K-1, 1,1 (⊥c) Wm-1K-1 |
| Laser induced damage threshold | >10 MW/cm2@10,6 μm, 150 ns |
| AgGaSe2 crystals | |
|---|---|
| Orientation accuracy | <30 arcmin |
| Clear aperture | >80% |
| Face dimensions tolerance | +0,0/-0,2 mm |
| Parallelism error | <30 arcsec |
| Perpendicularity error | <10 arcmin |
| Protective chamfers | <0,2 mm at 45° |
| Surface quality | 60-40 S-D |
| Coatings | BBAR/BBAR@1,7-2,7 µm/5-18 µm |
| Mount | Unmounted |
