AgGaS2

AGS is transparent from 0.53 to 12 µm. Although its nonlinear optical coefficient is the lowest among the mentioned infrared crystals, high short wavelength transparency edging at 550 nm is made use of in OPOs pumped by Nd:YAG laser; in numerous difference frequency mixing experiments with diode, Ti:Sapphire, Nd:YAG and IR dye lasers covering 3–12 µm range; in direct infrared countermeasure systems, and for SHG of CO2 laser. Thin AgGaS2 (AGS) crystal plates are popular for ultrashort pulse generation in mid IR range by difference frequency generation employing NIR wavelength pulses.

Applications

  • Generation second harmonics on CO and CO2 - lasers
  • Optical parametric oscilator
  • Different frequency generator to middle infrared regions up to 12 mkm.
  • Frequency mixing in the middle IR region from 4.0 to 18.3 µm
  • Tuneable solid state lasers (OPO pumped by Nd:YAG and others lasers operating in 1200 to 10000 nm region with efficiency 0.1 to 10 %)
  • Optical narrow-band filters in the region near isotropic point (0.4974 m at 300 °K), transmission band being tuned at temperature variation 
  • Up-conversion of CO2 laser radiation image into near-IR or visible region by using/ or use of Nd:YAG, ruby or dye lasers with efficiency up to 30 %

Basic Properties:

Crystal Structure
Tetragonal
Cell Parameters 
a=5.992 Å, c=10.886 Å
Melting Point
851 °C
Density 
5.700 g/cm3
Mohs Hardness
3-3.5
Absorption Coefficient
<0.05 cm-1 @ 1.064 µm
<0.02 cm-1 @ 10.6 µm
Relative Dielectric Constant @ 25 MHz
ε11s=10.5
ε11t=12.0
Thermal Expansion Coefficient 
||C: -8.1 x 10-6 /°C
⊥C: +19.8 x 10-6 /°C
Thermal Conductivity 
1.0 W/M/°C
Transparency Range
0.50-13.2 um
Thermo-Optic Coefficients
dno/dt=15.4 x 10-5/°C
dne/dt=15.5 x 10-5/°C
Phase-Matching SHG Range
1.8-11.2 um
NLO Coefficients @ 1.064 um
d36=d24=d15=23.6 pm/V
Linear Electro-optic Coefficients
Y41T=4.0 pm/V
Y63T=3.0 pm/V
Damage threshold
@ ~ 15 ns, 1.064 um
30 MW/cm2(surface)

Technical Parameters:

  • Wavefront distortion:less than λ/6 @ 633 nm
  • Dimension tolerance:(W +/-0.1 mm) x (H +/-0.1 mm) x (L +0.2 mm/-0.1 mm)

  • Clear aperture:> 90% central area 

  • Flatness:λ/6 @ 633 nm for T>=1.0mm

  • Surface Quality:Scratch/dig 20/10 per MIL-O-13830A

  • Parallelism:better than 1 arc min

  • Perpendicularity:5 arc minutes

  • Angle tolerance:Δθ < +/-0.25oΔφ < +/-0.25o