ZGP Crystal

ZnGeP₂（Zinc germanium phosphide）crystal has many good properties and is an mid-IR nonlinear crystal. The nonlinear susceptibility of ZnGeP₂ (ZGP) crystal is approximately 160 times large (d36~75 pm/V) as KDP,.ZGP shows good optical transparency over the 740 – 12000 nm and relatively high laser damage threshold, and is therefore well suited for producing near infrared tunable laser. ZGP is a very hopeful material for mid-infrared devices such as SHG, SFG, OPO, and OPG/OPA.

Parameter

Chemical and Physical properties

Property	Value
Chemical Formula	ZnGeP₂
Crystal Structure	Tetragonal,`42m
Lattice Parameter	a=b=5.467Å, c=12.736Å
Mass Density	4.16 g/cm³
Moh Hardness	5.5
Melting Point	About 1040°C
Thermal Conductivity	180 W/m/K
Thermal Expansion Coefficient	β‖,5×10^-6/K; β⊥,7.8×10^-6/K
Birefringence	positive uniaxial

Linear Optical Properties

Property	Value
Transparency Range	0.74 – 12 um
Absorption Coefficient	α<0.05cm-1 @2050-2100 nm
Refractive Indices
@ 2.05 um	n_o = 3.1478, n_e = 3.1891
@ 2.79 um	n_o = 3.1333, n_e = 3.1744
@ 5.30 um	n_o = 3.1136, n_e = 3.1547
@ 10.6 um	n_o = 3.0729, n_e = 3.1143

Nonlinear Optical Properties

Property	Value
SHG Phase Matchable Range	3177 ∼ 10357nm (Type I)
NLO coefficients	d₃₆=75 ± 8 pm/V
	Type Ⅰ d_eeo=d₃₆sin2θcos2φ
	Type Ⅱ d_oeo=d_eoo=d₃₆sinθsin2φ
Damage Threshold
at 2.79 um	30 GW/cm² (150 ps)
at 10.6 um	1 GW/cm² (2 ns)

Spectrums


ZGP Transmission Spectrum	SHG curves of ZGP (TypeI (eeo))

OPO tuning curves of ZGP with pump light of 2800 nm	OPO tuning curves of ZGP with pump light of 2090 nm