ZnGeP2 Nonlinear Crystals

ZnGeP2 Nonlinear Crystals
Product Details


Description

Zinc germanium phosphide (ZnGeP2) is an excellent mid-IR nonlinear crystal with many outstanding fundamental properties. ZnGeP2 (ZGP) crystal has large nonlinear susceptibility (d36~75 pm/V), which is approximately 160 times that of KDP. ZGP exhibits good optical transparency over the 0.74–12 um wavelength region and relatively high laser damage threshold, and is therefore well suited for producing tunable laser output in the near infrared. ZGP is a very promising material for applications such as SHG, SFG, OPO, and OPG/OPA in the mid-infrared region.

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             Note: The Transmission spectra of 15 mm long AR coated ZnGeP2 crystal  

Features

  • Wide transmission region from 0.74 um to 12um

  • Large nonlinear coefficient

  • Good mechanical and physical properties

  • Relatively high damage threshold 

  • Phase matchable over a broad spectral region

  • High thermal conductivity

Applications

  • Second, third, and fourth harmonic generation of CO2 laser

  • Optical parametric generation (OPO) with pumping at a wavelengths of 2.05-2.94 μm and possibility to generate effectively 3-10 μm ranges

  • Second harmonic generation of CO-laser

  • Producing coherent radiation in sub-millimeter-range from 70.0 μm to 1000 μm - terahertz range

  • Generation of combined frequencies of CO2- and CO-lasers radiation and other lasers are working in the crystal transparency region

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‖,5x10-6/K; β⊥,7.8x10-6/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 

@ 2.79 um 

@ 5.30 um 

@ 10.6 um 

 

no = 3.1478, ne = 3.1891

no = 3.1333, ne = 3.1744

no = 3.1136, ne = 3.1547

no = 3.0729, ne = 3.1143

Sellmeier Equations(λ in μm)

no2(λ) = 4.64467+5.10087/(λ2-0.13656)+4.27777λ2/(λ2-1653.89)

ne2(λ) = 4.71539+5.26358/(λ2-0.14386)+2.37310λ2/(λ2-1000.82)

Nonlinear Optical Properties

Property

Value

SHG Phase Matchable Range

3177 ∼ 10357nm (Type I)

NLO coefficients

d36=75 ± 8 pm/V

Type Ⅰ deeo=d36 sin2ϴcos2φ

Type Ⅱ doeo=deoo=d36 sinϴsin2φ

Damage Threshold

at 2.79 um

at 10.6 um    

 

30 GW/cm2 (150 ps)

1 GW/cm2 (2 ns)

Figure 2. OPO tuning curves of ZGP with pump light of 2090 nm

Figure 3. OPO tuning curves of ZGP with pump light of 2800 nm

Figure 4. SHG curves of ZGP (TypeI (eeo))

Polishing Specification

Property

Value

Orientation Tolerence

< 0.5°

Thickness/Diameter Tolerance

±0.05 mm

Surface Flatness

<λ/8@632 nm

Wavefront Distortion

<λ/4@632 nm

Surface Quality

10/5

Parallel

30〞

Perpendicular

15ˊ

Clear Aperture

>90%

Chamfer

<0.2×45°

Standard products

Crystal

dimension/mm

Application

Orientation

Theta/Phi deg

Coatings

7x5x15  

OPO @ 2.1-> 3.5-5 µm

54/0

AR@2.1µm+BBAR@3.5-5µm

7x5x20

OPO @ 2.1-> 3.5-5 µm

54/0

AR@2.1µm+BBAR@3.5-5µm

7x5x25

OPO @ 2.1-> 3.5-5 µm

54/0

AR@2.1µm+BBAR@3.5-5µm

Q&A

Q: What is phase mismatching?

A: A group of techniques for achieving efficient nonlinear interactions in a medium. Many phase-sensitive nonlinear processes, in particular parametric processes such as frequency doubling, sum and difference frequency generation, parametric amplification and oscillation, and also four-wave mixing, require phase matching to be efficient. Essentially, this means ensuring that a proper phase relationship between the interacting waves (for optimum nonlinear frequency conversion) is maintained along the propagation direction. Only if that condition is fulfilled, amplitude contributions from different locations to the product wave are all in phase at the end of the nonlinear crystal.

Q: What is Second harmonic generation (SHG)?

A: SHG is a nonlinear optical process, in which photons with the same frequency interacting with a nonlinear material are effectively "combined" to generate new photons with twice the energy, and therefore twice the frequency and half the wavelength of the initial photons.


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