KTP crystal is the most commonly used for SHG(Frequency doubling) of Nd-doped laser for green/red output. It is widely used in both commercial and military lasers including laboratory and medical systems, range-finders, lidar, optical communication and industrial systems.
Advantages:
1. Large nonlinear optical coefficient
2. High electro-optic coefficient and low dielectric constant
3. High thermal conductivity
4. Moisture free, chemically and mechanically stable
5. Large figure of merit
6. High electro-optic coefficient and low dielectric constant
Applications:
1. Second harmonic generator of radiation 1.064 μm
2. Optical parametric oscilator in near IR region up to 4 μm
3. Different frequency generator in near IR region
4. E-O Modulators, Optical Switches, Directional Couplers
Structure and physics properties of KTP crystal:
| Orthorhombic, space group Pna21,point group mm2 | |
| Cell parameters | a=6.404Å, b=10.616Å, c=12.814Å, Z=8 |
| Melting point | 1172ã¡C incongruent |
| Curie point | 936°C |
| Mohs hardness | ~5 |
| Density | 3.01 g/cm3 |
| Color | colorless |
| Hygroscopic susceptibility | no |
| Specific heat | 0.1643 cal/g°C |
| Thermal conductivity | 0.13 W/cm/°K |
| Electrical conductivity | 3.5x10-8 s/cm (c-axis, 22°C, 1KHz) |
Optics and nonlinear optics properties of KTP crystal:
| 350～4500nm | |
| SHG Phase Matchable Range | 497～1800nm (Type II) |
| Therm-optic Coefficients (/°C) | dnx/dT=1.1X10-5 dny/dT=1.3X10-5 dnz/dT=1.6X10-5 |
| Absorption Coefficients | <0.1%/cm at 1064nm <1%/cm at 532nm |
| For Type II SHG of a Nd:YAG laser at 1064nm | Temperature Acceptance: 24°C-cm Spectral Acceptance: 0.56nm-cm Angular Acceptance: 14.2mrad-cm (φ);55.3mrad-cm (θ) Walk-off Angle: 0.55° |
| NLO Coefficients | deff(II)≈(d24-d15)sin2φsin2θ-(d15sin2φ + d24cos2φ)sinθ |
| Non-vanished NLO susceptibilities | d31=6.5 pm/V d24=7.6 pm/V d32=5 pm/V d15=6.1 pm/V d33=13.7 pm/V |
| Sellmeier Equations (λ in μm) | nx2=3.0065+0.03901/(λ2-0.04251)-0.01327λ 2 ny2=3.0333+0.04154/(λ 2-0.04547)-0.01408λ2 nz2=3.3134+0.05694/(λ 2-0.05658)-0.01682λ2 |
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