KTP ( Potassium Titanyl Phosphate ,KTiOPO₄) (

KTP (KTiOPO₃ , Potassium Titanyl Phosphate) is an important non linear optical crystal which is widely used an efficient SHG device for Nd:YAG laser to obtain strong Monochromatic green light in many laser systems such as commercial, military, industrial, laboratory and medical lasers systems.

Advantages:

Large Nonlinear Optical (NLO) Coefficients

Wide Angular Bandwidth and Small Walk-off Angle  Broad Temperature and Spectral Bandwidth  High Electro-Optic (E-O) Coefficient and Low Dielectric Constant  Large Figure of Merit for an Optical Waveguide Modulator  Nonhygroscopic, Good Chemical and Mechanical Properties

Basic Properties

1. Structural and Physical Properties

Curie point	936 ^oC
Hygroscopic Susceptibility	no
Relative Dielectric Constant	_eff=13
Specific heat	0.1643 cal/g.^oC
Electrical conductivity	3.5x10^-8 s/cm (c-axis, 22^oC, 1KHz)

2. Linear Optical Properties

Transparency Range: 350 - 4500 nm, See Transparency Curve	KTP Transparency Curve
Refractive Indices: Wavelength n_x n_y n_z 1064 nm 1.7377 1.7453 1.8297 532 nm 1.7780 1.7886 1.8887
Therm-Optic Coefficients: dn_x/dT=1.1x10^-5/^oC dn_y/dT=1.3x10^-5/^oC dn_z/dT=1.6x10^-5/^oC
Sellmeier Equations: n²_x=3.0065+0.03901/(²-0.04251)-0.01327² n²_y=3.0333+0.04154/(²-0.04547)-0.01408² n²_z=3.3134+0.05694/(²-0.05658)-0.01682²

3. NonLinear Optical Properties

Phase-Matchable Output Range:		492- 1700 nm
NLO Coefficients: d₃₁=2.54pm/V, d₃₂=4.35pm/V, d₃₃=16.9pm/V d₂₄=3.64pm/V, d₁₅=1.91pm/V at 1064 nm d_eff(II)(d₂₄ - d₁₅)sin2sin2 - (d₁₅sin² + d₂₄cos²)sin
Electro ¨C optic coefficients	Low frequency (pm/V)		High frequency (pm/V)
r₁₃	9.5		8.8
r₂₃	15.7		13.8
r₃₃	36.3		35.0
r₅₁	7.3		6.9
r₄₂	9.3		8.8
Dielectric constant	Ε_eff=13

Basic Properties

Table 1. Chemical and Structural properties

Crystal Structure	Orthorhombic, space group Pna2₁,point group mm²
Lattice Parameter	a=6.404Å, b=10.616Å, c=12.814Å, Z=8
Melting Point	About 1172^oC
Mohs Hardness	5
Density	3.01 g/cm³
Thermal Conductivity	13W/m/K
Thermal Expansion Coefficient	α_x=11x10^-6/^oC, α_y=9x10^-6/^oC, α_z=0.6x10^-6/^oC

Table 2. Optical and Nonlinear Optical Properties

SHG Phase Matchable Range	497 ~ 1800nm (Type II)
Therm-optic Coefficient (/^oC, λ in μm)	dnx/dT=1.1X10^-5 dny/dT=1.3X10^-5 dnz/dT=1.6X10^-5
Linear Absorption Coefficient	<0.1%/cm at 1064nm <1%/cm at 532nm
For Type II SHG of a Nd:YAG laser at 1064nm	Temperature Acceptance: 24^oC-cm Spectral Acceptance: 0.56nm-cm Angular Acceptance: 14.2mrad-cm (φ);55.3mrad-cm (θ) Walk-off Angle: 0.55^o
NLO Coefficient	d_eff(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

4. Applications:

 Frequency Doubling (SHG) of Nd-doped Lasers for Green/Red Output.  Frequency Mixing (SFM) of Nd Laser and Diode Laser for Blue Output.  Parametric Sources (OPG, OPA and OPO) for 0.6m-4.5m Tunable Output.  E-O Modulators, Optical Switches, Directional Couplers.  Optical Waveguides for Integrated NLO and E-O Devices.

5. Typical size Of KTP crystal

* 6x6x16 mm for OPO @ 532 nm, Theta = 64 degree,Phi = 0 degree

AR 532 nm/AR 840 ¨C 880 nm

* 2X2X5 mm, SHG 1064 nm Type IIAR 1064 nm/532 nm

* 6X6X20 mm, Theta = 54 degree,Phi = 0 degree ,AR 1064 nm/205nm

* 2x2x7 mm, SHG 1064 nm, AR 1064 nm/532 nm

* 5x5x10 mm, x-cut, AR 1064 nm +AR1570 nm-1590 nm

* 5x5x2 mm. SHG 1064 nm,

Side 1:HR1064 nm, R>99.8% HT532 nm T>97%

Side 2:AR1064 nm+532 nm R<0.25%

* 3X3X10 mm, SHG 1064 nm,

Side 1:AR1064 nm, R<0.25% +HR 532 nm R>99.7%

Side 2:AR1064 nm+532 nm R<0.25%

* 10X10X7, SHG 1064 nm, type II AR 1064 nm+532 nm

* 6x8x15 mm,type II (OPO @1064 nm) Theta=55 degree,Phi=0 degree

AR 1064 nm + AR 1.91-2.4 μm