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Home >> NLO Crystal >> KTP 

KTP (KTiOPO4) is a nonlinear optical crystal, which possesses excellent nonlinear and electro-optic properties.It has large nonlinear optical coefficients and wide angular bandwidth and small walk-off angle,etc.which make it suitable for various nonlinear frequency conversion and wave guide application.

Due to very high effective nonlinearity (d eff ~8.3xd 36 (KDP)at 1.06 µm) and excellent optical properties,KTP perfectly suits as lasing material in various applications .The phase matching range of KTP crystal lies in 0.99-3.3 µm region .This allows us to use KTP as an intracavity and extracavity frequency double for the most commonly used lasers,such as Nd:YAG,Nd:Glass and Nd:YLF

Physical and Optical Properties
Crystal structure Orthorhombic, point group mm 2
Melting point 1172C incongruent
Cell parameters a=6.404Å, b=10.616Å, c=12.814Å, Z=8
Curie point 936C
Mohs hardness ~5
Density 3.01 g/cm 3
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, 22C, 1KHz)
Transmitting range 350nm~4500nm
Refractive indices n x n y n z
1064nm 1.7377 1.7453 1.8297
532nm 1.7780 1.7886 1.8887
Absorption coefficients a < 1%/cm @1.064 µm and 0.532 µm
Phase matchable range 0.984 - 3.4 µm
Therm-optic coefficients dn x /dT=1.1x10-5/C, dn y /dT=1.3x10-5/oC, dn z /dT=1.6x10-5/C
Nonlinear optical coefficients d 31 =2.54pm/V, d 31 =4.35pm/V, d 31 =16.9pm/V
d 24 =3.64pm/V, d 15 =1.91pm/V at 1.064 mm
d eff (II) (d 24 - d 15 )sin2 f sin2 q - (d 15 sin2f + d 24 cos2 f )sin q
Electro-optic coefficients Low frequency(pm/V) High requency(pm/V)
r 13
r 23
r 33
r 51
r 42
Dielectric constant e eff =13
Sellmeier equations n x 2 =3.0065+0.03901/( l 2 -0.04251)-0.01327 l 2
n y 2 =3.0333+0.04154/( l 2 -0.04547)-0.01408 l 2
n z 2 =3.3134+0.05694/( l 2 -0.05658)-0.01682 l 2
1)Aperture: 1x1 ~ 10x10mm
2)Length: 0.05 ~ 20mm
3)Phase Matching Angle: Determined by different homonic generartion
typical =90; =23.5 for SHG 1064nm
4)Phase matching type: Type II
5)Typical Coating: a) S1&S2: AR @1064nm R<0.1%; AR @ 532nm, R<0.25%.
b) S1: HR @1064nm, R>99.8%; HT @808nm, T>5%
S2: AR @1064nm, R<0.1%; AR @532nm, R<0.25%
Different coating specification upon customer request.
Typical Specification and Tolerance
1)Angle tolerance: < 0.5; < 0.5
2)Dimension tolerance: (W 0.1mm) x (H 0.1mm) x (L + 0.2mm/-0.1mm)
3)Flatness: /8 @ 633nm
4)Scratch/Dig code: better than 10/5 Scracth/dig per MIL-O-13830A
5)Parallelism: < 20 arc seconds
6)Perpendicularity: < 5 arc minutes
7)Wavefront distortion: < /8 @ 633nm
8)Clear aperture: > 90% central area


To inquiry or order a finished KTP crystals, please specify the specification listed above, we kindly request engineering drawing to specify orientation, Please consult us for the designs if you're sure about the phase matching angle for others' special application.

Fig. 1 represents Type 2 SHG tuning curve of KTP in x-y plane. In x-y plane the slope d(Dk)/dq is small. This corresponds to quasi-angular noncritical phase matching, which ensures the double advantage of a large acceptance angle and a small walk off

Fig.1        Fig.2

Fig. 2 represents Type 2 SHG tuning curve of KTP in x-z plane. in x-z plane the slope d(Dk)/dq is almost zero for wavelengths in the range 1.5-2.5 m m and this corresponds to quasi-wavelength noncritical phase matching, which ensures a large spectral acceptance. Wavelength noncritical phase matching is highly desirable for frequency conversion of short pulses.

Figures 3 and 4 show the phase matching angles for OPO/OPA pumped at 532 nm in x-y and x-z plane respectively. As a lasing material for OPG, OPA or OPO, KTP can most usefully be pumped by Nd lasers and their second harmonic or any other source with intermediate wavelength, such as a dye laser (near 600 nm).

Fig.3        Fig.4