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KTP Nonlinear Crystal

Potassium Titanium Oxide Phosphate (KTiOPO4 ), or KTP crystal is mostly used as nonlinear crystals for frequency doubling of solid-state Nd: YAG crystal or Nd: YVO4 crystal laser, as it has large nonlinear optical coefficients, wide angular bandwidth, and small walk-off angle, broad temperature and spectral bandwidth. KTP crystal also has high electro-optic(E-O) coefficient and low dielectric constant, and a large figure of merit, these features make it also widely used in the electro-optic application.

Honour Optics also offer GTR-KTP crystal, GTR-KTP crystal is GRAY TRACKING RESISTED KTP crystal, which has similar nonlinear, physical and chemical properties with normal KTP crystal, but has better gray tracking resisting property. When working under the laser of 532nm, GTR-KTP would not form a gray tracking over the light path, then it can keep the SHG laser energy the same as the beginning. GTR-KTP crystal has wide angular bandwidth and small walk-off angle and broad temperature and spectral bandwidth. Honour Optics is the professional high quality Chinese KTP nonlinear crystal manufacturer, purchasing large size KTP nonlinear crystal at factory price.

Typical Features of KTP crystal:

Efficient frequency conversion(1064nm SHG conversion efficiency is about 80%)
Large nonlinear optical coefficients(15 times that of KDP)
Wide angular bandwidth and small walk-off angle
Broad temperature and spectral bandwidth
High thermal conductivity (2 times that of BNN crystal )
Moisture free
Minimum mismatch gradient
Super-polished optical surface
No decomposition below 900°C
Mechanically stable
Low cost compare with BBO and LBO


Gray-tracking at high power limited its application to moderate power density
Additional applications for large size GTR-KTP nonlinear crystal include mixed frequency, electro-optical modulation, optical parametric generation, and the optical waveguide.

Typical Features for GTR-KTP crystal:
High gray track resistance
High damage threshold: ≥2 GW/cm2(@1064nm,TEM00,10ns,10Hz)
High conversion efficiency: up to 80% depending upon cube length and laser system
High homogeneity: Δn<10-5
Low absorption:   <1000ppm/cm (@532mm)
<150ppm/cm (@1064mm)
Low electrical conductivity: about 10-10Ω•cm
100W QCW output available
Single domain structure

High damage threshold KTP nonlinear crystal is widely used in frequency doubling of Nd-doped laser systems for Green/Red output; parametric sources(OPG, OPA, and OPO) for 600nm-4500nm tunable output; E-O modulators, Optical Switches, Directional Couplers; Optical Waveguides for Integrated NLO and E-O Devices etc.

SHG of Nd: lasers
Custom high purity KTP nonlinear crystal is the most commonly used material for frequency doubling of Nd: YAG lasers and other Nd-doped lasers, particularly at the low or medium power density. The following table lists the major NLO properties of KTP for frequency-doubling of an Nd: YAG laser.

 Phase matching angle  θ=90o, φ=23.5o
 Effective SHG Coefficient  deff = 8.3xd36(KDP)
 Angular Acceptance  20 brand-cm
 Temperature Acceptance  25 oC-cm
 Spectral Acceptance  5.6 Å-cm.
 Walk-off angle  4.5 med (0.26o)

Extra- and intra-cavity frequency doubled Nd: lasers using high quality Chinese KTP nonlinear crystal have become a preferred green laser source for many R&D, medical, industrial, and commercial applications. By using extra-cavity KTP SHG, a conversion efficiency of over 80%  and 700 mg green power were obtained with a 900 mg injection-seeded Q-switched Nd: YAG laser.

As an efficient OPO crystal pumped by the fundamental and second harmonics of an Nd: YAG or Nd: YLF laser, custom high purity KTP nonlinear crystal plays an important role in parametric sources for tunable output from visible (0.6 um) to mid-IR (4.5 um). The non-critical phase-matched (NCPM) OPO/OPA with an X-cut KTP pumped by 1064nm is particularly useful as the signal output @1.57 um is eye safe.  NCPM KTP OPO/OPA pumped by the tunable lasers such as Ti: Sapphire, Alexandrite, and Cr: LiSrAlF6 have also been reported with high efficiency of 45%.

Chemical and Structural Properties

Crystal structure Orthorhombic, point group mm 2
Melting point 1172°C incongruent
Cell parameters a=6.404?, b=10.616?, c=12.814?, Z=8
Curie point 936°C
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, 22°C, 1KHz)

E-O Devices:

In addition to unique NLO features, large size GTR-KTP nonlinear crystal also has promising E-O and dielectric properties that are comparable to LiNbO3. These advantaged properties make KTP extremely useful to various E-O devices. KTP is expected to replace LiNbO3 crystal in the considerable volume application of E-O modulators, when other merits of KTP are combined into account, such as high damage threshold, wide optical bandwidth (>15GHZ), thermal and mechanical stability, and low loss, etc.

Optical Waveguides:

Based on the ion-exchange process on KTP substrate, low loss optical waveguides developed for KTP have created novel applications in integrated optics. Recently, a type II SHG conversion efficiency of 20%/W/cm2 was achieved by the balanced phase matching, in which the phase mismatch from one section was balanced against a phase mismatch in the opposite sign from the second. Furthermore, segmented KTP waveguides have been applied to the type I quasi-phase-matchable SHG of a tunable Ti: Sapphire laser in the range of 760-960mm, and directly doubled diode lasers for the 400-430nm outputs.

Physical and optical properties:

Transmitting Range 350nm~4500nm

Refractive Indices


nx ny nz
1064nm 1.7377 1.7453 1.8297
532nm 1.7780 1.7886 1.8887
Absorption Coefficients α < 1% / cm @ 1.064 μm
Phase Matchable Range 0.984-3.4μm


Therm-Optic Coefficients dnx / dT= 1.1x10  /°C,dny / dT= 1.3x10  /°C,dnz / dT=1.6x10  /°C
Nonlinear Optical Coefficients


d31=2.54pm/V,  d32=1.35pm/V,  d33=16.9pm/V

d24=3.64pm/V,  d15=1.91pm/V,  at 1.064μm

deff(II)  (d24-d15)sin2Φsin2θ-(d10sin  Φ+d24cos  Φ)sinθ










Low frequency


High frequency


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 εeff=13

Sellmeier Equations


nx = 3.0065 + 0.03901/(λ - 0.04251) - 0.01327λ

ny = 3.0333 + 0.04154/(λ - 0.04547) - 0.01408λ

nz = 3.3134 + 0.05694/(λ - 0.05658) - 0.01682λ

Honour Optics provides the following KTP coatings:

Dual Band AR-coating (DBAR) of KTP for SHG of 1064nm.
Broad Band AR-coating (BBAR) of KTP for OPO applications.
High reflectivity coating: HR1064nm&HT532nm, R>99.8%@1064nm, T>90%@532nm.
Other coatings are available upon request.

Honour Optics standard specifications for KTP crystal
Dimension tolerance:(W±0.05)x(H±0.05)x(L+ /-0.1mm)
Clear aperture: central 90% of the diameter
No visible scattering paths or centers when inspected by a 50mW green laser
Flatness: less than λ/8 @ 633nm
Transmitting wavefront distortion: less than λ/8 @ 633nm Chamfer: ≤[email protected]°
Scratch/Dig code: better than 10/ 5(MIL-PRF-13830B)
Parallelism: better than 20 arc seconds
Perpendicularity: ≤5 arc minutes
Angle tolerance: △θ≤0.25°, △ф≤0.25°
Damage threshold (GW/cm2):
>0.5 for 1064nm, TEM00, 10ns, 10HZ (AR-coated)
>0.3 for 532nm, TEM00, 10ns, 10HZ (AR-coated)

Capabilities of KTP Crystal:
Aperture: 2x2 ~ 20x20mm
Lenght: 0.1 - 40mm, maximum up to60mm
Cutting Angle q and f: Determined by different kinds of harmonic generation
Phase matching type: Type I or Type II
End Configuration: Plano/Plano or Brewster/Brewster or Specified

We can customize crystal angle and size except for standard specification according to your request. It is available to re-polishing and coating for KTP crystals that you supply to us. Honour Optics is the professional high damage threshold KTP nonlinear crystal manufacturer, purchasing large size KTP nonlinear crystal at factory price.

Standard applications of KTP crystal:

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 0.6mm-4.5mm Tunable Output
Electrical Optical(E-O) Modulators, Optical Switches, and Directional Couplers
Optical Waveguides for Integrated NLO and E-O Devices

Honour Optics Warrant:

Strict quality control;
High inside quality without any defection.
Large crystal size up to 20x20x40mm3 and maximum length of 60mm;
Quick delivery (2 weeks for polished only, 3 weeks for coated);
Unbeatable price and quantity discount;
Technical support;
AR-coating, mounting and re-polishing service.
Quality Warranty Period: one year under proper use.

Honour Optics offers high-quality KTP and GTR-KTP crystal, size upon your request, and provide AR-coating, mounting and re-polishing service.

Honour Optics offers standard KTP crystal within 4-5 weeks

Size (mm) theta phi Coating
S1 S2
3x3x5 90° 23.5° [email protected] R<0.2%
[email protected] R<0.5%
[email protected] R<0.2%
[email protected] R<0.5%
3x3x5 90° 23.5° [email protected] R>99.8%
[email protected] 532nm R<0.5%
[email protected] R<0.2%
[email protected] R<0.5%
3x3x10 90° 23.5° [email protected] R>99.8%
[email protected] 532nm R<0.5%
[email protected] R<0.2%
[email protected] R<0.5%