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Products>Waveplates Crystals>Potassium Titanyl Phosphate

Si CaF2 Quartz KTP YAG Sapphire Birefringent
Ge MgF2 Calcite ZnSe YVO4 Lithium Niobate
Potassium Titanyl Phosphate (KTiOPO4 or KTP)
  • 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
  • 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.
    E-O Modulators, Optical Switches, Directional Couplers.
      Optical Waveguides for Integrated NLO and E-O Devices.
AZURE Provides:
  • Standard size of KTP crystal for DPSS application;
    Strict Quality Control;
    1 - 2 Weeks Delivery;
    Unbeatable Price and Special OEM Discount;
    Free Technical Support;
    AR-Coating, Mounting and Re-polishing Service;
    Mass Production to Support Industrial and Commercial Applications;
      New!: Precision Oven & Temperature Controller for Heating KTP.
Basic Properties
1. Structural and Physical Properties

Crystal Structure

Orthorhombic, point group mm2

Cell Parameters

a = 6.404Å, b = 10.616Å, c = 12.814Å Z = 8

Melting Point

1172 oC Incongruent

Curie point

936 oC

Mohs Hardness

» 5.0



Linear Absorption Coefficients

a <0.001 cm-1 @ l =1064 nm or 532 nm

Hygroscopic Susceptibility


Relative Dielectric Constant


Specific heat

0.1643 cal/g.oC

Electrical conductivity

3.5x10-8 s/cm (c-axis, 22oC, 1KHz)

Thermal Conductivity


2. Linear Optical Properties
Transparency Range:350-4500 nm,See Transparency Curve
Refractive Indices:

KTP Transparency Curve
Wavelength nx  ny  nz
1064 nm 1.7377 1.7453 1.8297
532 nm  1.7780 1.7886 1.8887
Therm-Optic Coefficients:

Sellmeier Equations:
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
deff(II)» (d24 - d15)sin2fsin2q - (d15sin2f + d24cos2f)sinq

Electro-Optic Coefficients:

Low Frequency (pm/V)

High Frequency(pm/V)





Applications for SHG and SFG of Nd:lasers

KTP 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 Nd:YAG laser.

PM angle

q=90o, f=23.5o,
where q & f are polar angles referring to Z and X.

Effective SHG coefficient

deff » 8.3xd36(KDP)

Angular acceptance

20 mrad-cm

Temperature acceptance


Spectral acceptance

5.6 Å-cm.

Walk-off angle

4.5mrad (0.26o)

Optical damage threshold

> 450MW/cm2, (@ 1.06mm, 10ns, 10Hz)

To date, extra- and intra-cavity frequency doubled Nd:lasers using KTP have become a preferred green laser source for many R&D, medical, industrial and commercial applications. By using extracavity KTP SHG, over 80% conversion efficiency and 700mJ green laser were obtained with a 900 mJ injection-seeded Q-switched Nd:YAG laser.

Applied to diode-pumped Nd:laser, KTP is a basic NLO crystal for the construction of compact visible solid state laser systems. Recent advances in interacavity-doubled Nd:YVO4 and Nd:YAG lasers have increased the demand for compact green lasers used in display, construction, optical disk and laser printer. Over 200 mw TEM00 green outputs are available from LD pumped Nd:YVO4 and Nd:YAG lasers and 3 W TEM00, mode-locked green laser was generated by interactivity SHG in a 5.3 W mode-locked diode-laser pumped Nd:YAG laser. Moreover, 2.5mW green light was obtained from 50mW LD pumped and interactivity doubled Nd:YVO4 mini-lasers with a 9mm long cavity.

KTP is also a powerful crystal for SHG and SFG of laser with wavelength from about 1mm to 3.4 mm. The SHG phase-matching angle and effective SHG coefficients (deff) of KTP in XY plane (0.9 mm to 1.08 mm) and XZ plane (1.1 mm to 3.3 mm) are showed as the figures. Although KTP cut in YZ plane can be phase-matched for SHG of 1 mm to 3.45 mm, it is seldom used in practices because of the low deff.


Type II SHG in XY Plane

Type II SHG in XZ Plane

Applications for OPG, OPA and OPO

◆ As an efficient OPO crystal pumped by the fundamental and second harmonics of a Nd:YAG or Nd:YLF laser, KTP plays an important role in parametric sources for tunable output from visible (0.6mm) to mid-IR (4.5mm). The phase-matching angles and effective NLO coefficient for OPO/OPA pumped at 532 nm and 1064 nm in XZ plane are showed as following figures. NCPM KTP OPO pumped by 1064nm, the signal output is around eye safe wavelength, find applications in eye-safe devices. The OPO/OPA in XY and YZ is seldom employed because of their low effective nonlinear coefficients and other limitation. For more information about the design of KTP-OPO, please contact AZURE.
KTP's OPO results in stable, continuous outputs of femtosecond pulse of 108 Hz repetition rate and miliwatt average power levels in both signal and idler outputs. KTP's OPO pumped by a 1064nm Nd:laser has generated above 66% conversion efficiency for degenerate conversion from 1064 to 2120 nm.
The recently developed new application is the non-critical phase-matched (NCPM) KTP OPO/OPA pumped by the tunable lasers such as Ti:Sapphire, Alexandrite and Cr:LiSrAlF6 (see right figure). The NCPM KTP OPO keeps the KTP crystal fixed in X-axis and tunes the pumping wavelength. If a tunable Ti:Sapphire laser is used as a pumping source (0.7 mm to 1 mm), the output can cover the wavelength range from 1.04mm to 1.45 mm (signal) and from 2.15 mm to 3.2 mm (idler). Due to the favorable NLO properties of NCPM KTP, as high as 45% conversion efficiency was obtained with narrow output bandwidth and good beam quality.



DPO Pumped at 532 nm

DPO Pumped at 1064nm

Quasi-Phase-Matched Waveguide
Recently, type II SHG conversion efficiency of 20%/W/cm2 was achieved by quasi-phase matched waveguide doubler, in which the phase mismatch from one section is balanced against a phase mismatch of the opposite sign from a second section. Furthermore, segmented KTP waveguides have been applied to type I quasi-phase-matchable SHG of 0.76-0.96mm for tunable Ti:Sapphire laser and directly doubled diode laser for 0.43-0.40m output. Conversion efficiency in excess of 100%/W/cm2 has been obtained.

Now, AZURE can provide as large as 30x30x1 mm KTP with -Z or both faces polished for waveguide applications. Other size is also available upon request.

Oven for heating KTP crystals:
Increasing the temperature of KTP crystal can enhance the damage threshold of KTP crystal. Therefore, for high power or high power density SHG of Nd lasers, heating KTP to a certain temperature (e.g., 80oC) is recommended. AZURE provides precision oven with temperature controller for heating KTP. A full assembly including KTP crystal, oven and temperature controller is also available. Please refer to page xx for more information about oven & temperature controler.

AZURE's warranty on KTP specifications:

Transmitting wavefront distortion:

less than l/4 @ 633nm

Dimension tolerance:

(W± 0.1mm)x(H ± 0.1mm)x(L+0.2mm/- 0.1)

Clear aperture:

> 90% central area


l/8 @ 633nm

Surface quality:

10/5 Scratch/Dig


better than 20 arc sec.


15 arc min.

Angle tolerance:

Deltaq < 0.5°, Deltaf < 0.5°

AR coating:

dual wave band AR coating at 1064/532 nm for both faces

residual reflectivity:

< 0.2% at 1064 nm and < 0.5% at 532 nm per surface

Quality Warranty Period:

one year under proper use

●AZURE has large quantities of standard size KTP crystals in-stock. The next-day delivery is available for the in-stock crystals. The standard size crystals include 2X2X5 mm, 3x3x5mm and 5x5x5mm etc. with dual-band AR-coating for frequency-doubling 1064 nm.

●AZURE provides free crystal samples for long term technical and business cooperation as well as the developments of KTP's new applications. Qualified end-users can also obtain free samples upon request.

●AR-coatings and High Reflection coatings (HR-coatings) at other wavelengths are available upon request.

●Technical information and specific designs for KTP crystals are provided by our sales engineers and the scientists in our R&D center.


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