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KTP Crystal

KTP (KTiOPO4) is one of most commonly used nonlinear optical crystals due to KTP's excellent nonlinear and electro-optic properties. KTP crystal is sometimes put in a temperature stabilized mount for higher damage threshold.

KTP Crystal

KTP Crystal Features

- Large Nonlinear Optical(NLO) Coefficients
- Wide Phase-matching Acceptance Angle
- Broad Temperature and Spectral Bandwidth
- High Electro-Optic(E-O) Coefficients
- Large Figure of Merit
- Nonhygroscopic, Good Chemical and Mechanical Properties
- Relatively High Damage Threshold for E-O modulator which make it suitable for various nonlinear frequency conversion and wave guide application.

KTP Crystal Applications

KTP phase matching

1. SHG of Nd:Laser - KTP is the most commonly used material for frequency doubling of Nd:YAG and other Nd-doped lasers, particularly when the power density is at a low or medium level. To date, extra- and intra-cavity frequency doubled Nd:lasers using KTP have become a preferred pumping source for visible dye lasers and tunable Ti:Sapphire lasers as well as their amplifiers. 1mW to 3W TEMoo green laser can be generated by intracavity SHG in Nd:YVO4 and Nd:YAG laser.

KTP is also being used for intracavity mixing of 0.81µm diode and 1.064µm Nd:YAG laser to generate blue light and intracavity SHG of Nd:YAG or Nd:YAP lasers at 1.3µm to produce red light.

2. OPO/OPA - KTP is suitable for Nd:YAG and SHG or Ti:Sapphire Laser pumped OPO/OPA. Pumped by the fundamental and second harmonic of a Nd:YAG or Nd:YLF Laser, KTP's OPO/OPA can generate tunable output in 600-4500nm. NCPM KTP OPO/OPA pumped by the tunable Ti:Sapphire Laser has generated 1.04-1.45um(signal) and 2.15-3.2um(idler) with as high as 45% conversion efficiency.

KTP phase matching

3. E-O Modulator - KTP is used as E-O modulator in mode-locking diode laser pumped Nd:YAG and Nd:YLF laser as well as Ti:Sapphire and Cr:LiSrAlF6 laser . Due to its higher damage threshold, wide optical bandwidth (>15GHZ), low loss, good thermal and mechanical stability, KTP is expected to replace LiNbO3 crystal in application of E-O modulators.

4. Application for Optical Waveguides - Based on the ion-exchange process on KTP substrate, KTP optical waveguides 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.

KTP Crystal Basic Properties

Crystal Structure: Orthorhombic, point group mm2
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/cm3
Color: colorless
Hygroscopic Susceptibility: no
Specific Heat: 0.1643 cal/g.K
Thermal Conductivity: 0.13W/cm/K
Electrical Conductivity: 3.5x10E-8 s/cm (c-axis,1KHz)

KTP Crystal Optical Properties

Transparency Range: 350~4500 nm
SHG Phase Matchable Range: 497~1800 nm (Type II)
Therm-optic Coefficients:
dnx/dT=1.1x10E-5, dny/dT=1.3x10E-5, dnz/dT=1.6x10E-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)sin(2φ)sin(2θ)-(d15sin2(φ) + d24cos2(φ))sin(θ)
Non-vanished NLO susceptibilities (pm/V):
d31=6.5, d24=7.6, d32=5, d15=6.1, d33=13.7
Sellmeier Equations(λ in um):
nx2= 3.0065 + 0.03901/(λ2 - 0.04251) - 0.01327λ2
ny2= 3.0333 + 0.04154/(λ2 - 0.04547) - 0.01408λ2
nz2= 3.3134 + 0.05694/(λ2 - 0.05658) - 0.01682λ2

KTP Specifications

Dimension Tolerance: +0/-0.1mm(WxH),+0/-0.2mm thickness
Surface Quality: 10-5 Scratch-dig
Flatness: <1/10 @633nm
Chamfer: 0.1mm@45°
Clear Aperture: Central 90% of Diameter
Parallelism: <10 arc seconds
Perpendicular: <10 arc minutes
Orientation Angle: +/-0.5°
Damage Threshold: >500MW/cm2 @1064nm (AR-coated)
>300MW/cm2 for 532nm, 10ns, 10HZ (AR-coated)
Dual Band AR coating: R<0.1%@ω & R<0.5%@2ω
HR coating: R>99.9%

Oven for heating KTP crystals

Increasing the temperature of KTP crystal can enhance the damage threshold of KTP crystal. Therefore, heating KTP to a certain temperature (e.g. 80°C) is recommended for high power laser application such as SHG of Nd lasers.

KTP Crystal Order Information


1. KTP Crystal

KTP 3x3x5mm Type II SHG@1064nm→532nm AR/AR
KTP 3x3x10mm Type II SHG@1064nm→532nm AR/AR
KTP 10x10x7mm Type II SHG@1064nm→532nm AR/AR
KTP 7x7x20mm Type II NCPM OPO 1064nm→1570nm
Additional message: qty. other size, holder...


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