Potassium Titanyl Phosphate (KTiOPO4,KTP)
Potassium Titanyl Phosphate (KTiOPO3 or KTP) is widely used in both commercial and military lasers including laboratory and medical systems, range-finders, lidar, optical communication and industrial systems.
LaserMa¡¯s KTP is featured by
• Large nonlinear optical coefficient
• Wide angular bandwidth and small walk-off angle
• Broad temperature and spectral bandwidth
• High electro-optic coefficient and low dielectric constant
• Large figure of merit
• Nonhydroscopic, chemically and mechanically stable
LaserMa offers
¡¤ Strict quality control ¡¤ 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
Table 1. Chemical and Structural properties
Crystal Structure |
Orthorhombic, space group Pna21,point group mm2 |
Lattice Parameter |
a=6.404?, b=10.616?, c=12.814?, Z=8 |
Melting Point |
About 1172¡ãC |
Mohs Hardness |
5 |
Density |
3.01 g/cm3 |
Thermal Conductivity |
13W/m/K |
Thermal Expansion Coefficient |
¦Áx=11x10-6/¡ãC, ¦Áy=9x10-6/¡ãC, ¦Áz=0.6x10-6/¡ãC |
Table 2. Optical and Nonlinear Optical Properties
Transparency Range |
350¡«4500nm |
SHG Phase Matchable Range |
497¡«1800nm (Type II) |
Therm-optic Coefficients(/¡ãC) |
dnx/dT=1.1X10-5 dny/dT=1.3X10-5 dnz/dT=1.6X10-5 |
Absorption Coefficients |
<0.1%/cm at 1064nm, <1%/cm at 532nm |
For Type II SHG of a Nd:YAG laser at 1064nm
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Temperature Acceptance: 24¡ãC-cm Spectral Acceptance: 0.56nm-cm Angular Acceptance: 14.2mrad-cm (¦Õ);55.3mrad-cm (¦È) Walk-off Angle: 0.55¡ã |
NLO Coefficients |
deff(II)¡Ö(d24-d15)sin2¦Õsin2¦È-(d15sin2¦Õ + d24cos2¦Õ)sin¦È |
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 |
Sellmeier Equations (¦Ë in ¦Ìm) |
nx2=3.0065+0.03901/(¦Ë2-0.04251)-0.01327¦Ë 2 ny2=3.0333+0.04154/(¦Ë 2-0.04547)-0.01408¦Ë2 nz2=3.0065+0.05694/(¦Ë 2-0.05658)-0.01682¦Ë2 |
Applications for SHG and SFG of Nd: lasers
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. They are also useful green sources for many research and industry applications. |
* More than 80% conversion efficiency and 700mJ green laser were obtained with a 900mJ injection-seeded Q-switch Nd:YAG lasers by using extra-cavity KTP. * 8W green laser was generated from a 15W LD pumped Nd:YVO4 with intra-cavity KTP. * 200mW green outputs are generated from 1 W LD pumped Nd:YVO4 lasers by using LASERMA ¡¯s 2x2x5mm KTP and 3x3x1mm Nd:YVO4. * 2-5mw green outputs are generated from 180mw LD pumped Nd:YVO4 and KTP glued crystals.For more details, please refer to Glued Crystals.
KTP is also being used for intracavity mixing of 0.81¦Ìm diode and 1.064¦Ìm Nd:YAG laser to generate blue light and intracavity SHG of Nd:YAG or Nd:YAP lasers at 1.3¦Ìm to produce red light. |
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Fig.1 Type II KTP SHG in XY Plane |
Fig 2 Type II KTP SHG in XZ Plane |
Applications for OPG, OPA and OPO
As an efficient OPO crystal pumped by a Nd:laser and its second harmonics, KTP plays an important role for parametric sources for tunable outputs from visible (600nm) to mid-IR (4500nm), as shown in Fig. 3 and Fig. 4.
Generally, KTP¡¯s OPOs provide stable and continuous pulse outputs (signal and idler) in fs, with 108 Hz repetition rate and a mW average power level. A KTP¡¯s OPO that are pumped by a 1064nm Nd:YAG laser has generated as high as above 66% efficiency for degenerately converting to 2120nm. |
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Fig.3 OPO pumped at 532 in X-Z plane |
Fig.4 OPO pumped at 532 in X-Y plane |
The novel developed application is the non-critical phase-matched(NCPM) KTP OPO/OPA pumped by the X-cut KTP crystal. As shown in Fig.5, for pumping wavelength range from 0.7¦Ìm to 1 ¦Ìm, the output can cover from 1.04¦Ìm to 1.45¦Ìm(signal) and from 2.15¦Ìm to 3.2¦Ìm(idler). More than 45% conversion efficiency was obtained with narrow output bandwidth and good beam quality. |
Applications for E-O Devices
In addition to unique NLO features, KTP also has promising E-O and dielectric properties that are comparable to LiNbO3These advantaged properties make KTP extremely useful to various E-O devices. Table 1 is a comparison of KTP with other E-O modulator materials commonly used: |
Table 1. Electro-Optic Modulator Materials
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Phase |
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Amplitude |
|
Material |
¦Å |
N |
R(pm/V) |
k(10-6/¡ãC) |
N7r2/¦Å(pm/V)2 |
r(pm/V) |
k(10-6/¡ãC) |
n7r2/¦Å(pm/V)2 |
KTP
LiNbO3
KD*P
LiIO3 |
15.42
27.9
48.0
5.9 |
1.80
2.20
1.47
1.74 |
35.0
8.8
24.0
6.4 |
31
82
9
24 |
6130
7410
178
335 |
27.0
20.1
24.0
1.2 |
11.7
42
8
15 |
3650
3500
178
124 |
From Table 1, clearly, 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. |
Applications for 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. Table 2 gives a comparison of KTP with other optical waveguide materials. 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. |
Table 2. Electro-Optic Waveguide Materials
Materials |
r (pm/V) |
n |
eeff (e11e33)1/2 |
n3r/eeff (pm/V) |
KTP
LiNbO3
KNbO3
BNN
BN
GaAs
BaTiO3 |
35
29
25
56
56-1340
1.2
28 |
1.86
2.20
2.17
2.22
2.22
3.6
2.36 |
13
37
30
86
119-3400
14
373 |
17.3
8.3
9.2
7.1
5.1-0.14
4.0
1.0 |
AR-coatings LASERMA provides the following AR-coatings: ¡¤Dual Band AR-coating (DBAR) of KTP for SHG of 1064nm. ¡¤low reflectance (R<0.2% at 1064nm and R<0.5% at 532nm ); ¡¤high damage threshold (>300MW/cm2 at both wavelengths); ¡¤long durability. ¡¤ 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.
LaserMa Warranty on KTP Specifications: ¡¤ Dimension tolerance: (W¡À0.1mm)x(H¡À0.1mm)x(L+0.5/-0.1mm) (L¡Ý2.5mm) (W¡À0.1mm)x(H¡À0.1mm)x(L+0.1/-0.1mm) (L<2.5mm) ¡¤ Clear aperture: central 90% of the diameter ¡¤ No visible scattering paths or centers when inspected by a 50mW green laser ¡¤ Flatness: less than ¦Ë/8 @ 633nm ¡¤ Transmitting wavefront distortion: less than ¦Ë/8 @ 633nm ¡¤ Chamfer: ¡Ü0.2mm@45¡ã ¡¤ Chip: ¡Ü0.1mm ¡¤ Scratch/Dig code: better than 10/ 5 to MIL-PRF-13830B ¡¤ Parallelism: better than 20 arc seconds ¡¤ Perpendicularity: ¡Ü5 arc minutes ¡¤ Angle tolerance: ¦¤¦È¡Ü0.25¡ã, ¦¤¦Õ¡Ü0.25¡ã ¡¤ Damage threshold[GW/cm ]: >0.5 for 1064nm, TEM00, 10ns, 10HZ (AR-coated) >0.3 for 532nm, TEM00, 10ns, 10HZ (AR-coated) ¡¤ Quality Warranty Period: one half year under proper use.
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