Potassium Titanyl Phosphate (KTiOPO4 or KTP) is a positive biaxial crystal, with the principal axes X, Y, and Z (nz>ny>nx) parallel to the crystallographic axes a, b, and c, respectively. It is a nonlinear crystal mostly used in extracavity configuration when a single pass through the crystal is required. KTP has large nonlinear coefficient and its effective nonlinear optical coefficient deff at 1064nm is more than 1.5 times that of BBO. Also, its damage threshold is near 1 GW/cm2 for 1 Hz 10 ns pulses at 1064nm.
Transmission characteristics of KTP.
KTP crystals from Photonchina are optimized for SHG intracavity configuration in low peak power CW lasers and are ideal choice in the visible to infrared spectral region with relatively low cost. They are widely seen in both commercial and military lasers including laboratory and medical system, range-finders, LiDAR, optical communication and industrial systems.
Properties of KTP/KTA Single Crystal
KTP and KTA(KTiOAsO4), also known as Potassium Titanyl Arsenate, are 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.
Optical Properties of KTP:
| Transmitting Range: | 350nm ~ 4500nm | |||
| Phase Matching Range: | 984nm ~ 3400nm | |||
| Refractive Indices: | @1064nm | 1.7377(nx) | 1.7453(ny) | 1.8297(nz) |
| @532nm | 1.7780(nx) | 1.7886(ny) | 1.8887(nz) | |
| Sellmeier Equations: (l in µm) | Nx2 = 3.0065 + 0.03901 / ( l2 – 0.04251) – 0.01327l2 | |||
| Ny2 = 3.0333 + 0.04154 / ( l2 – 0.04547) – 0.01408l2 | ||||
| Nz2 = 3.3134 + 0.05694 / ( l2 – 0.05658) – 0.01682l2 | ||||
| Therm-Optic Coefficient:(10-5/°C) | dnx/dT=1.1 | dny/dT=1.3 | dnz/dT=1.6 | |
| Absorption Coefficient: | a<1%/cm @1064nm and 532nm | |||
| Nonlinear Optical Coefficients and Equation: | @1064nm | d31=2.54pm/V | d32=4.35pm/V | d33=16.9pm/V |
| d24=3.64pm/V | d15=1.91pm/V | |||
| deff(II)=(d24-d15)sin2f sin2q – (d15sin2f +d24cos2q )sinq | ||||
| Electro-optic coefficients: | Low Frequency(pm/V) | High Frequency(pm/V) | ||
| 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: | eeff=13 | |||
Physical Properties of KTP:
| Crystal Structure: | Orthorhombic, point group mm2 | |||
| Cell Parameters: | a=6.404Å, b=10.616Å, c=12.814Å, z=8.00Å | |||
| Melting Point: | 1172°C | |||
| Curie Point: | 936°C | |||
| Mohs Hardness: | >5 | |||
| Density: | 3.01g/cm3 | |||
| Color: | Colorless | |||
| Hygroscopic Susceptibility | no | |||
| Specific Heat: | 0.1643cal/g°C | |||
| Thermal Conductivity: | 0.13W/cm·K | |||
| Electrical Conductivity: | 3.5×10-8 s/cm (c-axis, 22°C, 1KHz) | |||
| r13 | 11.5 | N/A | ||
| r23 | 15.4 | N/A | ||
| r33 | 37.5 | N/A | ||
| Dielectric constant: | eeff=42 | |||
| Specific Heat: | 0.687cal/g°C | |||
| Electrical Conductivity: | 0.7~3.4×10-6 s/cm (c-axis, 22°C, 2KHz) | |||
KTP features:
- Large nonlinear optical coefficients
- Wide angular bandwidth and small walk-off angle
- Broad temperature and spectral bandwidth
- Nonhydroscopic, chemically and mechanically stable
- High thermal conductivity
- Flux grown, extremely low cost compared to KTA, BBO and LBO
- High damage threshold, low absorption
- Production capacity to support industrial customers
- High performance optical coating, mounting service
Applications of Photonchina’s KTP:
In short, KTP mainly has the following usage,
- 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
In a more specific way, KTP has applications as follows,
1. Frequency Conversion:
KTP was first introduced as the NLO crystal for Nd doped laser systems with high conversion efficiency. Under certain conditions, the conversion efficiency was reported to 80%, which leaves other NLO crystals far behind.
With the development of laser diodes, KTP is widely used as SHG devices in diode pumped Nd:YVO4 solid laser systems to output green laser, and also to make the laser system very compact.
2.KTP for OPA, OPO Applications:
In addition to its wide use as a frequency doubling device in Nd-doped laser systems for Green/Red output, KTP is also one of the most important crystals in parametric sources for tunable output from visible (600nm) to mid-IR (4500nm) due to the popularity of its pumped sources, the fundamental and second harmonic of a Nd:YAG or Nd:YLF lasers.
One of the most useful applications is the non-critical phase-matched (NCPM) KTP OPO/OPA pumped by the tunable lasers to obtain a high conversion efficiency.
KTP OPO results in stable continuous outputs of femto-second pulse of 108 Hz repetition rate and milli-watt average power levels in both signal and idler outputs.
Pumped by Nd-doped lasers, KTP OPO has obtained above 66% conversion efficiency for down-conversion from 1060nm to 2120nm.
3.Electro-Optical modulators:
Except for unique NLO features, KTP 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.
The following table is a comparison of KTP with other E-O modulator materials commonly used:
Electro-Optic Modulator Materials
| Material | Phase | Amplitude | ||||||
| ε | N | R(pm/V) | k(10-6/°C) | N7r2/ε(pm/V)2 | r(pm/V) | k(10-6/°C) | n7r2/ε(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 |
4.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. 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.
Electro-Optic Waveguide Materials
| Material | r (pm/V) | N | εeff(ε11ε33)1/2 | n3r/εeff (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 |
Specifications of Photonchina KTP products：
• Standard size: 6x6x5mm；9x9x5mm；5x5x20mm,with the maximum length of 60mm.
• Clear aperture: ≥90%
• No visible scattering paths or centers when inspected by a 50mW green laser
• Flatness: less than λ/8 @ 633nm
• Transmitting wavefront distortion: < λ/8 @ 633nm
• Chamfer: ≤0.2mm@45°
• Chip:≤0.1mm
• Scratch/Dig code: 10-5，MIL-PRF-13830B
• Parallelism: >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)
- AR coating: R< 0.2% at 1064nm and R<1.0% at 532nm;
- HR@1570(R>99.8%)&HT@1064(T>99.5%)
- HR@1064(R>99.8%)&PR@1570(R=50,60,70%+/-2%)
Ordering Information in Photonchina:
| P/N | Type | Size(mm) | Optical Coating |
| WP-KTP663 | SHG | 6x6x3 | AR1064&532 |
| WP-KTP665 | SHG | 6x6x5 | AR1064&532 |
| WP-KTP775 | SHG | 7x7x5 | AR1064&532 |
| WP-KTP885 | SHG | 8x8x5 | AR1064&532 |
| WP-KTP995 | SHG | 9x9x5 | AR1064&532 |
| WP-KTP15156 | SHG | 15x15x6 | AR1064&532 |
| WP-KTP4420 | OPO | 4x4x20 | AR1570&1064 |
| WP-KTP6620 | OPO | 6x6x20 | AR1570&1064 |
| WP-KTP7720 | OPO | 7x7x20 | AR1570&1064 |
| WP-KTP4416 | OPO | 4x4x16 | HR1570,HT1064|HR1064,PR1570 |
| WP-KTP5520 | OPO | 5x5x20 | HR1570,HT1064|HR1064,PR1570 |
Note: other sizes and coating requirement are available upon request.
