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KTP - Potassium Titanyl Phosphate
Introduction
Potassium Titanyl Phosphate (KTiOPO4 or KTP) is widely used in both commercial and military lasers including laboratory and medical system, range-finders, LiDAR, optical communication and industrial systems.
CASTECH'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
CASTECH offers
- Strict quality control
- Large crystal size up to 20 × 20 × 40 mm3 and maximum length of 60 mm
- Quick delivery (15 working days for polished only, 20 working days for coated)
- Unbeatable price and quantity discount
- Technical support
- AR-coating, mounting and re-working service
Basic Properties
Table 1. Chemical and Structural Properties
| Crystal Structure | Orthorhombic, Space group Pna21, Point group mm2 |
| Lattice Parameter | a = 6.404 Å, b = 10.616 Å, c = 12.814 Å, Z = 8 |
| Melting Point | About 1172 ℃ |
| Mohs Hardness | 5 |
| Density | 3.01 g/cm3 |
| Thermal Conductivity | 13 W/m/K |
| Thermal Expansion Coefficients | αx = 11 × 10-6 /℃, αy = 9 × 10-6 /℃, αz = 0.6 × 10-6 /℃ |
Table 2. Optical and Nonlinear Optical Properties
| Transparency Range | 350-4500 nm | |
| SHG Phase Matchable Range | 497-1800 nm (Type Ⅱ) | |
| Therm-optic Coefficient ( λ in μm) | dnx/dT = 1.1×10-5 /℃ | |
| dny/dT = 1.3×10-5 /℃ | ||
| dnz/dT = 1.6×10-5 /℃ | ||
| Absorption Coefficients | < 0.1% /cm at 1064 nm, < 1% /cm at 532 nm | |
| For Type Ⅱ SHG of a Nd:YAG laser at 1064 nm | Temperature Acceptance | 24 ℃·cm |
| Spectral Acceptance | 0.56 nm·cm | |
| Angular Acceptance | 14.2 mrad·cm (Φ)；55.3mrad·cm (θ) | |
| Walk-off Angle | 0.55 ° | |
| NLO Coefficients | deff (Ⅱ) ≈ (d24 - d15) sin2Φ sin2θ - (d15 sin2Φ + d24 cos2Φ) sinθ | |
| 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 (λ in μm) | nx2 = 3.0065 + 0.03901 / (λ2 - 0.04251) - 0.01327 λ2 | |
| ny2 = 3.0333 + 0.04154 / (λ2 - 0.04547) - 0.01408 λ2 | ||
| nz2 = 3.3134 + 0.05694 / (λ2 - 0.05658) - 0.01682 λ2 | ||
|
Electro-optic Coefficients: r13 r23 r33 r51 r42 |
Low frequency (pm/V) High frequency (pm/V) 9.5 8.8 15.7 13.8 36.3 35.0 7.3 6.9 9.3 8.8 |
|
| Dielectric Constant | ɛeff = 13 | |
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. Up to now, Nd:lasers that use KTP for intra-cavity and extra-cavity frequency doubling have become a preferred pumping sources for visible dye lasers and tunable Ti:sapphire lasers as well as their amplifiers. They are also used as green sources for many research and industry applications.
Close to 80% conversion efficiency and 700 mJ green laser were obtained with a 900 mJ injection-seeded Q-switch Nd:YAG lasers by using extra-cavity KTP.
8 W green laser was generated from a 15 W LD pumped Nd:YVO4 with intra-cavity KTP.
KTP is also being used for intracavity mixing of 0.81 µm diode and 1.064 µm Nd:YAG laser to generate blue light and intracavity SHG of Nd:YAG or Nd:YAP lasers at 1.3 µm to produce red light.
Fig. 1 Type Ⅱ KTP SHG in XY Plane
Fig.2 Type Ⅱ 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 (600 nm) to mid-IR (4500 nm), 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 miniwatt average power level. A KTP's OPO that are pumped by a 1064 nm Nd:YAG laser has generated as high as above 66% efficiency for degenerately converting to 2120 nm.
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's OPO/OPA. As shown in Fig.5, for pumping wavelength range from 0.7 µm to 1 µm, the output can cover from 1.04 µm to 1.45 µm (signal) and from 2.15 µm to 3.2 µm (idler). More than 45% conversion efficiency was obtained with narrow output bandwidth and good beam quality.
Fig.5 Type Ⅱ NCPM OPO
Applications for E-O Devices
In addition to unique features, KTP also has promising E-O and dielectric properties that are comparable to LiNbO3. These excellent 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 3. Electro-Optic Modulator Materials
| Materials | ε | N | Phase | Amplitude | ||||
|
R (pm/V) |
K (10-6/℃) |
N7r2/ε (pm/V)2 |
r (pm/V) |
K (10-6/℃) |
n7r2/ε (pm/V)2 |
|||
| KTP | 15.42 | 1.8 | 35 | 31 | 6130 | 27 | 11.7 | 3650 |
| LiNbO3 | 27.9 | 2.2 | 8.8 | 82 | 7410 | 20.1 | 42 | 3500 |
| KD*P | 48 | 1.47 | 24 | 9 | 178 | 24 | 8 | 178 |
| LiIO3 | 5.9 | 1.74 | 6.4 | 24 | 335 | 1.2 | 15 | 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 (˃15 GHZ), 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 waveguide have been applied to the type Ⅰ quasi-phase-matchable SHG of a tunable Ti:Sapphire laser in the range of 760-960 mm, and directly doubled diode lasers for the 400-430 nm outputs.
Table 4. Electro-Optic Waveguide Materials
| Materials | r (pm/V) | n | εeff (ε11ε33)1/2 | n3r/εeff (pm/V) |
| KTP | 35 | 1.86 | 13 | 17.3 |
| LiNbO3 | 29 | 2.2 | 37 | 8.3 |
| KNbO3 | 25 | 2.17 | 30 | 9.2 |
| BNN | 56 | 2.22 | 86 | 7.1 |
| BN | 56-1340 | 2.22 | 119-3400 | 5.1-0.14 |
| GaAs | 1.2 | 3.6 | 14 | 4 |
| BaTiO3 | 28 | 2.36 | 373 | 1 |
KTP's Parameters
Table 5. Specifications
| Dimension Tolerance | (W ± 0.1 mm) × (H ± 0.1 mm) × (L + 0.5/-0.1 mm) (L≧2.5 mm)(W ± 0.1 mm) × (H ± 0.1 mm) × (L + 0.1/-0.1 mm) (L＜2.5 mm) |
| Clear Aperture | Central 90% of the diameter |
| Internal Quality | No visible scattering paths or centers when inspected by a 50 mW green laser |
| Surface Quality (Scratch/Dig) | 10/5 to MIL-PRF-13830B |
| Flatness | ≦ λ/8 @633 nm |
| Transmitted Wavefront Distortion | ≦ λ/8 @633 nm |
| Parallelism | 20 arc sec |
| Perpendicularity | ≦ 15 arc min |
| Angle Tolerance | ≦ 0.25 ° |
| Chamfer | ≦ 0.2 mm × 45 ° |
| Chip | ≦ 0.1 mm |
| Damage Threshold |
＞1 GW/cm2 @1064 nm, 10 ns, 10 Hz (AR-coated) ＞0.3 GW/cm2 @532 nm, 10 ns, 10 Hz (AR-coated) |
| Quality Warranty Period | One year under proper use. |
AR-coatings
CASTECH provides the following AR-coatings:
- Dual Band AR-coating (DBAR) of KTP for SHG of 1064 nm; low reflectance (R<0.2% @1064 nm and R<0.5% @532 nm)
- High reflectivity coating: HR 1064 nm & HT 532 nm, R˃99.8% @1064nm, T˃90% @532 nm
- Broad Band AR-coating (BBAR) of KTP for OPO applications
- High damage threshold (˃300 MW/cm2 at both wavelengths)
- Long durability
- Other coatings are available upon request
Products
-
KTP - Potassium Titanyl Phosphate
- KTP is the most commonly used material for SHG of Nd-doped lasers, and also for SFG to generate blue&red light. In addition to these functions, it is also applied to OPO, E-O devices and waveguides.
-
Introduction
Potassium Titanyl Phosphate (KTiOPO4 or KTP) is widely used in both commercial and military lasers including laboratory and medical system, range-finders, LiDAR, optical communication and industrial systems.
CASTECH'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
CASTECH offers
- Strict quality control
- Large crystal size up to 20 × 20 × 40 mm3 and maximum length of 60 mm
- Quick delivery (15 working days for polished only, 20 working days for coated)
- Unbeatable price and quantity discount
- Technical support
- AR-coating, mounting and re-working service
Basic Properties
Table 1. Chemical and Structural Properties
| Crystal Structure | Orthorhombic, Space group Pna21, Point group mm2 |
| Lattice Parameter | a = 6.404 Å, b = 10.616 Å, c = 12.814 Å, Z = 8 |
| Melting Point | About 1172 ℃ |
| Mohs Hardness | 5 |
| Density | 3.01 g/cm3 |
| Thermal Conductivity | 13 W/m/K |
| Thermal Expansion Coefficients | αx = 11 × 10-6 /℃, αy = 9 × 10-6 /℃, αz = 0.6 × 10-6 /℃ |
Table 2. Optical and Nonlinear Optical Properties
| Transparency Range | 350-4500 nm | |
| SHG Phase Matchable Range | 497-1800 nm (Type Ⅱ) | |
| Therm-optic Coefficient ( λ in μm) | dnx/dT = 1.1×10-5 /℃ | |
| dny/dT = 1.3×10-5 /℃ | ||
| dnz/dT = 1.6×10-5 /℃ | ||
| Absorption Coefficients | < 0.1% /cm at 1064 nm, < 1% /cm at 532 nm | |
| For Type Ⅱ SHG of a Nd:YAG laser at 1064 nm | Temperature Acceptance | 24 ℃·cm |
| Spectral Acceptance | 0.56 nm·cm | |
| Angular Acceptance | 14.2 mrad·cm (Φ)；55.3mrad·cm (θ) | |
| Walk-off Angle | 0.55 ° | |
| NLO Coefficients | deff (Ⅱ) ≈ (d24 - d15) sin2Φ sin2θ - (d15 sin2Φ + d24 cos2Φ) sinθ | |
| 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 (λ in μm) | nx2 = 3.0065 + 0.03901 / (λ2 - 0.04251) - 0.01327 λ2 | |
| ny2 = 3.0333 + 0.04154 / (λ2 - 0.04547) - 0.01408 λ2 | ||
| nz2 = 3.3134 + 0.05694 / (λ2 - 0.05658) - 0.01682 λ2 | ||
|
Electro-optic Coefficients: r13 r23 r33 r51 r42 |
Low frequency (pm/V) High frequency (pm/V) 9.5 8.8 15.7 13.8 36.3 35.0 7.3 6.9 9.3 8.8 |
|
| Dielectric Constant | ɛeff = 13 | |
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. Up to now, Nd:lasers that use KTP for intra-cavity and extra-cavity frequency doubling have become a preferred pumping sources for visible dye lasers and tunable Ti:sapphire lasers as well as their amplifiers. They are also used as green sources for many research and industry applications.
Close to 80% conversion efficiency and 700 mJ green laser were obtained with a 900 mJ injection-seeded Q-switch Nd:YAG lasers by using extra-cavity KTP.
8 W green laser was generated from a 15 W LD pumped Nd:YVO4 with intra-cavity KTP.
KTP is also being used for intracavity mixing of 0.81 µm diode and 1.064 µm Nd:YAG laser to generate blue light and intracavity SHG of Nd:YAG or Nd:YAP lasers at 1.3 µm to produce red light.
Fig. 1 Type Ⅱ KTP SHG in XY Plane
Fig.2 Type Ⅱ 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 (600 nm) to mid-IR (4500 nm), 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 miniwatt average power level. A KTP's OPO that are pumped by a 1064 nm Nd:YAG laser has generated as high as above 66% efficiency for degenerately converting to 2120 nm.
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's OPO/OPA. As shown in Fig.5, for pumping wavelength range from 0.7 µm to 1 µm, the output can cover from 1.04 µm to 1.45 µm (signal) and from 2.15 µm to 3.2 µm (idler). More than 45% conversion efficiency was obtained with narrow output bandwidth and good beam quality.
Fig.5 Type Ⅱ NCPM OPO
Applications for E-O Devices
In addition to unique features, KTP also has promising E-O and dielectric properties that are comparable to LiNbO3. These excellent 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 3. Electro-Optic Modulator Materials
| Materials | ε | N | Phase | Amplitude | ||||
|
R (pm/V) |
K (10-6/℃) |
N7r2/ε (pm/V)2 |
r (pm/V) |
K (10-6/℃) |
n7r2/ε (pm/V)2 |
|||
| KTP | 15.42 | 1.8 | 35 | 31 | 6130 | 27 | 11.7 | 3650 |
| LiNbO3 | 27.9 | 2.2 | 8.8 | 82 | 7410 | 20.1 | 42 | 3500 |
| KD*P | 48 | 1.47 | 24 | 9 | 178 | 24 | 8 | 178 |
| LiIO3 | 5.9 | 1.74 | 6.4 | 24 | 335 | 1.2 | 15 | 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 (˃15 GHZ), 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 waveguide have been applied to the type Ⅰ quasi-phase-matchable SHG of a tunable Ti:Sapphire laser in the range of 760-960 mm, and directly doubled diode lasers for the 400-430 nm outputs.
Table 4. Electro-Optic Waveguide Materials
| Materials | r (pm/V) | n | εeff (ε11ε33)1/2 | n3r/εeff (pm/V) |
| KTP | 35 | 1.86 | 13 | 17.3 |
| LiNbO3 | 29 | 2.2 | 37 | 8.3 |
| KNbO3 | 25 | 2.17 | 30 | 9.2 |
| BNN | 56 | 2.22 | 86 | 7.1 |
| BN | 56-1340 | 2.22 | 119-3400 | 5.1-0.14 |
| GaAs | 1.2 | 3.6 | 14 | 4 |
| BaTiO3 | 28 | 2.36 | 373 | 1 |
KTP's Parameters
Table 5. Specifications
| Dimension Tolerance | (W ± 0.1 mm) × (H ± 0.1 mm) × (L + 0.5/-0.1 mm) (L≧2.5 mm)(W ± 0.1 mm) × (H ± 0.1 mm) × (L + 0.1/-0.1 mm) (L＜2.5 mm) |
| Clear Aperture | Central 90% of the diameter |
| Internal Quality | No visible scattering paths or centers when inspected by a 50 mW green laser |
| Surface Quality (Scratch/Dig) | 10/5 to MIL-PRF-13830B |
| Flatness | ≦ λ/8 @633 nm |
| Transmitted Wavefront Distortion | ≦ λ/8 @633 nm |
| Parallelism | 20 arc sec |
| Perpendicularity | ≦ 15 arc min |
| Angle Tolerance | ≦ 0.25 ° |
| Chamfer | ≦ 0.2 mm × 45 ° |
| Chip | ≦ 0.1 mm |
| Damage Threshold |
＞1 GW/cm2 @1064 nm, 10 ns, 10 Hz (AR-coated) ＞0.3 GW/cm2 @532 nm, 10 ns, 10 Hz (AR-coated) |
| Quality Warranty Period | One year under proper use. |
AR-coatings
CASTECH provides the following AR-coatings:
- Dual Band AR-coating (DBAR) of KTP for SHG of 1064 nm; low reflectance (R<0.2% @1064 nm and R<0.5% @532 nm)
- High reflectivity coating: HR 1064 nm & HT 532 nm, R˃99.8% @1064nm, T˃90% @532 nm
- Broad Band AR-coating (BBAR) of KTP for OPO applications
- High damage threshold (˃300 MW/cm2 at both wavelengths)
- Long durability
- Other coatings are available upon request
Enquiry
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