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.
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 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°C
|
|
Mohs Hardness
|
5
|
|
Density
|
3.01 g/cm3
|
|
Thermal Conductivity
|
13W/m/K
|
|
Thermal Expansion Coefficient
|
αx=11x10-6/°C, αy=9x10-6/°C, αz=0.6x10-6/°C
|
Table 2. Optical and Nonlinear Optical Properties
|
Transparency Range
|
350～4500nm
|
|
SHG Phase Matchable Range
|
497～1800nm (Type II)
|
|
Therm-optic Coefficients
(/°C)
|
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
|
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)sin2φsin2θ-(d15sin2φ + d24cos2φ)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)-0.01327λ 2
ny2=3.0333+0.04154/(λ 2-0.04547)-0.01408λ2
nz2=3.3134+0.05694/(λ 2-0.05658)-0.01682λ2
|
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 CASTECH ’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 0.81μm 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.
|
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.
|
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 0.7μm to 1 μm, the output can cover from 1.04μm to 1.45μm(signal) and from 2.15μm to 3.2μm(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
|
|
|
|
|
Phase
|
|
|
Amplitude
|
|
|
Material
|
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
|
|
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
CASTECH 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.
CASTECH Warranty on KTP Specifications:
· Dimension tolerance: (W±0.1mm)x(H±0.1mm)x(L+0.5/-0.1mm) (L≥2.5mm)
(W±0.1mm)x(H±0.1mm)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 λ/8 @ 633nm
· Transmitting wavefront distortion: less than λ/8 @ 633nm
· Chamfer: ≤0.2mm@45°
· Chip: ≤0.1mm
· Scratch/Dig code: better than 10/ 5 to MIL-PRF-13830B
· Parallelism: better than 20 arc seconds
· Perpendicularity: ≤5 arc minutes
· Angle tolerance: Δθ≤0.25°, Δφ≤0.25°
· 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.
