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 offers for its KTP with:

· 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

Basic Properties

Table 1. Chemical and Structural properties

Crystal Structure

Orthorhombic, space group Pna21,point group mm2

Lattice Parameter

a=6.404Å, b=10.616Å, c=12.814Å, 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 Coefficient

(/°C, λ in μm)

dnx/dT=1.1X10-5

dny/dT=1.3X10-5

dnz/dT=1.6X10-5

Absorption  Coefficient

<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 Coefficient

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=3.0065+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.

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.
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.

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 0.7μm 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.

 

Fig.5 Type II NCPM OPO

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 range 760-960mm, and directly doubled diode lasers for the 400-430nm outputs. A conversion efficiency in excess of 100%/W/cm2 has been obtained.

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-coating

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-O-13830A

· 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.

 
 
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CONEX SYSTEMS TECHNOLOGY, Inc.
2880 Zanker Road, Suite 203
San Jose, CA 95134
Tel: 408-954-7329
Fax: 408-954-7330
Email: crystals@castech-us.com
 
 
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