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        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.