Potassium Titanyl Phosphate (KTiOPO4 or KTP)

Advantages:

  • Large Nonlinear Optical (NLO) Coefficients
  • Wide Angular Bandwidth and Small Walk-off Angle
  • Broad Temperature and Spectral Bandwidth
  • High Electro-Optic (E-O) Coefficient and Low Dielectric Constant
  • Large Figure of Merit for an Optical Waveguide Modulator
  • Nonhygroscopic, Good Chemical and Mechanical Properties

Applications:

  • 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.
  • E-O Modulators, Optical Switches, Directional Couplers.
  • Optical Waveguides for Integrated NLO and E-O Devices.

CASIX Provides:

  • Standard size of KTP crystal for DPSS application;
  • Strict Quality Control;
  • 1 - 2 Weeks Delivery;
  • Unbeatable Price and Special OEM Discount;
  • Free Technical Support;
  • AR-Coating, Mounting and Re-polishing Service;
  • Mass Production to Support Industrial and Commercial Applications;
  • New!: Precision Oven & Temperature Controller for Heating KTP.

 

Basic Properties

Applications for SHG and SFG of Nd:lasers

Applications for OPG, OPA and OPO

Basic Properties

1. Structural and Physical Properties

Crystal Structure

Orthorhombic, point group mm2

Cell Parameters

a = 6.404Å, b = 10.616Å, c = 12.814Å Z = 8

Melting Point

1172 oC Incongruent

Curie point

936 oC

Mohs Hardness

» 5.0

Density

3.01g/cm3

Linear Absorption Coefficients

a <0.001 cm-1 @ l =1064 nm or 532 nm

Hygroscopic Susceptibility

no

Relative Dielectric Constant

eeff=13

Specific heat

0.1643 cal/g.oC

Electrical conductivity

3.5x10-8 s/cm (c-axis, 22oC, 1KHz)

Thermal Conductivity

13W/m/K

 

2. Linear Optical Properties

Transparency Range:
350 - 4500 nm, See Transparency Curve


KTP Transparency Curve

Refractive Indices:
Wavelength nx  ny  nz
1064 nm 1.7377 1.7453 1.8297
532 nm  1.7780 1.7886 1.8887

Therm-Optic Coefficients:
dnx/dT=1.1x10-5/oC
dny/dT=1.3x10-5/oC
dnz/dT=1.6x10-5/oC

Sellmeier Equations:
n2x=3.0065+0.03901/(l2-0.04251)-0.01327l2
n2y=3.0333+0.04154/(l2-0.04547)-0.01408l2
n2z=3.3134+0.05694/(l2-0.05658)-0.01682l2

 

3. NonLinear Optical Properties

Phase-Matchable Output Range:

492- 1700 nm

NLO Coefficients:
d31=2.54pm/V, d32=4.35pm/V, d33=16.9pm/V
d24=3.64pm/V, d15=1.91pm/V at 1064 nm
deff(II)» (d24 - d15)sin2fsin2q - (d15sin2f + d24cos2f)sinq

Electro-Optic Coefficients:

Low Frequency (pm/V)

High Frequency(pm/V)

g13

9.5

8.8

g23 15.7 13.8
g33 36.3 35.0
g51 7.3 6.99
g42 9.3 8.8

 

Applications for SHG and SFG of Nd:lasers

KTP is the most commonly used material for frequency doubling of Nd:YAG lasers and other Nd-doped lasers, particularly at the low or medium power density. The following Table lists the major NLO properties of KTP for frequency-doubling of Nd:YAG laser.

PM angle

q=90o, f=23.5o,
where q & f are polar angles referring to Z and X.

Effective SHG coefficient

deff » 8.3xd36(KDP)

Angular acceptance

20 mrad-cm

Temperature acceptance

25oC-cm

Spectral acceptance

5.6 Å-cm.

Walk-off angle

4.5mrad (0.26o)

Optical damage threshold

> 450MW/cm2, (@ 1.06mm, 10ns, 10Hz)

 

To date, extra- and intra-cavity frequency doubled Nd:lasers using KTP have become a preferred green laser source for many R&D, medical, industrial and commercial applications. By using extracavity KTP SHG, over 80% conversion efficiency and 700mJ green laser were obtained with a 900 mJ injection-seeded Q-switched Nd:YAG laser.


Type II SHG in XY Plane



Type II SHG in XZ Plane

Applied to diode-pumped Nd:laser, KTP is a basic NLO crystal for the construction of compact visible solid state laser systems. Recent advances in intracavity-doubled Nd:YVO4 and Nd:YAG lasers have increased the demand for compact green lasers used in display, construction, optical disk and laser printer. Over 200 mw TEM00 green outputs are available from LD pumped Nd:YVO4 and Nd:YAG lasers and 3 W TEM00, mode-locked green laser was generated by intracavity SHG in a 5.3 W mode-locked diode-laser pumped Nd:YAG laser. Moreover, 2.5mW green light was obtained from 50mW LD pumped and intracavity doubled Nd:YVO4 mini-lasers with a 9mm long cavity.

KTP is also a powerful crystal for SHG and SFG of laser with wavelength from about 1mm to 3.4 mm. The SHG phase-matching angle and effective SHG coefficients (deff) of KTP in XY plane (0.9 mm to 1.08 mm) and XZ plane (1.1 mm to 3.3 mm) are showed as the figtures. Although KTP cut in YZ plane can be phase-matched for SHG of 1 mm to 3.45 mm, it is seldom used in practices because of the low deff.

Applications for OPG, OPA and OPO


DPO Pumped at 532 nm



DPO Pumped at 1064nm



DPO Pumped at 1064nm

As an efficient OPO crystal pumped by the fundamental and second harmonics of a Nd:YAG or Nd:YLF laser, KTP plays an important role in parametric sources for tunable output from visible (0.6mm) to mid-IR (4.5mm). The phase-matching angles and effective NLO coefficient for OPO/OPA pumped at 532 nm and 1064 nm in XZ plane are showed as following figures. NCPM KTP OPO pumped by 1064nm, the signal output is around eye safe wavelength, find applications in eye-safe devices. The OPO/OPA in XY and YZ is seldom employed because of their low effective nonlinear coefficients and other limitation. For more information about the design of KTP-OPO, please contact CASIX.

KTP's OPO results in stable, continuous outputs of femtosecond pulse of 108 Hz repetition rate and miliwatt average power levels in both signal and idler outputs. KTP's OPO pumped by a 1064nm Nd:laser has generated above 66% conversion efficiency for degenerate conversion from 1064 to 2120 nm.

The recently developed new application is the non-critical phase-matched (NCPM) KTP OPO/OPA pumped by the tunable lasers such as Ti:Sapphire, Alexandrite and Cr:LiSrAlF6 (see right figure). The NCPM KTP OPO keeps the KTP crystal fixed in X-axis and tunes the pumping wavelength. If a tunable Ti:Sapphire laser is used as a pumping source (0.7 mm to 1 mm), the output can cover the wavelength range from 1.04mm to 1.45 mm (signal) and from 2.15 mm to 3.2 mm (idler). Due to the favorable NLO properties of NCPM KTP, as high as 45% conversion efficiency was obtained with narrow output bandwidth and good beam quality.

Quasi-Phase-Matched Waveguide

Recently, type II SHG conversion efficiency of 20%/W/cm2 was achieved by quasi-phase matched waveguide doubler, in which the phase mismatch from one section is balanced against a phase mismatch of the opposite sign from a second section. Furthermore, segmented KTP waveguides have been applied to type I quasi-phase-matchable SHG of 0.76-0.96mm for tunable Ti:Sapphire laser and directly doubled diode laser for 0.43-0.40m output. Conversion efficiency in excess of 100%/W/cm2 has been obtained.

Now, CASIX can provide as large as 30x30x1 mm KTP with -Z or both faces polished for waveguide applications. Other size is also available upon request.

Oven for heating KTP crystals:

Increasing the temperature of KTP crystal can enhance the damage threshold of KTP crystal. Therefore, for high power or high power density SHG of Nd lasers, heating KTP to a certain temperature (e.g., 80oC) is recommended. CASIX provides precision oven with temperature controller for heating KTP. A full assembly including KTP crystal, oven and temperature controller is also available. Please refer to page xx for more information about oven & temperature controler.

CASIX's warranty on KTP specifications:


Transmitting wavefront distortion:

less than l/4 @ 633nm

Dimension tolerance:

(W± 0.1mm)x(H ± 0.1mm)x(L+0.2mm/- 0.1)

Clear aperture:

> 90% central area

Flatness:

l/8 @ 633nm

Surface quality:

10/5 Scratch/Dig

Parallelism:

better than 20 arc sec.

Perpendicularity:

15 arc min.

Angle tolerance:

Deltaq < 0.5°, Deltaf < 0.5°

AR coating:

dual wave band AR coating at 1064/532 nm for both faces

residual reflectivity:

< 0.2% at 1064 nm and < 0.5% at 532 nm per surface

Quality Warranty Period:

one year under proper use

 

Note:

1. CASIX has large quantities of standard size KTP crystals in-stock. The next-day delivery is available for the in-stock crystals. The standard size crystals include 2X2X5 mm, 3x3x5mm and 5x5x5mm etc. with dual-band AR-coating for frequency-doubling 1064 nm.

2. CASIX provides free crystal samples for long term technical and business cooperation as well as the developments of KTP's new applications. Qualified end-users can also obtain free samples upon request.

3. AR-coatings and High Reflection coatings (HR-coatings) at other wavelengths are available upon request.

4. Technical information and specific designs for KTP crystals are provided by our sales engineers and the scientists in our R&D center.