KTP (Potassium Titanium Oxide Phosphate)

KTP crystal

KTP crystals or Potassium Titanium Oxide Phosphate (KTiOPO4) is an efficient nonlinear optical crystal in the visible to infrared spectral region with relatively low cost. It has large nonlinear coefficient. The effective nonlinear optical coefficient of KTP deff at 1064nm is more than 1.5 times that of BBO. It's damage threshold is near 1 GW/cm2 for 1 Hz 10 ns pulses at 1064nm.

  Features:

  • Efficient frequency conversion (1064nm SHG conversion efficiency is about 80%)
  • Large nonlinear optical coefficients (15 times that of KDP)
  • Wide angular bandwidth and small walk-off angle
  • Broad temperature and spectral bandwidth
  • High thermal conductivity (2 times that of BNN crystal)
  • Moisture free
  • Minimum mismatch gradient
  • Super-polished optical surface
  • No decomposition below 900°C
  • Mechanically stable
  • Low cost compare with BBO and LBO

  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
  • Electrical Optical(E-O) Modulators, Optical Switches, and Directional Couplers
  • Optical Waveguides for Integrated NLO and E-O Devices Additional applications for KTP include mixed frequency, electro-optical modulation, optical parametric generation and optical waveguide.

Physical Properties:

Crystal Structure
Orthorhombic
Point Group
mm2
Melting Point
1172°C incongruent
Lattice Parameters
a=6.404Ã… b=10.615Ã… c=12.814Ã… Z=8
Temperature of Decomposition
~1150°C
Transition Temperature
936°C
Mohs Hardness
~5
Density
2.945 g/cm3
Color
colorless
Hygroscopic Susceptibility
no
Specific Heat
0.1737 cal/g.°C
Thermal Conductivity
0.13 W/cm/°C
Electrical Conductivity
3.5x10-8 s/cm (c-axis, 22°C, 1KHz)
Thermal Expansion Coefficients
a1 = 11 x 10-6 °C-1
a2 = 9 x 10-6 °C-1
a3 = 0.6 x 10-6 °C-1
Thermal Conductivity Coefficients
k1 = 2.0 x 10-2 W/cm °C
k2 = 3.0 x 10-2 W/cm °C
k3 = 3.3 x 10-2 W/cm °C
Dielectric Constant
eeff = 13

Optical Properties:

Transmitting Range
350nm ~ 4500nm
Refractive Indices
nx
ny
nz
1064nm
1.7400
1.7469
1.8304
532nm
1.7787
1.7924
1.8873
Absorption Coefficients
a < 1%/cm @1064nm and 532nm
Therm-Optic Coefficients
dnx/dT=1.1x10-5/°C
dny/dT=1.3x10-5/°C
dnz/dT=1.6x10-5/°C
Electro-Optic Coefficients
Low frequency (pm/V)
High frequency 
(pm/V)
r13
9.5
8.8
r23
15.7
13.8
r33
36.3
35.0
r51
7.3
6.9
r42
9.3
8.8
Sellmeier Equations
nx2=2.10468 + 0.89342λ2/(λ2-0.04438)-0.01036λ2 
ny2=2.14559 + 0.87629λ2/(λ2-0.0485)-0.01173λ2 
nz2=1.9446 + 1.3617λ2/(λ2-0.047)-0.01491λ2

Nonlinear Optical Properties

Phase Matching Range
497nm - 3300 nm
Nonlinear Coefficients (@1064nm)
d31=2.54pm/V, d31=4.35pm/V, d31=16.9pm/V
d24=3.64pm/V, d15=1.91pm/V at 1.064 mm
Effective Nonlinear Optical Coefficients
deff (II) ≈ (d24 - d15)sin2θsin2φ - (d15sin2φ + d24cos2φ)sinθ

Type II SHG of 1064nm Laser

Phase Matching Angle
θ=90° φ=23.2°
Effective Nonlinear Optical Coefficients
deff  ≈8.3 x d36(KDP) 
Angular Acceptance
Δθ= 75 mrad Δφ= 18 mrad
Temperature Acceptance
25°C.cm
Spectral Acceptance
5.6 Ã…m
Walk-Off Angle
1 mrad
Optical Samage Threshold
1.5-2.0MW/cm2

Main Specification:

Dimension
1x1x0.05mm - 30x30x40mm
Phase Matching Type
Type II, θ=90° φ=phase-matching angle
a) S1&S2: AR @1064nm R<0.1%; AR @ 532nm, R<0.25%.
b) S1: HR @1064nm, R>99.8%; HT @808nm, T>5%, S2: AR @1064nm, R<0.1%; AR @532nm,      R<0.25%
Typical Coating
Customized coating available upon customer request.
Angle Tolerance
6'
Dimension Tolerance
Δθ< ±0.5°, Δφ< ±0.5°, ±0.02 - 0.1 mm
Flatness
(W ±0.1mm) x (H ±0.1mm) x (L + 0.2mm/-0.1mm) for NKC series
λ/8 @ 633nm10/5 Scratch/dig per MIL-O-13830A
<10'
Scratch/Dig Code
better than 10 arc seconds for NKC series
Parallelism
5'
Perpendicularity
5 arc minutes for NKC series
Wavefront Distortion
less than λ/8 @ 633nm
Clear Aperture
90% central area
Working Temperature
25°C- 80°C
Homogeneity
dn ~10-6/cm 

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 Datasheet (PDF)