KTP Crystal

KTP crystal 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. However, it is now limited to moderate to low power applications due to it's gray-tracking problem. Recently we have developed gray-tracking-improved KTP (i-KTP) which has significantly raised the gray-tracking trigger power.

Advantage:

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

Disadvantage:

Gray-tracking at high power limited it's application to moderate power density

Additional applications for KTP include mixed frequency, electro-optical modulation, optical parametric generation and optical waveguide.

Application:

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

Main Specification:

Dimension	1x1x0.05 - 30x30x40 mm
Phase matching type	Type II, θ=90°; φ=phase-matching anglea) 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

Note:
To inquire or order a finished KTP crystals, please provide detailed specifications as listed in the above. We require engineering drawing for specific orientation. For special applications, please consult us for the designs if you are sure about the phase matching angle .

Physical Properties:

Crystal structure	Orthorhombic
Point group	mm2
Melting point	1172°C incongruent
Lattice parameters	a=6.404Å, b=10.615Å, c=12.814Å, 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	e_eff = 13

Optical Properties:

Transmitting range

350nm ~ 4500nm

Refractive indices

	n_x	n_y	n_z
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

dn_x/dT=1.1x10-5/°C
dn_y/dT=1.3x10-5/°C
dn_z/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

n_x2=2.10468 + 0.89342λ²/(λ²-0.04438)-0.01036λ²
n_y2=2.14559 + 0.87629λ²/(λ²-0.0485)-0.01173λ²
n_z2=1.9446 + 1.3617λ²/(λ²-0.047)-0.01491λ²

Nonlinear Optical Properties

Phase matching range	497nm – 3300 nm
Nonlinear coefficients (@ 10-64nm)	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	d_eff(II) ≈ (d₂₄ - d₁₅)sin²qsin²j - (d₁₅sin²j + d₂₄cos²j)sinq

Nonlinear Optical Properties

Phase matching range	497nm – 3300 nm
Nonlinear coefficients (@ 10-64nm)	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	d_eff(II) ≈ (d₂₄ - d₁₅)sin²qsin²j - (d₁₅sin²j + d₂₄cos²j)sinq

Type II SHG of 1064nm Laser:

Phase matching angle	q=90°, f=23.2°
Effective nonlinear optical coefficients	d_eff » 8.3 x d36(KDP)
Angular acceptance	Dθ= 75 mrad Dφ= 18 mrad
Temperature acceptance	25°C.cm
Spectral acceptance	5.6 Åcm
Walk-off angle	1 mrad
Optical damage threshold	1.5-2.0MW/cm²

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