KTA (Potassium Titanyl Arsenate, KTiOAsO4 )
 

KTA crystal features large non-linear optical and electro-optical coefficients in comparison to KTP and has the added benefit of significantly reduced absorption in the 2 to 5 µm region.  It has found more and more applications in second harmonic generation (SHG), sum and difference frequency generation (SFG)/(DFG), optical parametric oscillation/ amplification (OPO/OPA), and electro-optical Q-switching.

 

 KTA features

l         1Large nonlinear optical coefficients

l         1Wide angular bandwidth and small walk-off angle 

l         1Broad temperature and spectral bandwidth 

l         1Large electro-optic coefficients

l         1Lower absorption in the 3-4 μm range than KTP.

l         1Nonhydroscopic, chemically and mechanically stable 

l         1High thermal conductivity 

l         1High damage threshold

 

KTA is a positive biaxial crystal, with the principal axes X, Y, and Z ( nz>ny>nx ) parallel to the crystallographic axes a, b, and c, respectively. 

 

Structural and Physical Properties

Crystal Structure  

Orthorhombic, space group Pna21, point group mm2

Cell Parameters  

a=13.125Å, b=6.5716Å, c=10.786 Å, Z=8

Melting Point  

1130oC

Curie Point  

880oC

Mohs Hardness  

 ~ 5

Density  

3.45 g/cm3

Color  

colorless

Hygroscopic Susceptibility

No

Specific Heat  

0.687 J/g/K

Thermal Conductivity  

1.8 W/m/K

Electrical Conductivity  

0.7-3.4 x10-6 s/cm (c-axis, @22 oC, 1KHz)

 

Linear Optical Properties:

Transmitting Range    

350 nm - 5500 nm      

Refractive Indices:
               1064nm
                532nm  

    nx             ny            nz
1.7818      1.7866      1.8680
1.8264      1.8331      1.9310

Sellmeier Equations
(l in μm)  

nx2=1.90713+1.23522l2 /(l2-0.19692)-0.01025l2
ny2=2.15912+1.00099l2 /(l2-0.21844)-0.01096l2
nz2=2.14768+1.29559l2/(l2-0.22719)-0.01436l2

Thermo-optic Coefficients  

dnx/dT=1.1x10-5/oC, dny/dT=1.3x10-5/oC
dnz/dT=1.6x10-5/oC   

Absorption Coefficient   

a < 1% cm-1 @1064nm and 532nm   

 

Nonlinear Optical Properties:

Phasematchable SHG Range

542 - 1800nm  

Nonlinear Optical Coefficients

d31=2.8pm/v, d32=4.2pm/v,
d33=16.2pm/v,d24=3.2pm/v,
d15=2.3pm/v

Effective Nonlinearity Expressions 

deff(II)= (d24-d15)sin2fsin2q-(d15sin2f+d24cos2f)sinq

Electro-optic Coefficients
( Low frequency )

 r13= 11.5pm/V,   r23=15.4pm/V, r33=37.5pm/V

Dielectric Constant

eeff=42  

 

Specifications for finished KTA

Wavefront distortion: less than l/4 @ 633 nm 

Dimension tolerance: (W +/- 0.1 mm) x (H +/- 0.1 mm) x (L + 0.2 mm/-0.1mm) 

Clear aperture: > 90% central area 

Flatness: l/8 @ 633 nm 

Scratch/dig: 10/5 to MIL-O-13830A 

Parallelism: better than 20 arc seconds 

Perpendicularity: 5 arc minutes

Angle tolerance: Dq< +/-0.25o, Df< +/-0.25o

 

Coating and Mount

Standard dual band anti-reflection (DBAR) coatings at 1064nm/1530 nm, 1064/3200nm,  or 1320nm/660nm are available. Other coatings are also available upon request. Mounts may be provided free of charge.

 
  BBO        LBO         KTP