Introduction

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YCOB crystal was first found in 1990s. Because it has good nonlinear optical properties and high temperature piezoelectric properties and it is easy to grow large size crystal with high quality, it attracts attention new in recent years.

Compared with Lithium Tetraborate (LBO) crystals, which are commonly used in high power laser system, it has the following advantages:

  • no deliquescence,
  • larger effective NLO susceptibilities,
  • larger Temperature Acceptance,
  • similar laser induce damage threshold,
  • less parametric luminescence (three orders less),
  • smaller thermal expansion coefficient,
  • less anisotropy,
  • better processability,
  • shorter growth period by Cz method and cheaper to make larger aperture element.

YCOB crystal is suitable for applications in high energy and high power laser fields,including

  • Laser wavelength conversion: second-harmonic generation (SHG) and third-harmonic generation (THG),
  • optical parametric oscillator (OPO),
  • optical parametric amplification(OPA),
  • optical parametric chirped-pulse amplification (OPCPA).
  • Another application is in the field of piezoelectric devices at high temperature.

YCOB crystal has very high electric resistivity that can be fabricated as piezoelectric sensors working at the temperature as high as 1000ºC in aerospace engines.

 

Chemical and Structural Properties of YCOB Crystal

Crystal Structure

Monoclinic, Point group m

Lattice Parameter

a = 8.0770 Å, b = 16.0194 Å , c = 3.5308 Å , 

β = 101.167º, Z = 2

Melting Point    

About 1510 ℃

Mohs Hardness    

6 ~ 6.5

Density          

3.31 g/cm3

Thermal Conductivity   

2.6 W/m/K (║X), 2.33 W/m/K (║Y), 3.1 W/m/K (║Z)

Thermal Expansion Coefficient

ax = 10.8•10-5/K,  ay = -8.8•10-5/K,  az = 3.4•10-5/K

 

Optical and Nonlinear Optical Properties of YCOB compared with LBO

Properites

YCOB

LBO

Transparency Range

210 ~ 2600 nm

160 ~ 2600 nm

SHG Phase Matchable Range

724 ~ 2600 nm  (Type I)      

1030 ~ 2150 nm (Type II)

551 ~ 2600 nm  (Type I)      

790 ~ 2150 nm (Type II)

Thermo-optic Coefficient

(T in [°C], λ in [μm])

 

dnx/dT=-9.3•10-6
dny/dT=-13.6•10-6
dnz/dT=(-6.3 - 2.1λ)•10-6

Absorption  Coefficient

<0.1% cm-1 at 1064nm 

<0.1% cm-1 at 1064nm

<0.3% cm-1 at 532nm

Angle Acceptance

0.062 º-cm    (θ, Type I,1064 SHG)

0.19 º-cm    (φ, Type I,1064 SHG)

Temperature Acceptance

112°C-cm   (Type I, 1064 SHG)

4.7 °C-cm   (Type I, 1064 SHG)

Spectral Acceptance

1.19 nm-cm (Type I, 1064 SHG)

1.0 nm-cm (Type I, 1064 SHG)

Walk-off Angle 

1.26° (Type I  1064 SHG)

0.60° (Type I  1064 SHG)

NLO Coefficients

deff(I)=d13sinΦ     (Type I  in XY plane)
deff(I)=d13 sin2θ d12cos2θ   (Type I  in YZ plane)
deff(I)=d12cosθ- d32sinθ  (Type I in XZ plane, VZ>θ>0, Ф=0º)
deff(I)=d12cosθ d32sinθ   (Type I in XZ plane, VZ>θ>0, Ф=180º)

deff(I)=d32cosΦ     (Type I  in XY plane)
deff(I)=d31cos2θ d32sin2θ   (Type I  in XZ plane)
deff(II)=d31cosθ  (Type II in YZ plane)
deff(II)=d31cos2θ d32sin2θ   (Type II in XZ plane) 

Non-vanished NLO susceptibilities

d12 = 0.24 pm/V; d13 = -0.73 pm/V

d31 = 0.41 pm/V; d32 = 2.35 pm/V; 

d33 = -1.60 pm/V

d31 = 1.05 ± 0.09 pm/V
d32 = -0.98 ± 0.09 pm/V
d33 = 0.05 ± 0.006 pm/V

Sellmeier  Equations(λ in μm)      

nx2 = 2.7697  0.02034 / (λ2 - 0.01779) - 0.00643λ2

ny2 = 2.8741  0.02213 / (λ2 - 0.01871) - 0.01078λ2

nz2 = 2.9107  0.02232 / (λ2 - 0.01887) - 0.01256λ2

nx2 = 2.454140  0.011249 / (λ2- 0.011350) -
       0.014591λ2 - 6.60•10-5λ4
ny2 = 2.539070  0.012711 / (λ2- 0.012523) -
       0.018540λ2 - 2.0•10-4λ4
nz2 = 2.586179  0.013099 / (λ2- 0.011893) -
       0.017968λ2 - 2.26•10-4λ4

Piezoelectric Properties of YCOB

Recommended literature (e.g.):

FaPeng Yu et al.: Rare-Earth Calcium Oxyborate Piezoelectric Crystals ReCa4O(BO3)3: Growth and Piezoelectric Characterizations; Crystals 2014,4(3),241-261.

See http://www.mdpi.com/2073-4352/4/3/241/htm

YCOB Elements for Nonlinear Optics (NLO) Applications

Application Size [mm] Theta Phi deff [pm/V]
2nd Harmonic Generation (SHG) 30x30x15 30.8° 180° 1.14
3rd Harmonic Generation (THG) 4x4x7 106° 77.2° NA
Optical Parametric Amplifier (OPA) 15x15x20 28° 180° 1.32

 

Other sizes and cut angles can be fabricated according to customer requirements

 

If you have any inquiries or questions please contact AXTAL