22 May 2019 Description
YCOB (YCa4O(BO3)3, Yttrium Calcium Oxyborate)—Nonlinear crystal considered to have good prospects of UV band optical frequency multiplier
YCOB crystal is one of the most widely used nonlinear optical crystals. Its nonlinear optical coefficient is equivalent to that of BBO crystal and LBO crystal. The effective frequency multiplication coefficients of the second and third order reach 2, 8 and 1, 4 times of KDP respectively.The YCOB crystal has the following advantages : large aperture, high damage intensity in femtosecond regime,about2000-2500GW/cm2 wide allowable Angle range and allowable temperature range,small dispersion Angle, shorter growth period by Cz method.At the same time, it has stable physical and chemical properties (non-deliquescent) and good machining properties. Therefore, it is considered to have good application prospects of blue-green light and UV band optical frequency multiplier crystal.
One of the latest technical achievements connected with YCOB is the generation of 2.35-W CW green output (λ = 532 nm) in a 1.2-cm-long crystal (θ = 64.5◦, φ =35.5◦) via inter cavity SHG of a diode-array end-pumped Nd:YVO4 laser (P = 5.6W). Another similar application is THG of NdYVO4 laser radiation. Using the KTP crystal for frequency doubling and a 1.1-cm-longYCOB crystal (θ = 106◦, φ =77.2◦), the authors managed to obtain 124mW of quasi-CW light (pulse repetition frequency 20 kHz) at 355 nm.
Parameter
Chemical and Physical properties
| 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 1510ºC |
| 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) |
Polishing
| Orientation Tolerence |
< 0.5° |
| Thickness/Diameter Tolerance |
±0.01 mm |
| Surface Flatness |
<λ/8 @632nm |
| Wavefront Distortion |
<λ/4 @632nm |
| Surface Quality |
10/5 |
| Parallel |
30〞 |
| Perpendicular |
15ˊ |
| Clear Aperture |
>90% |
| Chamfer |
<0.2×45° |
Experimental Values of Phase-matching Angle for SHG and SFG in Principal Planes of YCOB Crystal at T =293K
| Interacting wavelengths[μm] |
Φpm [deg] |
θpm [deg] |
| XY plane,θ =90° |
|
|
| SHG,o+o ⇒ e |
|
|
| 1.0642⇒0.5321 |
35 |
|
| 0.7379⇒0.36895 |
77.3 |
|
| SHG, type I, along Y |
|
|
| 0.724⇒0.362 |
90 |
|
| SFG, o+o ⇒ e |
|
|
| 1.0642+0.5321⇒0.3547 |
73.4/74.8/75.2/75.3 |
|
| SHG, type II, along Y |
|
|
| 1.03⇒0.515 |
90 |
|
| SFG, e+o ⇒ e |
|
|
| 1.9079+1.0642⇒0.6831 |
81.2 |
|
| YZ plane, Φ=90◦ |
|
|
| SHG, e+e ⇒ o |
|
|
| 0.7379⇒0.36895 |
|
66.9 |
| SFG, e+e ⇒ o |
|
|
| 1.0642+0.5321⇒0.3547 |
|
58.7/59.7/59.8/59.9 |
| SHG, e+o ⇒ o |
|
|
| 1.0642⇒0.5321 |
|
58.7/51.1/62.7 |
| SFG, e+o ⇒ o |
|
|
| 1.9079+1.0642⇒0.6831 |
|
73.5 |
| XZ plane, Φ=0◦, θ<VZ |
|
|
| SHG, type I, along Z |
|
|
| 0.83⇒0.415 |
|
0 |
| 0.8325⇒0.41625 |
|
0 |
| SHG, o+o ⇒ e |
|
|
| 0.9⇒0.45 |
|
18.7 |
| 0.954⇒0.477 |
|
24.1 |
| 1.0642⇒0.5321 |
|
30.8/31.7 |
| 1.3382⇒0.6691 |
|
38.2/38.3 |
| SFG, o+o ⇒ e |
|
|
| 1.0642+0.7379⇒0.4358 |
|
17.1 |
| 1.569+0.5321⇒0.3973 |
|
18.6 |
| 1.3188+0.6594⇒0.4396 |
|
23 |
| 1.9079+0.5321⇒0.4161 |
|
26.6 |
Experimental Values of Internal Angular Bandwidth for SHG and SFG in Principal Planes of YCOB Crystal
| Interacting wavelengths[μm] |
Φpm [deg] |
θpm [deg] |
Δϕint[deg] |
Δθint[deg] |
| XY plane, θ =90◦ |
|
|
|
|
| SHG, o+o ⇒ e |
|
|
|
|
| 1.0642⇒0.5321 |
35 |
|
0.09 |
|
| SHG, e+o ⇒ e |
|
|
|
|
| 1.0642⇒0.5321 |
73.4 |
|
0.32 |
|
| SFG, o+o ⇒ e |
|
|
|
|
| 1.0642+0.5321⇒0.3547 |
73.2 |
|
0.11 |
|
| YZ plane, φ =90◦ |
|
|
|
|
| SHG, e+o ⇒ o |
|
|
|
|
| 1.0642⇒0.5321 |
|
58.7 |
|
0.74 |
| SFG, e+e ⇒ o |
|
|
|
|
| 1.0642+0.5321⇒0.3547 |
|
58.7 |
|
0.19 |
| XZ plane, Φ=0◦,θ<VZ |
|
|
|
|
| SHG, o+o ⇒ e |
|
|
|
|
| 1.0642⇒0.5321 |
|
31.7 |
|
0.08 |
|
Note: For a biaxial crystal, two angular acceptances exist: one in θ and other in . The authors have presented only the smallest one.
|
Experimental Values of Temperature Bandwidth for SHG And SFG in principal planes of YCOB crystal
| Interacting wavelengths[μm] |
ΔT[℃] |
Note |
| XY plane, θ =90◦ |
|
|
| SHG, o+e ⇒ e |
|
|
| 1.0642⇒0.5321 |
32.7 |
|
| 32.8 |
Φ=75.3° |
| SFG, o+o ⇒e |
|
|
| 1 .0642+0.5321⇒0.3547 |
8.6 |
Φ=73.7° |
| 9.7/10 |
|
| YZ plane, φ =90◦ |
|
|
| SHG, o+e ⇒ o |
|
|
| 1.0642⇒0.5321 |
31.5 |
θ =62.7° |
| 31.7/29.2 |
|
| SFG, e+e ⇒ o |
|
|
| 1.0642+0.5321⇒0.3547 |
6.2/8.5 |
|
| XZ plane, φ =0◦, θ>180◦−VZ |
|
|
| SHG, type I, along Z |
|
|
| 0.8325⇒0.41625 |
21.6/31.5 |
|
| SHG, o+o ⇒ e |
|
|
| 0.9⇒0.45 |
24.6 |
θ =18.7° |
| 45.3 |
θ =161.3° |
| 1 .0642⇒0.5321 |
75 |
θ =30.8° |
| 1 .3382⇒0.669 |
61 |
θ =141.7° |
| SFG, o+o ⇒ e |
|
|
| 1 .0642+0.7379⇒0.4358 |
36.5 |
θ =162.9° |
| 1 .569+0.5321⇒0.3973 |
16.9 |
θ =18.6° |
| 33.8 |
θ =161.4° |
Experimental Values of Effective Second-order Nonlinear Coefficient for Some Specific Phase-matching Directions (SHG, type I, 1.0642µm ⇒0.5321µm) in YCOB Crystal
| Phase-matching direction |
deff [pm/V] |
| θ =90˚,Φ=35.3˚ (XY plane) |
0.39 |
| θ =90˚,Φ=35˚ (XY plane) |
0.42 |
| θ =31.7˚,Φ=0˚ (XZ plane) |
0.78 |
| 1.03 |
| θ =148.3˚,Φ=0˚ (XZ plane) |
1.36 |
| 1.44 |
| θ =65˚,Φ=36.5˚ |
1.14 |
| θ =65.9˚,Φ=36.5˚ |
0.91 |
| θ =66.3˚,Φ=143.5˚ |
1.45 |
| θ =67˚,Φ=143.5˚ |
1.73 |
| θ =66˚,Φ=145˚ |
1.8 |
|
The properties of deff in the case of YCOB crystal include mirror and inversion symmetries. T his means that the spatial distribution of deff can fully be described by choosing two independent quadrants, for example,(0°＜θ＜90°,0°＜Φ＜90°) and (0°＜θ＜90°,90°＜Φ＜180°).After that, the deff value in each (θ, Φ) direction in these two quadrants is equal to that in (180°-θ, 180°-Φ) direction and vice versa. For example, the directions (θ =33°, ϕ=9°) and (θ =147°, Φ=171°) possess equal deff values.
|
Experimental Values of THG Conversion Efficiency (type I, 1.0642µm+ 0.5321µm ⇒0.3547µm, I =0.8GW/cm2, l =1.04cm) for Some Specific Phase-matching Directions in YCOB Crystal
| Phase-matching direction |
THG conversion efficiency[%] |
| θ =65˚, φ =82.8˚ |
2 |
| θ =90˚, φ =73.8˚ (XY plane) |
7 |
| θ =111˚, φ =79.6˚ |
20 |
| θ =106˚, φ =77.2˚ |
26 |
Laser-induced Bulk Damage Threshold
| λ[μm] |
τp[ns] |
Ithr[GW/cm2] |
Note |
| 0.532 |
6 |
1 |
|
| 1.064 |
10 |
85 |
1 pulse |
| 6 |
>1 |
10Hz |
| 1.1 |
18.4 |
along Y axis, E||Z |
Other Parameters
| Mean Values of Linear Thermal Expansion Coefficient |
| T [K] |
αt×106[K-1],||c |
αt×106[K-1],||c |
αt×106[K-1],||c |
| 293–473 |
8.39 |
5.18 |
9.17 |
| 293–1173 |
9.9 |
8.2 |
12.8 |
| Specific Heat Capacity cp at P =0.101325MPa |
| T [K] |
cp[J/kgK] |
|
|
| 373 |
729.7 |
|
|
| Thermal Conductivity Coefficient at T =293K |
| κ[W/mK],||X |
κ[W/mK],||Y |
κ[W/mK],||Z |
|
| 2.6 |
2.33 |
3.01 |
|
| Thermal Conductivity Coefficient at T =373K |
| κ[W/mK],||a |
κ[W/mK],||b |
κ[W/mK],||c |
|
| 1.83 |
1.72 |
2.17 |
|
| Linear Absorption Coefficient α |
| λ[µm] |
α[cm-1] |
|
|
| 0.21 |
1 |
|
|
| Experimental values of internal angular bandwidth for some specific phase-matching direction (SHG, type I, 0.946µm ⇒0.473µm) inYCOB crystal |
| Phase-matching direction |
Δ[deg] |
|
|
| θ =67.9◦, Φ=136.8◦ |
0.06 |
|
|
Features
-
Electric resistivity is high
-
Temperature acceptance is high
-
Laser induce damage threshold is high
-
Less anisotropy
-
Thermal expansion coefficient is small
-
Less parametric luminescence
Applications
-
SHG(second-harmonic generation),THG(third-harmonic generation)
-
OPO(optical parametric oscillator)
-
OPA(optical parametric amplification)
-
OPCPA (optical parametric chirped-pulse amplification)
-
Piezoelectric acceleration sensors
-
Pressure sensors
-
Gas sensors
|
