All-solid-state ultraviolet lasers have been widely used in the fields of mechanical flaw detection, lithography, micromachining and medicine for the advantages of small volume, long life, high efficiency, good beam quality, wide tuning and narrow spectral line, etc. Utilizing high power near-infrared coherent light source as the fundamental frequency source based on nonlinear tuning technology, generating ultraviolet coherent radiation by multistage frequency conversion is regarded as an important way to develop the ultraviolet coherent light source. The key problem of ultraviolet coherent light source mainly focuses on the development of nonlinear optical frequency conversion crystal in ultraviolet band. The nonlinear optical crystal is one of the conditions for frequency transformation, so the growth, size, damage resistance, conversion efficiency and allowable parameter range of nonlinear optical crystal are required more and more.
Non-linear crystal CLBO for frequency conversion of visible and near-IR laser radiation to the UV range
Cesium lithium borate crystal, CsLiB6O10 (CLBO), is a novel nonlinear optical borate crystal possessing excellent NLO properties in the UV range. Because of its good NLO properties, such as sufficient large nonlinear coefficient, short absorption edge, large values of angular, spectral, and temperature bandwidths, CLBO crystal is well suited for second and higher-order harmonic generation and an excellent material to produce UV and deep UV all-solid-state lasers. Its UV absorption edge reaches 180 nm. The effective nonlinear optical coefficient of CLBO for frequency doubling at 1064nm is about twice as large as that of KDP. CLBO crystals can be grown from the stoichiometric melt with lower viscosity.
Parameter
| Chemical formula | CsLiB6O10 |
| Crystal structure | Tetragonal,Negative uniaxial crystal,42 m |
| Lattice constants | a=10.494Å,c = 8.939Å,Z=4 |
| Mass density | 2.461 g/cm3 |
| Moh hardness | 5.5 |
| Melting point | 1118 K |
| Molecular mass | 364.706 |
| Thermal conductivity | 1.25 W/m K |
| Property | Value |
| Transparency Range | 180-2750 nm |
| Absorption coefficient | 0.0013 cm−1 |
| Refractive Indices | |
| 1.064 μm | ne = 1.4340, no = 1.4838 |
| 0.532 μm | ne = 1.4445, no = 1.4971 |
| Sellmeier Equations(λ in μm) | no2 = 2.2104+0.01018/(λ2-0.01424)-0.01258λ2 |
| ne2 = 2.0588+0.00838/(λ2-0.01363)-0.00607λ2 | |
| Property | Value | |||||
| NLO coefficients | deff(I)=d36sinθmsin(2φ) | |||||
| deff(II)=d36sin(2θm)cos(2φ) | ||||||
| Therm-Optic Coefficients | dno/dT=-1.9*10-6/℃ | |||||
| dne/dT=-0.5*10-6/℃ | ||||||
| Damage Threshold | 26 GW/cm2 | |||||
| Wavelength(nm) | Phase Matching Angle(°) | Deff(pm/V) | Angle Tolerence(mrad·cm) | Walk-off Angle(°) | Spectral Acceptance(nm·cm) | Temperature Acceptance(℃·cm) |
| 532+532=266 | 61.7 | 0.84 | 0.49 | 1.83 | 0.13 | 8.3 |
| 1064+266=213 | 68.4 | 0.87 | 0.42 | 1.69 | 0.16 | 4.6 |
| λ [μm] | 0.2 |
| τp [ns] | 0.00014 |
| β × 1011 [cm/W] | 120 ± 20 |
| λ[µm] | no | ne |
| 0.420 | 1.5058 | 1.4517 |
| 0.450 | 1.503 | 1.4493 |
| 0.480 | 1.5006 | 1.4474 |
| 0.500 | 1.4991 | 1.4462 |
| 0.532 | 1.4971 | 1.4445 |
| 0.560 | 1.4957 | 1.4434 |
| 0.590 | 1.4943 | 1.4422 |
| 0.610 | 1.4935 | 1.4414 |
| 0.6328 | 1.4928 | 1.4409 |
| 0.670 | 1.4915 | 1.4398 |
| 0.700 | 1.4907 | 1.4392 |
| 0.720 | 1.4902 | 1.4387 |
| 1.064 | 1.4838 | 1.434 |
| d36(0.532 μm) = 0.92 pm/V | |
| d14(0.852 μm) = 0.69 pm/V | |
| d36(0.852 μm) = 0.83 pm/V | |
| d36(1.064μm) = 0.74 pm/V |
| Interacting wavelengths [μm] | θpm [deg] | T [◦C] | Δθint [deg] | ΔT [◦C] |
| SHG, o + o ⇒ e | ||||
| 0.946 ⇒ 0.473 | 90 | -15 | 5.0 | |
| 0.5235 ⇒ 0.26175 | 65.8 | ~160 | ||
| 0.5321 ⇒ 0.26605 | 62 | ~140 | ||
| 61.4 | 20 | 0.23 | 6.2 | |
| 1.0642 ⇒ 0.5321 | 29.5 | 20 | 0.043 | 52.7 |
| 1.3382 ⇒ 0.6691 | 27.7 | 20 | 68.7 | |
| SFG, o + o ⇒ e | ||||
| 1.0642 + 0.26605 ⇒ 0.21284 | 67.3 | 20 | 3.6 | |
| 1.547 + 0.221 ⇒ 0.19338 | 61.7 | 150 | ||
| 1.9079 + 0.2128 ⇒ 0.1914 | 55 | 20 | 1.2 | |
| 1.0642 + 0.35473 ⇒ 0.26605 | 50.6 | 20 | 6.1 | |
| 1.0642 + 0.5321 ⇒ 0.35473 | 39.1 | 20 | 18.0 | |
| SHG, e + o ⇒ e | ||||
| 1.0642 ⇒ 0.5321 | 42.4 | 20 | 49.4 | |
| SFG, e + o ⇒ e | ||||
| 1.9079 + 0.2128 ⇒ 0.1914 | 57.4 | 20 | 1.1 | |
| 1.0642 + 0.5321 ⇒ 0.35473 | 48.9 | 20 | 17.0 | |
| λ [μm] | τp [ns] | Ithr [GW/cm2] | Note |
| 0.2 | 0.00014 | >250 | 1 kHz |
| 0.266 | 8 | 17-19 | solution-stirring growth |
| 0.75 | 6.4 | ||
| 0.75 | 9-10 | dislocation density∼1.5×104 cm−3 | |
| 0.75 | 15-20 | dislocation density(0.7 to 1)×104 cm−3 | |
| 0.75 | 25 | solution-stirring TSSG growth | |
| 0.511 | 20 | >0.5 | 12 kHz |
| 0.527 | 0.0015 | >47 | 1/6 Hz |
| 0.532 | 70 | >0.043 | 1 kHz |
| 7 | >0.13 | 10 Hz | |
| 0.014 | 130-520 | train of 80 pulses | |
| 0.5395 | 7 | >0.67 | 10 Hz |
| 0.576 | 8 | >0.1 | 10 Hz |
| 0.800 | CW | >0.0000038 | |
| 0.0014 | >600 | 1 kHz | |
| 1.053 | 0.0015 | >100 | |
| 1.064 | CW | 0.000088 | |
| 13 | >0.35 | 10 Hz | |
| 7 | >0.37 | 10 Hz | |
| 1.1 | 16–19 | along [100] direction | |
| 1.1 | 29 | along [001] direction | |
| λ [μm] | τp [ns] | Ithr [GW/cm2] | Note |
| 0.266 | 8 | 1.4–1.6 | conventional crystals |
| 2.0 | solution-stirring growth | ||
| 1.3–1.5 | conventional crystals,mechanical polishing | ||
| 2.3 | conventional crystals,ion-beam etching | ||
| 1.9 | high-quality crystals,mechanical polishing | ||
| 2.9 | high-quality crystals,ion-beam etching |
| Temperature derivative of refractive indices | dno/dT=-12.8-0.328/λ |
| dne/dT=-8.36+0.047/λ-0.039/λ2+0.014/λ3 | |
| Effective second-order nonlinear coefficient | dooe = −d36sin(θ+ρ)sin 2φ |
| deoe = doee = 2d36sin(θ+ρ)cos(θ+ρ)cos 2φ |
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| Calculation result of second-harmonic conversion efficiency as a function of input fundamental pulse energy | CLBO Transmittance Spectrum |
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| Refractive index dispersion | Phase-matching angle for typesIandII as a function of the wavelength of fundamental wave |
- Its UV absorptionedge reaches 180 nm
- High effective nonlinear opticalcoefficient
- Largevalues of angular, spectral and temperature bandwidths
- High laser damage threshold
- Small discrete angle
- High frequency conversion efficiency
- Easy to grow big size single crystal
- Lowabsorption coefficient
- All-solid-state ultraviolet lasers
- Semiconductor lithography
- PCBdrilling
- Optical parametric oscillator
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