LBO is phase-matchable for SHG and THG of Nd:YAG and Nd:YLF lasers by using either type I or type II interaction. For SHG at room temperature, type I phase-matching can be reached and has maximum effective SHG coefficient in the principal XY and XZ planes in a wide wavelength range from 551 nm to about 3 μm. The optimum type II phase-matching falls in the principal YZ and XZ planes.
Type I SHG Tuning Curve of LBO
Type II SHG Tuning Curve of LBO
SHG conversion efficiencies of more than 70% for pulse and 30% for cw Nd:YAG lasers, and THG conversion effi-ciency of over 60% for pulse Nd:YAG laser have been observed respectively. The SHG conversion efficiency of LBO in an unstable resonator Nd:YAG laser vs the average power density in comparison with that of KTP is shown in right figure.
Internal SHG Conversion Efficiency
Applications:
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More than 480 mW output at 395 nm is generated by frequency-doubling a 2W mode-locked Ti:Sapphire laser (<2ps, 82MHz). The wavelength range of 700 - 900 nm is covered by a 5x3x8 mm3 LBO crystal.
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Over 60 W green output is obtained by SHG of a Q-switched Nd:YAG laser in a type II, 18 mm long LBO crystal.
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The frequency-doubling of a Spectra-Physics TFR diode pumped Nd:YLF laser ( > 500 mJ @ 1047 nm, < 7 ns, 0-10 KHz) reaches over 40% conversion efficiency in a 9 mm LBO.
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The VUV output at 187.7 nm is obtained by sum-frequency generation.
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2 mJ/pulse diffraction-limited beam at 355 nm is obtained by intracavity tripling a Q-switched Nd:YAG laser.
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LBO is very promising for the generation of 266 nm from Nd:YAG, Nd:YVO4 laser because of its low absorption at 266 nm.
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Due to its high damage threshold and small group velocity dispersion, LBO is an excellent crystal for SHG, THG and autocorrelators of ultrashort pulsed lasers including Ti:Sapphire, Cr:LiSrAlF and Cr:LiCaAlF lasers. KASTON can provide LBO crystal as thin as 0.02 mm for 10 fs lasers. To select the best LBO crystal design for your ultrashort pulsed lasers, please consult KASTON.
Non-Critical Phase-Matching
Non-Critical Phase-Matching (NCPM) of LBO is featured by no walk-off, very wide acceptance angle and maximum effective coefficient. It promotes LBO to work in its optimal condition. The SHG conversion efficiencies of more than 70% for pulse and 30% for cw Nd:YAG lasers have been obtained with good output stability and beam quality.
Type I and type II NCPM can be reached along x-axis (θ = 90o, φ= 0o) and z-axis ( θ= 0o,φ= 0o), respectively. As shown in the figure, NCPM SHG over a broad wavelength range from 900 nm to about 1700 nm was measured. The properties of NCPM SHG of Nd:YAG laser at 1.064μm are listed in following table.
Properties of type I NCPM SHG at 1.064 mm
NCPM Temperature
148 oC
Acceptance Angle
52 mrad-cm1/2
Walk-off Angle
0
Temperature Bandwidth
4 oC -cm
Effective SHG Coefficient
2.69 d36(KDP)
KASTON develops an assembly of stabilized oven and temperature controller for NCPM SHG of Nd:YAG, Nd:YLF and Nd:Glass lasers as well as NCPM OPO and OPA systems. The assembly can keep LBO crystal within ±0.1OC from room temperature to 200 OC. Please refer to page 64 for more information about oven and temperature controller.
NCPM Temperature Tuning Curves of LBO
SHG of Nd:YLF Antares with LBO
Applications:
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Over 10 W and highly stable green output @ 532 nm was obtained with NCPM LBO for frequency doubling of diode pumped Nd:YVO4 lasers. All solid state SLM, Q-switched green and UV lasers are available.
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Over 100 W green output was achieved with type II LBO for frequency doubling of Q-switched Nd:YAG laser.
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LBO can reach both temperature NCPM and spectral NCPM (very wide spectral bandwidth) at 1.3 mm.
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More than 11 W @ 532 nm was obtained by extracavity SHG of a 25 W mode-locked Nd:YAG laser. Following drawing shows the SHG output vs input power of Nd:YLF laser (76MHz, 45ps).
OPO and OPA
LBO is an excellent NLO crystal for the widely tunable wavelength range and high power OPO and OPA. The type I and type II OPO and OPA pumped by SHG and THG of Nd:YAG laser and XeCl excimer laser at 308 nm have been reported. The figure shows the calculated OPO tuning curves of a type I LBO pumped by SHG, THG and 4HG of Nd:YAG laser in XY plane at room temperature, and also shows the calculated OPO tuning curves of a type II LBO pumped by SHG and THG of Nd:YAG laser in YZ and XZ planes.
Type I OPO Tuning Curves
of LBO
Type II OPO Tuning Curves of LBO Pumped at 532 nm
Type II OPO Tuning Curves of LBO Pumped at 355 nm
Applications
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By using 90O NCPM LBO, Spectra-Physics SPPO OPO synchronously pumped by femtosecond Ti:Sapphire laser generates < 130 fs pulse from 1.1 to 2.6 mm.
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Type I OPA pumped at 355 nm with pump-to-signal energy conversion efficiency of 30% has been reported.
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By using the NCPM technique, type I OPA pumped by SHG of Nd:YAG laser at 532 nm was also observed to cover a widely tunable range from 0.75 mm to 1.8mm by temperature-tuning from 106.5C to 148.5C.
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By using type II NCPM LBO as an optical parametric generator (OPG) and type I critical phase-matched BBO as an OPA, narrow linewidth (0.15 nm) and high pump-to-signal energy conversion efficiency (32.7%) were obtained when it is pumped by a 4.8 mJ, 30ps laser at 355nm. Wavelength tuning range from 482.6 to 415.9 nm is covered by increasing the temperature of LBO.
AR-Coatings
KASTON provides the following AR-coatings:
1. Dual-band AR-coating of LBO for SHG of Nd:YAG lasers. ◇◇Low reflectance ◇◇( < 0.2% at 1.064 mm and < 0.5% at 0.532 mm); ◇◇High damage threshold ◇◇( > 500 MW/cm2 at both wavelengths); ◇◇Long durability.
2. Broad Band AR-coating for frequency doubling Ti:Sapphire laser.
3. Other coatings are available upon request.
LBO AR-Coating Curve
KASTON'S Warranty on LBO Specifications
Transmitting wavefront distortion
less than l/8 @ 633nm
Dimension tolerance
(W± 0.1 mm) x (H± 0.1 mm) x (L + 0.2 mm/-0.1 mm)
Clear aperture
central 80% diameter
No visible scattering paths or centers when inspected by a 30 mW green laser
Flatness
l/8 @ 633nm
Surface Quality
10/5 Scratch/Dig to MIL-O-13830A
Parallelism
better than 20 arc seconds
Perpendicularity
15 arc minutes
Angle tolerance
Dq < ±0.5o, Df <± 0.5o
Damage threshokd:
15 GW/cm2 for a TEMoo mode, 1.3 ns, 1 Hz laser at 1.064 mm
1 GW/cm2 for a cw, mode-locked laser at 1.064 mm
Quality warranty period
one year under proper use
NOTE
1.
LBO has a very low susceptibility to moisture. Users are advised to provide dry conditions for both use and preservation of LBO.
2.
Users are advised to cautiously protect polished surfaces of LBO.
3.
KASTON engineers can select and design the best crystal for you if parameters of your laser are provided, for example, energy per pulse, pulse width and repetition rate for a pulsed laser, power for a cw laser, laser beam diameter, mode condition, divergence, wavelength tuning range, etc.
4.
KASTON provides mounts and sealed housing for LBO crystals.
