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LBO

Related link: LBO Crystal Components     

 

LBO Crystal Basic Properties

 

LBO Crystal Physical Properties

 Crystal Structure

 Orthorhombic, Space group Pna21, Point group mm2

 Lattice Parameter

 a=8.4473Å, b=7.3788Å , c=5.1395Å , Z=2

 Melting Point

 About 834

 Mohs Hardness

 6

 Density

 2.47 g/cm3

 Thermal Conductivity

 3.5W/m/K

 Thermal Expansion Coefficient

 ax=10.8x10-5/K, ay= -8.8x10-5/K, az=3.4x10-5/K

 

LBO Optical and Nonlinear Optical Properties

 Transparency Range

 160-2600nm

 SHG Phase Matchable Range

 551 ~ 2600nm (Type I),
 790-2150nm (Type II)

 Therm-optic Coefficient (°C, λ in μm)

 dnx/dT=-9.3X10-6,
 dny/dT=-13.6X10-6 ,
 dnz/dT=(-6.3-2.1λ)X10-6

 Absorption Coefficient

 <0.1%/cm at 1064nm,
 <0.3%/cm at 532nm

 Angle Acceptance

 6.54mrad/cm (φ, Type I,1064 SHG),
 15.27mrad/cm (q, Type II,1064 SHG)

 Temperature Acceptance

 4.7°C/cm (Type I, 1064 SHG),
 7.5°C/cm (Type II,1064 SHG)

 Spectral Acceptance

 1.0nm/cm (Type I, 1064 SHG),
 1.3nm/cm (Type II,1064 SHG)

 Walk-off Angle

 0.60° (Type I 1064 SHG),
 0.12° (Type II 1064 SHG)

 NLO Coefficients

 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

 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=2.454140+0.011249/(λ2-0.011350)-0.014591λ2-6.60x10-5λ4,
 ny2=2.539070+0.012711/(λ2-0.012523)-0.018540λ2+2.0x10-4λ4,
 nz2=2.586179+0.013099/(λ2-0.011893)-0.017968λ2-2.26x10-4λ4

 

LBO's Harmonic Generation Applications:

 

SHG conversion efficiencies of more than 70% for pulse and 30% for cw Nd:YAG lasers, and THG conversion efficiency over 60% for pulse Nd:YAG laser have been observed by using high quality LBO crystal.

More than 480mW output at 395nm is generated by frequency doubling a 2W mode-locked Ti:Sapphire laser (<2ps, 82MHz). The wavelength range of 700-900nm is covered by a 5x3x8mm3 LBO crystal.

Over 80W green output is obtained by SHG of a Q-switched Nd:YAG laser in a type II 18mm long LBO crystal.

The frequency doubling of a diode pumped Nd:YLF laser (>500µJ @ 1047nm, <7ns, 0-10KHz) reaches over 40% conversion efficiency in a 9mm long LBO crystal.

The VUV output at 187.7 nm is obtained by sum-frequency generation.

2mJ/pulse diffraction-limited beam at 355nm is obtained by intra-cavity frequency tripling a Q-switched Nd:YAG laser.

 

LBO's Non-Critical Phase-Matching

 

Table 3. Properties of type I NCPM SHG at 1064nm

 NCPM Temperature

 148°C

 Acceptance Angle

 52 mrad-cm1/2

 Walk-off Angle

 0

 Temperature Bandwidth

 4°C-cm

 Effective SHG Coefficient

 2.69 d36(KDP)Bottom of Form

 

AS shown in table 3, 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. 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 non-critical phase-matching can be reached along x-axis and z-axis at room temperature, respectively.(The assembly of oven and temperature controller is recommended for NCPM applications).

By using LBO crystal,over 11W of average power at 532nm was obtained by extra-cavity SHG of a 25W Antares mode-locked Nd:YAG laser (76MHz, 80ps).

By using LBO crystal,20W green output was generated by frequency doubling a medical, multi-mode Q-switched Nd:YAG laser. Much higher green output is expected with higher input.


LBO’s OPO and OPA

 

LBO is an excellent NLO crystal for OPOs and OPAs with a widely tunable wavelength range and high powers. These OPO and OPA that are pumped by the SHG and THG of Nd:YAG laser and XeCl excimer laser at 308nm have been reported. The unique properties of type I and type II phase matching as well as the NCPM leave a big room in the research and applications of LBO’s OPO and OPA. Fig.4 shows the calculated type I OPO tuning curves of LBO pumped by the SHG, THG and 4HG of Nd:YAG laser in XY plane at the room temperature. And Fig. 5 illustrates type II OPO tuning curves of LBO pumped by the SHG and THG of Nd:YAG laser in XZ plane.

 

A quite high overall conversion efficiency and 540-1030nm tunable wavelength range were obtained with OPO pumped at 355nm.

Type I OPA pumped at 355nm with the pump-to-signal energy conversion efficiency of 30% has been reported.

Type II NCPM OPO pumped by a XeCl excimer laser at 308nm has achieved 16.5% conversion efficiency, and moderate tunable wavelength ranges can be obtained with different pumping sources and temperature tuning.

By using the NCPM technique, type I OPA pumped by the SHG of a Nd:YAG laser at 532nm was also observed to cover a wide tunable range from 750nm to 1800nm by temperature tuning from 106.5°C to 148.5°C.

By using type II NCPM LBO as an optical parametric generator (OPG) and type I critical phase-matched BBO as an OPA, a narrow linewidth (0.15nm) and high pump-to-signal energy conversion efficiency (32.7%) were obtained when it is pumped by a 4.8mJ, 30ps laser at 354.7nm. Wavelength tuning range from 482.6nm to 415.9nm was covered by increasing the temperature of LBO or rotating BBO.

 

LBO’s Spectral NCPM

 

Not only the ordinary non-critical phase matching (NCPM) for angular variation but also the noncritical phase matching for spectral variation (SNCPM) can be achieved in the LBO crystal. As shown in Fig.2, the phase matching retracing positions are λ1=1.31μm with θ =86.4°, φ=0° for Type I and λ2=1.30μm with θ=4.8°, φ=0° for Type II. The phase matching at these positions possess very large spectral acceptances Δλ. The calculated Δλ at λ1 and λ2are 57nm-cm-1/2 and 74nm-cm-1/2 respectively, which are much larger than the other NLO crystals. These spectral characteristics are very suitable for doubling broadband coherent radiations near 1.3μm, such as those from some diode lasers, and some OPA/OPO output without linewidth-narrowing components.

The crystal holder(free) and oven & Temperature Controller (for NCPM,OPO,OPA applications) are available for BBO & LBO.