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LBO Crystals

LBO Crystals
LBO Crystals LBO Crystals LBO Crystals

LBO crystal is one of the most versatile nonlinear optical crystamaterials available. It has a very broad transmission range from vacuum UV to mid infrared, a very high damage threshold (actually the highest among the common nonlinear crystals) and is capable of noncritical phase matching (NCPM) in the near IR region, making it the material of choice for high power, high efficiency second harmonic generation (SHG) and optical parametric processes (OPO/OPA).  Newlight Photonics keeps a large stock of LBO crystals which can be delivered within one week upon receipt of the purchase order.

LBO products on this page are thick crystals (>= 3 mm) for applications with picosecond (ps), nanosecond (ns), or long pulse/CW  lasers.
 
For thin LBO products (Thickness < 3mm) developed for frequency conversions of ultrafast femtosecond (fs) lasers, please go to thin LBO crystals.


Crystals for NCPM at an elavated temperature can be premounted in an oven with precision controller. Crystals used at ~ 20 - 50 oC can also be premounted in a compatible water-cooled or TEC (ThermoElectric Cooler) cooled mount upon request.

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Newlight's LBO features:
 

 WB01158_1.GIF (255 bytes) Very broad transparency range from 160nm to 2600 nm
 WB01158_1.GIF (255 bytes) High optical homogeneity (δn ~ 10-6 /cm) and  free of defects
 WB01158_1.GIF (255 bytes) Moderate effective SHG coefficient (about three times that of KDP)
 WB01158_1.GIF (255 bytes) High damage threshold (18.9 GW/cm2 for a 1.3 ns Nd laser)
 WB01158_1.GIF (255 bytes) Wide acceptance angle and small angular walkoff
 WB01158_1.GIF (255 bytes) Both Type I and II NCPM in a wide wavelength range is possible.
 WB01158_1.GIF (255 bytes) Spectral NCPM near 1300 nm

 

 

 

 

 



Structural and Physical Properties:
 

Crystal Structure Orthorhombic, Space group Pna21, Point group mm2
Cell Parameters a=8.4473 Å, b=7.3788 Å, c=5.1395 Å, Z=2
Melting Point ~834 °C
Mohs Hardness 6
Density  2.47 g/cm3
Hygroscopic Susceptibility Low
Thermal Expansion Coefficients αx=10.8x10-5/K,αy= -8.8x10-5/K,αz=3.4x10-5/K
Thermal Conductivity 3.5 W/M/K


Linear Optical Properties:
 

Transparency Range 160 - 2600 nm
Thermo-optic Coefficient
(1/°C, λ in µm)
dnx/dT = (-3.76λ+2.30) x 10-6
dny/dT = (6.01λ-19.40) x 10-6
dnz/dT = (1.50λ-9.70) x 10-6
Optical Homogeneity δn ~10-6 /cm
Bulk Absorption Coefficient < 100 ppm/cm at 1064 nm,  < 150 ppm/cm at 532 nm
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+2.00x10-4λ4
nz2=2.586179+0.013099/(λ2-0.011893)-0.017968λ2-2.26x10-4λ4
Refractive Indices:
              @ 1064 nm
              @ 532 nm
              @ 266 nm

nx = 1.5656, ny = 1.5905, nz=1.6055
nx = 1.5785, ny = 1.6065, nz=1.6212
nx = 1.5973, ny = 1.6286, nz=1.6444


Nonlinear Optical Properties:
 

SHG Phase Matchable Range 551 ~ 2600 nm  (Type I); 790-2150 nm (Type II)
NLO Coefficients d31=1.05 ± 0.09 pm/V
d32= -0.98 ± 0.09 pm/V
d33=0.05 ± 0.006 pm/V
Effective Nonlinearity Coefficients dooe=d32cosφ(in XY plane)
deeo=d31cos2θ+d32sin2θ (in XZ plane)
doeo=d31cosθ(in YZ plane)
deoe=d31cos2θ+d32sin2θ (in XZ plane)
Damage Threshold (Bulk)
@ 1064 nm
@ 532 nm

9 GW/cm2 (9 ns); 19 GW/cm2 (1.3 ns)
2.2 GW/cm2 (10 ns); 45 GW/cm2 (100 ps)
NCPM Temperature 148 oC for SHG @ 1064 nm,  
162 oC for SHG @ 1053 nm
172 oC for SHG @ 1047 nm


Damage Threshold:

LBO has a very large bulk damage threshold and is the crystal of choice for high power second and third harmonic generations of Nd:YAG, Nd:YLF, and Nd:YVO4  lasers,


Comparison of bulk damage threshold (@1064 nm, 1.3 ns):

Crystal Energy Fluence (J/cm2) Power Density (GW/cm2)
KTP 6.0 4.6
KDP 10.9 8.4
BBO 12.9 9.9
LBO 24.6 18.9



Application Examples:
 

 WB01158_1.GIF (255 bytes) SHG, SFG for a broad range of wavelength:  phase matching cutoff wavelength:
   SHG-554 nm, THG-794 nm, SFM-down to 160 nm
 WB01158_1.GIF (255 bytes) SHG and THG for middle and high power Nd: lasers at 1064 nm for medical, industrial and military applications
 WB01158_1.GIF (255 bytes) SHG for Ti:Sapphire, Alexandrite and Cr:LiSAF lasers
 WB01158_1.GIF (255 bytes) SHG and THG of high power Nd: lasers at 1342 nm & 1319 nm for red and blue laser
 WB01158_1.GIF (255 bytes) SHG for the Nd: Lasers at 914 nm & 946 nm for blue laser.
 WB01158_1.GIF (255 bytes) The VUV output at 187.7 nm is obtained by sum-frequency generation.
 WB01158_1.GIF (255 bytes) NCPM SHG over a broad wavelength range from 900 -1700 nm was measured.
 WB01158_1.GIF (255 bytes) Optical Parametric Amplifiers (OPA) and Oscillators (OPO) application.

 

SHG and THG at Room Temperature:


LBO is phase matchable for the SHG and THG of Nd:YAG and Nd:YLF lasers, using either type I or type II interaction. For the SHG at room temperature, type I phase matching can be reached and has the maximum effective SHG coefficient in the principal XY and XZ planes in a wide wavelength range from 551 nm to about 3000 nm. LBO is the first choice for making doubler or tripler for lasers such as Nd:YAG where high power density, high stability, and long time operation are required. 
 

SHG tuning curves of LBO 

NCPM temperature tuning curves of LBO 

 

 More than 480 mW output at 395 nm is generated by frequency doubling a 2 W mode-locked Ti:Sapphire laser (< 2 ps, 82 MHz). The wavelength range of 700-900 nm is covered by a 5x3x8 mm LBO crystal.

WB01158_1.GIF (255 bytes) Over 80 W green output is obtained by SHG of a Q-switched Nd:YAG laser in a Type II phase matching 18 mm long LBO crystal.
WB01158_1.GIF (255 bytes) The frequency doubling of a diode pumped Nd:YLF laser (>500 mJ @ 1047 nm, < 7 ns,1-10 KHz) reaches a conversion efficiency over 40% in a 9mm long LBO crystal.
WB01158_1.GIF (255 bytes) The VUV output at 187.7 nm is obtained by sum-frequency generation in LBO.
WB01158_1.GIF (255 bytes) 2 mJ/pulse diffraction-limited beam at 355 nm is obtained by intracavity frequency tripling a Q-switched Nd:YAG laser.


Non-Critical Phase-Matching at an Elevated Temperature:
 

 WB01158_1.GIF (255 bytes) Non-Critical Phase-Matching (NCPM) of LBO is featured by zero walk -off, very wide
 acceptance angle and maximized effective coefficient. Type I NCPM and Type II NCPM are along x-axis (θ=90°, φ=0°) and z-axis (θ=0°, φ=0°), respectively.

 WB01158_1.GIF (255 bytes) Over 11 W of average power at 532 nm was obtained by extracavity SHG of a 25 W Antares mode-locked Nd:YAG laser (76 MHz, 80 ps).

 WB01158_1.GIF (255 bytes) 20 W green output was generated by frequency doubling a multimode Q-switched medical Nd:YAG laser.


LBO can reach both temperature NCPM and spectral NCPM (with a very wide spectral bandwidth) at 1300 nm. This is favorable for the SHG of very broadband or ultrafast pulses at ~ 1300 nm.   


Properties for type I NCPM SHG at 1064 nm:
 

NCPM Temperature 14 8°C
Acceptance Angle 52  mrad-cm1/2
Walk-off Angle 0
Temperature Bandwidth 4 °C-cm
Effective SHG Coefficient 2.69 x d36(KDP)



OPO and OPA with LBO:

LBO is an excellent NLO crystal for OPOs and OPAs with a widely tunable wavelength range and high powers. 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.
 

 

 WB01158_1.GIF (255 bytes) A high overall conversion efficiency and 540-1030 nm tunable wavelength range were obtained with OPO pumped at 355 nm.
 WB01158_1.GIF (255 bytes) Type I OPA pumped at 355 nm with the pump-to-signal energy conversion efficiency of 30% has been reported.
 WB01158_1.GIF (255 bytes) 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.
 WB01158_1.GIF (255 bytes) By using the NCPM technique, type I OPA pumped by the SHG of a Nd:YAG laser at 532 nm was also observed to cover a wide tunable range from 750 nm to 1800 nm by temperature tuning from 106.5 °C to 148.5 °C.
 WB01158_1.GIF (255 bytes) Using type II NCPM LBO as an optical parametric generator (OPG) and type I critical phase matched BBO as an OPA, a narrow linewidth (0.15 nm) and high pump-to-signal energy conversion efficiency (32.7%) were obtained, when pumped by a 4.8 mJ, 30 ps laser at 354.7 nm. Wavelength tuning range from 482.6 nm to 415.9 nm was covered by increasing the temperature of LBO and rotating BBO.
 


LBO Specifications:
 

Wavefront Distortion < λ/8 @ 633 nm
Dimension Tolerance (W+/-0.1 mm) x (H+/-0.1 mm) x (L+0.2/-0.1 mm)
 * (L+0.5/-0.1 mm) for large crystals.
Clear Aperture > 90% central area
Flatness λ/8 @ 633 nm
Surface Quality Scratch/Dig 10/5 per MIL-O-13830A
Parallelism better than 20 arc seconds
Perpendicularity 5 arc minutes
Angle Tolerance Δθ < +/-0.25o, Δφ < +/-0.25o


Coatings:

The following coatings on LBO surfaces are available upon request:

(1) Multi-layer dielectric single-band, dual-band or broad-band AR coatings


 Coating curves (typical):

AR1064/532 nm, AR1064/532/355 nm, AR976/473 nm, AR1550/775 nm,
 Broad band AR for OPO/A

(2) Single-layer protective coatings (P-coating)

    Coating curves: P-coating @ 400 nm 



Brewster ends:

LBO crystals with one end or both ends cut at the Brewster angle and uncoated are available. Such crystals are often used to minimize the surface loss without reduction of the damage threshold by an AR coating for high power applications. 



Mounts:

For customer convenience and protection of crystals, standard 1" anodized aluminum (Al) mounts can be offered upon request. The mounted crystals may be further mounted in a conventional  1" mirror mount to be angle tuned for phase matching (as shown to the right, mirror mounts and posts are not included). For laser powers > 1 W, the standard aluminum mounts are not suitable due to the temperature increase of the crystal and the consequent output instability. Water-cooled mounts for high power application are available upon request. 


Oven and temperature controller:

We provide precision oven and temperature controller to maintain LBO crystals at a preset temperature for noncritical phasematching (NCPM) for SHG and OPO/OPA. Crystals may be pre-installed into the oven free of charge in our factory for your convenience.

Learn more about oven and controller
 

Cleaning the Crystals:
 

Dust and stains on crystal surfaces can cause scattering/loss of light and can even react with light to damage optical surfaces at a high incident laser power.

You can inspect the crystal surface for dust and stains by holding it near a bright visible-light source. Viewing at different angles helps to see scattering from dust and stains. The crystal surface has to be cleaned if dust and stains are found.

You should perform the following cleaning procedures in a clean, low-dust environment while wearing powder-free gloves or finger cots.

1. Blowing off the crystal surface

A canister of compressed N2/clean air or a blower bulb (http://www.adorama.com/GTRABS.html ) should be first used to blow off dust and other loose contaminants. If a dry nitrogen line is available in the lab, an air gun can also be used  to blow away dust particles. Blow off the surface gently. Do not blow off the crystal itself from your hand !

2. Drop and Drag Method

Hold the crystal so that the crystal surface is horizontal and slightly above your fingers. Take a fresh, clean sheet of lens tissue and place it on the crystal.  Make sure the lens tissue can be drawn across the crystal surface. Next place a small drop of pure isopropyl alcohol (IPA) on the lens tissue on top of the crystal surface. The weight of the solvent will cause the lens tissue to come into contact with the crystal surface. Slowly but steadily drag the damp lens tissue across the crystal surface being careful not to lift the lens tissue off of the surface. Continue dragging the lens tissue until it is off of the surface.

The amount of the solvent can be adjusted for various crystal size so the lens tissue is kept damp for the entire drag but there is not any visible trace of solvent on the crystal surface after the drag is finished. Inspect the surface and repeat if necessary, but only use each sheet of lens tissue once.

If the crystal surfaces are still “dirty” after the above cleaning procedures, the surfaces might have been damaged. Please contact us for rework of the crystals.

 

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