KTP crystal is the most commonly used for SHG (Frequency doubling) of Nd-doped laser for green/red output. It is widely used in both commercial and military lasers including laboratory and medical systems, rang-finders, lidar, optical communication and industrial systems.
Advantages
Large nonlinear optical coefficient
High electro-optic coefficient and low dielectric constant
High thermal conductivity
Moisture free,chemically and mechanically stable
Large figure of merit
Chemical and Structural Properties
| Orthorhombic, Space group Pna21, Point group mm2 |
| a=6.404Å, b=10.616Å, c=12.814Å, Z=8 |
| 1172ºC incongruent |
| ~5 |
| 3.01g/cm3 |
| 0.13W/cm/K |
| αx=11x10-6/K, αy=9x10-6/K, αz=0.6x10-6/K |
Optical and nonlinear optical properties
| Transparency Range | 350-4500nm |
| SHG Phase Matchabel Range | 497~1800nm (TypeII) |
| Therm-optic Coefficients(/ºC) | dnx/dT=-1.1x10-5,dny/dT=-1.3x10-5,dnz/dT=1.6x10-5 |
| Absorption Coefficients | <0.1%/cm at 1064nm, <1%/cm at 532nm |
For Type II SHG of a Nd:YAG Laser at 1064nm | Temperature Acceptance:24ºC-cm Spectral Acceptance:0.56nm-cm Angular Acceptance:14.2mrad-cm(φ）;55.3mrad-cm(θ) Walk-off Angle:0.55° |
| NLO Coefficients | deff(II)≈(d24-d15)sin2 φsin2θ-(d15sin2φ+d24cos2 φ)sinθ |
Non-vanished NLO Susceptibilities | d31=6.5pm/V, d24=-7.6pm/V, d32=5pm/V d15=6.1pm/V, d33=13.7pm/V |
Sellmeier Equations(λ in μm) | nx2=3.0065+0.03901/(λ2-0.04251)-0.01327λ2 ny2=3.0333+0.04154/(λ2-0.04547)-0.01408λ2 nz2=3.3134+0.05694/(λ2-0.05658)-0.01682λ2 |
Specifications of KTP Slabs
| Dimension Tolerance | WxH:±0.1mm, L≤2.5mm:±0.1mm, L>2.5mm:+0.5/-0.1mm |
| Flatness | <λ/10@632.8nm |
| Wavefront Distortion | <λ/8@632.8nm |
| Surface Quality | 10/5 S/D |
| Paralellism | ≤10'' |
| Perpendicularity | ≤5' |
| Angle Tolerance | ≤0.25° |
| Damage Threshold | >500MW/cm ² for 1064nm, >300MW/cm ² for 532nm |
KDP and KD*P are among the most widely-used commercial NLO materials, characterized by good UV transmission, high damage threshold, and high birefringence. They are usually used for doubling, tripling and quadrupling of a Nd:YAG laser at the room temperature. In addition, they are also excellent electro-optic crystals with high electro-optic coefficients, widely used as electro-optical modulators, such as Q-switches, Pockels Cells, etc.
Applications
Second,third,and fourth harmonic generation of Nd:lasers
Frequency doubling of dyer laser
High power laser frequency conversion materials
Shutter for high speed photography
Electro-optical modulator and Q switches
| Basic Properties | KDP | KD*P |
| Chemical Formula | KH2PO4 | KD2PO4 |
| Transparency Range | 200-1500nm | 200-1600nm |
| NLO Coefficients | d36=0.44pm/V | d36=0.40pm/V |
| Refractive Index (at 1064nm) | no=1.4938, ne=1.4599 | no=1.4938, ne=1.4599 |
| Electro-optical Coefficients | r41=0.88pm/V, r63=10.3pm/V | r41=8.8pm/V, r63=25pm/V |
| Longgitudinal Half-wave Voltage | Vπ=7.65KV (λ=546nm) | Vπ=2.98KV (λ=546nm) |
| Absorptance | 0.07/cm | 0.006/cm |
| Optical Damage Threshold | >5 GW/cm2 | >3 GW/cm2 |
| Extinction Ratio: | 30 dB | |
| Sellmeier Equations of KDP (λ in μm) | ||
| n02=2.259276+0.01008956/(λ2-0.012942625)+13.00522λ2/(λ2-400) | ||
| ne2=2.132668+0.008637494/(λ2-0.012281043)+3.2279924λ2/(λ2-400) | ||
| Sellmeier Equations of KD*P (λ in μm) | ||
| n02=1.9575544+0.2901391λ2/(λ2-0.0281399)-0.02824391λ2+0.004977826λ4 | ||
| n02=1.5005779+0.6276034λ2/(λ2-0.0131558)-0.01054063λ2+0.002243821λ4 | ||
Specifications of KDP & KD*P slabs
| Dimension Tolerance | WxH:±0.1mm, L≤2.5mm:±0.1mm, L>2.5mm:+0.5/-0.1mm |
| Flatness | <λ/10@632.8nm |
| Wavefront Distortion | <λ/8@632.8nm |
| Surface Quality | 10/5 S/D |
| Paralellism | ≤10'' |
| Perpendicularity | ≤5' |
| Angle Tolerance | ≤0.25° |
BBO crystal combines very wide transparency, moderately high nonlinear coupling, high damage threshold and good chemical and mechanical properties. BBO phase match covers a wide range, yielding SHG from 190nm to 1780nm.
Advantages
Broad phase-matching range from 409.6nm to 3500nm
Wide transmission region from 190nm to 3500nm
Large effective second-harmonic-generation(SHG) coefficient
High damage threshold
High optical homogeneity with dn≈10-6/cm
Wide temperature-bandwidth of about 55℃
Chemical and Structural Properties
| Crystal structure | Trigonal, Space group R3c |
| Lattice Parameters | a=b=12.532Å, c=12.717Å, c=12.814Å, Z=6 |
| Melting point: | About 1095ºC |
| Mohs hasrdess | 4 |
| Density | 3.85g/cm3 |
| Thermal Conductivity | 1.2W/cm/K(⊥c), 1.6W/m/K(∥c) |
| Electrical Expansion Coefficients | α11=4x10-6/K, α33=36x10-6/K |
Optical and Nonlinear Optical Properties
| Transparency Range | 190-3500nm |
| SHG Phase Matchabel Range | 409.6-3500nm (Type I), 525-3500nm (Type I) |
| Therm-optic Coefficients (/ºC) | dno/dT=-16.6x10-6, dne/dT=-9.3x10-6 |
| Absorption Coefficient | <0.1%/cm at 1064nm, <1%/cm at 532nm |
Angel Acceptance | 0.8mrad-cm (θ,Type I,1064 SHG) 1.27mrad-cm (θ,Type II,1064 SHG) |
| Temperature Acceptance | 55ºC-cm |
| Spectral Acceptance | 1.1nm-cm |
| Walk-off Angle | 2.7°(Type I,1064 SHG), 3.2°(Type II,1064 SHG) |
NLO Coefficients | deff(I)=d31sinθ+(d11cos3Φ-d22sin3Φ)cosθ deff(II)=(d11sin3Φ+d22cos3Φ)cos2θ |
| Non-vanished NLO Susceptibilities | d11=5.8xd36(KDP), d31=0.05xd11, d22<0.05xd11 |
| Sellmeier Equations (λ in μm) | no2=2.7359+0.01878/(λ2-0.01822)-0.01354λ2 ne2=2.3753+0.01224/(λ2-0.01667)-0.011516λ2 |
| Electro-optic Coefficients | γ22=2.7pm/V |
Specifications of BBO slabs
| Dimension Tolerance | WxH:±0.1mm, L≤2.5mm:±0.1mm, L>2.5mm:+0.5/-0.1mm |
| Flatness | <λ/10@632.8nm |
| Wavefront Distortion | <λ/8@632.8nm |
| Surface Quality | 10/5 S/D |
| Paralellism | ≤10'' |
| Perpendicularity | ≤5' |
| Angle Tolerance | ≤0.25° |
| Damage Threshold | >500MW/cm ² for 1064nm, >300MW/cm ² for 532nm |
LBO crystal is an excellent nonlinear optical crystal. For frequency doubling (SHG), tripling (THG) of Nd:YAG,, Nd:YLF, Nd:YVO4 lasers, it is one of the most useful nonlinear optical materials in ultraviolet and visible laser applications.
Advantages
Broad transparency range from 160nm to 2600nm(SHG rangefrom 550nm to 2600nm)
Relatively large effective SHG coefficient(about three times that of KDP)
High damage threshold(18.9GW/cm2 for a 1.3ns laser at 1064nm)
TypeⅠand type Ⅱ non-critical phase-matching(NCPM) over a wide wavelength range
Spectral NCPM near 1300nm
Chemical and Structural 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 834ºC |
| Mohs hasrdess | 6 |
| Density | 2.47g/cm3 |
| Thermal Conductivity | 3.5W/m/K |
| Thermal Expansion Coefficient | αx=10.8x10-5/K, αy=8.8x10-5/K, αz=3.4x10-5/K |
Optical and Nonlinear Optical Properties
| Transparency Range | 160-2600nm |
| SHG Phase Matchabel Range | 551~2600nm (Type I), 790~2150nm(Type II) |
| Therm-optic Coefficient(ºC) | 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 |
Angel Acceptance | 6.54mrad-cm (Φ,Type I,1064 SHG) |
| 15.27mrad-cm (θ,Type II,1064 SHG) | |
| Temperature Acceptance | 4.7ºC-cm(Type I,1064SHG), 7.5ºC-cm(Type II,1064 SHG) |
| Spectral Acceptance | 1.0nm-cm(Type I,1064SHG), 1.3nm-cm(Type II,1064 SHG) |
| Walk-off Angle | 0.6°(Type I,1064 SHG), 1.2°(Type II,1064 SHG) |
NLO Coefficients | deff(I)=d32cosΦ (Type I in XY plane) |
| deff(I)=d31cos2 θ+d32sin2θ (Type I in XZ plane) | |
| deff(II)=d31cos θ (Type II in YZ plane) | |
| deff(II)=d31cos2θ+d32sin2θ (Type II in XZ plane) | |
| Non-vanished NLO | d31=1.05±0.09pm/V,d32=-0.98±0.09pm/V,d33=0.05±0.006pm/V |
| Susceptibilities | |
| Sellmeier Equations (λ in μm) | nx2=2.454140+0.011249/(λ2-0.011350)-0.014591 λ2-6.60x10-5λ4 |
| ny2=2.539070+0.012711/(λ2-0.012523)-0.018540 λ2-2.0x10-4λ4 | |
| nz2=2.586179+0.013099/(λ2-0.011893)-0.017968 λ2-2.26x10-4λ4 |
Specifications of LBO slabs
| Dimension Tolerance | WxH:±0.1mm, L≤2.5mm:±0.1mm, L>2.5mm:+0.5/-0.1mm |
| Flatness | <λ/10@632.8nm |
| Wavefront Distortion | <λ/8@632.8nm |
| Surface Quality | 10/5 S/D |
| Paralellism | ≤10'' |
| Perpendicularity | ≤5' |
| Angle Tolerance | ≤0.25° |
| Damage Threshold | >500MW/cm ² for 1064nm, >300MW/cm ² for 532nm |
