Description
Two-micron Tm3+ lasers are of interest for many applications in the scientific, defence, and medical fields. Thulium readily substitutes into many crystal hosts that are suitable for high-average-power laser systems and it has an absorption band at ~0.8 μm allowing excitation with commercially available high power laser diodes. Thulium doped yttrium fluoride lithium crystals have low nonlinear refractive index and thermo optic constant , which are very suitable for the application in the fields of scientific research, production, education and other optoelectronic fields. The crystal is a negative uniaxial crystal with a negative refractive index temperature coefficient, which can offset some thermal distortion and thus has high beam quality output. The pump wavelength is 792 nm, and the linear polarized laser with wavelength of 1.9 mm outputs at in the direction of a axis. outputting light from c axis is non-linear polarized. High power laser output can be obtained by selecting proper crystal size and doping concentration.
Physical and Chemical Properties
| Crystal Structure | Tetragonal |
| Lattice Constants | a=5.16Å; c=10.85Å |
| Density | 3.99 g/cm³ |
| Melting Point | 819℃ |
| Thermal Conductivity | 6 Wm-1K-1 |
| Thermal Optical Coefficient(dn/dT) | π = 4.3 x 10-6 x °K-1; σ = 2.0 x 10-6 x °K-1 |
| Thermal Expansion /（10-6·K-1@25°C ） | 10.1×10-6 (//c) K-1, 14.3×10-6((//a) K-1 |
| Hardness (Mohs) | 5 |
| Shear Modulus /Gpa | 85 |
| Specific Heat | 0.79 J/gK |
| Poisson Ratio | 0.3 |
Optical and Spectral Properties
| Laser Transition | 3F4→3H6 |
| Laser Wavelength | π:1880 nm; σ:1908 nm |
| Absorption Cross-section at Peak | 0.55×10-20 cm2 |
| Absorption Bandwidth at Peak Wavelength | 16 nm |
| Absorption Peak Wavelength | 792 nm |
| Lifetime of 3F4 Thulium Energy Level | 16 ms |
| Quantum Efficiency | 2 |
| Non-linear Index n2 | 0.6 x 10-13 |
| Optical Quality | < 0.3 x 10-5 |
| Refractive Index @1064 nm | no=1.448, ne=1.470 |
| Laser Induced Damage Threshold | >10 J/cm2@1900 nm, 10 ns |
| Coatings | R<0,5% @792 nm + R<0,15% @1800-1960 nm on both sides; custom coatings also available |
Absorption and Emission Spectrum
Material and Specifications
| Concentration Tolerance (atm%) | 2-4 at.% |
| Lattice Constants | 4~5 |
| Orientation | a-cut, other orientations also available |
| Parallelism | <10” |
| Perpendicularity | <5” |
| Surface Quality | 10-5 scratch & dig |
| Wavefront Distortion | λ/8 @ 633nm |
| Surface Flatness | λ/10 @ 633nm |
| Clear Aperture | 95% |
| Length Tolerance | ±0.1 mm |
| Face Dimensions Tolerance | +0/-0,1 mm |
| Protective Chamfers | <0,1 mm at 45˚ |
| Damage Threshold | over 15J/cm2 TEM00, 10ns, 10Hz |
Low nonlinear refractive index
Low thermo-optical constant
Low polarization loss
Long upper energy level fluorescence lifetime
Small up-conversion effect
No absorption loss of sensitized ions
Medical diagnosis and treatment
Laser radar
Laser ranging
Electro-optical countermeasure
Laser remote sensing
Laser imaging
Optical signal processing
Material processing