Thulium-doped yttrium lithium fluoride (Tm:YLF) crystal is an important mid-infrared laser material. It can reduce some thermal aberrations and provide high-quality light since it is a negative uniaxial crystal with a negative thermal refractive index coefficient. This conveniently pumps at 792 nm, outputting a 1.9 μm linearly polarized beam in the a-axis and a nonlinearly polarized beam in the c-axis. Alfa Chemistry is an expert in customizing laser crystals, and we will carefully and patiently walk our customers through the Tm:YLF laser crystal modification process online. We use the Czochralski technique to grow Tm:YLF laser crystals.
Advantages of Tm:YLF Crystals
Tm3+ is a common 2 μm active ion with the advantages of long fluorescence lifetime and high quantum efficiency. Tm:YLF crystal, a naturally birefringent crystal with linearly polarized output, has been used to achieve CW laser output powers up to 87.5 W at 1907.8 nm. Tm:YLF crystals are excellent for study in photonics, optics, laser technology, and telecommunications because they exhibit low nonlinear refractive index values and low thermo-optical constants.
Fig 1. σ-polarized Tm:YLF emission and absorption cross-sections, and Ho:YAG absorption cross-section. (So S, et al. 2006)
Ho:YAG laser's optimal pump source is the Tm:YLF laser. This is because the Ho:YAG absorption and Tm:YLF emission spectra have a strong overlap, and because linearly polarized outputs are possible. More significantly, as temperature rises, the refractive index of Tm:YLF crystals falls.
Advantages:
- Low polarization loss
- Long upper-level fluorescence lifetime
- Up-conversion effect is small
- No absorption loss of sensitizing ions
- Linearly polarized output beam
- Efficient cross relaxation of Tm3+
- LD pumping efficiency
Properties of Tm:YLF Crystals
| Optical and Physical Properties | |
|---|---|
| Crystal Structure | Tetragonal |
| Typical Doping Level | 2~4% |
| Density | 3.99 g/cm3 |
| Melting Point | 819 ℃ |
| Mohs Hardness | 5 |
| Thermal Conductivity | 6 W·m-1·K-1 |
| Thermal Expansion Coefficients | (@25°C) 10.1×10-6 (//c) K-1, 14.3×10-6 (//a) K-1 |
| Refractive Index | (@1064 nm) no=1.448, ne=1.470 |
| dn/dT | 4.3×10-6 (||c) K-1, 2.0×10-6 (||a) K-1 |
| Specific Heat | 0.79 J/gK |
| Poisson Ratio | 0.3 |
| Absorption Peak Wavelength | 792 nm |
| Emission Cross Section | 0.4×10-20 cm2 |
| Absorption Bandwidth at Peak Wavelength | 16 nm |
| Absorption Cross Section at Peak | 0.55×10-20 cm2 |
| Laser Wavelength | 1900 nm |
| Alfa Chemistry offers Tm:YLF specification | |
| Dimension | Upon customer request |
| Dimension Tolerance | Diameter +0.0/-0.05 mm, Length ±0.1mm |
| Doping(atm%) | 2% ~ 12% |
| Orientation | a-cut / c-cut crystalline direction |
| Flatness | λ/10 @ 632.8nm |
| Surface Quality | 10/5 Scratch/Dig MIL-O-1380A |
| Clear Aperture | > 90% |
| Damage Threshold | 750MW/cm2 at 1064nm, TEM00, 10ns, 10Hz |
| Coating | AR/HR/PR coating upon customer's request |
| Quality Warranty Period | One year under proper use |
Why Choose Alfa Chemistry?
Alfa Chemistry grows Tm:YLF crystals using the CZ growth method. To guarantee that every crystal satisfies customer requirements and works effectively, we use high-quality starting materials for crystal growth, bulk ingot interferometry, accurate inspection of scattered particles in crystals using He-Ne lasers, and precise volume loss measurement using spectrophotometers.
If you need technical advice, please contact our technical team to learn more about our high-quality services.
Reference
- So S, et al. (2006). "Intra-Cavity Side-Pumped Ho:YAG Laser." Optics Express. 14(22): 10481-10487.