03 Jul 2020 Description
Ho:YLF is a very attractive laser material, because the lifetime of the upper laser level is much longer ( ~ 14 ms) than in Ho:YAG and the emission cross sections are higher. Additionally the thermal lens in Ho:YLF is much weaker, which helps to generate diffraction limited beams even under intense end-pumping.
The primary advantage of directly pumping the Ho 5I7 is that it does not have to depend on energy transfer, which lends itself to various radiative and non-radiative losses. Up-conversion losses that have deleterious effect in high-energy Q-switched lasers are eliminated. In the near future experiments with different Ho:YLF crystals are planned to reduce the laser threshold and increase the maximum output power.
Parameter
| Orientation |
a-cut |
| Clear aperture |
>90% |
| Face dimensions tolerance |
+0/-0,1 mm |
| Length tolerance |
±0,1 mm |
| Parallelism error |
|
| Perpendicularity error |
|
| Protective chamfers |
<0,1 mm at 45˚ |
| Surface quality |
10-5 S-D |
| Surface flatness |
<λ/10@632,8 nm |
| Coatings |
R<0,35%@1900-2100 nm on both faces |
| LIDT |
>10 J/cm2@2060 nm, 10 ns |
| Mount |
Unmounted |
| Crystal structure |
tetragonal |
| Density |
3.95 g/cm3 |
| Mohs hardness |
5 |
| Thermal conductivity |
6 Wm-1K-1 |
| dn/dT |
-4.6×10-6 (||c) K-1, -6.6×10-6 (||a) K-1 |
| Thermal expansion coefficient |
10.1×10-6 (||c) K-1, 14.3×10-6 ((||a) K-1 |
| Typical doping level |
0.5-1% |
| Absorption peak wavelength |
1940 nm |
| Absorption cross-section at peak |
1.2×10-20 cm2 |
| Absorption bandwidth at peak wavelength |
~18 nm |
| Laser wavelength |
2060 nm |
| Lifetime of 5I7 energy level |
10 ms |
| Emission cross-section |
1.8×10-20 cm2 |
| Refractive index @1064 nm |
no=1.448, ne=1.470 |
Spectrum
Feature
- Long upper laser level lifetime ~ 15 ms
- Higher emission cross-section
- Naturally birefringent material
- Low dn/dT –> weak thermal lensing
- Highest (to the best of our knowledge) CW output of 21 W for 2-μm Ho:YLF laser
- Efficient Q-switched operation (up to 37 mJ per pulse)
Application
- Remote sensing
- Pollutant Control
- Military defense
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