What is yttrium lithium fluoride?

Publish Time: 2022-09-06 Origin: Site

The chemical formula of Yttrium lithium fluoride is LiYF4, sometimes referred to as YLF. It is a new type of matrix material with good spectral and laser properties. It is suitable for the introduction of trivalent rare earth ions. When mixed with different activating ions at room temperature, the material can emit laser at different wavelengths.

Neodymium-doped lithium yttrium fluoride (Nd:YLF)

Neodymium-doped lithium yttrium fluoride (Nd:YLF) is an active laser medium used in solid state lasers for arc lamp pumping and laser diodes. Lithium yttrium fluoride crystal (LiYF4) itself has birefringence property, commonly used in 1047nm and 1053nm laser.

Neodymium-doped lithium yttrium fluoride is used in Q-switching systems because of its long fluorescent time. Similar to the ND-YAg laser, Q-switched ND-doped lithium generates shorter wavelengths in conjunction with harmonic generation. A common application of frequency doubling neodymium doped lithium yttrium fluoride is pumping ultrafast titanium-sapphire laser chirped pulses.

Nd-doped lithium Yttrium fluoride can produce higher pulse energies than ND-YAG laser at repetition rates below a few kHz. However, neodymium-doped lithium yttrium fluoride is a brittle material, prone to fracture, and slightly soluble in water. The neodymium-doped lithium yttrium fluoride will slowly dissolve in the surrounding cooling water.

Ytterbium-doped yttrium lithium fluoride (Yb:YLF)

Crystal structure Tetragonal

Point group I41/a

Lattice parameters а = 5,164 Å, c = 10,741 Å

Thermal expansion 4×10-6 / ºC

Thermal conductivity 4,36 W/mK

Density 3,95 g/cm³

Mohs’ hardness 5

Melting temperature 825 ºC

Transmission range 0.2-5 μm

Refractive indices (λ=1.06 μm) no = 1,448, ne = 1,470

dno/dT -2,0×10-6 / ºK

dne/dT -4,1×10-6 / ºK

Fluorescence lifetime 2.1 ms

Emission cross section 7.5x10-21 cm² @1017nm, E//c

Emission bandwidth 60 nm

Absorption cross section 10.6x10-21 cm² @959 nm, E//c

The Yb-doped material has the highest quantum efficiency (>90%) among commercial laser materials. Yb:LiYF4 (Yb:YLF) have wider emission spectra than Yb:YAG, which is necessary for the generation and amplification of ultrashort pulses. A YLF host crystal has higher thermal conductivity than glass, resulting in negligible lower thermal lensing. The YLF crystal also has the capability of a high degree of doping with ytterbium ions.

Holmium - doped lithium yttrium fluoride (Ho:YLF)

Ho:YLF crystal is a natural birefringent material with high laser horizontal lifetime and high emission cross section.

Direct pumping of Ho:YLF crystals from holmium doped crystals excludes the loss of Tm 3+ →Ho 3+ energy transfer process and has a high laser horizontal lifetime.

Ho:YLF holmium - doped lithium yttrium fluoride crystal main characteristics

- High laser level lifetime

- High emission cross section - natural birefringent material

- Low Dn /dT value → weak thermal lens

- Custom crystals available upon request

Main applications of Ho:YLF crystal

- Remote sensing and pollutant detection

Praseodymium doped lithium Yttrium fluoride (Pr:YLF)

There are not many laser materials that can achieve the desired characteristics of laser emission in the visible spectrum. Pr :YLF crystal is a promising laser material that has been found to be directly used in the production of visible light lasers. It can be used in diode-pumped solid-state lasers for the efficient processing of metals such as copper or gold.

In a trivalent (Pr 3+) energy level scheme, it provides several transitions in red light (640 nm,3 P 0 to 3 F2) and is therefore used with solid-state lasers in the visible spectral range. Pr :YLF crystal has high absorption and emission cross sections.

Main characteristics of praseodymium doped lithium Yttrium fluoride crystal (Pr:YLF crystal)

- High absorption and emission cross sections (? 10-19 cm2)

- Absorption bands and emission in the blue spectral region

-InGaN laser diode and 2ω-OPSL line