Description of Thulium-Doped Yttrium Lithium Fluoride Crystal
Two-micron Tm3+ lasers are of interest for many applications in the scientific, defense, and medical fields. Thulium readily substitutes 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 a low nonlinear refractive index and thermal optic constant, which are very suitable for 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 a wavelength of 1900nm outputs in the direction of an axis. outputting light from the c axis is non-linear polarized. High-power laser output can be obtained by selecting the proper crystal size and doping concentration.
Advantages of Tm: YLF:
- 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
Specifications of Thulium-Doped Yttrium Lithium Fluoride Crystal
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Material specifications
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Concentration Tolerance (atm%)
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2-4 at. %
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Lattice Constants
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4~5
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Orientation
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a-cut, other orientations are also available
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Parallelism
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<10”
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Perpendicularity
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<5”
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Surface Quality
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10-5 scratch & dig
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Wavefront Distortion
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λ/8 @ 633nm
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Surface Flatness
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λ/10 @ 633nm
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Clear Aperture
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0.95
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Length Tolerance
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±0.1 mm
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Face Dimensions Tolerance
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+0/-0,1 mm
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Protective Chamfers
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<0.1 mm at 45˚
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Damage Threshold
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over 15J/cm2 TEM00, 10ns, 10Hz
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Optical and spectral properties
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Laser Transition
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3F4→3H6
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Laser Wavelength
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π:1880 nm; σ:1908 nm
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Absorption Cross-section at Peak
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0.55×10-20 cm2
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Absorption Bandwidth at Peak Wavelength
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16 nm
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Absorption Peak Wavelength
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792 nm
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Lifetime of 3F4 Thulium Energy Level
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16 ms
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Quantum Efficiency
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2
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Non-linear Index n2
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0.6 x 10-13
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Optical Quality
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< 0.3 x 10-5
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Refractive Index @1064 nm
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no=1.448, ne=1.470
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Laser-Induced Damage Threshold
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>10 J/cm2@1900 nm, 10 ns
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Coatings
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R<0,5% @792 nm + R<0,15% @1800-1960 nm on both sides; custom coatings also available
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Applications of Thulium-Doped Yttrium Lithium Fluoride Crystal
- Medical diagnosis and treatment
- Laser radar
- Laser ranging
- Electro-optical countermeasure
- Laser remote sensing
- Laser imaging
- Optical signal processing
- Material processing
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