Thulium-doped yttrium fluoride lithium (Tm: YLF) crystals have a low nonlinear refractive index and thermo optic constant, suitable for application in scientific research, production, education, and other optoelectronic fields.

Tm: YLF crystal is a negative uniaxial crystal with a negative refractive index temperature coefficient, which can offset some thermal distortion and thus has a high beam quality output. The pump wavelength is 792 nm, and the linear polarized laser with a wavelength of 1900 nm outputs in the direction of an axis.

Outputting light from the c axis is nonlinearly polarized. High-power laser output can be obtained by selecting the proper crystal size and doping concentration. Two-micron Tm3+ lasers are of interest for many scientific, defense, and medical applications. Thulium readily substitutes many crystal hosts suitable for high-average-power laser systems. It has an absorption band at ~0.8 μm, allowing excitation with commercially available high-power laser diodes.

  • 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

Material Specifications

Concentration Tolerance (atm%)2-4 at.%
Lattice Constants4~5
Orientationa-cut, other orientations also available
Surface Finish
10-5 S/D
Wavefront Distortion
λ/8 @ 633nm
λ/10 @ 633nm
Clear Aperture
Length Tolerance±0.1 mm
Face Dimensions Tolerance+0/-0,1 mm
<0,1 mm @45˚
Damage Threshold
over 15J/cm2 TEM00, 10ns, 10Hz

Physical and Chemical Properties

Crystal Structure
Lattice Constant
a=5.16Å; c=10.85Å
3.99 g/cm³
Melting Point
Thermal Conductivity
6 Wm-1K-1
Thermal Optical Coefficientπ = 4.3 x 10-6 x °K-1;
σ = 2.0 x 10-6 x °K-1
Thermal Expansivity /(10-6·K-1 @ 25°C)10.1×10-6 (//c) K-1
14.3×10-6((//a)  K-1
Mohs Hardness
Shear Modulus
Specific Heat Capacity
0.79 J/gK
Poisson Ratio

Optical and Spectral Properties

Laser Transition3F43H6
Laser Wavelengthπ:1880 nm; σ:1908 nm
Absorption Cross-section at Peak0.55×10-20 cm2
Absorption Bandwidth at Peak Wavelength16 nm
Absorption Peak Wavelength792 nm
Lifetime of3F4 Thulium Energy Level16 ms
Quantum Efficiency2
Quantum Efficiency n20.6 x 10-13
Optical Quality< 0.3 x 10-5
Refractive Index @1064 nmno=1.448, ne=1.470
Laser Induced Damage Threshold>10 J/cm2@1900 nm, 10 ns
CoatingsR<0,5% @792 nm + R<0,15% @1800-1960 nm on both sides; custom coatings also available

Absorption and Emission Spectra

TmYLF-σ-angle-Absorption-Spectrum-CRYLINKTm-YLF Laser crystal - Emission spectrum 2-CRYLINK
Laser crystal TmYLF π andle absorption spectrum-CRYLINKTmYLF-π-angle-Emission-Spectrum-CRYLINK


[1] Yue, Chen, Xin-Yu, et al. A compact high efficient Tm:YLF laser dual-end-pumped by an equidirectional-polarizing fiber coupled laser diode at room temperature[J]. Optik: Zeitschrift fur Licht- und Elektronenoptik: = Journal for Light-and Electronoptic, 2018, 158:1553-1557.
[2]  Cui Z ,  Yao B Q ,  Duan X M , et al. A graphene saturable absorber for a Tm:YLF pumped passively Q-switched Ho:LuAG laser[J]. Optik – International Journal for Light and Electron Optics, 2016, 127(5):3082-3085.
[3]  Duan X M ,  Ding Y ,  Dai T Y , et al. A linewidth-narrowed Tm:YLF laser using by two etalons[J]. Optik – International Journal for Light and Electron Optics, 2015, 126(19):2108-2109.
[4]  Wang Y P ,  Dai T Y ,  Wu J , et al. A Q-switched Ho: YAG laser with double anti-misalignment corner cubes pumped by a diode-pumped Tm: YLF laser[J]. Infrared Physics & Technology, 2018, 91:8-11.
[5]  Dai Y ,  Li Y ,  Zou X , et al. Compact passively Q-switched Tm:YLF laser with a polycrystalline Cr:ZnS saturable absorber[J]. Optics & Laser Technology, 2014, 57:202-205.
[6]  Zhang B ,  Li L ,  He C , et al. Compact self-Q-switched Tm:YLF laser at 1.91 μm[J]. Optics & Laser Technology, 2018, 100.
[7]  Antipov O L ,  Zakharov N G ,  Fedorov M , et al. Cutting effects induced by 2 μm laser radiation of cw Tm:YLF and cw and Q-switched Ho:YAG lasers on ex-vivo tissue[J]. Medical Laser Application, 2011, 26(2):67-75.
[8] Linjun, Li, Xining, et al. High beam quality passively Q-switched operation of a slab Tm:YLF laser with a MoS2 saturable absorber mirror – ScienceDirect[J]. Optics & Laser Technology, 2019, 112:39-42.
[9]  Duan X M ,  Ding Y ,  Yao B Q , et al. High power acousto-optical Q-switched Tm:YLF-pumped Ho:GdVO4 laser[J]. Optik – International Journal for Light and Electron Optics, 2018, 163:39-42.
[10]  Ding Y ,  Han L ,  Yao B Q , et al. High power Tm:YLF bulk laser wavelength-stabilized by two F-P etalons[J]. Optik – International Journal for Light and Electron Optics, 2015, 126(9-10):990-992.
[11] Y, Ding,  D. X , et al. High power Tm:YLF laser operating at 1.94 μm[J]. Optik International Journal for Light & Electron Optics, 2015.
[12]  Yang X T ,  Mu Y L ,  Zhao N B . Ho:SSO solid-state saturable-absorber Q switch for pulsed Ho:YAG laser resonantly pumped by a Tm:YLF laser[J]. Optics & Laser Technology, 2018, 107:398-401.
[13]  Yokozawa T ,  Izawa J ,  Hara H . Mode control of a Tm:YLF microchip laser by a multiple resonator[J]. Optics Communications, 1998, 145( 1–6):98-100.
[14]  Hecht H ,  Burshtein Z ,  Katzir A , et al. Passive Q-switching of a Tm:YLF laser with a Co2+ doped silver halide saturable absorber[J]. Optical Materials, 2017, 64:64-69.
[15]  Razumova I ,  Tkachuk A ,  Nikitichev A , et al. Spectral-luminescent properties of Tm:YLF crystal[J]. JOURNAL OF ALLOYS AND COMPOUNDS, 1995, 225(1-2):129-132.
[16]  Kalachev Y L ,  Mihailov V A ,  Podreshetnikov V V , et al. The study of a Tm:YLF laser pumped by a Raman shifted Erbium fiber laser at 1678 nm[J]. Optics Communications, 2011, 284(13):3357-3360.

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