Pr:YLF (Praseodymium-Doped Yttrium Lithium Fluoride) Single Crystal

Advantages

• Direct visible laser emission: Pr³⁺ in YLF enables direct diode-pumped laser operation in the visible spectrum, producing blue, green, orange, red, and deep-red wavelengths without nonlinear frequency conversion.
• Multi-wavelength capability: Laser oscillation has been demonstrated at 522 nm, 545 nm, 604 nm, 607 nm, 639 nm, 640 nm, 718.5 nm, and 720.8 nm, covering the visible and deep-red regions.
• Broad near-infrared emission: The ¹D₂ manifold provides broadband emission extending from 0.75 to 1.09 μm, enabling tunable NIR laser operation.
• Femtosecond pulse generation: Pr:YLF has achieved 451 fs pulses at 915 nm under diode pumping, representing the first demonstration of a diode-pumped femtosecond Pr laser.
• Long fluorescence lifetime and large emission cross-section: Pr:YLF exhibits relatively long energy level lifetimes with large stimulated emission cross-sections (20 × 10⁻²⁰ cm² at 640 nm).
• Low-phonon fluoride host: YLF provides low non-radiative multiphonon relaxation losses and reduced excited-state absorption compared with oxide hosts, beneficial for visible laser efficiency.

Typical Specifications

• Chemical formula: Pr³⁺:LiYF₄
• Crystal structure: Tetragonal, scheelite-type, space group I4₁/a
• Pr doping concentration: 0.3-1.0 at.%
• Laser transitions: ³P₀ → ³H₄ (blue/green), ³P₀ → ³H₅ (orange), ³P₀ → ³F₂ (red), ¹D₂ → ³F₃/³F₄ (NIR)
• Emission wavelengths: 522 nm, 545 nm, 604 nm, 607 nm, 639 nm, 640 nm, 718.5 nm, 720.8 nm (visible/deep-red); 895 nm, 915 nm, 922 nm, 924 nm (NIR)
• Absorption peak wavelength: 444 nm (³H₄ → ³P₀/¹I₆)
• Absorption cross-section: 8 × 10⁻²⁰ cm² at 444 nm
• Emission cross-section: 20 × 10⁻²⁰ cm² at 640 nm
• Fluorescence lifetime: ~50 μs
• Thermal conductivity: 6.3 W/(m·K)
• Thermal expansion coefficient: 7.6 × 10⁻⁶/K (∥c), 5.2 × 10⁻⁶/K (⊥c)
• Melting point: 819 °C
• Mohs hardness: 5
• Refractive index (YLF host): nₒ = 1.448, nₑ = 1.470 @ 1064 nm

Standard Fabrication Specifications

• Standard dimensions: 2 × 2 × 5/10/15 mm³; 3 × 3 × 5/10/15/18 mm³
• Doping concentrations: 0.3 at.% Pr, 0.5 at.% Pr
• Coating: S1: AR/HR; S2: AR (dual-pass coating)

Main Applications

• Pr:YLF is a leading gain medium for diode-pumped visible lasers, with demonstrated high-power outputs including 4.88 W at 607 nm with 49% slope efficiency.
• Orange laser sources: Widely tunable orange emission covering 602.2–631.5 nm has been achieved, enabling applications in spectroscopy, biomedicine, and display technology.
• Deep-red lasers: High-power operation at 718.5 nm (3.95 W, 41.3% slope efficiency) and 720.8 nm has been demonstrated, with potential for frequency-doubled UV generation.
• Ultraviolet laser generation: Intracavity frequency doubling of 604 nm produces 302 nm UV output for applications requiring compact UV sources.
• Femtosecond NIR lasers: Mode-locked Pr:YLF enables sub-500 fs pulses at 915 nm for ultrafast spectroscopy and microscopy .
• Optical vortex lasers: Pr:YLF has been demonstrated as a source of visible vortex beams and vortex Hermite-Gaussian beams .

Notes on data variability: Reported doping concentrations vary between 0.3-2.0 at.%. Laser performance depends strongly on crystal quality, doping level, and cavity design. The 640 nm emission is commonly cited as the primary visible laser line , while 607 nm provides the highest demonstrated power . Fluorescence lifetime and emission cross-section values are doping-dependent. Pr:YLF crystals are typically grown by Bridgman-Stockbarger or Czochralski methods under controlled atmospheres to avoid HF exposure.