Optical spectroscopy of Nd³⁺ in LiLuF₄ single crystals

Abstract

The polarized absorption spectra, polarized fluorescence spectra and fluorescence decay curve of Nd3+ : LiLuF4 crystals are measured at room temperature. The peak absorption cross-sections are 6.944×10−20 cm2 and 1.664 × 10−20 cm2 at around 795 nm with full-width at half-maximum of 3.4 nm and 3.2 nm for π-polarization and σ-polarization, respectively. Based on Judd–Ofelt theory, the spectral parameters of Nd3+ in LiLuF4 crystals are investigated. The emission probabilities, branching ratio and radiative lifetime for the transitions from 4F3/2 are calculated. The radiative lifetime, fluorescence lifetime and quantum efficiency are 536 µs, 489 µs and 91%, respectively. Its spectroscopic parameters are also compared with those of some other important Nd3+-doped laser crystals.

Growth, optical characterization and evaluation of laser properties of Nd:LaF3 crystal

“…The emission properties of the compound from the 4 F 3/2 manifold mainly depend on the parameters U 4 and U 6 [22]. For this Nd:LaF 3 crystal sample, the spectroscopic quality parameter U 4 /U 6 equals to 0.76, which is less than 1 and thus indicates the emission of 4 F 3/ 2 / 4 I 11/2 is more feasible than that of 4 F 3/2 / 4 I 9/2 .…”

Optical spectroscopy of Nd3+/Mg2+co-doped LiTaO3laser crystal

“…where h is Planck's constant and c the speed of light, N 0 means the number density of Nd 3+ ions, λ q is the barycenter wavelength of the specific absorption band that corresponds to the J → J transition, L is the sample thickness, OD q (λ) is the [20] measured optical density and n q is the refractive index of the sample. The refractive indices of LiTaO 3 crystal are 2.138 and 2.188 for the ordinary and extraordinary rays, respectively.…”

Efficient dual-wavelength Nd:LuLiF_4 laser

“…Another fluoride crystal Nd:LuLiF 4 (Nd:LLF), like its isomorphs YLF, has emerged as a new promising laser crystal for diode pumping. Compared with Nd:YLF, Nd:LLF has several advantages; for instance, larger-emission cross section 5.1 × 10 −20 cm 2 for π and 2.2 × 10 −20 cm 2 for σ at 1.3 μm (Nd:YLF, 2-2.5 × 10 −20 cm 2 for the two polarizations [8]), and comparably long fluorescence lifetime of 489 μs [10]. Usually, the heat generation of 1.3 μm laser is more serious than lasing at 1.0 μm due to larger quantum defect.…”

“…With this focused pump beam size, the Rayleigh length inside the Nd:LLF crystal was calculated to be ∼1.83 mm. We adjusted the operation temperature of LD to force the pump wavelength to match the Nd:LLF absorption peak at 792.2 nm [10]. The measured single-pass pump absorption under nonlasing was 68%, corresponding to maximum absorbed pump power (P abs ) of 20 W. For negative thermal refractive index laser crystal, whether the thermal lens is positive or negative depends on the competition between bulging of the crystal end facets and the intensity-induced negative thermal refractive index (−dn∕dT) [5].…”

“…3(b)] because of the coupling of the lattice field of the LLF crystal to energy levels of Nd 3 . The 1321 nm π polarized laser first oscillated because it has larger branching ratio and emission cross section than the 1314 nm σ polarization [10], so it had a lower lasing threshold. With increasing the pump power, a larger population inversion will increase the gain of the 4 F 3∕2 → stark level 1 of 4 F 13∕2 transition at 1314 nm to overcome its cavity loss [ Fig.…”