Fiber amplification of radially and azimuthally polarized laser light

The results on amplifying either radially or azimuthally polarized light with a fiber amplifier are presented. Experimental results reveal that more than 85% polarization purity can be retained at the output even with 40dB amplification, and that efficient conversion of the amplified light to linear polarization can be obtained.Comment: 3 pages, 4 figures, submitted to optics letter

Thermal characterization, crystal field analysis and in-band pumped laser performance of Er doped NaY(WO(4))(2) disordered laser crystals.

Undoped and Er-doped NaY(WO4)2 disordered single crystals have been grown by the Czochralski technique. The specific heat and thermal conductivity (κ) of these crystals have been characterized from T = 4 K to 700 K and 360 K, respectively. It is shown that κ exhibits anisotropy characteristic of single crystals as well as a κ(T) behavior observed in glasses, with a saturation mean free phonon path of 3.6 Å and 4.5 Å for propagation along a and c crystal axes, respectively. The relative energy positions and irreducible representations of Stark Er(3+) levels up to (4)G(7/2) multiplet have been determined by the combination of experimental low (<10 K) temperature optical absorption and photoluminescence measurements and simulations with a single-electron Hamiltonian including both free-ion and crystal field interactions. Absorption, emission and gain cross sections of the (4)I(13/2)↔(4)I(15/2) laser related transition have been determined at 77 K. The (4)I(13/2) Er(3+) lifetime (τ) was measured in the temperature range of 77-300 K, and was found to change from τ (77K) ≈ 4.5 ms to τ (300K) ≈ 3.5 ms. Laser operation is demonstrated at 77 K and 300 K by resonantly pumping the (4)I(13/2) multiplet at λ≈1500 nm with a broadband (FWHM≈20 nm) diode laser source perfectly matching the 77 K crystal (4)I(15/2) → (4)I(13/2) absorption profile. At 77 K as much as 5.5 W of output power were obtained in π-polarized configuration with a slope efficiency versus absorbed pump power of 57%, the free running laser wavelength in air was λ≈1611 nm with the laser output bandwidth of 3.5 nm. The laser emission was tunable over 30.7 nm, from 1590.7 nm to 1621.4 nm, for the same π-polarized configuration

Thermal characterization, crystal field analysis and in-band pumped laser performance of Er Doped NaY(WO4)2 disordered laser crystals

Undoped and Er-doped NaY(WO4)2 disordered single crystals have been grown by the Czochralski technique. The specific heat and thermal conductivity (κ) of these crystals have been characterized from T = 4 K to 700 K and 360 K, respectively. It is shown that κ exhibits anisotropy characteristic of single crystals as well as a κ(T) behavior observed in glasses, with a saturation mean free phonon path of 3.6 Å and 4.5 Å for propagation along a and c crystal axes, respectively. The relative energy positions and irreducible representations of Stark Er3+ levels up to 4G7/2 multiplet have been determined by the combination of experimental low (<10 K) temperature optical absorption and photoluminescence measurements and simulations with a single-electron Hamiltonian including both free-ion and crystal field interactions. Absorption, emission and gain cross sections of the 4I13/2↔4I15/2 laser related transition have been determined at 77 K. The 4I13/2 Er3+ lifetime (τ) was measured in the temperature range of 77-300 K, and was found to change from τ (77K) ≈ 4.5 ms to τ (300K) ≈ 3.5 ms. Laser operation is demonstrated at 77 K and 300 K by resonantly pumping the 4I13/2 multiplet at λ≈1500 nm with a broadband (FWHM≈20 nm) diode laser source perfectly matching the 77 K crystal 4I15/2 → 4I13/2 absorption profile. At 77 K as much as 5.5 W of output power were obtained in π-polarized configuration with a slope efficiency versus absorbed pump power of 57%, the free running laser wavelength in air was λ≈1611 nm with the laser output bandwidth of 3.5 nm. The laser emission was tunable over 30.7 nm, from 1590.7 nm to 1621.4 nm, for the same π-polarized configuration.This work has been partially supported by the USAITC W911NF-10-1-0234 contract and by the Spanish Ministry of Economy and Competitiveness under project MAT2011-29255-C02-01. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.Peer reviewe

Polarization resolved emission cross sections of the ⁴I_13/2 → ⁴I_15/2 transition of Er³⁺ in NaY(WO₄)₂ single crystal measured at 77 K (red continuous line) and 300 K (black dashed line): (a) π-polarized spectra, (b) σ-polarized spectra.

<p>Polarization resolved emission cross sections of the ⁴I_13/2 → ⁴I_15/2 transition of Er³⁺ in NaY(WO₄)₂ single crystal measured at 77 K (red continuous line) and 300 K (black dashed line): (a) π-polarized spectra, (b) σ-polarized spectra.</p

Evolution of the thermal conductivity of undoped (□), 1 at% Er− (○) and 15 at% Er− (Δ) doped NaY(WO₄)₂ crystals upon cooling from 360 K to 4 K.

<p>Heat propagation parallel to <i>c</i>-axis (a) and <i>a</i>-axis (b). The line in (b) shows for comparison the <i>κ</i>(<i>T</i>)<i>//c</i> of 1 at% Er-doped NaY(WO₄)₂ crystal.</p

The lifetime of the ⁴I_13/2 manifold versus temperature for the pulverized 0.02 at% Er-doped NaY(WO₄)₂ crystal.

<p>The lifetime of the ⁴I_13/2 manifold versus temperature for the pulverized 0.02 at% Er-doped NaY(WO₄)₂ crystal.</p