Neodymium-doped Potassium Gadolinium Tungstate Research Articles

Multiwatt continuous wave Nd:KGW laser with hot-band diode pumping.

We have demonstrated what we believe is the first continuous wave neodymium-doped potassium gadolinium tungstate crystal (Nd:KGW) laser with hot-band diode pumping at ∼910 nm. This pumping wavelength reduced the quantum defect by >46% as compared to conventional ∼810 nm pumping and resulted in significantly lower thermal lensing. The laser produced 2.9W of average output power at 1067nm in a diffraction-limited beam for an absorbed pump power of 8.3W. The slope efficiency and optical-to-optical efficiency were found to be 43% and 35%, respectively. Significant reduction of quantum defect offered by this pumping wavelength and availability of suitable high-power laser diodes opens up an attractive way to further power and efficiency scaling of Nd:KGW lasers.

Composition, structural and electrical properties of thin films prepared by laser ablation of neodymium-doped potassium gadolinium tungstate

Thin films were grown on (001) SiO 2, SiO 2/(100) Si or (100) MgO substrates by laser ablation of neodymium-doped potassium gadolinium tungstate (Nd:KGW) single crystal target. The films were deposited at temperatures between room temperature and 750 °C and pressures between 1 × 10 − 4 Pa and 50 Pa of oxygen ambient. The influence of the deposition conditions on the composition, structure, morphology and electrical properties of the films was investigated. Special attention was paid to the films deposited in vacuum (1 × 10 − 4 Pa) or at very low oxygen pressures. Under such conditions, the potassium (K), gadolinium (Gd) and oxygen (O) content decreased strongly as the temperature was increased. At room temperature, the films were K and O stoichiometric, in contrast with Gd, which showed a concentration twice higher. The films were polycrystalline, with the exception of those deposited at temperatures below 500 °C, which were amorphous. However, all were smooth and dense. The films grown in vacuum and at temperatures between 500 and 700 °C consist mainly of “â-tungsten” – tungsten oxide (W 3O) phase. The films grown on SiO 2/Si possessed the best surface quality with nano-size relief. The resistivity measurements as a function of the temperature showed that the films produced in vacuum and at temperatures below 500 °C were highly insulating, whereas at 600 °C they exhibited semiconducting behavior or a metallic one at 700 °C. This behavior can be attributed to the existence of various valence states for tungsten below W 6+ in the films and to their crystal structure.

Structural and fluorescence properties of thin films fabricated by pulsed laser deposition technique from Nd:KGW single crystal

Textured and amorphous thin films were deposited by KrF laser ablation of neodymium doped potassium gadolinium tungstate, KGd 1− x Nd x (WO 4 ) 2 (Nd:KGW) single crystal in oxygen ambient atmosphere on MgO, YAP (YAlO 3 ) and YAG (Y 3 Al 5 O 12 ) substrates at temperatures up to 800 °C. The influence of substrate nature and substrate temperature ( T s ) on films crystallinity and morphology were studied by conventional X-ray diffraction (XRD), micro-Raman spectroscopy (μRS) and scanning electron microscopy (SEM). Related emission and excitation spectra and fluorescence decay were examined. The strongly textured polycrystalline Nd:KGW films with fluorescence spectra very close to those of bulk single crystal were deposited only on YAG substrate at higher T s , whereas the smoother films were obtained at T s = 400 °C on all types of substrates. Fluorescence properties of the films corresponding to the transitions from the 4 F 3/2 doublet to the 4 I 9/2 , 4 I 11/2 and 4 I 13/2 multiplets, at about 890 nm, 1.06 μm and 1.3 μm, bring a new information about the structure of the film at the scale of the Nd 3+ ions environment, which could not be detected by XRD method. The fluorescence decay was almost exponential, with a lifetime of about 110 μs for polycrystalline KGW films.

The study of laser characteristics of Nd3+:KGd(WO4)2 crystal

This paper presents laser characteristics of neodymium-doped potassium gadolinium tungstate (KGW) crystals grown in our institute. The maximum laser output was 358.4 mJ a pulse at wavelength 1.067 μm when a Nd 3+ :KGW rod with dimensions of ∅3.4 mm ×24 mm was pumped by a single xenon flashlamp. The overall and slope efficiencies are 1.7% and 3.3%, respectively. A laser output of 204 mW with an optical to optical efficiency of 60% has been obtained when the KGW:Nd 3+ crystal with dimensions of 5 mm ×5 mm ×5 mm was pumped by a sapphire laser.

Passively Q-switched m diode pumped Nd:KGW laser with V:YAG saturable absorber

Abstract Passively Q-switched 1.35 μm diode pumped laser operation in neodymium-doped potassium gadolinium tungstate –KGd(WO4)2:Nd3+ – has been obtained using a vanadium-doped yttrium aluminium garnet (V:YAG) bulk crystal as a saturable absorber. Slope efficiency of 15% and maximum average output power of 87 mW at 1100 mW of pump power were achieved. The spectrum of intracavity second harmonic generation has been investigated for both continuous wave and Q-switched operation.

High Efficient Laser Operation of the Nd:KGd(WO4)2 Crystal Grown by Flux Method

The laser performance of Neodymium-doped potassium gadolinium tungstate (Nd:KGd(WO4)2) crystal was studied by using Ti:Sapphire laser as the pump source. The maximum optical-to-optical efficiencies for the 1.067 and 1.3 μm laser outputs were measured to be 60% and 32.3%, respectively. The internal loss coefficient of the crystal for 1.067 μm laser was estimated to be as low as 0.004 cm-1. The oscillation thresholds at 1.067 and 1.3 μm for different output transmittances are also given.

Narrowing of the emission spectrum of a solid-state laser with a slow-response saturable absorber and negative feedback

A strong (by a factor of almost 100) narrowing of the spectrum was observed in quasi-stady operation of a solid-state laser with neodymium-doped potassium gadolinium tungstate when the cavity contained a negative feedback loop and a slow-response saturable absorber. The role of a nonlinear narrow-band selector, which reduced the width of the spectrum, was played by a periodic saturated-absorption grating formed by a standing intracavity laser radiation wave in a lithium fluoride crystal containing F2- colour centres and used as a saturable absorber.

Laser and nonlinear properties of the potassium gadolinium tungstate laser crystal <inline-formula><roman>KGd(WO</roman><sub><roman>4</roman></sub><roman>)</roman><sub><roman>2</roman></sub><roman>:Nd</roman><sup><roman>3+</roman></sup><roman>-(KGW:Nd)</roman></inline-formula>

S. I. Vavilov State Optical InstituteState Research CenterScientific Research and TechnologicalInstitute of Optical Materials ScienceSt. Petersburg 193171, RussiaAbstract. The mechanical, thermophysical, spectroscopic, nonlinear,and laser properties are presented for one of the most efficient lasercrystals: neodymium-doped potassium gadolinium tungstate,KGd(WO

Lasing properties of diode-laser-pumped Nd:KGW

The laser performance of Nd:KGW (neodymium-doped potassium gadolinium tungstate) end pumped by cw or quasi-cw high-power diode laser bars is studied and compared to Nd:YAG. In cw operation, thermal problems in Nd:KGW are quite important, whereas in quasi-cw operation, the optical and slope efficiencies attained with Nd:KGW are clearly better than with Nd:YAG.