47 research outputs found
Correlation between compositional and refractive index profiles in LiNbO3 : Zn diffused optical waveguides
No full textWaveguides fabrication in Z- and X-cut LiNbO3 crystals by vapor zinc diffusion has been studied by secondary ion mass spectrometry and optical measurements. Compositional analysis of diffused substrates shows the formation of a Zn rich superficial layer, followed by a deeper region with decreasing Zn concentration. A subsequent thermal annealing process has been performed to let zinc ions further diffuse into the substrates. The composition profiles have been correlated with the refractive index profiles, reconstructed by optical reflectivity measurements. The results and the nature of the detected layers are discussed and correlated with previous x-ray studies obtained in the same samples
Compositional characterisation of Zn-diffused lithium niobate waveguides
No full textRutherford backscattering (RBS) and secondary- ion mass spectrometry techniques have been used to investigate the two-step process involved during waveguide fabrication in LiNbO3 using Zn-vapour diffusion. Compositional analysis (O, Nb, Li and Zn) in the two steps has been characterised. RBS analysis reveals that the first step, involving a heating of the substrate under a metallic Zn atmosphere, gives rise to a partial exchange between the Nb and Li ions from the crystals and the Zn from the vapour source. The second treatment at higher tem- perature in an open atmosphere diffuses the Zn deeper into the substrate, thus forming an optical waveguide, while the Nb and Li ions recover their bulk values
Time resolved and site-selective spectroscopy of thulium- doped into germano- and alumino-silicate optical fibres and preforms
No full textOptical properties of thulium ions doped in varying concentrations into germano- and alumino-silicate glass fibres and their preforms are studied. Absorption and fluorescence spectra are shown to vary little with thulium concentrations up to 12000 ppm. but vary drastically with germanium or aluminium codopant. Resonant fluorescence studies of Tm3+ show correlations in the movements of the Stark levels of the ground state, indicating systematic correlations between the ion site and Stark level position. An upper limit of 10 /cm for the homogeneous line width of thulium in alumino-silicate glass is established at 9 K. The lifetimes of the 1G4 and 3F4 levels are studied and are related to codopant influence and cross-relaxation which are linked to fibre drawing and Tm3+- concentration. A significant lifetime shortening is observed on drawing preform to fibre. A model is presented for non-exponential decay of the 3F4 level. Three- and four-level rate equations have been successfully used to simulate the observed rise of the 3F4 fluorescence and decay of the 1D2 fluorescence, excited resonantly and by up-conversion processes, respectively. These models yield both the excitation pump rate and cross-relaxation rates
Fabrication and characterisation of reverse proton exchange optical waveguides in Neodymium doped lithium niobate crystals
No full textIn this work, the complete fabrication process which combines Proton Exchange (PE) and Reverse Proton Exchange (RPE) in Neodymium doped LiNbO3 channel waveguides is reported. To produce the PE-RPE channel waveguides the fabrication of dielectric SiO2 masks had to be implemented. For this propose, we adopted a technique based on the Ion Plating Plasma Assisted Deposition of SiO2 followed by the standard ultraviolet photolithographic patterning. On the other hand, we determined the main optical and spectroscopic properties of Nd3+ ions in the channel waveguides including the study of the lifetime as function as the polarisation
Imaginary distance BPM as an efficient tool for modelling optical waveguide fabrication by ion diffusion
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Optical transition probabilities in Er3+- and Tm3+-doped LiLa9(SiO4)6O2 crystals
No full textIn this work, Er3+ and Tm3+-doped LiLa9(SiO4)(6)O-2 crystals have been grown from an Li2MoO4 flux in the 1360-940 degrees C temperature range. Optical absorption spectra have been measured to obtain the experimental oscillator strengths of the transitions from the ground state to the excited levels. Judd-Ofelt calculations have been performed to estimate the Omega(2), Omega(4) and Omega(6) intensity parameters. The dynamics of selected Er3+ and Tm3+ manifolds have been investigated under selective pulsed excitation in order to determine the energy gap law by comparing the observed decay rates with the Judd-Ofelt predictions
Dual-polarization-pump CW laser operation in Nd3+:LiNbO3 channel waveguides fabricated by reverse proton exchange
No full textIn this work, continuous-wave laser action at 1084.5 nm at room temperature in LiNbO3:Nd3+ channel waveguides, fabricated by reverse proton exchange (RPE), is reported. The sample was pumped at k = 808 nm in either s or p-polarized configurations, TE and TM-pumping schemes, being the laser emission p-polarized at all power levels. The laser characteristics, as function of the pumping scheme (TE or TM), have been obtained. In both cases, the laser emission was stable, without any reduction in the output power even under continuous pump operation at maximum power at room temperature, indicating high resistance to photorefractive damage
