A heavily magnesium (5.0 mol%) and erbium (2.0 mol%) codoped lithium niobate crystal has been grown using Czochralski method. The crystal is highly transparent and has strong resistance to photorefractive damage. Spectroscopic study showed that the crystal exhibits the typical f-f transitions of erbium ions. Photoluminescence at 1.54 micrometers was measured under excitations at 514 nm from an Ar+ laser and 980 nm from a GaAs laser diode. The temporal evolution of the 1.54 micrometers emission showed a single-exponential decay with a lifetime of approximately 5 ms. Upconversion property of the crystal under 980 nm excitation was also studied and the transient spectrum of the green emission at 548 nm also yields a single-exponential decay with a lifetime of approximately 35 microsecond(s) . The results have shown that clustering and pairing of Er ions could be effectively avoided by magnesium codoping.
The Nd3+ ions doped bulk glasses and thin films with the trimethylphosphate (TMP) as the precursor of P2O5 were prepared by the sol-gel technique. Their optical properties have been investigated. The Fourier Transform IR (FTIR) of Nd3+ doped SiO2-TiO2-P2O5 films have been measured to study the influence of P2O5 content in the removal of hydroxyl group. Fluorescence spectral results show stronger fluorescence intensity along with the narrowing of the emission bands due to the availability of the co-dopant P2O5 in the sol-gel glasses compared with those of aluminum co-doped glasses. Our experimental results show that up to 6wt percent of Nd2O3 could be incorporated into the P2O5-SiO2 glass matrix without significant fluorescence quenching effect due to the usage of the TMP as a precursor. We have also found that the hydroxyl groups could easily be removed at lower temperatures, as we increase the P2O5 content. It indicates that the P2O5 co-doping has a great potentiality in reducing the process temperature.
We report here the processing and optical characterization of Nd3+-doped SiO2-TiO2-Al2O3 planar waveguides deposited on SOS substrates by the sol-gel route combined with spin-coating and rapid thermal annealing. The recipes used for preparing the solutions by sol-gel route are in mole ratio of 93SiO2:20AlO1.5: x ErO1.5. In order to verify the residual OH content in the films, FTIR spectra were measured and the morphology of the material by the XRD analysis. Five 2-layer films annealed at a maximum temperature of 500 degrees C, 700 degrees C, 900 degrees, 1000 degrees C, 1100 degrees C respectively were fabricated on silicon. The FTIR and XRD curves show that annealing at 1050 degrees C for 15s effectively removes the OH in the materia and keeps the material amorphous. The propagation loss of the planar waveguides was measured by using the method based on scattering in measurements and the result was obtained to be 1.54dB/cm. The fluorescence spectra were measured with 514nm wavelength of Ar+ laser by directly shining the pump beam on the film instead of prism coupling. The results show that the 1 mole Nd3+ content recipe has the strongest emission efficiency among the four samples investigated.
In the present paper, we report the preparation of Er3+ doped SiO (formula available in paper) planar waveguides deposited on SOS Silica on silicon substrates using sol-gel process combining with spin-coating and rapid thermal annealing. The recipes used for preparing the solutions by sol-gel process are (formula available in paper). The fluorescence spectra and lifetimes of the planar waveguides were measured under the excitation of 514 nm wavelength from an Ar+ laser. The lifetimes of 3.80 ms, 3.07 ms and 1.59 ms were obtained for 0.5 mole, 1.0 mole and 2.0 mole of Er3+ content planar waveguides respectively. The decay mechanism and the factors that influence the lifetime of the sol-gel planar waveguides have been analyzed.
For rare earth doped silica-based glasses derived by sol-gel process, Al was used as a modifier in order to improve the dispersion of the rare earth ion in silica lattices, and thus, make the higher rare earth doped silica glasses without clustering possible. In this research, the influence of the ratio of Al to Nd on the fluorescence intensity and lifetime was studied in details to get the material which has a strong fluorescence intensity as well as the long fluorescence lifetime enough for integrated amplifier and laser use. Ten samples in the from of powder with different Al/Nd and different Nd concentration were prepared by sol- gel process. These powders were gotten by heating the dried gels in a surface in air environment. The result of the fluorescence intensity and lifetime show that the Al/Nd equals 10 with 1 mole Nd, that is the recipe 100SiO2:10AlO1.5:1 NdO1.5 has the strongest fluorescence intensity in the ten samples. But its τ1/e is only 110 μs. For 100SiO2:20ALO1.5:0.25 NdO1.5, the obtained τ1/e is 216 μs without special OH movement treatment. The research results show that we need to balance the fluorescence intensity and the lifetime to choose the suitable recipe for practice use.
In this research, silica based planar waveguide and powdered glasses doped with Er2O3, Yb2O3, TiO2 and Al2O3 have been fabricated by sol-gel process. The photoluminescence enhancement has been demonstrated to be seven and four times that without Yb co-doping when pumped by a 980 nm laser diode and a 488 nm Ar+ laser respectively. The strongest fluorescence is observed form the 93 SiO2: 7 TiO2: 10 AlO1.5: 1 YbO1.5 glass. Dependence of the photoluminescence intensity and lifetime on Er3+ as well as Yb3+ concentration has been experimentally studied.
Using the sol-gel process, we prepared three groups of Er-doped glasses, namely, Er-doped Si02-A101.5 (SAB) glass, Er-doped Si02-Ti02-A101.5 (STAE) glass, and Er-doped Si02-Ge02-Al01.5 (SGAE) glass. Various erbium concentration and
different host composition under the same processing condition have been studied in order to optimize the material composition to get the strongest fluorescence emission for each material system. It has been found that for SAE glass, the strongest fluorescence emission is obtained when the mole ratio of the three constituent oxides is lOOSiO2 : 20A101.5 2ErO1.5. For the STAE material system, the best composition ratio for the strongest fluorescence emission is 93 Si02 : 7TiO2: 20A101.5 : lErO1.5, whereas the value for SGAE glass is 9OSiO2:lOGeO2 : 2OAlO1.5: 1ErO1.5. But the relative lifetimes were obtained with the recipe lOOSiO2:10A101.5:1ErO1.5 for SAE series, 90 Si02:lOGeO2:1OAlO1.5: 1ErO1.5 for STAE group and 93 Si02:7Ti02:20A101.5:1ErO1.5 for STAE group. Using these recipes, three 20-layer (up to 2.5 μm) crack-free films have been deposited on silica-on-silicon (SOS) substrates with multiple spin-coating and rapid thermal annealing (RTA). Only the STAE film and the SGAE film are found to guide light. The experimental results show that STAB glasses have
higher hydrophilicity than SGAE glasses and SGAE glasses has lower crystallization temperature than STAE glasses. The fact that these waveguiding films emit relatively strong fluorescence around the wavelength of 1.55 μm implies that such planar waveguides are potential candidates from which integrated optical waveguide amplifiers and lasers operating at the third optical fiber communication window can be fabricated.
Silica based planar waveguides co-doped with Er3+, TiO2 and Al2O3 have been fabricated on SOS (silica on silicon) by a sol-gel process using multiple spin-coating and rapid thermal processing (RTP). Their characteristics, such as refractive index, thickness photoluminescence (PL), FTIR (Furior Transform infrared spectrum), XRD (X-ray diffraction), and surface roughness are investigated. The relatively strong PL emitted from planar waveguide has been got using the recipe of 93SiO2:7TiO2:10Al2O3:0.5Er2O3 (mole ratio). The presence of O2 during annealing in RTP is indispensable for sol-gel waveguide to guide light. Both the average refractive index and thickness of multilayer film increase as the layer number increases.
Based on the effects of mode-volume mismatch and lateral bending, a new type of optical fiber intensity sensors are presented. These sensors do not require the use of external structures to impose perturbations on fibers. Instead, the topological structures are formed directly onto the fiber cladding. The geometry of the features is defined by thermal engraving and the structures are formed by chemical etching. The etched fiber sensing elements have been fabricated with asymmetric structures and tested as strain sensors. It has been shown in experiment that the responses of the optical fiber strain gauges are linear, repeatable, have a high cyclic endurance and temperature stability and no measurable hysteresis. The etched fiberoptic sensing array embedded in composites and the principle and technology of array sensing signal processing in artificial neural network are also described.
In this paper a broad-band and accurate current sensor for the electric power system is described. The sensor uses the Faraday effect in optical glass and standard polarilnetric irieasurement. The design and performance of the sensor are discussed with a view to a practical working sensor.
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