Potential of polymer optical amplifier doped with europium complex has been analyzed for practical use in visible range. Europium this(2-thenoyltrifluoroacetonate)-1,10- phenanthroline was used as the amplification dopant and PMMA as matrix. Spectroscopic properties of the dopant such as metastable excited state lifetime, simulated emission cross section, and stimulated absorption cross section were obtained using the photoluminescence spectroscopy, UV visible spectrophotometry and time-resolved spectroscopy. Lifetime of ⁵D₀ metastable state is 0.9 ms, which is longer than usual rare earth complex. Its emission cross section is comparable to erbium ions and absorption cross section is 4 orders of magnitude higher than bare rare earth ions. Optical amplifier was fabricated by the dip-coating method. The refractive index profile of the polymer optical amplifier was designed to manifest a single mode structure for the optimization of amplification performance. Amplification characteristics were simulated with respect to pump power, amplifier length, and number density of Eu(TTA)₃phen. The simulations showed that optical gains are saturated above some maximum po9int. More than 30 dB optical gain can be achieved with 5 m long amplifier at 300 mW pump power.

Two novel simple and flexible WDM laser sources are demonstrated using loop erbium-doped fiber amplifier configuration. The loop serves as a mirror and as an amplification medium. The laser cavity was made form loop mirror and either a set of fiber Bragg gratings (FBGs) in the first design, or a 100 percent reflecting mirror in the second scheme. The FBGs select the proper lasing wavelengths in the first technique, while a combination of stress induced effect of erbium-doped fiber and the presence of fused fiber filter in the laser cavity determine the lasing wavelengths in the second design. The FBGs can be placed either in parallel or in series at the input of the loop configuration. Optical attenuators are placed in front of the FBG to control the flatness of the laser source output and determine the required lasing condition for each wavelength to avoid competition of the different lasing wavelengths. This configuration is flexible for adding any number of wavelengths as long as enough amplified spontaneous emission is generated in the loop. Signal to noise ratio as high as 55-dB can be achieved.

Erbium doped polymer waveguide amplifier for operation at 1.55 micrometers was studied. A fluorinated polyimide was doped with Er ions using ion implantation. The samples were irradiated at room temperature by 320 keV Er²⁺ and 160 keV Er⁺ ions. Doses used were 1 by 10¹⁵/cm² and 1 by 10¹⁴/cm² respectively. The implanted samples were characterized using Rutherford Backscattering and SIMS analysis. The implanted ion profile was nearly Gaussian with range of 0.25 micrometers for the 320 keV implant and 0.12 micrometers for the 160 keV implant. A Gaussian implanted ion profile, matched with the electric field profile of the waveguide mode, can enhance the efficiency of energy transfer between the waveguide mode and the active ions. The implant depth of Er in polyimide at the energies used is shallow. In order to achieve the overlap with the electric field profile, a two layer waveguide amplifier structure is proposed. Such doping and waveguide fabrication techniques are compatible with the existing silicon technology.

Erbium-activated silica-titania planar waveguides were prepared by rf-sputtering technique. The films were deposited both on v-SiO₂ and silica-on-silica substrates obtained by plasma-enhanced chemical vapor deposition. The refractive index, the thickness and the total attenuation coefficient of the waveguides were measured by prism coupling technique. Scanning electron microscopy was used to analyze the morphology of both substrates and waveguiding film. Energy Dispersive Spectroscopy was performed in order to obtain a compositional analysis. Roughness measurements were carried out by means of a stylus profilometer. After thermal annealing at 600 degrees C for 6 hours the waveguides exhibited several well confined TE and TM propagating modes at 633 nm and one mode at 1550 nm. The attenuation coefficient at 1550 nm was 0.9 and 0.7 dB/cm for the films deposited on silica-on-silicon waveguide Raman spectroscopy. Waveguide luminescence spectroscopy was used to study the ⁴I_13/2 yields ⁴I_15/2 transition of Er³⁺ ion. The emission at 1530 nm was observed at room temperature upon continuous wave excitation at 514.2 nm. A lifetime of 3.7 ms for the metastable ⁴I_13/2 level was measured.

This paper reports the preparation of planar waveguides in an Er³⁺ doped tellurite glass with a composition, 15Ns₂O-25WO₃-60TeO₂- 1Er₂O₃, by Ag⁺-Na⁺ ion-exchange. The glass was chemically stable during ion-exchange process. Single-mode and multi- mode planar and buried waveguides in the tellurite glasses have been prepared, which is the first demonstrated of waveguides in tellurite glasses fabricated by ion-exchange technique to the best of our knowledge. The depths of the waveguides could be controlled by varying ion-exchange temperatures and times. The diffusion parameters, diffusion coefficients and activation energy were estimated. It is indicated that the tellurite glass is a prospective candidate for active integrated optics.

A model for population dynamics of Er³⁺ in tellurite glasses with high erbium concentrations is proposed. Luminescence decay curves from transitions of ⁴I_13/2 yields ⁴I_15/2 and ⁴S_3/2 yields ⁴I_15/2 were measured experimentally. Cooperative upconversion coefficients were obtained by numerically solving the rate equations of the model to fit the population dynamics of the ⁴I_13/2 and ⁴S_3/2 levels. The cooperative upconversion coefficient for ⁴I_13/2 + ⁴I_9/2 yields ⁴I_15/2 + ⁴I_15/2 is found to be 2.74 X 10^-18 cm³/s and for ⁴I_11/2 + ⁴I_11/2 yields ⁴I_15/2 + ²F_7/2 is 1.09 X 10^-18 cm³/s. The model provides a god basis for explaining the experiment data as it shows a high sensitivity to the input fitting parameters. This model can be used to analyze spectroscopic properties of Er³⁺ ions in glass hosts where various energy levels of Er³⁺ and transitions between them cannot be neglected.

A tunable laser operating near 944nm is important for micro LIDAR systems. In this work, we have carried out a systematic study of Nd doped fiber glass materials which can be used for this purpose. The emission cross-sections of these materials at 944nm have been calculated. The wavelength dependence of emission of these materials has been studied. Among the silica-based material Nd doped silica fiber glass has the largest cross section for 944nm laser emission. The co-dopants reduce this cross section. Some Nd doped non-silica materials have higher stimulated emission cross-section than silica-based materials.

We have measured persistent spectral hole burning (PSHB) for ⁵D₀-⁷F₀ transition of Er³⁺ doped in binary Ns₂O-B₂O₃ glasses. While room-temperature PSHB is observed in the glasses prepared in reducing conditions, it does not occur in the glasses melted in air. ¹⁵¹Eu Mossbauer effect measurements reveal that the glasses prepared in reducing conditions contain both Eu³⁺ and Eu²⁺ ions. The hole area varies depending on the concentration of Eu³⁺ in al the presented glasses. Besides, the hole area increases with an increase in the concentration of Ns₂O when the molar ratio of Eu²⁺ remains constant. Also, we demonstrate high-temperature PSHB of Eu³⁺ in sodium borate glasses irradiated with near-IR femtosecond laser pulses.

Persistent spectral hole burning (PSHB) spectra were observed at room temperature in Eu³⁺ ions-doped glasses treated with either H₂ gas or X-ray. The Eu³⁺-doped Al₂O₃-SiO₂ glasses were prepare by sol-gel process. The glasses were heated at 500 to 800 degrees C in H₂ gas, and irradiated with x-ray. The PSHB spectra were burned on the ⁷F₀ yields ⁵D₀ transition of the Eu³⁺ ions. The hole depth increased with increasing heat treatment time and is maximum for the samples heated at 600 degrees C for 1h. In the x-ray-irradiated glasses, the PSHB spectra were observed at room temperature for the first time, to our knowledge, and the hole depth increases with increasing irradiation time. In the x-ray-irradiated glasses, no fluorescence was observed form the Eu³⁺ ions. A novel. Model for hole burning is proposed on the basis of the excitation of the Eu³⁺ ions and subsequent hole trapping in the oxygen- defect centers of the Al-O polyhedra.

Recent studies on optical properties of Tm³⁺-doped tellurite glasses are presented as candidate materials of 1.4 micrometers amplifier. Usually, non-oxide fiber hosts with lower phonon energy are required, because the initial ³H₄ level is easily quenched in high-phonon-energy environment. However, the restriction is not so server as that of the Pr³⁺:¹G₄ for 1.3(Mu) M amplifiers due to the moderate energy gap. The Judd-Ofelt analysis showed 96 percent quantum efficiency in a tellurite host. To overcome the problem of intensity amplified spontaneous emission of competitive 0.80micrometers transition from the initial ³H₄ level, an Nd-doped cladding was proposed utilizing a strong absorption band. Improved emission was obtained as a result of radiative energy transfers between Tm³⁺ and Nd³⁺ ion. Also, the effect of codopants, such as Eu³⁺, Tb³⁺, Ho³⁺, on the lifetime of the Tm³⁺-levels was investigated for efficient population inversion between the ³H₄ and ³F₄. The Ho³⁺ showed the best selectivity in quenching effect. Owing to its quantum efficiency and better fiberizability than fluorides, the Tm-doped tellurite glass can be a potential candidate of the amplifier at the S⁺-band in the WDM telecommunication.

New alkaline free phosphate glass compositions are presented. Phosphate glass with a temperature coefficient of refractive index close to zero and a good chemical durability can be achieve. These new glass compositions are very promising for high quality optical fibers with a constant mode profile, and erbium doped fiber amplifiers with a high gain per unit length.

Based on chemical, physical, and economical reasons oxide glasses are and will be the materials of choice for advanced optical and electronic applications. Engineered rare earth materials are envisioned to have unique optical and electronic properties. Depending on the application, higher or lower rare earth solubility in glass may be required. Many issues arise including how the presence of lanthanide oxides in silicates leads to heterogenous phenomena such as nanoclustering, precipitation, crystal nucleation or phase separation. True solubility of rare earth elements in binary glass systems without cluster formation is very limited, whereas, higher solubility can be achieved in multi- component glass systems. In this work, the local environment of La in silicate glasses has been investigated using molecule dynamics computer simulation. Structural features that have been determined include simulated neutron diffraction and EXAFS patterns. Analysis to better understand the underlying driving forces of clustering is also presented.

In this work we report on spectroscopic properties of Er³⁺-doped aluminum fluorophosphate glasses of molar composition 29.8AlF₃:3.5 MgF₂: 19.8 CaF₂: 10.9 SrF₂: 12.8 BaF₂: 8.4 YF₃:9.8 ZrF₄:4 NaPO₃:1 ErF₃ and 30 AlF₃:3.5 MgF₂:20 CaF₂: 11 SrF₂: 13 BaF₂: 8.4 YF₃: 10 ZrF₄: 4 NaPO₃: 0.1 ErF₃, and Er³⁺-doped tellurite glasses of molar composition 75 TeO₂: 12 ZnO: 10 Na₂O: 2 PbO: 1 Er₂O₃ and 75 TeO₂: 12 ZnO: 10 Na₂O: 2 GeO₂: 1 Er₂O₃. Absorption and Stokes luminescence upon visible excitation were measured. Emission in the third telecom window was observed upon excitation at 514.5 nm and the lifetime of the ⁴I_13/2 level was measured. IR-to-visible up conversion emission under continuous-wave laser excitation at 976 nm was observed. The up conversion results in a strong green emission and a weaker red emission, whose intensity shows a quadratic dependence on the excitation power, indicating that two photons are involved in the process. Lifetime measurements were performed in order to study the dynamical behavior of the up conversion emission and to clarify the contributions of excited state absorption and energy transfer to the up conversion process.

Effect of soaking temperature on concentration of rare-earth ions in the optical fiber core during solution doping process was investigated. The dopant concentration of Er³⁺ and Ho³⁺ in the preforms and the fibers measured by the electron probe microanalysis and the optical spectrum analyzer was found to increase with decreasing the soaking temperature. The increase in the concentration of the Er³⁺ and the Ho³⁺ was attributed to the precipitation of the dopants due to the decrease in the solubility by decreasing the temperature.

We have carried out a systematic study of optical emission in Yb doped fiber glass materials which can be used for fiber laser applications. The stimulated emissions cross- sections of these materials have been calculated. The wavelength dependence of emission of these materials has been studied. The peak emission cross section in Yb doped Silica glass is 2.6 pm² and the peak wavelength is at 974 nm. The co-dopants do not significantly alter the emission cross section or the peak wavelength of this cross section.

The Er³⁺ luminescent properties of Er-doped Si/SiO₂ superlattices are investigated. The superlattices were deposited either by electron cyclotron resonance plasma enhanced chemical vapor deposition or by ultra-high vacuum ion beam sputter deposition method and subsequently annealed at 950 degrees C. The thickness of the layers was varied 0.6 to 4.8 nm, and location of Er controlled within sub-nm. The structure and the composition of the films were confirmed using transmissions electron microscopy and medium energy ion spectroscopy. By carefully controlling the Si and SiO₂ layer thickness and the locations of Er, we demonstrate several orders of magnitude enhancement of Er³⁺ luminescence and suppression of de-excitation mechanisms. We also demonstrate fabrication of waveguides using Er-doped Si/SiO₂ superlattices, and discuss implications for possible applications.

Incorporation of Si nanocrystal into Er-doped glasses strongly enhances the IR luminescence of Er³⁺. The enhancement is believed to be due to the energy transfer from nc-Si. However, the mechanism of the interaction between nc-Si and Er³⁺ has not been fully understood. In this work, we have studied the interaction between nc-Si and Er³⁺ by photoluminescence (PL) spectroscopy and PL decay dynamics. In order to tune the luminescence energy of nc-Si to the energy separations between the discrete electronic sates of Er³⁺, the size of nc-Si was changed in a wide range; the PL energy of nc-Si was changed from 1.2 to 1.5 eV. At low temperatures, periodic features were observed in the PL spectra of nc-Si. The observation of the features is the first spectroscopic evidence that indicates the strong coupling between nc-Si and Er³⁺. Furthermore, size dependence of the energy transfer rate was estimated from the delay time of the Er³⁺. The effects of quantum confinement of excitons in nc-Si on the high PL efficiency of Er³⁺ are discussed.

Room temperature photoluminescence (RT PL) has been obtained from Er₂O₃ thin films fabricated via reactive sputtering of Er metal in Ar/O₂ and subsequently annealed. Upon annealing, the PL spectra develop maxima at 1549 nm and 1541 nm for films treated at 650 degrees C and 1020 degrees C, respectively. Crystallization at high temperature results in RT PL and a lifetime of approximately 10 ms at 4K.

Excitation and de-excitation mechanisms of rare earth doped nanocrystalline silicon and its implications for waveguide amplifier applications are investigated. Er, Nd, and Pr doped silicon rich silicon oxide (SRSO) thin films were prepared by electron cyclotron resonance enhanced chemical vapor deposition with co-sputtering of target and subsequent anneal at 950 degrees C. Temperature and pump-power dependence of Er³⁺ photoluminescence shows that carrier-mediated non-radiative de-excitation are strongly suppressed indicating feasibility of population inversion. Detailed investigations of dependence of Er³⁺ luminescence intensity and lifetime on pump width indicate that exciton-erbium coupling is dominant over carrier- exciton coupling, and that the luminescent Er ions are not inside the Si nanoclusters but in the SiO₂ matrix near the clusters. Luminescence properties of Nd-doped SRSO is similar to that of Er-doped SRSO, but the temperature dependence of Nd³⁺ luminescence intensity is different from that of Er³⁺ luminescence, an effect which we ascribe to its higher transition energy. In contrast, no luminescence could be observed from Pr-doped SRSO. Erbium-doped SRSO waveguides are fabricated using the standard Si processing techniques, and guiding of 1.55 micrometers light with strong Er luminescence is observed. These results indicate that for rare erath-doped SRSO waveguides to become practical, formation of high density of small Si nanoclusters must be induced.

Coupling between silicon nanoclusters and erbium ions n silicon-rich silica hosts can enhance the technologically important erbium 4f emission at 1535nm and relax the restrictions on pump wavelength. We presents luminescence results showing that the enhancement of the erbium absorption cross-section due to the presence of silicon nanoclusters can be around 4 orders of magnitude. Temperature quenching of luminescence in this material is very weak, indicating that the Auger non-radiative decay channels which limit erbium emission in bulk silicon are largely absent in silicon-rich silica. We also demonstrate broad-band flashlamp pumping of erbium-doped silicon-rich samples with a power efficiency of 0.01 percent. With the growing requirement for broad-band access to telecomms networks and the provision of fiber-to-the-home systems, this material is a promising candidate for use in cheap flashlamp pumped gain elements for use in WDM.

Rare earth elements have been used as optical dopants in glasses for many years. Boro-silicate glass films doped with rare-earths were deposited on glass substrates by using a simple sol-gel method. To avoid the undesirable precipitation due to the different hydrolysis rates between silicon and boron alkoxides, two solutions were used for dip-coating separately. One solution consisted of silicon tetraethoxide, ethanol, water and terbium nitrate as the Tb dopant. Another consisted of triethyl borate. Layer-by-layer deposition was applied by dipping into solutions containing metal alkoxides in sequence. The fluorescence properties of Tb³⁺ were investigated for the boro-silicate samples in relation to the firing effect. As-deposited silicate and boro-silicate samples showed similar fluorescence spectra under UV excitation. After firings at about 800 degrees C, a remarkable increase of the Tb³⁺-ion fluorescence was observed for the boro-silicate samples, while the silicate sample showed a little increase in fluorescence intensity. These experimental results suggested the formation of boro- silicate network and the incorporation of Tb³⁺ into the boro-silicate matrix. The multilayer process was found useful to fabricate multi-component sol-gel films.

Recent results obtained for Er₂O₃-SiO₂ monolithic xerogels and erbium activated SiO₂-TiO₂ planar waveguides are presented. Monolithic erbium-activated silica xerogels with erbium content ranging from 0 up to 40000 ppm were prepared by the sol-gel technique. Samples were densified by thermal treatment in air at 950 degrees C for 120 hours. The densification degree and the relative content of hydroxyl groups were studied by NIR absorption and Raman spectroscopies. Emission at 1.5 micrometers , characteristic of the ⁴I_13/2 yields ⁴I_15/2 transition of Er³⁺ ions, was observed at room temperature for all monolithic samples upon continuous wave excitation at 980 nm. For the 5000 Er/Si ppm doped xerogel, an intense photoluminescence was observed with a lifetime of 8 ms for the metastable ⁴I_13/2 level. Passive and erbium-activated SiO₂-TiO₂ planar waveguides, monomode at 632.8 nm, were prepared by a dip-coating technique. Some parameters such as H₂O content, intermediate and final thermal treatments, and the molar ratio TiO₂/SiO₂ were modified during the preparation of the solution in order to minimize the final content of residual hydroxyl groups and the phase separation between silica and titania. Raman spectroscopy was used to check the structural properties of the waveguides. A lifetime of 7 ms was measured for the metastable ⁴I_13/2 level in a 93SiO₂-7TiO₂ planar waveguide activated by 10000 ppm Er/(Si + Ti). The best value of the attenuation coefficient was of 0.5 dB/cm at 632.8 nm.

Er-doped sodium-niobium phosphate glasses have been produced by the melting technique. Their optical properties have been fully characterized and show a broad fluorescence band around 1.5 micrometers . The fluorescence lifetime of the ⁴I_13/2 metastable state is long enough to make these glasses suitable to be used in optical ampl9ification devices. Waveguides have been produced by diluted Ag⁺/Na⁺ ion exchange and their properties are described here.

Optical fiber laser can be used in future optical communication systems. We designed an all fiber ring laser. Erbium doped fiber was used in the ring. Pumped at 980nm, the fiber laser operated at dual wavelengths, 1599.75nm and 1560.6nm, respectively. We measured the linewidth, and slope efficiency. The threshold was low.

The fluorescence and absorption variation of spectra of Er- and Yb/Er-doped phosphate and silicate glasses under CW Ti- sapphire laser were investigated. On pumping, the differential spectra demonstrated variations of spectral profiles. The reason of these variations is heating effect under high pump power. These variations were explained by a redistribution of the populations of the Stark sublevels of the ⁴I_15/2 ground and the ⁴I_13/2 excited manifolds. The heating effect under pumping was taken into account for measurement of quantum yield and determination of absolute values of up-conversion coefficients. Several techniques that reduce the heating effect on fluorescence, excited state absorption, and ground state absorption spectra due to pumping were proposed.

The mechanism of non-radiative energy transfer between Tb³⁺ and Nd³⁺ ions in fluorophosphate glass has been analyzed with the Forster-Dexter theory. Several/transfer parameters such as the transfer probability, transfer efficiency, critical transfer distance, and critical concentration have been evaluated by fitting the experimental fluorescence spectrum of those ions with that theory. The recorded emission spectrum of Tb³⁺ with different Nd³⁺ ion concentrations shows that the transfer process from the ⁵D₄ state of Tb³⁺ to the ⁴G_5/2 state of Nd³⁺ is driven predominantly by a dipole-dipole interaction. The effect of this energy transfer is to considerably enhance the optical gain of the ⁴F_3/2 to ⁴I_11/2 emission band of Nd³⁺ ions. The reduction in optical gain at high activator concentrations is attributed to the concentration quenching in Nd³⁺ ion pairs. In addition to this, the dependence of the J-O parameters, several radiative properties of Nd³⁺ ions in the phosphate content as well as the nature of alkali content were also studied.

A novel four-wavelength all-fiber laser based on fiber Bragg gratings is presented. The four wavelengths are 1555.8, 1556.6, 1557.4 and 1558.s nm, respectively. Each output laser is < 0.3 nm in line-width and > 1 mW in power. The suppression ratio between adjacent wavelengths is > 30 dB. The laser was applied in a wavelength division multiplexing system and the 100 km transmission of 1.2 Gb/s nonreturn-to-zero code, 1.2 Gb/s return-to-zero, 2.5 GHz analogue signal and 5 GHz analogue signal was realized with it.

In order to obtain a high laser efficiency from Xe pumped Nd laser systems, a novel cavity filter glass doped with Eu³⁺ and Sm³⁺ was investigated using a phosphate host. Sm³⁺, which served to inhibit ASE also was found to strongly transfer its energy to the Eu³⁺. The Eu³⁺ emits an efficient red emission from the ⁵D₀ yields ⁷F₁ transition which is located exactly at the Nd³⁺ absorption band and therein radiatively sensitizes the Nd laser emission. The energy transfer and back transfer of these two rare-earth ions in phosphate will be discussed. This doubly-doped phosphate glass cavity samples produced an increase in output power by 50 percent over undoped filters in a Xe pumped pulsed Nd:glass laser system.

It is demonstrated that the commercially-available imaging plate (IP) using BaFBr:Eu photostimulable phosphor is useful as a phosphore material for 2D UV image sensor though the sensitivity of the IP for UV-ray is not so high. The new phosphore materials as alternative materials for the IP are surveyed for many possible phosphore materials and consequently we find out that the Ca_xSr_1-xS:Eu,Sm phosphore ceramics exhibited a high photo stimulated luminescence (PSL) intensity for UV-ray irradiation. It is found that the SrS:Eu,Sm phosphore ceramics exhibits good PSL characteristics for UV-ray imaging and the PSL characteristics are depended on the content of CaS and the concentration of Eu and Sm doped.

In this work we report the upconversion processes that produce blue, green, orange, and red emission in K₅Nd(MoO₄)₄ stiochiometric crystal together with the dynamics and spectral properties of the laser emission. It was found that upconversion energy transfer processes reduce the energy storage capacity through the reduction of the fluorescence lifetimes of the metastable ⁴F_3/2 level. The experiments were conducted in such a way that the dynamics of the IR and visible fluorescence was performed under lasing and nonlasing conditions. The dynamics of the unconverted emission shows that both upconversion energy transfer and excited state absorption of the laser emission occur.