A spectroscopic study of the population mechanisms in erbium-doped amorphous aluminum oxide up to the H-2(11/2)/S-4(3/2) levels is performed. Via luminescence decay measurements, absorption and emission spectra, and a Judd-Ofelt analysis, we determine luminescence lifetimes, radiative and nonradiative decay-rate constants, and branching ratios of the Er3+ intermanifold transitions. With a continuous-wave pump-probe technique, the excited-state absorption (ESA) spectrum is recorded between 900 and 1800 nm and the cross sections of the ESA transitions I-4(13/2) -> I-4(9/2), I-4(13/2) -> F-4(9/2), and I-4(11/2) -> F-4(7/2) are determined. The microparameters and efficiencies of resonant and phonon-assisted energy-migration and energy-transfer upconversion (ETU) processes among Er3+ ions occurring from the first and second excited states are evaluated. From the ratio of the S-4(3/2) and F-4(9/2) luminescence intensities as a function of Er3+ concentration, we prove the existence and quantify the macroscopic ETU coefficient of the two-phonon-assisted ETU process (I-4(13/2,) I-4(11/2)) -> (I-4(15/2,) F-4(9/2)). (c) 2013 Optical Society of America

We report the high-temperature growth, spectroscopic and passive waveguiding properties of crystalline Er,Yb:YAl3(BO3)4 films grown with LPE on undoped YAl3(BO3)4 substrates. The absorption and emission spectra and the fluorescence lifetimes have been measured. Multimode passive waveguiding has been observed in a 50-μm-thick Er,Yb:YAB film. The propagation losses have been measured to be 2dB/cm.

In this paper, Er,Yb:YAl 3 (BO 3 ) 4 layers were tested as passive optical waveguides. Using a microscope objective with a numerical aperture of 0.4, the beam of a Ti: sapphire laser at 900 nm was focused onto the incoupling end-face of the waveguide. The outcoupled light was collected with another microscope objective and imaged onto the chip of a CCD camera. As expected for a 50 mum thick film, several waveguide modes were observed. The propagation losses were measured, which is based on the determination of the longitudinal distribution of fluorescence light along the waveguiding direction, obtained at different excitation wavelengths. The excitation wavelength was tuned from 900 to 1000 nm and the resulting fluorescence intensity at 1.5 mum was detected using a Ge photodiode. The parasitic propagation losses were measured to be approximately 2 dB/cm in the 50 mum-thick Er,Yb:YAl 3 (BO 3 ) 4 waveguide.

At high Er3+ doping, electric dipole-dipole interactions between neighboring ions such as energy migration and energy-transfer upconversion (ETU) take place, thereby reducing the population inversion and negatively affecting the gain performance of the amplifier. These effects are investigated by lifetime and gain measurements respectively, in Al2O3:Er3+ waveguides and analyzed the results in the frame of the microscopic model developed by Zubenko et al.

We report on a Yb(3+)-doped sesquioxide waveguide laser based on a lattice-matched Yb(3+)(3%):(Gd,Lu)(2)O(3) film that has been epitaxially grown on Y(2)O(3) using pulsed laser deposition. Rib-channel waveguides have been structured by reactive ion etching. Laser emission at 976.8 nm was observed under pumping with a Ti(3+):Al(2)O(3) laser at 905 nm. A laser threshold of 17 mW and a slope efficiency of 6.7% have been achieved with respect to input power. For an incident pump power of 200 mW, a maximum output power of 12 mW could be realized.

We report the first waveguide laser based on a rare-earth-doped sesquioxide. A 2 microm thick lattice matched Nd(0.5%):(Gd, Lu)(2)O(3) film with a nearly atomically flat surface has been epitaxially grown on a Y(2)O(3) substrate, using pulsed laser deposition. The film has been structured with reactive ion etching and a rib channel waveguide laser has been realized. Laser radiation at 1075 nm and 1079 nm has been observed under 820-nm pumping. The laser possesses a threshold power of about 0.8 mW and a preliminary slope efficiency of 0.5% versus incident pump power. A maximum output power of 1.8 mW has been obtained for 370 mW incident pump power.

The use of Yb3+ as a sensitizer for Er3+ doped laser materials is a common technique because of the high Yb3+ absorption cross sections. Energy transfer processes from Yb3+ to Er3+ in Sc2O3 are studied by two different methods. Transfer parameters describing the interactions between Er3+ and Yb3+ ions are obtained on the one hand from the ratio of emitted photons around 1.55μm by Er3+ ions and around 1μm by Yb3+ ions at cw excitation of Yb3+, on the other hand by lifetime measurements of Yb3+ ions in the codoped samples. Laser experiments are performed to study the suitability of Er3+,Yb3+:Sc2O3 as a laser material. Comparisons with energy transfer in Er3+,Yb3+:glass are made.

Erbium-doped aluminum oxide (Al2O3:Er) is a promising material for integrated amplifier or tunable laser applications due to its wide gain spectrum around 1550 nm. We deposited Al2O3 layers on thermally oxidized Si-wafers by reactive co-sputtering at 550°C. Propagation losses were 0.11 dB/cm at λ =1.5 μm. Channel waveguides were fabricated by reactive ion etching with propagation losses down to 0.21 dB/cm. Under pumping at 977 nm, the optical small-signal gain at 1533 nm is 0.84 dB/cm, resulting in 5.4 dB net gain over the waveguide length of 6.4 cm. Net gain is obtained over a wavelength range of 41 nm. The Er concentration was measured using Rutherford Back-Scattering (RBS). Lifetimes of the 4I13/2 level of up to 7 ms were measured for Er concentrations around 2×1020 cm-3. A faster decay with an increasingly non-exponential initial component is measured for higher Er concentrations (Fig. 2). While the initial quenching is probably due to migration-accelerated energy-transfer upconversion between neighboring Er3+ ions in the 4I13/2 level, the decreasing exponential tail is due to either pair-induced energy-transfer upconversion or quenching by impurity ions. Detailed investigations of the quenching mechanisms are currently under way.

The excitation and relaxation processes relevant for establishing optical gain in Al2O3:Er3+ on the 4I13/2 -> 4I15/2 transition at 1.5 µm are investigated. Excited-state absorption in the wavelength range from 900-1800 nm is measured in a pump-probe experiment. The 4I13/2 and 4I11/2 lifetimes are measured after direct excitation and the macroscopic parameter of the energy-transfer-upconversion (ETU) process (4I13/2, 4I13/2) -> (4I15/2, 4I9/2) is determined independently from both decay curves. By use of the Zubenko model the microscopic parameters of ETU and energy migration are derived. It is found that above the Er3+ concentration at which the transition from static to migration-accelerated ETU takes place also the 1.5-µm amplifier gain is diminished by this process.

Epitaxially grown Nd(0.5%):(Gd, Lu)2O3 and Er(0.6%):(Gd, Lu)2O3 waveguides deposited on Y2O3 by pulsed laser deposition, providing peak emission cross sections comparable with those of Lu2O3 bulk crystals, have been fabricated and structured. Rib waveguiding has been shown.

PCT No. PCT/EP93/02622 Sec. 371 Date May 27, 1994 Sec. 102(e) Date May 27, 1994 PCT Filed Sep. 27, 1993 PCT Pub. No. WO94/08169 PCT Pub. Date Apr. 14, 1994.In a flexible connection arrangement for two pipe portions having a metallic bellows which is connected axially on either side in a gastight manner with connection pieces, the sides of the connection pieces facing the bellows are provided with radially widened end portions. Also provided are a damping insert, which extends coaxially relative to the bellows a along its length and is in a working connection therewith, and heat protection device for the bellows acting in the radially inward direction. The damping insert encloses the bellows radially outwardly such that the turns of the bellows contact the damping insert. The lateral end regions of the damping insert are held in the widened end portions without being fastened thereto and are supported radially outwardly by the latter. The connection pieces are connected with one another via a spring which surrounds the damping insert radially outwardly. The heat protection means are formed by a pipe segment which extends within the bellows coaxially relative to the bellows at a radial distance from the latter and which is fastened to the connection piece located in the front as viewed in the direction of flow.

Monocrystalline lattice matched Er(0.6%):(Gd, Lu)2O3 films with thicknesses up to 3 m and nearly atomically flat surfaces have been deposited on Y2O3 substrates by Pulsed Laser Deposition (PLD). The epitaxial growth has been verified in-situ by Reflection High Energy Electron Diffraction (RHEED). As first test structures channel waveguides with widths ranging from 2 to 5 m and heights from 400 to 700 nm have been fabricated by Reactive Ion Etching and finally covered by about 1.5 m thick a-Al2O3 top claddings to reduce scattering losses at the surface. Due to the refractive index difference between film and substrate (0.03 at 1.55 m) rib waveguiding could be demonstrated. The fluorescence spectra of the films are comparable with those of Er:Y2O3 bulk crystals. Therefore, a theoretical gain spectrum could be calculated from the absorption and emission spectra of Er:Y2O3. Bleaching at the pump wavelength of 1480 nm results in an inversion ratio 0.75 between the 4I13/2 and 4I15/2 multiplet of Er3+ and thus to a theoretical gain of 260% at 1535 nm for a 7 mm long waveguide. Gain measurements using a tunable diode laser (1530 nm to 1583 nm) as signal and a pump diode at 1480 nm have been performed. Both sources have been combined in a single mode fiber and then coupled into the waveguide. Using the lock-in technique and a monochromator, the signal intensity I of the outcoupled light could be measured in dependance of the pump power (up to 100 mW before coupling into the waveguide) and the gain determined as (Ipumped – Iunpumped) / Iunpumped. Calculations show that the small waveguide dimensions allow bleaching with absorbed powers well below 1 mW. It has been experimentally verified that the incident signal of 0.5 mW was sufficient to already bleach the waveguide in the unpumped case. Therefore, the reduction of signal absorption in the pumped case can be neglected and does not falsify our measured gain. At 1535 nm a maximum gain of 150% (4 dB) could be measured for the 7 mm long sample, resulting in a gain of 5.7 dB/cm. The measured gain is lower than the theoretically expected, because the intensity distribution of the guided mode is not limited to the doped regions. Taking this into account by normalizing the theoretical gain spectrum to the maximum measured gain of 150% results in a good accordance of the experimentally determined gain at various wavelengths with the theoretical spectrum (see Fig. 1c). The high gain obtainable due to bleaching in the small waveguiding structures combined with the relative high peak cross sections of crystalline RE doped (Gd, Lu)2O3 makes these waveguides promising for the development of compact lasers with low lasing threshold and high frequency stability.

We present an efficient in-band-pumped Er(0.2 at%):Sc(2)O(3)-laser at 1581 nm with a maximum output power of 0.95 W and a maximum slope efficiency of 31%. (C) 2008 Optical Society of America

The spectroscopic properties of Al2O3:Er thin films have been investigated by lifetime measurements. The luminescence decay curves show an initial non-exponential component, followed by an exponential tail, whose decay time decreases with increasing Er concentration. This behavior can be described with good accuracy by a microscopic treatment that takes into account both energy migration and energytransfer upconversion among Er ions. Parameters such as the migration mean time τ0 and the donor-acceptor transfer probability CDA are derived. We show that, in the concentration range of interest for waveguide amplifiers at 1.5 μm, upconversion occurs mostly in the static regime.

This letter focuses on epitaxial growth of a 1-μm-thick lattice matched Nd-doped monocrystalline (Gd,Lu)2O3 film deposited on a {100} oriented Y2O3 substrate by pulsed laser deposition. Layer-by-layer growth indicated by in situ reflection high energy electron diffraction was observed up to film thicknesses of 100nm. The subsequent growth behavior could be explained by a multilevel growth mode. Thus, the growth mode was two-dimensional and epitaxial. Lattice matching of up to 99.3% was achieved. The evolution of the structural and topographical properties of the films was verified by ex situ x-ray diffraction analysis and atomic force microscopy, respectively.

A nondestructive loss-measurement method for active planar waveguides has been developed. It is based on the determination of the longitudinal distribution of fluorescence light along the waveguiding direction, obtained at different excitation wavelengths. First measurements have been performed on a 10 mu m thick Nd:Sc2O3 waveguiding film, deposited on a sapphire substrate by pulsed laser deposition, and on a 35 mu m thick diffusion-bonded Nd:YAG waveguide between sapphire layers. Their scattering losses have been determined to be (11.6 +/- 0.9) and (6.9 +/- 0.9) dB/cm, respectively. (c) 2007 Optical Society of America.