T. Yu. Ivanova

Er3+ to glass matrix energy transfer in Ga–Ge–S:Er3+ system

Abstract Spectroscopic characteristics (spontaneous emission probabilities, radiative lifetimes, oscillator strengths, branching ratios and quantum efficiency) of Er 3+ in Ga 2 S 3 –GeS 2 –Er 2 S 3 glassy system are investigated by use of Judd–Ofelt theory. Lifetime measurements 4 S 3/2 level of Er 3+ in Ga 2 S 3 –GeS 2 –Er 2 S 3 glasses with various Er 3+ concentrations and optical gap energy are performed. Estimations of the non-radiative relaxation rate and the multiphonon relaxation rate demonstrate the occurrence of energy transfer from Er 3+ ion to the electronic states of the glass matrix. The way of the practical application of this non-radiative energy transfer is suggested.

Up-conversion luminescence efficiency in Er-doped chalcogenide glasses

Abstract The efficiency of up-conversion luminescence of Er 3+ ions (excited by laser light operating at 810 nm) in the GeS 2 –Ga 2 S 3 :Er 2 S 3 system strongly depends on the energy position of the fundamental absorption edge. This dependence is due to non-radiative energy exchange between the electronic subsystem of the glassy matrix and excited levels of Er 3+ ions. In chalcogenide glasses Ge and Ga atoms are fourfold coordinated. Except for the M (M=Ge, Ga)–S heterobonds, the rest are M–M homobonds. These homobonds can be detected with Raman spectroscopy. The energy position of the absorption tail of the fundamental band depends on the concentration of M–M homobonds. When the concentration of these bonds increases the absorption edge shifts to longer wavelengths and the intensity of up-conversion luminescence decreases. The relative concentration of M–M bonds depends not only on composition of the glassy matrix but also on the synthesis and on concentration of extrinsic impurities such as OH − , SH − and –CH 2 –. Another cause of reduction of up-conversion luminescence intensity is the inhomogeneous distribution of REI in the Ga 2 S 3 –GeS 2 glasses. The simple model describing dependence of luminescence intensity on type of REI distribution in the glassy matrix is discussed.

Laser-Induced Copper Deposition on the Surface of an Oxide Glass from an Electrolyte Solution

Continuous copper patterns were grown on the surface of oxide glass substrates through laserinduced chemical liquid-phase deposition (LCLD). The deposition was performed with the use of a continuouswave argon laser operating in a multimode regime. The deposition occurred as a result of the reducing chemical reaction initiated by laser radiation. Continuous metal patterns were produced by scanning focused laser radiation along the substrate-electrolyte interface. The morphology and the chemical composition of the deposited patterns were examined with the use of a CEM-SCAN 4 DV scanning electron microscope equipped with an energy-dispersive spectrometer. The morphology of the deposited patterns was investigated as a function of the laser radiation power and the number of scans. It was demonstrated that high-quality continuous patterns can be fabricated using one scan of the laser beam.

Non-radiative energy transfer from Er3+ ions to the electronic states of the chalcogenide glass matrix

Lifetime spectroscopy of the chalcogenide systems Ga-Ge-S:Er 3+ and Ga-Ge-S-Se:Er 3+ has shown that the non-radiative energy transfer from rare-earth ions to the electronic states of the chalcogenide matrix is important. Numerical calculations of transition probabilities (W R , W mph , W CR ) allowed estimation of the probability of the energy transfer to the chalcogenide matrix. It was found that when the optical bandgap of the matrix approaches the Er 3+ level, the probability of such energy transfer process will increase as long as a complete resonance is not achieved.

Feedback-enhanced self-organization of atoms in an optical cavity

We considered an application of a feedback loop to enhance the self-organization of atoms in a cavity. In contrast to the original setup, we assumed the light leaking from the cavity was photo-detected and the signal was used to appropriately adjust the atomic potential. It was shown that no additional feedback-induced quantum noise was introduced into the system. Numerical simulations performed in classical approximation showed that the application of feedback weakened the requirement for the atom-field coupling needed to observe the self-organization.

Erbium-mediated photoconductivity of Ga?Ge?S?Se?:?Er3+ chalcogenide glasses

Photoconductivity mediated by erbium ions in chalcogenide glasses Ga–Ge–S has been found. The conductivity of glasses undoped and doped with erbium has been studied under irradiation by laser light at λ = 813 nm. In both cases the optical band-gap energy exceeds by several times the laser photon energy. It has been observed that the exposure to sub-band-gap light does not change the conductivity of the undoped glass, whereas it leads to a significant increase in the conductivity of the glass doped with erbium. We propose a two-photon mechanism of the photoconductivity in this glass, where erbium accumulates laser energy and then transfers it nonradiatively to the glass matrix (energy backtransfer).

Analysis of the spectroscopic parameters of chalcogenide glasses in the Ga-Ge-S: Er3+ system

The spectroscopic characteristics of chalcogenide glasses in the Ga-Ge-S: Er3+ system are determined. The oscillator strengths, the Judd-Ofelt intensity parameters, the probabilities of spontaneous radiative transitions, and the radiative lifetimes of levels are calculated from the absorption spectroscopy data for two series of Ga-Ge-S chalcogenide glasses doped with Er3+ ions. In the first series, the Er2S3 content is varied from 0.49 to 4.64 mol % at the fixed composition of the glass matrix (0.15Ga2S3 · 0.85GeS2). In the second series, the Ga2S3 content is varied from 10 to 30 mol % at the fixed Er2S3 content (1.94 mol %). The aforementioned spectroscopic parameters are analyzed as a function of the chalcogenide glass composition. It is revealed that the values of the oscillator strengths and the probabilities of spontaneous radiative transitions in Er3+ ions in the chalcogenide matrix are larger than those in phosphate, germanate, and tellurite matrices.

Quantum limits of feedback cooling in optical lattices

A quantum-mechanical analysis of feedback cooling [see Phys. Rev. Lett. 94, 153002 (2005)] of atoms trapped in a far-off-resonant optical lattice is presented. The model considered is valid for ultralow energies of atoms, thus, allowing for the study of an ultimate cooling limit. The influence of the measurement-induced noise and feedback-induced atom-atom correlations on the cooling efficiency is discussed. It is shown that there are regimes where the quantum noise can be effectively compensated for.

Rapid determination of the gas temperature in magnetooptical traps

We have considered a simple method for estimating the gas temperature in a magnetooptical trap. In this method, only one of three laser beams in the magnetooptical trap is shut down. Then, the light scattered by the atoms of the remaining beams makes it possible to observe the spread of the atoms in real time without using additional lasers. An analysis of the measuring data has convincingly proved their conformity with theoretical estimates. This method can be useful for the approximate express analysis of the magnetooptical trap performance.

Feasibility of a feedback control of atomic self-organization in an optical cavity

Many interesting nonlinear effects are based on the strong interaction of motional degrees of freedom of atoms with an optical cavity field. Among them is the spatial self-organization of atoms in a pattern where the atoms group in either odd or even sites of the cavity-induced optical potential. An experimental observation of this effect can be simplified by using, along with the original cavity-induced feedback, an additional electronic feedback based on the detection of light leaking the cavity and the control of the optical potential for the atoms. Following our previous study, we show that this approach is more efficient from the laser power perspective than the original scheme without the electronic feedback.