In recent years the synthesis of antiferromagnetic rings traced a path to the observation of interesting quantum coherence phenomena in heterometallic Single Molecule Magnets. Because of the presence of different magnetic centers, it is crucial to understand the distribution of the molecular spin on all the sites. 57Fe Mössbauer spectroscopy is an efficient and powerful technique to contribute to this knowledge in antiferromagnetic wheels containing iron ions. We analyze the Cr7FeII wheel: the Mössbauer line shape evolution of low temperature spectra (2.1 K) at different external fields is illustrated and the mean spin value of the iron ion is evaluated.

In the present paper we describe the results of Mössbauer measurements on the antiferromagnetic wheel Cr7Fe(II). From the spectra without external field in [1.8,14.8] K range we analyse the spin dynamics vs. T and we evaluate the electric hyperfine parameters. From the 1.8 K spectrum collected in the presence of a 1.5 10−2 T magnetic field, we determine the hyperfine field intensity. The corresponding spin of the iron ion in the complex is estimated and it is found to be in agreement with reported results of original calculations.

The interpretation of Mössbauer spectra often requires the use of the Transmission Integral function (TI). It contains the quantity , where fs is the source Mössbauer factor and B depends on the background radiation rate and on the inhomogeneity of the target: both of them usually obtained by ancillary measurements and tests. We present a simple method, that avoids ancillary measurements in evaluating the quantity . It is useful when the Mössbauer line-shape rapidly evolves in narrow temperature ranges: a real application for single molecule magnets spectra and an analytical example are reported, too

The structures of proton-exchanged and implanted waveguides are studied by X diffraction analysis and vibration spectroscopy. On the basis of the absorption’s spectroscopy data in the visible region and the data on the shift of the fundamental absorption edge in the nearultraviolet region, a comparative analysis of technologically conditioned variations in the nonlinear optical properties of proton-exchanged and implanted waveguides in stoichiometric LiNbO 3 crystals is conducted.

We report the investigation of the physical phenomena which occur in LiNbO3 during its surface irradiation by electron beam (EB) in order to fabricate 2D photonic band gap (PBG) grating. In order to better understand the mechanism of unusual holes formation by post-chemical etching, the induced micro structural modifications are studied by means of micro-Raman microscopy. We carried out EB bombardment on substrates of congruent z-cut lithium niobate. The main objective consists of the optimization of PBG grating fabrication process for applications in the field of optical telecommunications.

The magnetic anisotropy and the spin fluctuations of the paramagnetic molecule [Fe(OMe)(dpm)2]2 are analyzed by means of Mössbauer spectroscopy in the temperature range [7.6–33]K. Spectra in the presence of a 5T magnetic field directed along the γ rays were collected, by using a sample of pseudo-single crystal prepared by oriented grains. From the fits of the spectra, the hyperfine parameters are determined. Fits give also the value and direction of the magnetic anisotropy, referred to the electric field gradient (EFG) principal axes. The latter, together with the EFG components, were evaluated by means of ROHF ab initio calculations. Lastly, the rate of the spin transitions in function of T is discussed.

The paper shows how polysiloxane particles encapsulating fluorophores can be successfully used to detect biotin-streptavidin binding by two types of technique. After functionalization of the particles by streptavidin, the fixation of the biomolecule can indeed be detected by a shift of the localized surface plasmon resonance of the biotinylated gold dots used as substrate and by the luminescence of the fluorophores evidenced by scanning near-field optical microscopy. The development of particles allowing such a double detection opens a route for increasing the reliability of biological detection and for multi-labelling strategies crossing both detection principles.

This communication presents optical and spectroscopic characterizations of the first Yb3+:CaF2 waveguides fabricated by H+ implantation. The technique allows to obtain 1cm long channel waveguides, with mode sizes of about 10μm×10μm. Details on fabrication process and characterization of such waveguides are discussed.

In this work, we report the investigation of 2D photonic crystals in lithium niobate associated with waveguiding structures fabricated by He + implantation. From the material point of view, the investigation of PBG structures in lithium niobate is of great interest for optoelectronics technology since this crystal is one of the most important materials widely used in integrated and non linear optics. The choice of the implantation technique to produce the waveguide is motivated by the possibility of having both Transverse Electric (TE) and Transverse Magnetic (TM) guided modes in order to obtain a total photonic band gap (PBG).

Y - or Z- cut LiNbO3 crystals were implanted at room temperature by helium with energy in the MeV range and various doses with a specific care for the 1010–1016ions∕cm2 range. The induced structure defects were investigated by micro-Raman and IR reflectivity. IR Brewster angle technique was applied for detailed measurements on both indices variations in nuclear collision damaged areas. It is established that a transition from point to extended defects occurs at some threshold dose around 1.5×1015ions∕cm2 and that the extraordinary index is increased in a specific dose range around this threshold. A model based on depolarized cluster formation is proposed to explain the difference observed between the changes of ordinary and extraordinary refractive indices.

An optical planar waveguide is investigated in ZnO-doped periodically poled lithium niobate formed by He + implantation. Optical losses were found to be 2 dB/cm. Second-harmonic generation is used to produce a green laser beam by quasi-phase matching in the obtained waveguide. The conversion efficiency was found to be 10 -2 %/W. Photorefractive resistance properties are reported and discussed relating to un-doped periodically poled lithium niobate.

Continuous laser emission near 780 nm was demonstrated in proton-implantated Ti:sapphire buried channel waveguides. Absorbed pump power thresholds as low as 230mW and output powers of 17mW for 1-W absorbed power were obtained.

Fabrication and laser operation of proton-implanted Ti:sapphire buried channel waveguides is reported for the first time to our knowledge. Without any postimplantation annealing of the structures, continuous laser operation near 780 nm was demonstrated at room temperature at an absorbed pump power threshold of 230 mW. Single-transverse-mode laser emission was observed with measured beam propagation factors M(2)(x) and M(2)(y) of 1.5 and 1.2, respectively. An output power of 12.4 mW for 1 W pump power was obtained with an output coupler of 4.6% transmission at the signal wavelength. Higher output powers were measured in waveguides with larger cross sections exhibiting multimode laser emission.

Optical waveguides have been produced in Nd:YAG and Nd:YVO4 crystals by either proton or carbon implantation. The analysis includes refractive index profiles, spectroscopic properties and particularly laser emission characteristics in the YAG guides. Typical optical barrier profiles were obtained when protons were used. In the case of YVO4, carbon implantation produced a considerable refractive index variation in the guiding region, increasing the ordinary index and reducing the extraordinary index. The spectroscopic studies show that emission bands coming from the 4F3/2 level are not significantly altered by the ion beam process, thus maintaining the crystal quality in the guiding region. The YAG waveguides exhibit good laser emission characteristics at 1 064 nm and high stability in the CW regime.

Laser emission near 780 nm with 2 mW output power and 3.3% slope efficiency from a Ti:sapphire buried channel waveguide is demonstrated. The sample was fabricated by proton implantation.

The light ion implantation technique is applied to perform several planar and channel waveguides in 1 at.% Er3+doped YAlO3 single crystal. Waveguides of different dimensions are obtained using different doses and energies of H+ or He+. Under cw infrared sapphire–titanium laser excitation, the guided green upconverted luminescence of Er3+ is studied. It is the result of an excited state absorption mechanism and its intensity increases with the light ion dose used for the waveguide fabrication.

This work reports the formation of planar waveguides by proton and helium implantation in Nd:YVO4. Double and triple implants were realised using energies between 0.4MeV and 1.75MeV and doses around 1016ions/cm2, thus generating wide barriers; in particular a double waveguide was generated with a triple implantation. The analysis includes refractive index profiles, spectroscopic properties and near field imaging.

For the first time active planar optical microcavities with a thin colored lithium fluoride film as spacer have been fabricated by ion implantation. Irradiation has been realized through the top Bragg mirror of the passive microcavity, already fully deposited, to produce stable visible-emitting F2 and F3+ color centers in the LiF film. The spectral and spatial emission features of the microcavities demonstrate the feasibility of such an irradiation method and the possibility of controlling the radiative properties of compact light sources based on point defects in this interesting material.

Optical waveguides have been formed by proton implantation in Nd:YVO4 crystals using energies from 0.4 to 1 MeV and doses of the order of 1x10(16) ions/cm(2). Double implants were realized to generate wide optical barriers and a triple implant produced stacked waveguides. Waveguide characterization comprises propagation modes, refractive index profiles, near field imaging and spectroscopic properties. Differences between the waveguides were found in terms of mode confinement which is important for integrated devices.

In this paper, we have developed a new route to fabricate channel waveguides, by using ion implantation technique in buried epitaxial crystalline YAG:Nd,Tm layers. Excited state absorption and energy transfer upconversion mechanisms are discussed in view of a single beam pumped infrared to blue upconversion laser for integrated optics.