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The improvement of cascaded second-order nonlinearity h (2) : h (2) effects in a quasiphase-matching (QPM) structure constituted by a periodically poled lithium niobate (PPLN) waveguide is obtained utilizing an integrated metal mirror placed after an additional waveguide segment. The resulting double-pass device, which can be employed for wavelength conversion, is refined by choosing the most advantageous length of the segment waveguide and by taking into account both the thermal and electro-optic effects. In the ideal case of perfect QPM, for a grating length z G4 = 25 mm, the calculated double-pass maximum efficiency is eta dp = 22.86 dB, which is almost the triple of eta sp = 8.20 dB, calculated for the single-pass version (without mirror) for the same value of the pump and signal powers.

Two original computer codes for the design of rare-earth-doped dielectric microspheres have been ad hoc developed. The former code is based on a finite-difference time-domain algorithm, suitably extended to model the amplification of the whispering-gallery modes propagating into rare-earth-doped microspheres. It takes into account the wavelength dispersion of the microsphere refractive index and the polarization obtained via the density matrix model. The design of an Er3+-doped silica microsphere coupled with a tapered silica fiber is reported. The latter home-made computer code solves the rate equations and the power propagation equations in frequency domain. The results are in excellent agreement.

This paper describes the optical properties of praseodymium-doped chalcogenide (GeS 2 –Ga 2 S 3 –CsI) thin films deposited by the pulsed laser deposition (PLD) technique using XeCl (308 nm) and KrF (248 nm) excimer lasers. Optical transmission and reflection spectra, at normal incidence, were recorded in the 200–2500 nm spectral region. The optical constants (refractive index n and extinction coefficient k ) versus wavelength, as well as the film thickness, were calculated from these spectra and a computer code. The waveguiding properties of the deposited films were investigated by the prism coupling technique (m-lines spectroscopy). The presence of praseodymium in the doped chalcogenide thin film was analysed by exciting the electrons to the 1 G 4 level and collecting the photoluminescence spectrum in the 1.335 μm region. Moreover, compositional, morphological and structural characteristics of the films were obtained by Rutherford backscattering spectrometry (RBS), scanning electron microscopy (SEM) and X-ray diffraction (XRD) analyses.

SiO 2 (silica) and ITO (indium tin oxide) films, SiO 2 /ITO bilayers and multilayers and Pr 3+ -doped chalcogenide glass films were deposited by excimer laser (λ = 308, 248 and 193 nm) ablation. Dense, stoichiometric SiO 2 films, almost droplet-free and with low surface roughness (

Praseodymium-doped GeS 2 –Ga 2 S 3 –CsI thin films were prepared by the pulsed laser deposition (PLD) technique. We ablated chalcogenide glass, Pr 3+ -doped, targets in vacuum with XeCl laser pulses (308 nm). The films were deposited on microscope slide glass substrates at room temperature. Film characteristics were investigated by many different techniques. The deposited films were well adhesive to their substrates. They were plain without cracks or corrugations and with stoichiometric composition close to that of the target. Micro-sized droplets were detected on the surface of films. The spectrophotometric measurements of transmittance and reflectance allowed to determine the real and imaginary parts of complex refractive index vs. wavelength, as well as the film thickness, by using a computer code. The waveguide guiding properties of the films deposited were investigated by prism-coupling technique (m-lines spectroscopy).