A dedicated beamline with a broad energy range of photons and with high flux and a high degree of circular polarization has been designed for the ELETTRA storage ring. The beamline exploits the circularly polarized radiation produced by an electromagnetic elliptical wiggler and cover the (5–1200) eV photon energy range using a double-incidence spherical grating monochromator.

A single-line-defect low-loss photonic crystal waveguide based on a perforated GaAs membrane in an aluminium-free material system is demonstrated. The GaInP lattice is matched to GaAs as the cladding/sacrificial layer. Fabry-Perot resonances are analyzed to obtain the group velocity dispersion for a 1-mm long guide. The losses are deduced to be close to 5 dB/cm, taking into account the wavelength dependent reflectivity of the guide extremities. In this framework, side-coupled nanocavities are also investigated. Feasibility of low-loss photonic-crystal-based devices combined with a reliable industrial material systems is thus demonstrated.

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We discuss here the feasibility of an optical parametric oscillator integrated on a GaAs chip, after reviewing the recent frequency conversion experiments using form birefringence in GaAs/oxidized-AlAs (Alox) waveguides.Recently, phase-matching has been demonstrated for the first time in a GaAs-based waveguide, using form birefringence in multilayer heterostructures GaAs/Alox [1]. Birefringences n(TE)-n(TM) froni 0.15 to 0.2 have been measured for different GaAs/Alox waveguides, which is sufficient to phase match mid-infrared generation l)et\veen 3 pm and 10 tm by difference frequency generation from two near-infrared beams.A second step vas the observation of parametric fluorescence. Results on parametric fluorescence at 2.1 pm will be described, in an oxidized A1GaAs form-birefringent waveguide, consisting of a high-index, strongly hirefringent GaAs-Alox core embedded in an AlGaAs cladding.One of the most exciting perspectives opened with this new type of nonlinear material is the realization of all optical 1)ararnetric oscillator on a GaAs chip. To this aim, minimization of losses is the most crucial point. A typical calculated value for this threshold is less than 70 rnW (in the guide) for 1 cm1 losses, and with 90% reflection coefficients. The level of losses has been reduced from 2 cm1 in ridges obtained by a standard reactive ion etching technique, to less than 0.5 cn1 in ridges realized with a more refined reactive ion etching process, using a 'three layer" mask. There is still a need for an improvement of the waveguide fabrication process, before reaching the oscillation threshold.keywords : frequency conversion , difference frequency generation , parametric fluorescence optical parametric oscillators, form birefringence, oxidized AlAs.