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The solid-state interactions at the Ni/(111) and (001) GaAs interfaces were investigated in the temperature range 25–600 °C by Rutherford backscattering spectrometry and channeling experiments, x-ray diffractometry, and four-point probe. The samples were prepared by depositing nickel films, 70 nm thick, onto clean (111) and (001) GaAs single-crystal substrates under 5×10−10 Torr vacuum. Then they were annealed for 1 h at increasing temperatures under a flow of forming gas (90% N2-10% H2). The sequence of phase formation was the following: first, a ternary phase at 200 °C, then a mixture of two ternary phases at 250 and 350 °C, and finally from 400 to 580 °C a mixture of a ternary phase and NiAs. This last structure was stable up to 600 °C on (111) GaAs, but at this temperature a further consumption of GaAs led to a mixture of (NiGa+NiAs) onto (001) GaAs. Small differences were observed versus the orientation of the GaAs samples but all the ternary and binary phases exhibited epitaxial arrangements with both the (111) and (001) GaAs substrates. The ternary-phase diagram for the bulk Ni-Ga-As system provides the basis for understanding the sequence of the above results and much of the information in the literature about Ni/GaAs interfacial reactions.

In this paper, we present an original work on subwavelength optical switching performed over a coherent multiband orthogonal frequency-division multiplexing (MB-OFDM) super-channel operating at 100 Gbps. After having demonstrated that dual-polarization MB-OFDM (DP-MB-OFDM) is as efficient as single-carrier dual-polarization quaternary phase shift keying (DP-QPSK) technology to transport 100 Gbps data-rate over a 10 × 100-km G.652 fiber-based transmission line, we show that optical add-drop of OFDM sub-bands as narrow as 8 GHz inside a 100 Gbps DP-MB-OFDM signal constituted of four sub-bands is feasible in the middle of this 1000-km transmission line. The flexible optical add-drop multiplexer (FOADM) implemented here is constituted by the association of an ultra-narrow pass-band and stopband optical filter. The design and realization of such ultra-selective optical filters is presented, while the impact of their physical features over the quality of transmission is discussed. To prove that several add-drop multiplexers can be cascaded, our FOADM is introduced into a G.652 fiber-based recirculating loop and the impact of the cumulated filtering transfer function as well as the crosstalk inside the OADM are investigated. A typical use case for the introduction of such FOADM into long-haul transport networks is given, and the capital expenditure (CAPEX) cost advantage for the multi-layer transport networks is highlighted. By the proof of concept delivered here, combination of super-channel and subwavelength optical switching pushes network flexibility far away of what is today proposed by system vendors, opening new horizons for an optimized use of multi-layer transport networks.

The production and annealing of radiation damage in GaSb Ne-implanted at high energy are studied by transmission electron microscopy and Rutherford backscattering spectrometry in combination with the channeling technique. The anomalous swelling phenomenon of implanted GaSb, previously reported, is found to be related to the formation of voids and microtwins in the crystalline implanted layer. These defects appear when the introduced damage exceeds a critical amount and lead to the formation of a porous polycrystalline GaSb layer, whereas in most other III-V materials an amorphous layer is formed. Provided the swelling is avoided, there is a good recovery of the lattice upon rapid thermal annealing at 600 °C. Otherwise, a heavily perturbed layer remains, containing voids, dislocations and, at sufficiently high doses, polycrystalline GaSb. From previously published results, it is inferred that the InSb behavior towards radiation damage is similar to that of GaSb.

A new concept is proposed for lensed fibres fabricated according to a collective and low cost process. This process is based on cleaving and splicing of optical fibre ribbons and is suitable for the coupling of laser diode arrays and fibre ribbons.