Marcel Bensoussan

Full mapping of optical noise in photonic devices: an evaluation by near-field scanning microscopy

We demonstrate the possibility of mapping the transverse spatial distribution of optical noise at the output of photonic devices. Maps of local low-frequency noise are obtained by using statistics on multiple-sampling data from near-field scanning optical microscopy (NSOM). On selected laser diodes, the signatures of basic types of transverse mode instabilities (relative phase and amplitude of modes) are unambiguously obtained. On more complex systems, the types of mode instability can be identified and their intensity can be monitored. Such noise mapping opens a new path for analyzing noise origins and for optimizing device design.

Laser-Induced Surface Defects

The influence of pulsed laser processing (PLP) on the structure and composition of Si, GaAs, Inp and au surfaces has been investigated as a function of the laser fluence. Above a threshold fluence, all initial structures turn into a (1×1) structure and the V-element content of the compound surfaces is decreased. The structure change is shown to be related to the existence of a number of atomic steps on the Plp surface (up to 101 14 /cm 2 equivalent broken bonds). These defects can be eliminated by further annealings. On the other hand, the stoechiometry defects, which are less numerous (10 12 −10 13 /cm 2 ) cannot be eliminated. A model for the mechanisms of defect creation and annihilation during PLP is outlined. The incidence of PLP-induced defects on device technology is evaluated.

Normal-incidence second-harmonic generation in ordered Ga/sub 0.5/In/sub 0.5/P

Summary form only given. Usual III-V semiconductors have the strong zinc-blende 43m symmetry that leads to the existence of only one non-linear coefficient (d/sub 14/) for the second-order susceptibility tensor. Though this coefficient is extremely large one important consequence of the symmetry rules is that second-order processes are forbidden along the three common substrate orientations crystal axes [100], [010] and [001]. This vanishing susceptibility prevents any second-order nonlinear opto-electronic device grown on usual crystal direction GaAs from working in a normal incidence configuration (i.e. with fields propagating along the [001] direction). We demonstrate experimentally that ordered semiconductors, changing the crystal symmetry from the usual zinc-blende for III-V semiconductors to CuPt-type can overcome this limitation.