Silicon-based photonics has generated an increasing interest in the recent year, mainly for optical telecommunications or for optical interconnects in microelectronic circuits. The development of elementary components (I/O couplers, modulators, passive functions, and photodetectors) has achieved such a performance level that the integration challenge of silicon photonics with microelectronics has been discussed  in the literature and products have been announced in the near future . The rationale of silicon photonics is the reduction of the cost of photonic systems through the integration of photonic components and an integrated circuit (IC) on a common chip, or in the longer term, the enhancement of IC performance with the introduction of optics inside a high-performance chip. To achieve such a high level of photonic function integration, the light has to be strongly confined in submicron waveguides with a medium () to large () refractive index contrast between the core and the cladding. Most of these studies have relied on the use of SOI substrates because they are accepted for CMOS technology. When one wants to integrate a CMOS circuit with some photonic functions in order to build a photonic integrated circuit on CMOS (PICMOS), the question of how to combine the photonic with the electronic parts is raised. The goal of this paper is to illustrate some routes and challenges of PICMOS in conjunction with presenting some technical achievements of our laboratories.

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