Self-aligned micromachining process for large-scale, free-space optical cross-connects

A new micromachining process for large-scale optical cross-connects is presented. It satisfies the high-accuracy optical alignment required for free-space optics. A self-aligned batch-process allowing the simultaneous fabrication of vertical mirrors and fiber guides is performed with only one-mask. This process is based on bulk micromachining of (100) silicon. A first demonstration is performed on a 2 x 2 elementary cell then, it is extended to the fabrication of larger mirror arrays. Promising performances such as insertion loss lower than 0.5 dB, sub-millisecond switching time (0.3 ms) and reliable operation (more than 20 million cycles) are demonstrated on a bypass switch. An improved fabrication process, leading to an increase of integration density is also presented. It is based on the combination of deep dry-etching and anisotropic wet-etching.