Micro-optical and opto-mechanical systems fabricated by the LIGA technique

The LIGA process is used to fabricate micro-optical benches which allow to mount hybridically active and passive optical components with very high precision and without active alignment. Moreover, also micro mechanical structures like electromechanical actuators are fabricated on the same substrate. To avoid any lateral misalignment all fixing structures in the optical bench are produced in the lithography step. Due to the high precision of X-ray lithography lateral tolerances are in the range of 0.1 to 0.2 mu m depending on thermal distortions. Thus, optical losses for these components are rather small. The potential of the free space concept based on LIGA technology for the fabrication of devices for optical telecommunication has been demonstrated by a bi-directional transceiver module as well as an optical bypass. In the case of the optical bypass element, a movable mirror is fabricated on the substrate together with the fixing elements. This movable mirror is the end face of an electrostatic actuator which allows to move the mirror into the collimated light beam between two fibers and thus, change the direction of the light. For the first prototypes the losses in the beam without mirror are about 1.7 dB, whereas the losses in the deflected beam are about 4.5 dB.