Micromechanical optical switch

#Optical switches have been developed using guided wave devices or free-space mechanical devices. Guided wave devices use waveguides, whereas free-space devices use optical beams in free space with movable optical elements such as mirrors or lenses.

#Guided wave devices typically divert light from one arm of the device into the other by changing the refractive index of one of the arms of the device. This is typically done using electrical, thermal, or some other actuating mechanism.

#The free-space approach has an advantage over the guided-wave approach in some applications. It has very low cross talk because the waveguides are physically isolated from one another and coupling cannot occur. The principal source of cross talk in this approach is scattering off the movable optical element. In addition, free-space devices are wavelength-independent and often temperature-independent.

#FIGS. 1A-1K illustrate a method of fabricating an optical switch in accordance with the invention.

#FIG. 2 is a schematic cross-sectional view of a preferred embodiment of an optical switch in accordance with the invention.

#FIG. 3 illustrates the switching time of a preferred embodiment of the invention.

#The foregoing and other objects, features and advantages of the invention will be apparent from the following more particular description of preferred embodiments of the invention, as illustrated in the accompanying drawings in which like reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention.

#A preferred method of fabricating a micromechanical optical switch is illustrated in the process sequence of Figures 1A-1K. This method begins with a substrate 10, such as silica wafer, in which a cavity or trench 12 has been formed by standard etching techniques. As described in detail below, the substrate can include one or more optical waveguides. A first mask pattern is formed for conductive routing lines by depositing a photoresist layer 14 and selectively removing portions thereof to define the metallization pattern 16,18.

#In Figure 1B, a conductor layer 20 is formed, preferably by evaporation of a metal. In a preferred embodiment, a plurality of layers including a titanium layer, a nickel layer and a gold layer are used to provide the desired electrical and mechanical properties. In an example, the titanium layer has a thickness of 500 Å, the nickel layer has a thickness of 1500 Å and the gold layer has a thickness of 3000 Å. A rinse can be used to remove excess metal and the photoresist and overlying metal is than removed to provide conductive routing lines 30 shown in FIG. 1C.