Figure 1) Top-view schematic of the directional coupler in the unpowered state; the optical signal remains in the upper waveguide.
Figure 2) Top-view schematic of the directional coupler in the powered state; the optical signal is coupled into the lower waveguide.
The demand for speed, access, and data delivery over the Internet initially fueled the development of photonic integrated chip (PIC) technology. PIC technology held the promise of being able to fully leverage underutilized fiber bandwidth while simultaneously increasing network flexibility and efficiency. Incidentally, the inherent qualities of PIC technology envisaged new applications of interest outside of its intended purpose. Specifically, PIC technology found use in so-called lab-on-a-chip applications where evanescent fields are used to interrogate chemical and biological environments for drug discovery, chemical detection and protein characterization. Moreover PIC technology has been identified as the technology to supplant bandwidth-limited copper wires in order to better serve high-speed central processing units (CPU) communication in state-of-the-art computer systems.
A five-generation family of planar, electromechanically-reconfigurable, high-index-contrast optical switches was developed in order to further extend the functionality of PIC technology. A family of mechanical switches were designed to operate at a center wavelength of 1550nm with desired per device loss of less than 0.3dB, with an isolation and cross-talk of less than -30dB, and bandwidths greater than 100nm. Although these figures of merit for the mechanical optical switches may preclude their use in very large scale integration applications, these optical switches are more than capable of meeting the needs of small scale integration as well as being useful in applications that do not require premium signal-fidelity. On the other hand, these reconfigurable optical switches can be tailored for use in switching fabrics with the monolithic integration of waveguide-based optical amplifiers. Furthermore, switching fabrics that are based on planar electromechanical optical switches, can either be used for broadband switching as-is or for wavelength-specific switching with the monolithic integration of arrayed waveguide gratings.
The family of planar, electromechanically-reconfigurable, high-index-contrast optical switches rely on butt-coupling, directional-coupling, and adiabatic-coupling in order to facilitate the transfer of light between waveguides; electromechanical parallel plate actuators facilitate the spatial reconfiguration of the waveguides. In particular, the in-plane adiabatic directional-coupler switch (generation 5 of the family of switches as shown in Figures 1 and 2) features electromechanical switching for a variety of waveguide-based devices (e.g., lasers, biologically-functionalized waveguides) without imposing design restrictions (e.g., doping levels, material alloy compositions) on the waveguide structure. In general, all of the generations of switches can be implemented in a variety of material systems with the only requirement being that the chosen material system has a high-index of refraction (n~3).
