Ajbrui core technology is based on the concept of Moving Silicon Waveguides that can be shifted on chip in and out of the silicon plane in order to perform functions such as attenuation and switching. These Moving Waveguides when incorporated with monolithic passive functions and hybrid power monitoring enable unique chip scale integration similar to the IC industry. This technology is based on a standard well-developed silicon micro fabrication processes and packaging solutions such as flip-chip and wafer level packaging. The resemblances to VLSI technology insure high yield, repeatability and mass production capability, which are essential in striving for high performance low cost products.
Optical devices library
Current devices library includes VOA, small switches and Add/Drop multiplexers. Figure 1 shows a VOA made from Moving Waveguide connected to Actuator 1. By pulling the moving part of the waveguide, an optical mismatch between the two waveguides is formed leading to attenuation.
One of the main features of VOA is the minimal insertion loss (IL). This feature is also examined under temperature, polarization and wavelength changes. By controlling the gap between the two waveguides with Actuator 2, the IL can be kept at the minimum even with temperature and wavelength changes. The top right enlargement in Figure 1 shows 1:99 splitter that is based on Multi-Mode Interferometer (MMI). Such splitters are placed before and after the attenuator and the 1% light is channeled to hybrid photodiodes, which feeds an on-chip feedback and controlling unit.
In Figure 1 only the splitter before the attenuator is shown. The controlling unit is fabricated separately and is connected hybridly to the MEMS chip.
Typically, optical cards such as line cards include functions such as switching, attenuation and power monitoring. Since the devices in Ajbrui's library differ from each other only by their mask design, a multifunctional single-chip with equivalent optical-card functionally can be realized. This allows Ajbrui to work closely with systems and subsystems customers and to tailor designs that suit their needs.
Chip Packaging and Wafer level Sealing
Packaging is another major issue. The maturity of a new technology is measured by its packaging maturity. Since the fabrication technology is based mainly on silicon, variety of packaging solutions are feasible including flip-chip and wafer level packaging. Ajbrui adopted these packaging methods to the optical environment using a technique that results in wafer level sealing of the MEMS and optical parts. After die singulation the dies are mounted on their socket by standard VLSI pick & place, as shown in Figure 2. The difference is that in addition to the standard wire bonding, fiber bonding takes place. Ajbrui developed a unique solution in which the I/O fibers feed the optical components that are sealed inside the chip, through the sealing walls. This concept is very similar to the wire bonding in the sense that the wires are connected to pads that on the other side are connected to electrical channels that carry the electrical signals into the different elements inside the chip.
The Future of Interconnectivity - Optical motherboards
The ability to manipulate waveguides enables implementation of an Optical Motherboard (OMB), in which these waveguides are used as flexible interconnects between the different components that are placed on the board. The OMB is another example of a system on a chip which integrates several Moving Waveguides with embedded Spot Size Converter (SSC) for optimized optical matching.