An integrated optical displacement sensor based on a reflective Mach–Zehnder interferometer (MZI) was developed. The sensor features a low-loss autocollimation measurement head fabricated using a 62.5-μm gradient index fiber as lens, which separates the incoming and reflected light. The mounting of the lenses and the fiber coupling were performed using a passive alignment assembly technology. Using a 3 × 3 directional coupler (DC), the direction of the phase shift can be resolved. The measurement head exhibits low losses compared to a conventional DC to separate the reflected light. A measurement range of 225 μm could be achieved in good agreement with the expected 230 μm. The results show a good agreement between simulation and measurements. Using basic measurement electronics, movements of 2 nm can be resolved, while a resolution of <1 nm is expected using optimized measurement equipment.
The field of silicon photonics is attracting a lot of attention due to the prospect of low-cost and compact circuits that integrate photonic and microelectronic elements on a single chip. Such silicon chips have applications in optical transmitter and receiver circuits for short-distance communications as well as for long-haul optical transmissions. Silicon photonics has proven to be a successful platform for many functional elements such as low-loss waveguides, filters, multiplexers/demultiplexers, optical modulators and Ge-on-Si photodiodes. On-going developments for advanced photonic integrated circuits include compact and energy-efficient silicon modulators, temperature-insensitive passive devices and hybrid III-V on Silicon lasers.
The European COSMICC project gathers key industrial and research partners in the field of silicon photonics, CMOS electronics, printed circuit board packaging, optical transceivers and datacenters, aiming at developing low-cost and low-energy consumption 50 Gb/s 4-wavelength coarse wavelength division multiplexing optical transceivers that will be packaged on-board. Combining CMOS electronics and Si-photonics with innovative high-throughput fiber attachment techniques, the developed solutions will be scalable beyond 1 Tb/s to meet the future data-transmission requirements in data-centers and super computing systems.
A silicon device to simplify the coupling of multiple single-mode fibers to embedded single-mode waveguides has been developed. The silicon device features alignment structures that enable a passive alignment of fibers to integrated waveguides. For passive alignment, precisely machined V-grooves on a silicon device are used and the planar lightwave circuit board features high-precision structures acting as a mechanical stop. The approach has been tested for up to eight fiber-to-waveguide connections. The alignment approach, the design, and the fabrication of the silicon device as well as the assembly process are presented. The characterization of the fiber-to-waveguide link reveals total coupling losses of (0.45±0.20 dB) per coupling interface, which is significantly lower than the values reported in earlier works. Subsequent climate tests reveal that the coupling losses remain stable during thermal cycling but increases significantly during an 85°C/85 Rh-test. All applied fabrication and bonding steps have been performed using standard MOEMS fabrication and packaging processes.