Controlling optical return loss in production silicon photonic metamaterial fiber couplers.

A cost-efficient and low-complexity optical input/output (I/O) packaging solution is a substantial challenge for volume production of photonic integrated circuits. To address this, metamaterial fiber couplers are an attractive solution for integrated photonic devices especially for optical I/O, interfacing standard optical fibers to photonic chips. They offer the advantages of refractive index engineering to achieve better mode match as well as higher fabrication tolerances. Metamaterial waveguides, as a fundamental building block of these fiber couplers, have attracted tremendous attention in recent years. Here, we report on effective optical return loss control in Si metamaterial waveguide designs to achieve ultra-low reflection loss in CMOS-compatible silicon photonics implemented in a 300 mm production line. Low backscattering is a substantial consideration for a range of applications. Here, a return loss of better than -30dB is achieved.

Beam shaping for ultra-compact waveguide crossings on monolithic silicon photonics platform.

A beam shaping approach has been implemented to realize high-performance waveguide crossings based on cosine tapers. Devices with a compact footprint of 4.7µm×4.7µm were fabricated on the GLOBALFOUNDRIES 45 nm monolithic silicon photonics platform (45 CLO technology). Fabricated devices are found to be nearly wavelength independent (±0.035dB for 1260nm≤λ≤1360nm) with low insertion loss (∼0.2dB) and crosstalk (-35dB). The measured response of the devices is consistent with the three-dimensional finite-difference time-domain simulation results. The design stability is validated by measuring the device insertion loss on eight chips, which is found to be 0.197±0.017dB at the designed center wavelength of 1310 nm.