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 4.7 µm × 4.7 µm were fabricated on the GLOBALFOUNDRIES 45 nm monolithic silicon photonics platform (45 CLO technology). Fabricated devices are found to be nearly wavelength independent (±0.035 dB for 1260 nm ≤ λ ≤ 1360 nm) with low insertion loss (∼ 0.2 dB) and crosstalk (−35 dB). 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 ± 0.017 dB at the designed center wavelength of 1310 nm.