  A compact, single-etch silicon photonics waveguide crossing based on low
quality factor cavity and optimized by a genetic algorithm is demonstrated. The
device has 0.1~0.3 dB insertion loss and < -35 dB crosstalk per crossing for
fundamental TE mode in the 1550-1600 nm wavelength band, with a footprint of 5
x 5 {\mu}m$^2$.
