  Integrated optical devices are becoming a common tool in modern optical
science and engineering. This devices should be designed to allow for precise
control and manipulation of light. The femtosecond laser written (FSLW)
photonic chips have proven to cope with the most current demands of integrated
photonics. However, up to date the polarization degree of freedom has rarely
been exploited in experiments performed on the FSLW integrated platform. The
main obstacle is an intrinsically low anisotropy of laser written waveguides,
preventing the design of polarizing integrated devices with small footprint. In
this Letter we demonstrate the approach based on stress-induced anisotropy
allowing us to decrease the size of polarizing directional couplers fabricated
with the FSLW technology by almost an order of magnitude. We provide an
accurate account for the effects emerging in waveguides written in a close
proximity to each over.
