On-Chip Polarization Rotators

On-chip polarization manipulation is proposed via a waveguide that is adiabatically twisted along its longitudinal axis, which can be fundamental building blocks for polarization-encoded optical communication and information processing. With the help of femtosecond direct laser writing, the polarization rotators for both telecom and visible wavelengths are fabricated, which show polarization conversion efficiencies of >90% at 1550 nm and approximate to 80% at 646 nm, respectively. Furthermore, a polarization router consisting of multiple waveguides with different twisting angles is demonstrated. With the polarization router, photons with different polarizations are directed to different paths. Based on such platform, the path entanglement between the photons can be transformed to polarization entanglement, which will extend the quantum information technology to higher-dimensional Hilbert space.