Three-dimensional broadband 90° optical hybrid with low crosstalk and phase error processed via femtosecond laser direct writing

The 90°optical hybrid is a key component for decoding phase information, and its performance is limited by the crosstalk of crossed waveguide and bandwidth. We proposed an optical hybrid with a three-dimensional spiral structure, which can effectively avoid crosstalk and has only a 2.8° cross angle. The three-dimensional optical hybrid is successfully processed using femtosecond laser direct writing with beam shaping as well as precise machining attitude and speed control, which exhibits a phase error of less than 3° within a wavelength range of 625–725 nm. Its broadband stability and low occupied space are applicable to future integrated photonic devices.