On-chip converter of waveguide polarization mode to free-space optical angular momentum mode

An integrated photonic device for converting on-chip waveguide modes to free-space optical angular momentum beams is proposed, which is composed of a polarization splitter rotator and a waveguide surface holographic grating. The output orbital angular momentum (OAM) state can be manipulated by the input polarization state. Therefore, the superposition of OAM states can be realized by controlling the on-chip input. According to the numerical results, the conversion efficiency of the transverse-magnetic (transverse-electric) mode to the optical angular momentum mode with l = - 1 ( + 1 ) is above 14% (18%), with the highest fidelity up to 0.84 and a working bandwidth of approximately 40 nm for a fidelity above 0.8. The proposed device provides a feasible information channel between the integrated optics and the free space and holds the potential for applications including the on-chip detection of the optical angular momentum beam.

Automated summary

An integrated photonic device that converts on-chip waveguide modes to free-space optical angular momentum beams is proposed. The device consists of a polarization splitter rotator and a waveguide surface holographic grating. The output orbital angular momentum state can be controlled by the input polarization state. Numerical results show a conversion efficiency of above 14% (18%) for the transverse-magnetic (transverse-electric) mode to the optical angular momentum mode with l = - 1 (+ 1), with a fidelity up to 0.84 and a working bandwidth of approximately 40 nm for a fidelity above 0.8. The proposed device provides a feasible information channel between integrated optics and free space.