Reconfigurable ultra-broadband mode converter based on a two-mode fiber with pressure-loaded phase-shifted long-period alloyed waveguide grating.

We present a reconfigurable ultra-broadband mode converter, which consists of a two-mode fiber (TMF) and pressure-loaded phase-shifted long-period alloyed waveguide grating. We design and fabricate the long-period alloyed waveguide gratings (LPAWG) with SU-8, chromium, and titanium via the photo-lithography and electric beam evaporation technique. With the help of the pressure loaded or released from the LPAWG onto the TMF, the device can realize reconfigurable mode conversion between the LP mode and the LP mode in the TMF, which is weak sensitive to the state of polarization. The mode conversion efficiency larger than 10 dB can be achieved with operation wavelength range of about 105 nm, which ranges from 1501.9 nm to 1606.7 nm. The proposed device can be further used in the large bandwidth mode division multiplexing (MDM) transmission and optical fiber sensing system based on few-mode fibers.