Method for mode conversion by femtosecond laser direct writing offset butt joint waveguide and application thereof

Abstract

The application discloses a mode conversion method and application of femtosecond laser direct writing offset butt joint waveguide, and belongs to the technical field of laser processing. The method directly butts joint a single-mode waveguide and a multi-mode waveguide, and solves the mode conversion problem during waveguide direct writing by using a femtosecond laser. The main principle is that when a single-mode light beam is incident into the multi-mode waveguide by offsetting the center position or transmission direction of the multi-mode waveguide, a high-order mode is excited in the multi-mode waveguide, and low-loss mode conversion can be realized by changing the incident position or angle of the single-mode light. The single-mode waveguide and the multi-mode waveguide are butted, the positional relationship between the single-mode waveguide and the multi-mode waveguide during butt joint is changed, the original single-mode transmission light beam in the single-mode waveguide is converted into a high-order mode in the multi-mode waveguide, and through fine control of the processing parameters of the single-mode waveguide and the multi-mode waveguide and the position during butt joint, the insertion loss of the waveguide device can be effectively reduced, on-chip low-loss, low-cost and small area occupation mode conversion is realized.

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