Asymmetric waveguide optical fiber end face coupler with two unequal-height arms based on mode evolution

Abstract

The invention discloses an asymmetric waveguide optical fiber end face coupler with two unequal-height arms based on mode evolution. A high-arm waveguide is composed of an input wide straight waveguide, a conical coupling waveguide group and an output narrow bent waveguide which are connected in sequence, and a low-arm waveguide is composed of an input narrow bent waveguide, a conical coupling waveguide group and an output conical waveguide which are connected in sequence; the width of the high-arm waveguide is gradually reduced, and the width of the low-arm waveguide is gradually increased; a certain distance exists between the two arm waveguides, and then the distance between the high-arm waveguide and the low-arm waveguide gradually approaches until the distance is kept unchanged and then the distance is increased; and a transverse electric fundamental mode and a transverse magnetic fundamental mode are input through the high-arm input waveguide, evolve in the two-arm waveguide to form a super mode, are finally coupled into the low-arm waveguide, are output through the conical waveguide and are subjected to end face coupling with an optical fiber. The asymmetric waveguide optical fiber end face coupler can effectively enlarge the size of the spot size, and has the advantages of large bandwidth, large tolerance, compact structure and the like.

Description

technical field [0001] The invention relates to an on-chip waveguide fiber end-face coupler, in particular to a mode evolution-based asymmetrical waveguide fiber end-face coupler with two arms of unequal height that realizes high coupling efficiency and large bandwidth. Background technique [0002] A waveguide fiber coupler refers to coupling a mode from an optical fiber to an on-chip optical waveguide. It is essentially a mode spot converter that converts a larger mode spot in the fiber into a smaller mode spot in the waveguide. With the continuous development of on-chip optical communication technology, there is an increasing demand for effectively coupling an on-chip optical signal into an optical fiber. [0003] In terms of the performance requirements of the waveguide fiber coupler, on the one hand, it has high requirements for high coupling efficiency, which can meet the needs of various communication systems; on the other hand, the on-chip waveguide fiber coupler is ...

AI Technical Summary

Problems solved by technology

The scheme of grating coupling: Although this scheme can achieve relatively simple coupling, facilitate wafer testing and packaging, and has low requirements on the process, due to the limitation of its physical mechanism, it is difficult to achieve polarization insensitivity and wide bandwidth. Small, the coupling efficiency is difficult to rise to a new height

However, for the currently commonly used end face coupling scheme, limited by the technological level, it can only realize the coupling with gradual changes in the width direction, that is, the traditional tapered waveguide, but cannot well realize the coupling structure that changes in the height direction.

In recent years, there have also been some coupling structures that can achieve gradual changes in the height direction. For example, although the newly proposed double-layer tapered waveguide structure can reduce the restriction on the mode spot in height, it is limited by the process accuracy. There is a sudden change at the end of the shaped waveguide because the width is not narrow enough, which causes a non-negligible loss in the transmission process of the mode

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