CN100392443C

CN100392443C - Design method for cross section corrected bending optical waveguide structure

Info

Publication number: CN100392443C
Application number: CNB2006100407687A
Authority: CN
Inventors: 张彤; 崔一平
Original assignee: Southeast University
Current assignee: Southeast University
Priority date: 2006-06-01
Filing date: 2006-06-01
Publication date: 2008-06-04
Anticipated expiration: 2026-06-01
Also published as: CN1858625A

Abstract

The present invention relates to a design method of a bending optical waveguide structure with corrected cross section, which is a method for decreasing optical waveguide mode leakage by changing the shape of the cross section of an optical waveguide. That is to correct traditional shaft symmetry cross section structure for increasing the outer dimension of the optical waveguide and accommodating more transmission modes as much as possibly. Consequently, the outer leakage of the transmission field mode is effectively decreased; the transmission efficiency is enhanced, and the light loss is decreased. The present invention has the concrete method that the bending optical waveguide is composed of a core layer (2) and a coating layer (1), wherein the core layer (2) is positioned in the coating layer (1). The thickness or the height of the outer side (22) of the bending optical waveguide core layer (2) is larger than the thickness or the height of the inner side (21) of the optical waveguide core layer; or the thickness or the height on the bending surface of the optical waveguide core layer is increased. The refractivity of the core layer (2) is larger than that of the coating layer (1).

Description

The method for designing of the bending optical waveguide structure that the cross section is revised

Technical field

The present invention is the bending optical waveguide structure method for designing that a kind of cross section is revised, and belongs to the technical field of bending optical waveguide structure design.

Background technology

Optical waveguide is basic physical notion in the integrated optics, also is the basic structure form of integrated optical device.Say that broadly the physical arrangement or the device that can conduct light wave can be called optical waveguide.Optical waveguide is widely used in optic communication device, the integrated optical device as the most basic a kind of version.Bent lightguide is meant and has crooked optical waveguide on geometry.Bent lightguide has important effect in light path connection, optical resonance ring, photo-coupler, waveguide array grating integrated optical devices such as (AWG).Optical Waveguide Bending can be brought bending loss, and bending loss can cause weakening of light signal usually.Therefore, reducing the bending loss of bent lightguide effectively, improve light transmissioning efficiency, is a key issue in bent lightguide design and the preparation.

Usually practical optical waveguide has two-dimensional fundamental form and three-dimensional optical waveguide.Two-dimensional fundamental form claims planar waveguide again, and its structure as shown in Figure 1.The middle layer of optical waveguide is called sandwich layer, two-layer up and down top covering and the under-clad layer of being called, because the sandwich layer refractive index is greater than cladding index, the light wave of some pattern is limited in sandwich layer and propagates.Three-dimensional optical waveguide is prepared into stripe shape or ridge type structure usually.As Fig. 2, shown in Figure 3, its cross sectional shape is rectangle (square is a kind of for rectangle), trapezoidal or convex.At present, Wan Qu three-dimensional optical waveguide also has only simple form such as bar shaped and ridge type usually.But bent lightguide has its singularity with respect to straight wave guide.Because the asymmetry of its left and right sides geometric scale, the light wave that causes wherein transmitting has bigger pattern to reveal in the outside of its bending, and this is the inward nature that bending loss produces.Therefore, patent of the present invention has proposed the bending optical waveguide structure method for designing that a kind of cross section is revised at the characteristics of bent lightguide.This method can be optimized design to the optical waveguide cross section at its sandwich layer, cladding index and optical waveguide radius-of-curvature, thereby reduces because the guided wave mode that Optical Waveguide Bending is brought is revealed, to reduce the loss of bent lightguide.This method can be applied in the design and preparation of fiber waveguide device.

Summary of the invention

Technical matters: the objective of the invention is to propose the method for designing of the bending optical waveguide structure revised in a kind of cross section, solve shortcomings such as bendingof light loss that prior art exists is big.

Technical scheme: technical scheme of the present invention is to realize like this, for straight wave guide, it is rectangle, trapezoidal or ridge shape structure that optical waveguide is designed to the cross section, have axisymmetric characteristics, structure, size and sandwich layer, cladding index by the design straight wave guide can realize the transmission of light wave effectively.For bent lightguide,, reveal serious by the optical waveguide outside transmission mode that bending causes because there is bending in waveguide itself.The present invention proposes to utilize change optical waveguide cross sectional shape, promptly traditional rotational symmetry cross section structure is revised, make the optical waveguide side dimension increase, to hold more transmission mode as much as possible, thereby reduced leaking outside of transmission field mode effectively, improve transfer efficiency, reduced optical loss.This kind method is especially less in the optical waveguide structure size, holds under the less situation of conduction mode, and is effective especially.

The method for designing of the bending optical waveguide structure that cross section of the present invention is revised is that this bent lightguide is made of sandwich layer and covering, sandwich layer is arranged in covering, the thickness in the sandwich layer outside of bent lightguide sandwich layer or height are greater than the thickness or the height in the optical waveguide sandwich layer outside, the perhaps thickness on its flexure plane or increase highly to some extent.The refractive index of sandwich layer is greater than cladding index.When bent lightguide was flat structure, covering comprised top covering and under-clad layer, and sandwich layer is between top covering and under-clad layer.In the outside of sandwich layer sweep, its thickness increases to some extent.

Beneficial effect: the present invention has following advantage compared with prior art:

The present invention is according to the characteristics of bent lightguide, cast aside traditional rotational symmetry waveguide core layer design philosophy, the design philosophy and the method for end face correction have been proposed, adopt the bent lightguide side dimension to increase to remedy because the optical transmission mode that waveguide bend brings leakage, solved in traditional rotational symmetry waveguide core layer design the problem that the curved waveguide loss is excessive.

Description of drawings

Fig. 1 is the planar waveguide synoptic diagram.

Fig. 2 is a three-dimensional rectangle bar waveguide synoptic diagram.

Fig. 3 is trapezoidal and ridge shape waveguide core layer cross section structure synoptic diagram.

Fig. 4 is the bent lightguide sandwich layer schematic cross-section that the cross section is revised.

Fig. 5 is the multiple structural representation in bent lightguide sandwich layer cross section that the cross section is revised.

Among the above figure optical waveguide top covering 1 is arranged, top covering 11, under-clad layer 12, sandwich layer 2, sandwich layer inboard 21, the sandwich layer outside 22.

Embodiment

Method for designing of the present invention is, at bent lightguide outboard wick layer thickness or highly always greater than using the optical waveguide inboard, and the perhaps thickness on its flexure plane or increase highly to some extent.The refractive index of sandwich layer 2 is greater than covering 1 refractive index.When bent lightguide was flat structure, covering 1 comprised top covering 11 and under-clad layer 12, and sandwich layer 2 is between top covering 11 and under-clad layer 12, and the refractive index of sandwich layer 2 is greater than the refractive index of top covering 11 or under-clad layer 12.

The structural design synoptic diagram (Fig. 4) that above-mentioned cross section is revised just illustrates method for designing of the present invention, can not the designed figure of this method of limit whole.In the bent lightguide design, design, all belongs within this patent protection and holds to reduce the method that optical waveguide mode is revealed by increasing or optimize the end face structure size.

It below is the embodiment that adopts the bending optical waveguide structure method for designing of cross section correction.

Design for bent lightguide, " rotational symmetry cross section " waveguides such as its bent-strip waveguide or the waveguide of ridge type are designed to nonaxisymmetrical cross sectional shape according to its degree of crook, the characteristics of this shape be the lateral surface thickness of curved waveguide or height greater than medial surface, to reduce since conduction mode that waveguide bend was brought reveal.When bent lightguide was flat structure, covering 1 comprised top covering 11 and under-clad layer 12, and sandwich layer 2 is between top covering 11 and under-clad layer 12, and in the outside of sandwich layer 2 sweeps, its thickness increases to some extent.

The material that is used to prepare this curved waveguide can comprise that all can be used to prepare the material of waveguide.I.e. this method for designing restriction in addition not special itself to the material of preparation optical waveguide.

Claims

1. the method for designing of the bending optical waveguide structure revised of a cross section, it is characterized in that at first this bent lightguide being designed to constituting by sandwich layer (2) and covering (1), sandwich layer (2) is arranged in covering (1), and then the thickness in the sandwich layer outside (22) that is designed to bent lightguide sandwich layer (2) is greater than the thickness of optical waveguide sandwich layer inboard (21); The refractive index of sandwich layer (2) is greater than covering (1) refractive index.

2. the method for designing of the bending optical waveguide structure that cross section according to claim 1 is revised, when it is characterized in that bent lightguide is flat structure, covering (1) comprises top covering (11) and under-clad layer (12), sandwich layer (2) is positioned between top covering (11) and the under-clad layer (12), in the outside of sandwich layer (2) sweep, its thickness increases to some extent.