CN102004282A - Method for manufacturing planar waveguide superimposed grating - Google Patents

Abstract

The invention relates to a method for manufacturing a planar waveguide superimposed grating. The planar waveguide superimposed grating with high refractive index is made of a photosensitive material, and a highly tin-doped planar waveguide is manufactured by a sol-gel method, so that the problem that the difference of refractive indexes among a plurality of groups of gratings is too small is solved; and a superimposed grating is written in the planar waveguide by phase masking technology, so that the defect that reflected light has single wavelength is overcome. On the basis of not changing the modularization of a wavelength division multiplexing (WDM) device, the manufacturing method ensures that the wavelength interval of the reflected light is reduced and crosstalk does not exist among channels, improves wavelength division demultiplexing performance, can be widely applied in the fields of optical communication and aerospace, and lays a solid foundation for meeting the requirements of high speed and large capacity of a communication network.

Description

A kind of method for making of slab guide superimposed type grating

Technical field

The present invention relates to a kind of optical communication field, particularly a kind of method for making based on the slab guide superimposed type grating of mixing the tin silica glass.

Background technology

Along with popularizing of internet, people improve constantly message capacity and traffic rate demand, and wavelength-division multiplex (WDM) technology has been subjected to people's growing interest as the preferred plan that solves the communication network capacity crisis at present.The principle of WDM technology: the light signal of different wave length is coexisted as on the single optical fiber, when different wavelength polymerization, individual other signal constipation altogether or multi-tasking, and when having arrived receiving end, signal then need separatedly come or separate multitask, as shown in Figure 1.The development of the development of WDM technology and device industry is closely related, the appearance of various WDM devices and the fast-developing development that has promoted WDM technology thereof.

Utilize photosensitive material to make high index of refraction slab guide superimposed type grating, greatly improve the performance of understanding wavelength-division multiplex as a kind of new WDM device.Waveguide grating structural representation as shown in Figure 4 explains orally the key property of slab guide below by coupled mode theory: because the coupling of waveguide grating belongs to the category of counter coupled, and Complex amplitude for incident light wave ,

Complex amplitude for reflecting light , Be coupling coefficient,

With

Be respectively the propagation constant of incident light wave and reflecting light ,

Be grating space ,

Be called the phase mismatch factor, so its coupling mode equations of deriving is:

(1)

(2)

Coupling coefficient wherein

Different expression-forms to TE ripple and TM ripple are:

（3）

From expression-form, the same incident angle of coupling coefficient

Relevant, according to coupled mode theory and be counter coupled, its reflectivity can be expressed as:

(4) (getting boundary condition is:

,

;

,

)

For the situation of low-angle incident, though can cause reflectivity to reduce, realize that the reduction of reflection bandwidth and each channel do not have to crosstalk, as shown in Figure 3, realize the purpose of separating wavelength-division multiplex.

People are in order to form slab guide, usually adopt spraying process, the ion sputtering method, vapour deposition process, collosol and gel (sol-gel) method, vacuum steaming degree method, and the slab guide of adopting the sol-gel technology to prepare, the advantage that had both had low-temperature operation, ratio that again can strict controlled doping, but also overcome additive method in the preparation difficulty during than the large-area planar waveguide.As shown in Figure 2, when utilizing the phase mask method in slab guide, to write one group of grating, find that this device can only reflect single wavelength and not have the effect of separating wavelength-division multiplex, if adopt the superimposed type grating, meeting each interchannel occurs and produces the situation of crosstalking in reflectance spectrum because the refringence between two groups of gratings is too little.

Summary of the invention

The present invention be directed to the shortcoming problem of present technology, a kind of method for making of slab guide superimposed type grating has been proposed, utilize photosensitive material to make high index of refraction slab guide superimposed type grating, make highly doped tin slab guide in order to solve the too little problem of refringence between many group gratings by sol-gal process; In slab guide, write the stack grating by the phase mask technology, improve the single situation of reflected light wavelength.

Technical scheme of the present invention is: a kind of method for making of slab guide superimposed type grating comprises that concrete steps are as follows:

1) sol-gel process prepares height and mixes the slab guide of Sn silicon dioxide: prepare silicon dioxide and tin ash colloidal sol at first respectively, then silicon dioxide gel and tin ash colloidal sol are proportionally mixed, again with its stirring, and under constant temperature, reflux, aging 24 hours afterwards, obtain the silicon dioxide tin ash colloidal sol of homogeneous transparent, afterwards again by micro porous filtration, obtain to make the colloidal sol of film, adopt at last czochralski method or spin-coating method with sol coating in the quartz glass substrate, obtain waveguide device;

2) slab guide is write grating: ultraviolet light passes through phase mask plate, and impinges upon on the plane waveguiding device of below, is subjected to the areas diffract rate of illumination to form permanent change, not modulated by the zone formation refractive index cycle of illumination;

3) write the stack grating: use the method for multiexposure, multiple exposure to write, the mask plate of same size is used in each exposure, but all will change the exposure angle when each exposure, makes reflectance spectrum be separated from each other, and the number of times of exposure is equal to the group number of grating.

Beneficial effect of the present invention is: the method for making of a kind of slab guide superimposed type of the present invention grating, on the basis that does not change the WDM device blocksization, reflected light wavelength spacing of cut is little, each interchannel does not have and crosstalks, improve the performance of separating wavelength-division multiplex, can be widely used in optical communication and aerospace field, for the high-speed jumbo demand that realizes communication network lays a solid foundation.

Description of drawings

Fig. 1 is the wavelength-division multiplex synoptic diagram;

Fig. 2 carves raster pattern for the phase mask method;

Fig. 3 is a superimposed type grating reflection spectrogram;

Fig. 4 is the waveguide grating structural representation;

Fig. 5 is the reflected light synoptic diagram of two groups of stack gratings;

Fig. 6 is the reflected light synoptic diagram of many group stack gratings.

Embodiment

Because slab guide made by photosensitive material,, modulate with the zone formation refractive index cycle that is not subjected to illumination so after in slab guide, writing grating with the phase mask method, be subjected to the areas diffract rate of illumination to form permanent change.Because the index disturbance in cycle only can exert an influence to very narrow a bit of spectrum, therefore, when if a branch of light wave transmits in grating, incident optical energy will be reflected on correspondent frequency, remaining transmitted spectrum is then unaffected, like this, grating has just played the effect of light wave selection catoptron.

The reflection kernel wavelength by

Determine, wherein It is the effective refractive index of waveguide.Adjust the grating cycle

Can realize by changing mask plate.

When

Have when constant

Each

All with unique

Corresponding.

By reflection kernel wavelength formula

Does not wait at the interval of every group of grating as can be known, and the short wavelength is corresponding closely-spaced, and vice versa.If have only the light of two kinds of wavelength in a branch of light

With

, inciding in the slab guide that is written into two groups of specific gratings, grating constant is respectively

With

When

Through being spaced apart corresponding to grating

The A group grating cycle index disturbance by same frequency reflect,

Be spaced apart through grating

The index disturbance in B group grating cycle also reflected by same frequency ground because A group and B organize grating an angle is arranged

So, through the modulation wavelength of periodic refractive index be Reflection angle is slightly larger than wavelength

Reflection angle, each self-corresponding light wave is reflexed to different directions, as shown in Figure 5 two groups the stack gratings the reflected light synoptic diagram.

This theory is generalized to multiple beam incident: incident light comprises some light beams

And wavelength length is successively decreased, and the stack grating at interval

And grating successively decreases at interval.When Being coupled to every group of grating constant is respectively

Slab guide superimposed type grating in the time, through after the index modulation of periodic optical grating, its reflectance spectrum tapers off from down to up according to wavelength and arranges and to each other apart from bigger, this just realizes understanding wavelength-division multiplex fully, the reflected light synoptic diagram of many as shown in Figure 6 group stack gratings.

The making of slab guide superimposed type grating divides three steps:

1, sol-gel process prepares height and mixes the slab guide of Sn silicon dioxide: prepare silicon dioxide and tin ash colloidal sol at first respectively, then silicon dioxide gel and tin ash colloidal sol are mixed according to required ratio, again with its stirring, and under constant temperature, reflux, aging 24 hours afterwards, obtain the silicon dioxide tin ash colloidal sol of homogeneous transparent,, obtain to make the colloidal sol of film afterwards again by micro porous filtration.Adopt at last czochralski method or spin-coating method with sol coating in the quartz glass substrate, obtain waveguide device.

2, slab guide is write grating: ultraviolet light passes through phase mask plate, and impinge upon in the slab guide of below, because this slab guide is to be made by photosensitive material, nonvolatil change will take place so be subjected to the local refractive index of illumination, and the local refractive index that does not shine can not change, and will show refractive index like this in the zone of regulation and be periodically variable situation (as shown in Figure 2).

3, write the stack grating: use the method for multiexposure, multiple exposure to write, the mask plate of same size is used in each exposure, but all will change the exposure angle when each exposure, makes reflectance spectrum be separated from each other, and the number of times of exposure is equal to the group number of grating.

Incident light is coupled in the slab guide, the reflected light synoptic diagram of many as shown in Figure 6 group stack gratings, and through the periodic modulation of stack grating, satisfactory wavelength is reflected with different reflection angle, finally finishes the function of separating wavelength division multiplexer.

Claims (1)

1. the method for making of a slab guide superimposed type grating is characterized in that, comprises that concrete steps are as follows:

1) sol-gel process prepares height and mixes the slab guide of Sn silicon dioxide: prepare silicon dioxide and tin ash colloidal sol at first respectively, then silicon dioxide gel and tin ash colloidal sol are proportionally mixed, again with its stirring, and under constant temperature, reflux, aging 24 hours afterwards, obtain the silicon dioxide tin ash colloidal sol of homogeneous transparent, afterwards again by micro porous filtration, obtain to make the colloidal sol of film, adopt at last czochralski method or spin-coating method with sol coating in the quartz glass substrate, obtain waveguide device;

2) slab guide is write grating: ultraviolet light passes through phase mask plate, and impinges upon on the plane waveguiding device of below, is subjected to the areas diffract rate of illumination to form permanent change, not modulated by the zone formation refractive index cycle of illumination;

3) write the stack grating: use the method for multiexposure, multiple exposure to write, the mask plate of same size is used in each exposure, but all will change the exposure angle when each exposure, makes reflectance spectrum be separated from each other, and the number of times of exposure is equal to the group number of grating.

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