CN1936629A

CN1936629A - Optical element and its manufacturing method

Info

Publication number: CN1936629A
Application number: CN 200610139557
Authority: CN
Inventors: 杉田知也; 水内公典; 山本和久
Original assignee: Matsushita Electric Industrial Co Ltd
Current assignee: Panasonic Holdings Corp
Priority date: 2002-05-31
Filing date: 2003-06-02
Publication date: 2007-03-28
Also published as: CN1916673A; CN1916673B

Abstract

The invention provides an optical element which can easily be manufactured, has high selectivity of substrates, and is constituted by joining the substrates together, wherein the method comprises forming a recess to function as a non-bonding region on a principal surface of at least one of a waveguide substrate and a base substrate; and bonding the waveguide substrate and the base substrate with each other so that the non-bonding region is interposed between the waveguide substrate and the base substrate.

Description

The manufacture method of optical element

The application is that the denomination of invention of submitting on June 2nd, 2003 is Chinese patent application number 03137985.0 divides an application of " optical element and manufacture method thereof ".

Technical field

The manufacture method of the optical element that the present invention relates on assembling substrates, form.

Background technology

2 substrates are joined together the optical element of formation, a substrate is carried out carrying out ridged processing after the sheet, can form ridge optical waveguide.Under the situation that this substrate is engaged, do not use bonding agent etc. to make the technology of firm engagement between the substrate, be known that direct joining technique.Utilize directly to engage, can carry out high-precision joint, be hopeful to be applied to optical element various materials such as glass, semiconductor, strong dielectric, piezoelectric ceramics.Example as the optical element in the direct assembling substrates such as dielectric substrates, semiconductor chip, glass substrate has proposed the optical-waveguide-type element.In No. 2574594 communique of (Japan) patent and the flat 06-222229 communique of Te Kai, the method that makes strong dielectric crystallization substrate lithium niobate and lithium tantalate form optical waveguide with directly engaging with kind substrate or glass substrate is disclosed for example.

And the optical element that by film its joint is formed between two substrates has also proposed several schemes.With 2 substrates, a optical element as ducting layer, become the substrate of ducting layer, refractive index is not high not all right.Therefore, between substrate, arrange the low film of refractive index ratio ducting layer, can not be subjected to the influence of substrate waveguide rate, light is carried out waveguide.For example, in No. 2574594 communique of above-mentioned (Japan) patent and the flat 06-222229 communique of Te Kai, illustrate and adopt SiO ₂With SiN as membraneous material.And, in No. 2574606 communique of (Japan) patent, illustrate and adopt low-melting glass as membraneous material.And, in the flat 06-289347 communique of (Japan) open patent, illustrate and adopt metal oxide etc. as membraneous material.

As previously mentioned, thin layer is not set, but, can not uses as optical waveguide with the optical element that the congener substrate that refractive index equates constitutes.And, for example, as the situation that directly engages lithium niobate substrate and Mg doped lithium columbate substrate, even, can not on the little substrate of refractive index, form optical waveguide directly engaging under the situation of 2 kinds of different substrates of refractive index.

Between 2 substrates, film is set, just can addresses the above problem.But it is very difficult that film is set between 2 substrates.Shown in No. 2574594 communiques of (Japan) patent and the flat 06-222229 communique of Te Kai, for example adopting SiO ₂Under the situation as film, be difficult to the surface smoothness of control thin layer, by the film of sputter and evaporation deposition, its poor surface smoothness.This surface smoothness is not suitable for direct joint.For example, wait with CVD (chemical vapour deposition) equipment to form film, can improve surface smoothness.But the problem that CVD equipment exists is to cost an arm and a leg, and volume is big.And according to differences such as film formation conditions, the being adjacent to property of film and substrate and bond strength skewness when the substrate that has engaged is carried out machining, do not reach enough adaptation intensity.

In addition, shown in No. 2574606 communiques of (Japan) patent, adopting under the situation of low-melting glass as thin layer, for example the method for Cai Yonging is, applies the glass that dissolves of pulpous state on substrate, and the substrate that engages carries out sintering after being adjacent to.So, the homogeneity of very difficult control thickness.Have, open in the described technology of flat 06-289347 communique the spy, specifically the used metal oxide materials of certain thin films lacks practicality.

And, on direct assembling substrates, the height control of the optical waveguide when forming optical waveguide and the high homogeneity control of optical waveguide, important measures is that the thickness and the homogeneity that form the substrate of optical waveguide in the substrate of direct joint are measured.But the problem of existence is that general, above-mentioned optical waveguide is measured with respect to the thickness evenness that forms substrate and is difficult to carry out photographically, but relies on the thickness measure of direct assembling substrates integral body, so the thickness evenness of optical waveguide is very poor.

Summary of the invention

The manufacture method of the optical element of the structure that the selectivity that the purpose of this invention is to provide a kind of easy making and substrate for use is strong, substrate is engaged.

The manufacture method of optical element of the present invention is, on the interarea at least on one side of waveguide substrate and substrate, form recess as disengaged zone, above-mentioned disengaged zone is clamped between above-mentioned waveguide substrate and the above-mentioned substrate, for this engages above-mentioned waveguide substrate and above-mentioned substrate.Like this, no matter the refractive index of waveguide substrate and substrate how, can both be produced guide properties good optical element.

Moreover, wish on the thickness direction of substrate, carrying out concavity processing on the interarea on the arbitrary limit in above-mentioned waveguide substrate and the above-mentioned substrate, to form above-mentioned recess.Like this, without film, no matter the refractive index of waveguide substrate and substrate how, all can be made guide properties good optical element.

And, also can on the interarea on arbitrary limit of above-mentioned substrate and waveguide substrate, form film, on thickness direction, this film is carried out concavity processing, form above-mentioned recess like this.

Moreover, hope forms film on the face that carries out concavity processing, the face that forms above-mentioned film is carried out CMP processing, makes it smooth, directly engage between the interarea to above-mentioned waveguide substrate and substrate, above-mentioned disengaged zone is clamped between above-mentioned waveguide substrate and the substrate.Like this, can produce the optical element that film is connected with waveguide substrate.Therefore, no matter the refractive index of waveguide substrate and substrate how, all can be made guide properties good optical element.

And, wish on above-mentioned substrate, to form above-mentioned recess, on the interarea of above-mentioned waveguide substrate, form film, to engaging between above-mentioned waveguide substrate and the substrate, above-mentioned film is formed in the above-mentioned disengaged zone.Like this, needn't the grinding film layer, can reduce process number.

Moreover, after wishing between to above-mentioned waveguide substrate and substrate, to engage, between above-mentioned waveguide substrate and substrate, in the gap that forms by above-mentioned recess, the little compaction material of the above-mentioned waveguide substrate of a kind of refractive index ratio of filling.Like this, can produce the optical element that resin is connected with waveguide substrate.Therefore, no matter the refractive index of waveguide substrate and substrate how, all can be produced guide properties good optical element.

And, wish that the joint between above-mentioned waveguide substrate and the substrate is direct joint.Like this, can make the high optical element of joint precision.

Moreover, the manufacture method of other optical elements of the present invention, by on thickness direction, substrate being carried out concavity processing, form a plurality of grooves of arranging by uniformly-spaced, on above-mentioned substrate, other substrate are engaged, make each mutual opposite of above-mentioned groove, and each above-mentioned groove is vertical, above-mentioned substrate is ground, above-mentioned groove is exposed.Form the lamination operation of lamination substrate like this,, repeat above-mentioned lamination operation by pre-determined number to above-mentioned lamination substrate.Make photonic crystal like this, easily.

Description of drawings

Fig. 1 is the oblique view that expression relates to the optical element structure of the present invention the 1st embodiment.

Fig. 2 is the figure of surface smoothness measurement result of the atomic force microscope of expression sputtered film, and Fig. 2 (a) is the surface smoothness measurement result of expression Ta oxide sputtered film, and Fig. 2 (b) represents SiO ₂The surface smoothness measurement result of sputtered film.

Fig. 3 is the oblique view of another kind of structure that expression relates to the optical element of the present invention the 1st embodiment.

Fig. 4 is the orthograph of third quadrant method of the optical element of Fig. 3.

Fig. 5 is the oblique view of structure that expression relates to the optical element of the present invention the 2nd embodiment.

Fig. 6 is each the lip-deep catoptrical key diagram about thin layer.

Fig. 7 is the performance plot of the relation of expression thickness T of thin layer and light reflectivity R.

Fig. 8 is the oblique view of structure that expression relates to the optical element of the present invention the 3rd embodiment.

Fig. 9 is the figure that the position in disengaged zone of the optical element of expression the 3rd embodiment is used, and is the orthograph that adopts the third quadrant method.

Figure 10 is the oblique view of other structures that expression relates to the optical element of the present invention the 3rd embodiment.

Figure 11 is the oblique view of structure that expression relates to the optical element of the present invention the 4th embodiment.

Figure 12 is the oblique view of other structures that expression relates to the optical element of the present invention the 4th embodiment.

Figure 13 is the oblique view of another other structures that expression relates to the optical element of the present invention the 4th embodiment.

Figure 14 is a front elevation of representing to relate to the optical element of the 5th embodiment of the present invention by manufacturing process's order.

Figure 15 is the figure of structure that expression relates to other optical elements of the present invention the 5th embodiment, and Figure 15 (a) is the oblique view of optical element, and Figure 15 (b) is the front elevation of optical element.

Figure 16 is the oblique view of structure that expression relates to the optical element of the present invention the 6th embodiment.

Figure 17 is the oblique view of structure that expression relates to other optical elements of the present invention the 6th embodiment.

Embodiment

Below describe embodiments of the invention in detail.At this, optical element is an example with the optical-waveguide-type element, forms the material of the waveguide substrate of optical waveguide, adopts the strong dielectric crystal, is the LiNbO of doped with Mg O ₃Crystal (being designated hereinafter simply as the MgO:LN crystal) is to the substrate as the substrate of optical element, to adopt LiNbO ₃The situation of crystal (hereinafter to be referred as the LN crystal) is that example describes.The present invention is not limited only to this structure.

[the 1st embodiment]

Directly joining technique is known that and does not adopt bonding agent etc., makes substrate carry out the technology of firm engagement, and it can carry out high precision to various materials such as glass, semiconductor, strong dielectric, piezoelectric ceramics and engage.Directly assembling substrates for example can make in the assembling substrates (two one group substrate of joint) two use as optical waveguide through carrying out ridged processing after the sheets, and it is as one of effective ways of making optical element, and is noticeable.Past is at LN crystal, LiTaO ₃In the various oxide substrates such as crystal (hereinafter to be referred as the LT crystal), MgO:LN crystal, sapphire, between with the kind substrate and directly engage between the variety classes substrate.And, the example that directly engages by film between these substrates is also arranged.Membraneous material adopts SiO ₂With SiN, low-melting glass, metal oxide etc.

The optical element of the 1st embodiment is the optical element of such structure, for example by LiNb _xTa _(1-x)O ₃Engage by thin layer between the strong dielectric crystal that (0≤x≤1) constitutes and other substrates.Thin layer especially adopts and comprises such film at interior thin layer, and promptly this film is with Ta ₂O ₅Or Nb ₂O ₅Be principal ingredient.And, so-called with Ta ₂O ₅Or Nb ₂O ₅For being meant to contain, principal ingredient is no less than 80% Ta ₂O ₅Or Nb ₂O ₅And, if content is no less than 90% then better.

Like this, can control the thickness of thin layer with high precision.So, for example, as LiNb _xTa _(1-x)O ₃A kind of MgO:LN crystal substrates and the LN crystal substrates of crystal engage, and producing with fast light damaging good MgO:LN easily is the optical element of optical waveguide.And, by LiNb _xTa _(1-x)O ₃The strong dielectric crystal that constitutes is the strong dielectric crystal with optical nonlinearity, utilizes this crystal to constitute optical element, can realize utilizing the photomodulator and the Wavelength conversion element of nonlinear optical effect.

The inventor has confirmed to adopt with Ta in thin layer by actual measurement ₂O ₅Or Nb ₂O ₅For the effect that film produced of principal ingredient, as follows.At first, the thermal expansivity of thin layer is near LiNb _xTa _(1-x)O ₃The thermal expansivity of crystal substrates, so, even pyroprocessing can film not occur and substrate is peeled off yet.And,, during the RF spatter film forming, can make the flatness of film forming good as easier film build method.And in comprising direct joint technology that water wettability is handled and later optical element manufacture craft thereof, chemical proofing is good, and the quality influence to film during processing is little.And, film strength and LiNb _xTa _(1-x)O ₃The stickiness of crystal substrates is good, directly the intensity height of Jie Heing.Even in metal oxide, Ta especially ₂O ₅Or Nb ₂O ₅As by LiNb _xTa _(1-x)O ₃The thin layer that the strong dielectric crystal that constitutes directly engages is the material of particularly suitable.And, Ta ₂O ₅Film and Nb ₂O ₅Film is compared, and refractive index is low, with LiNb _xTa _(1-x)O ₃Crystal substrates is compared, and also is that refractive index is low.So Ta ₂O ₅Film is particularly useful for making employing LiNb _xTa _(1-x)O ₃The optical-waveguide-type element of crystal substrates.

Directly one of useful purposes of joining technique is a precision height when engaging between the substrate of different nature, and intensity is good, can realize having the element of various characteristics.Direct joint between the variety classes substrate, its serviceability is very outstanding.The simple case that adopts that the variety classes substrate of strong dielectric crystal directly engages is the direct joint of the variety classes substrate of glass and LN crystal and glass and LT crystal.But general direct joint method is to heat-treat in hundreds of ℃～1000 ℃ of scopes, so the thermal expansivity that requires assembling substrates about equally.Therefore, can think, for example, with said structure (the direct joint of the direct joint of glass and LN crystal and glass and LT crystal is compared), the thermal expansivity of LN crystal and MgO:LN crystal about equally, the refractive index difference adopts the method ratio of this material to be easier to.

In the past, the direct joint of LN crystal and MgO:LN crystal has been proposed.Adopt the optical-waveguide-type optical element of this method also to illustrate.In the case, the refractive index of LN crystal is greater than the refractive index of MgO:LN crystal, so adopt the LN crystal as optical waveguide.LN crystal and MgO:LN crystal, both are the strong dielectric crystal with optical nonlinearity, and nonlinear optical constant is about equally.And, to compare with the MgO:LN crystal, LN crystal price is low, so utilize under the situation of the photomodulator of nonlinear optical effect and the wavelength conversion that carries out the long wavelength, mostly adopts the LN crystal optical waveguide.But for example, the short wavelength below wavelength 500nm carries out in the optical waveguide type wavelength inverting element of wavelength conversion, follow rayed and produce uneven local indexes of refraction and change (being commonly referred to as the phenomenon of optical damage), so, be difficult to adopt the LN crystal optical waveguide.

On the other hand, the MgO:LN crystal is known fast light damaging good material, and is especially very hopeful as short wavelength's Wavelength conversion element material.So, in the case, with adopt the MgO:LN crystal as optical waveguide for well.

Like this, consider the function aspects or the cost aspect of direct assembling substrates, can find a kind of method of selection, promptly no matter the refractive index of various substrates how, all can be used as optical element.

In the past, about adopting the optical element of direct joint, the scheme of proposition is to arrange SiO between substrate ₂, middle layer (thin layer) such as SiN, low-melting glass.For example special opening discloses such direct joint optical element and manufacture method thereof in the flat 06-289347 communique, promptly the refractive index of the material in its middle layer is lower than the refractive index of the substrate material that forms optical waveguide.Like this, the MgO:LN crystal that refractive index ratio LN crystal is low can be used as optical waveguide.But the method that forms the middle layer and directly engage during for example as the use low-melting glass for example adopts following method, promptly, after dissolving on the substrate that glass material in solvent etc. is coated in joint, Yi Bian being combined closely, itself and the substrate that engages pressurize, Yi Bian carry out sintering.Therefore, the problem of existence is, the thickness evenness of low-melting glass is restive, and, the SiO that forms with easy method such as evaporation deposition and sputter ₂Film and SiN film, its profile pattern (flatness) is poor, therefore can not directly engage.

Therefore, the inventor has carried out characteristic research at the thin dielectric film that can evenly control thickness at the formed rete in centre that directly engages.It found that, for example can adopt with Ta ₂O ₅And Nb ₂O ₅Be dielectric film of principal ingredient etc.

Below utilize accompanying drawing, describe the optical element that relates to the present invention the 1st embodiment in detail.

Fig. 1 is the oblique view of structure of the optical element of expression the 1st embodiment.As shown in Figure 1, the optical element of the 1st embodiment, its structure is that substrate 2 and waveguide substrate 1 carry out lamination by thin layer 4.

For example, on waveguide substrate 1, adopt the MgO:LN crystal substrates of X cutting.And, the LN crystal substrates that on substrate 2, adopts X to cut.And, on waveguide substrate 1, carry out ridged processing, form ridge optical waveguide 3.Thin layer 4 adopts with Ta ₂O ₅Dielectric monofilm for principal ingredient.

Below the method for the optical element of the 1st embodiment is made in explanation.At first, form thin layer 4 on a certain interarea in waveguide substrate 1 or substrate 2, the formation method of thin layer 4 for example, can adopt RF (high frequency) sputter, the Ta of thin layer 4 ₂O ₅Film is that 100nm～400nm is thick, for example is formed on the LN crystal waveguide substrate 1.At this moment according to sputtering condition, change with Ta ₂O ₅Refractive index for the thin layer 4 of principal ingredient.Measured result is: the optical index to wavelength 623.8nm changes in 2.05～2.10 scopes.To the light of identical wavelength, waveguide substrate 1 is that the refractive index of MgO:LN crystal is about 2.17, so, when the optical element of the 1st embodiment is finished, can in optical waveguide 3, send into the light of wavelength 623.8nm, make it carry out waveguide.

After having formed thin layer 4 on the waveguide substrate 1, handle carrying out water wettability as the surface of the substrate 2 of the surface of the direct thin layer 4 on composition surface and LN crystal.Specifically, on waveguide substrate 1, carried out after the acetone ultrasonic cleaning on formed thin layer 4 and the substrate 2, at ammoniacal liquor: aquae hydrogenii dioxidi: dipping is more than 15 minutes in the mixed solution (hereinafter referred to as the ammonia aquae hydrogenii dioxidi) of pure water=1: 1: 6, in pure water, clean, carry out dried then.And the ammonia aquae hydrogenii dioxidi can use general concentration, promptly 20%～40%.The concentration of ammonia aquae hydrogenii dioxidi is preferably 30%.

Then, under the state that the crystallographic axis direction separately of waveguide substrate 1 and substrate 2 is aimed at, the surface of thin layer 4 and the surface of substrate 2 are contacted, slightly pressurization.Like this, thin layer 4 and substrate 2 form the state that is adjacent to.Further, the thin layer 4 and the substrate 2 that are formed on the waveguide substrate 1 are heat-treated, like this, thin layer 4 and substrate 2 are directly engaged.When thermal treatment, use stove,, under 350～800 ℃, heat-treat in order to prevent that assembling substrates from peeling off and sharply to heat and cause breakage, programming rate for example to be predefined for 100～500 ℃/hour.

And what is called directly engages, and is meant the method for not using bonding agent and resin etc. to make 2 substrate firm engagement.For example make and form intimate-association state between the substrate with the hydrogen bond of said method by the OH base.Further, make the OH base as H again by heating ₂The O molecule breaks away from from the composition surface, so, can form more firm bonding state between the substrate.And, beyond the method, the method that yet useful electrostatic attraction directly engages.

By directly engaging on the direct assembling substrates that obtains,, waveguide substrate 1 is carried out surface grinding and sheet like this, thickness is reduced to till 3～4 μ m in order to form optical waveguide 3.Then, utilize photoetching process to make the optical waveguide figure, at attenuate the surface of waveguide substrate 1 on, form the step of 1.5～2 μ m by dry etching, form ridge optical waveguide 3 like this.And the both ends of the surface of optical waveguide 3 (incident exit facet) are carried out mirror ultrafinish after forming ridged.

At this, further describe thin layer 4.General using sputter and evaporation deposition method, under the situation of lining dielectric film on the substrate, people know that because of membrance casting condition (temperature and film forming ambient gas) is different, the characteristic of the film of formation (refractive index and absorption coefficient) changes.And, the surface state of known membrane (surface smoothness), very big-difference is arranged because of the film build method that comprises film-forming apparatus is different, evaporation deposition for example, the difference of method and apparatus such as RF sputter, CVD makes the homogeneity of film and little density, surface smoothness that very big-difference be arranged, and, promptly use same kind of method, also make its surface state difference because of material is different.

But in the optical element of first embodiment, when thin layer 4 and substrate 2 were engaged, the surface smoothness of the thin layer 4 that forms on waveguide substrate 1 can influence engagement state.For example, during poor surface smoothness, the precision of optical element is low.Especially utilize directly to engage when thin layer 4 and substrate 2 engaged, because the poor surface smoothness of thin layer 4, and can't engage.For example, with RF sputter or ECR sputter and the SiO that forms ₂Film knownly can not directly engage because of poor surface smoothness.According to the experimental result in this past, generally directly engage without the dielectric sputtered film.But as the present invention, thin layer 4 adopts with Ta ₂O ₅Or Nb ₂O ₅Be the single or multiple lift film of principal ingredient, promptly use sputtering method to come film forming, also can make the smooth finish of thin layer 4 very high, can reach the required smooth finish of direct joint.

Fig. 2 represents the surface smoothness of sputtered film.Fig. 2 (a) is that (target as sputtering source is Ta to tantalum pentoxide ₂O ₅) the surface smoothness measurement result of employing atomic force microscope of sputtered film, Fig. 2 (b) represents SiO ₂Sputtered film adopts the measurement result of the surface smoothness of atomic force microscope.As can be seen from Figure 2, the surface smoothness of tantalum pentoxide (maximal value 2nm) is better than SiO ₂Surface smoothness (about maximal value 6nm).With the surface smoothness of tantalum pentoxide sputtered film same degree, for example (target is Nb to the niobium oxide sputtered film ₂O ₅Film) also can reach above-mentioned surface smoothness.But the refractive index of niobium oxide film is 2.25～2.35 to wavelength 632.8nm light, greater than the MgO:LN crystal.Therefore, be under the situation of MgO:LN crystal at waveguide substrate 1, can not seal light, can not form optical waveguide 3.But, adopting the higher material of refractive index, for example under the situation of semiconductor material such as silicon chip, can utilize the niobium oxide film as thin layer 4.The refractive index of thin layer 4 is lower than waveguide substrate 1, and the material difference used according to waveguide substrate 1 can suitably be selected for use with Ta ₂O ₅Or Nb ₂O ₅A certain suitable in the dielectric film for principal ingredient.

Experiment showed, that its chemical proofing is strong.This is directly to engage necessary characteristic.For example, in above-mentioned water wettability when directly engaging is handled, carry out the ammonia hydrogen peroxide treatment, SiO ₂Sputtered film because of the ammonia hydrogen peroxide by etch, the inner evenness of thickness further worsens, so can not be applicable to the thin layer 4 of direct joint.On the other hand, with Ta ₂O ₅Or Nb ₂O ₅For the dielectric film of principal ingredient is not corroded by the ammonia hydrogen peroxide, and to the organic solvent that in other technologies, uses and buffering hydrofluorite (hydrofluorite: ammonium fluoride: the mixed solution of water=1: 5: 50) very strong corrosion stability is arranged also.

At this, following Ta ₂O ₅For the dielectric film of principal ingredient makes the optical element that is used for making the 1st embodiment as thin layer 4, its result is expressed as follows.Intervention is with Ta ₂O ₅Direct assembling substrates for the thin layer 4 of principal ingredient, in the technology (the sheet grinding of the waveguide substrate 1 of MgO:LN crystal, photoetching, dry etching, end surface grinding etc.) after directly engaging, do not find to peel off and deterioration, kept very good engagement state.Especially as sputtering condition, in being not less than 100 ℃ temperature atmosphere, carry out film forming, like this Ta of thin layer 4 ₂O ₅The intensity of sputtered film itself and very firm to the being adjacent to property of waveguide substrate 1 prevents to peel off with degradation effects fine on composition surface and the sputter face when grinding for sheet.

And the guide properties of established optical waveguide 3 is also fine.Light blocking effect and low-loss optically waveguide fully is firmly established.And,, must critically carry out the refractive index control of thin layer 4 and the shape control of optical waveguide 3 in order to form single mode with optical waveguide 3.As with Ta ₂O ₅Such for the dielectric of principal ingredient, adopt MgO:LN crystal and the approaching material of refractive index as waveguide substrate 1, its effect is to increase substantially the optical waveguide design margin.

With Ta ₂O ₅For the dielectric film of principal ingredient as thin layer 4.In addition, adopting with Nb ₂O ₅Under the situation of dielectric film for principal ingredient as thin layer 4, same, in directly engaging, also can keep very good engagement state.Moreover the optical waveguide in the optical waveguide 3 also is good.And, with Ta ₂O ₅Or Nb ₂O ₅Phase specific refractivity height, so, can select for use respectively according to material used in the waveguide substrate 1.

More than illustrated with Ta ₂O ₅For the dielectric monofilm of principal ingredient as thin layer 4, but also can be with Ta ₂O ₅For the multilayer film of principal ingredient uses as thin layer 4.For example, to Ta ₂O ₅Be film forming atmosphere gas (the case internal pressure of the flow of argon gas and oxygen and the sputtering equipment) change of the dielectric film of principal ingredient, perhaps the institute to film-forming temperature and sputtering equipment adds the electric power change, can form the different film of refractive index.For example, on MgO:LN crystal (refractive index to wavelength 632.8nm light is 2.17) waveguide substrate 1, utilizing refractive index to the light of wavelength 632.8nm is 2 kinds of Ta of 2.05 and 2.10 ₂O ₅Film for principal ingredient, can form multilayer film. the layer employing refractive index that waveguide substrate 1 is connected with substrate 2 is 2.05 layer. and, the thickness that is 2.05 rete to refractive index is decided to be 77nm, is refractive index that the thickness of 2.10 rete is 75nm only, and it is alternately carried out film forming.Constitute like this, the thin layer 4 that is made of 9 layers multilayer films, its reflectivity are that the reflectivity of thin layer 4 of 2.3%, 19 layer multilayer film is 7.1%.That is to say, refractive index is risen by increasing the number of plies.On the other hand, with Ta ₂O ₅Be the monofilm of principal ingredient, reflectivity is 0.32%.In contrast to this, obtain reflectivity more than 10 times easily.

And same, multilayer film that is made of niobium oxide and the multilayer film that is made of Ta oxide and niobium oxide can be used as thin layer 4 and directly engage.Like this, can produce low-loss, the optical-waveguide-type element of abundant light blocking effect is arranged.Under the situation that adopts the multilayer film that constitutes by tantalum pentoxide and niobium oxide, for example forming makes the tantalum pentoxide rete of low-refraction be connected with optical waveguide 3, on the face of opposition side, utilize the niobium oxidation film layer of high index of refraction to form thin layer 4, substrate 2 and niobium oxidation film layer also can adopt direct connected structure.If adopt this structure, then the closed state of light can be controlled to the state of hope.

And thin layer 4 also can adopt sandwich construction, promptly wherein comprises with Ta ₂O ₅Or Nb ₂O ₅The metal level that constitutes for the film of principal ingredient and by metal material is at interior sandwich construction.For example also can on the face that directly engages, constitute metal level.

From the reflected light of direct assembling substrates the inside, for by the reflected light on waveguide substrate 1 surface and from the interference stripes that reflected light produced of thin layer 4, become the clutter composition and occur.For example, when grinding operation in employed maintenance platform and waveguide substrate 1 bonding, occur dust sneak into the irregular situation of bonding agent under, because directly the inside of assembling substrates and abrasive surface surface keeps heeling condition, so, can observe the reflected light of from direct assembling substrates the inside (direct assembling substrates and the face that keeps platform to be connected) and the interference stripes that waveguide substrate 1 lip-deep reflected light is caused.Like this, be difficult for seeing clearly from the reflected light of the thin layer 4 that was observed originally and the interference stripes that reflected light caused of sheet substrate surface.Therefore,, can eliminate this clutter composition, carry out by the reduction processing of the substrate of sheet easily by metal level being arranged in the middle layer of direct joint.

As shown in Figure 3, on substrate 2, form thin layer 4, form waveguide substrate 1 on it again with ridge optical waveguide 3.The component part of thin layer 4 is: the metal level 5 that is made of metal materials such as tantalums and with Ta ₂O ₅Or Nb ₂O ₅Dielectric layer 6 for principal ingredient.For example, metal level 5 is formed on substrate 2 sides, and dielectric layer 6 is formed on waveguide substrate 1 side.And, when making this optical element, on the substrate 2 of the LN crystal substrates that X cuts, form thin layer 4.Then, the waveguide substrate 1 and the direct bonding method of thin layer 4 usefulness of the MgO:LN crystal substrates of X cutting engage, and form optical waveguide 3 on waveguide substrate 1.On the metal level 5 of thin layer 4, for example use the Ta film, dielectric layer 6 adopts with Ta ₂O ₅Monofilm for principal ingredient.And metal level 5 also can adopt any metal, as long as can obtain and above-mentioned same effect.

Metal level 5 and the waveguide substrate 1 that is constituted as the MgO:LN crystal of strong dielectric crystal or metal level 5 and LN crystal are on the interface of substrate 2, can not carry out firm joint with direct bonding method.With Ta ₂O ₅Dielectric layer that monofilm constituted 6 and waveguide substrate 1 for principal ingredient can directly engage well, so, it is directly engaged.At this moment, if metal level 5 too near optical waveguide 3, then can cause the absorption loss of waveguide light.For example, under the big situation of waveguide luminous power, can cause the optical element breakage.So metal level 5 must leave optical waveguide 3, its degree of leaving reaches evanescent (evanescent) of waveguide light more than the zone.Metal level 5 and waveguide substrate 1 get final product more than leaving 50nm.And so-called evanescent zone is meant when light transmits the time in optical waveguide to leak out the zone of outside.If form metal level 5, then waveguide light is subjected to the influence of metal level 5, may cause the optical element breakage in this zone.

When utilizing direct joint to make optical element, at first on substrate 2, form metal level 5 and dielectric layer 6 successively by the RF sputter.The thickness of metal level 5 is 5nm～100nm, and the thickness of dielectric layer 6 is 10～200nm.

Then, utilize direct bonding method as mentioned above thin layer 4 and waveguide substrate 1 to be engaged, carry out the formation of optical waveguide 3.In this optical element, the distance of metal level 5 and optical waveguide 3 (waveguide substrate 1) equals the thickness of dielectric layer 6.Be not less than at this thickness under the situation of 50nm, the guide properties of this optical element is good, and light blocking effect and low-loss optically waveguide fully is firmly established.

Fig. 4 is the orthograph that the optical element of Fig. 3 adopts the third quadrant method.Shown in the vertical view of Fig. 4 (a), metal level 5 is not to be formed on the whole assembling substrates face, but utilizes the graphic making method, is formed on the metal removal position 5a that does not form metal level 5.And, in the vertical view of Fig. 4 (a), figured metal level 5, in fact, on metal level 5, gone back lamination thin layer 6 and waveguide substrate 1.See through these, can see metal level 5.

Metal level 5 carries out graphic making shown in Fig. 4 (a), like this, judge the position when forming optical waveguide 3 easily.That is to say that 5a serves as a mark the metal removal position, aligned position gets final product.Like this, its advantage is can reach very high installation accuracy when optical element is installed.In the optical waveguide 3 of the optical element that LN crystal that is adopted in waveguide substrate 1 and the substrate 2 and MgO:LN crystal are constituted, occur depending on these crystal axis to waveguide loss.For example, utilizing the X cutting substrate of LN crystal, forming under the situation of optical waveguide 3 of Y direction transmission, forming optical waveguide departing from the Y-axis direction several times, waveguide loss is extremely increased.Therefore, consider crystal axis to, the formation direction of alignment light waveguide 3 is very important on the direction of the characteristic that can obtain to wish.

And, especially,, must form the cycle shape polarization reversal structure that makes crystal polarised direction periodic inversion in order to improve wavelength conversion efficient utilizing optical waveguide 3 to make under the situation of Wavelength conversion element.The polarised direction of the LN crystal of single polarization is positioned at the C direction of principal axis (=Z-direction) of crystal, and is for example known, utilizes cycle shape electrode to apply high voltage electric field, can form above-mentioned polarization reversal periodically.Wavelength conversion wishes that the direction of vibration of light beats and polarised direction are consistent.Therefore, in order to carry out the high-level efficiency wavelength conversion, wish to form the vertical state of this cycle shape polarization reversal structure and optical waveguide 3.Like this, adopt direct assembling substrates, for example as must judge in the production process of the optical element of Wavelength conversion element crystal axis to.

In the optical waveguide production process in the past, the not shown method that the crystal substrates direction is judged.Therefore, must on the substrate the inside (optical waveguide forms face and opposite face) that directly engages, utilize the laser labelling method to wait the mark that is formed for position alignment.But, as mentioned above,, waveguide substrate 1 and substrate 2 are engaged by comprising the thin layer 4 of the metal level 5 of making figure, like this, do not need the mark that is used to aim at.That is to say, on substrate 2, formed the thin layer 4 that comprises the metal level 5 that has formed figure.Above it, when placing waveguide substrate 1, the metal removal position 5a that forms by this graphic making is engaged as standard, crystal axis is to not being offset like this.

And, be formed near the metal level 5 on the part incident end 3a of optical waveguide 3, when being coupled, be easy to generate the element breakage that light absorption causes from the incident light of laser instrument and optical waveguide 3.So for example shown in Fig. 4 (b), near the incident end 3a of optical waveguide 3, it is effective that metal removal position 5a is set.According to actual measurement, the incident end 3a surface 1 μ m that leaves optical waveguide 3 at least with interior zone in, do not have metal level to get final product.That is to say that the recessed depth d of metal removal position 5a is not less than 1 μ m and gets final product.

In the 1st embodiment, be illustrated in by LiNb _xTa _(1-x)O ₃In the strong dielectric crystal substrates that constitutes and the direct joint of other crystal substrates, by with Ta ₂O ₅Or Nb ₂O ₅Be the dielectric film of principal ingredient, promptly thin layer 4 engages the situation of making optical element.But, except by LiNb _xTa _(1-x)O ₃Outside the substrate that constitutes, for example at Si sheet and SiO ₂In the substrate etc., under the situation about engaging by thin layer, also be to utilize with Ta ₂O ₅Or Nb ₂O ₅For the dielectric film of principal ingredient is a thin layer 4, equally can be effectively as flatness is good, chemical proofing is strong thin layer 4.

[the 2nd embodiment]

The optical element of the 2nd embodiment is that one of substrate of engaging by film can carry out the optical element that high-precision homogeneity is identified to substrate thickness when carrying out slimming.Below describe the good thickness evenness that sheet can reach in detail.And, in the 2nd embodiment, illustrated, as the example that the optical element that adopts the sheet substrate is made, on the direct assembling substrates of LN crystal and MgO:LN crystal, the MgO:LN crystal is carried out slimming, form the situation of optical waveguide.The present invention is not limited only to this structure and optical-waveguide-type element, also is not limited only to direct joint on joint method.

Form the method for optical waveguide in LN crystal and MgO:LN crystal, the past has proposed multiple.For example, in the Wavelength conversion element of the nonlinear optical properties that utilizes LN crystal and MgO:LN crystal, the method as forming optical waveguide has proposed proton exchange method and titanium diffusion method.But known, these methods have adopted the variations in refractive index of implanted dopant in crystal, so nonlinear optical constant degenerates thereupon.To this, the optical-waveguide-type element of employing assembling substrates utilizes the refringence of engaged substrate, has the light blocking effect of substrate thickness direction, only carries out the shape processing of direct assembling substrates, form optical waveguide, so its advantage is the characteristic that can not influence crystal on principle.Therefore, utilize this nonlinear optical effect to realize the method for optical-waveguide-type element, can be described as very effective method.

General in the formation of optical-waveguide-type element, optical waveguide shape (thickness and width) is required the homogeneity height.Especially in the optical waveguide type wavelength inverting element with cycle shape polarization reversal structure, the phase matching of input basic wave and harmonic wave reaches in whole wave guide evenly, like this, can carry out high efficiency wavelength conversion.Phase matching wavelengths depends on the actual effect refractive index of polarization reversal cycle and basic wave and harmonic wave, so if change with respect to wave guide direction, then conversion efficiency significantly reduces optical waveguide shape (width and height).For example forming with dry etching under the situation of ridge optical waveguide, the optical waveguide width depends on the photoresist graphic making precision of using as etching mask, so, can realize the high precision of sub-micron.

On the other hand, the control of the height of optical waveguide for example can be carried out sheet with polishing.But be difficult to reach the height control of sub-micrometer precision.Its reason is, adopt the height absolute value and the uniformity testing method of short-cut method limited, that has adopted has following two kinds, a kind of is thickness absolute value measuring method, its employing platform valency cathetometer etc. is measured, another kind is a uniformity evaluating method, and it shines from substrate surface with laser, utilizes interferometer to observe from the reflected light of the surface and the inside of direct assembling substrates.Especially shown in the 1st embodiment like that, in the direct assembling substrates of LN crystal and MgO:LN crystal, for forming optical waveguide in the MgO:LN crystal, the direct joint by thin layer is effective.But in the thin layer of Ti Chuing, the thin layer inside the substrate that is positioned at sheet can not get sufficient reflected light, can not carry out Evaluation for Uniformity with interferometer in the past.So, be difficult to reach high-precision high homogeneity.

Below utilize accompanying drawing, describe the optical element that relates to the present invention the 2nd embodiment in detail.Owing on the direct assembling substrates that passes through film shown in the 1st embodiment, form optical waveguide, so in one the sheet in engaged substrate, the thickness of the substrate of sheet is hopeful to reach high-precision homogeneity.The optical element of the 2nd embodiment can be estimated the thickness of the waveguide substrate that forms optical waveguide, can make the thickness evenness of sheet good.And, in the 2nd embodiment, following optical element is described, the example that i.e. conduct adopts the optical element of sheet substrate to make, with the LN crystal as substrate, as waveguide substrate, these substrate and waveguide substrate engage by thin layer with the MgO:LN crystal, waveguide substrate is carried out sheet form optical waveguide.And the material and the structure of optical element are not limited only to this.

The optical element of the 2nd embodiment, in the substrate that engages by thin layer, the waveguide substrate of sheet is only transparent to certain wavelengths λ's, and the refractive index of waveguide substrate is n concerning the light of wavelength X ₁And the substrate that engages by waveguide substrate and thin layer is n to the refractive index of the light of wavelength X ₂And, make the thin layer that use in the middle layer of waveguide substrate and substrate, be n to the refractive index of wavelength X light ₃(≠ n ₁≠ n ₂), it is k that the thickness T of thin layer establishes natural number, its pass is T ≠ (k * λ)/(2 * n ₃).By satisfying above condition, utilize the high-precision film thickness uniformity of thin layer and, measure the homogeneity of waveguide substrate from the reflected light of thin layer, carry out sheet.Specifically, the formed interference stripes of reflected light that surface and thin layer from the waveguide substrate of sheet come are observed, energy measurement goes out the thickness evenness of crystal substrates.Like this, realized having the optical element of the sheet substrate of excellent homogeneity.On this sheet substrate sections, carry out ridged processing, can produce the optical-waveguide-type element.

Fig. 5 is the oblique view that expression relates to the optical element structure of the present invention the 2nd embodiment.Its expression engages an example of the optical element that constitutes to LN crystal substrates and MgO:LN crystal substrates by thin layer.In Fig. 5,, engage by thin layer 4 as the substrate 2 of the MgO:LN crystal substrates of X cutting with as the waveguide substrate 1 of the LN crystal substrates of X cutting.And waveguide substrate 1 and thin layer 4 engage by direct bonding method.That is to say, on substrate 2, form thin layer 4 with methods such as sputters, moreover, to Ta ₂O ₅For the dielectric monofilm of principal ingredient is a thin layer 4, and directly engage as the waveguide substrate 1 of the LN crystal substrates of X cutting.And like this, waveguide substrate 1 and substrate 2 are called direct assembling substrates by the state that thin layer 4 engages.Then, the waveguide substrate 1 of direct assembling substrates is carried out sheet, can produce optical element.And thin layer 4 conducts are with Ta ₂O ₅Dielectric monofilm for principal ingredient.

By grinding waveguide substrate 1 to carry out under the situation of sheet, should make the thickness of the waveguide substrate 1 of sheet reach uniformity to direct assembling substrates.For realizing this purpose, except requiring the own depth of parallelism of direct assembling substrates good (thickness is even), also need to keep platform to have certain surface accuracy, so that when grinding, keep assembling substrates not move, and, require direct assembling substrates and keep multiple factor such as the bonding homogeneity of platform, the film thickness uniformity of thin layer 4 to keep high precision.

In order to reduce the thickness offset of the waveguide substrate 1 after the sheet, at first, can adopt the depth of parallelism good waveguide substrate 1 and substrate 2.And, when grinding, guarantee direct assembling substrates is carried out the flatness of bonding maintenance platform.Moreover, keep grinding on the platform because utilize bonding agent that direct assembling substrates is bonded to, so if bonding agent is in uneven thickness, then the thickness of the waveguide substrate of sheet is inhomogeneous certainly.For anti-phenomenon here, for example utilize the Thermocurable bonding agent, method coatings equably on the back side of direct assembling substrates such as employing spin coated are carried out pressurized, heated to handle, and are bonded in to keep on the platform.But, so also still can make bonding direct assembling substrates produce small distortion, so, be standard with the back side of direct assembling substrates (keep platform and directly the bonding plane of assembling substrates), carry out sheet, also can produce in uneven thickness.Therefore, further adopt following method.

Generally, under waveguide substrate 1 was transparent situation, it was the interference stripes observations that the method that thickness evenness is observed has easy and high-precision optical means.Interference stripes observation is illumination wavelength 633 μ m laser for example on substrate surface, and the catoptrical disturbance state on the thin layer surface of the reflected light of observation substrate surface and lower floor thereof, checks the substrate thickness homogeneity.When thickness has error, produce interference stripes, so check out in uneven thickness easily.But, when the sheet of the waveguide substrate 1 of the direct assembling substrates by thin layer 4 since from the reflected light of thin layer 4 a little less than, so, the problem of observation interference stripes appears being difficult to.

Therefore, the optical element of the 2nd embodiment, its structure has fully increased from the reflected light of thin layer 4, and Fig. 6 is each the lip-deep catoptrical key diagram about thin layer 4.And Fig. 7 is the performance plot of the relation of expression thickness T of thin layer 4 and light reflectivity R.In Fig. 6, reflected light 8 is the reflected light on the interface of thin layer 4 and waveguide substrate 1; Reflected light 9 is the reflected light on the interface of thin layer 4 and substrate 2.Generally, be respectively n in refractive index _a, n _b2 kinds of dielectrics in, from n _aDielectric vertically be injected into n _bDielectric in the reflectivity R of the Fei Nieer reflection of light on dielectric interface be expressed from the next

R＝|(n _a-n _b)/(n _a+n _b)| ²×100(％)。

For example, expression waveguide substrate 1 is that MgO:LN crystal substrates, substrate 2 are Ta for LN crystal substrates, thin layer 4 ₂O ₅The time calculated value.For example, be 2.166 to the refractive index of wavelength 632.8nm optical waveguide substrate 1, the refractive index of thin layer 4 is 2.10, the refractive index of substrate is 2.23, obtains reflectivity R from above-mentioned formula.By calculating as can be seen: the refractive index R at the interface of waveguide substrate 1 and thin layer 4 is 0.024%, and the reflectivity R at the interface of substrate 2 and thin layer 4 is 0.09%, and is very little.At this, if reflected light excessively a little less than, the interference stripes that can not observe reflected light produce then.Therefore, utilize the refractive index n of light wavelength lambda and thin layer 4 ₃With natural number k, if film thickness T satisfies the following formula condition,

T≠(k×λ)/(2×n ₃)

Then can utilize the interference of reflected light 8 and reflected light 9, increase consequent reflected light from thin layer 4.

As can be seen from Figure 7, for example, the wavelength X of the light source that uses in interference stripes observation is 632.8nm, to the thin layer 4 (Ta of wavelength X ₂O ₅) refractive index n ₃Be 2.1, so if the thickness T of thin layer 4 is 150.67nm and several times thereof, then the reflectivity from thin layer 4 is almost 0%, does not have reflected light.So it is many more to depart from this thickness T, reflected light is strong more.

Make that k is a natural number, the thickness T of thin layer 4 is as follows:

T＝(2k-1)×λ/(4×n ₃)

Be desirable in the case, reflected light 8, reflected light 9 become the mutual maximum disturbed condition that strengthens, and increase to more than 10 times of Fei Nieer reflection from the reflection light quantity of thin layer 4.Like this, can observe by from the surface reflection of the reflected light of thin layer 4 and waveguide substrate 1 and the interference stripes that form.Utilize this interference stripes observation, can estimate the thickness evenness of the waveguide substrate 1 in grinding.According to the disturbed condition of observation, for reducing unevenness, for example change increasing the weight of when grinding and distribute, grind arbitrarily, can make waveguide substrate 1 sheet equably.

The inventor, the interference stripes that utilize said method to observe grind under the state in face below 1, utilize the step cathetometer to measure the thickness absolute value of waveguide substrate 1 simultaneously, make the success of waveguide substrate 1 sheet at last, reach thickness 3.5 μ m, below the thickness error 300nm.And, utilize the light source of wavelength 632.8nm to carry out interference stripes observation, can judge the unevenness that each bar interference stripes has 300nm approximately.By actual measurement, confirm, utilize the waveguide substrate 1 of this sheet, by dry etching, for example form ridge optical waveguide shown in Figure 1, can obtain good waveguide properties.And, also can form in polarization reversal formation of the enterprising line period shape of sheet substrate and optical waveguide, also can make Wavelength conversion element.In this Wavelength conversion element, by improving the thickness evenness of optical waveguide, can reach good phase matching state, realize high wavelength conversion efficient.

And, representing natural number with k, thickness T is expressed from the next:

T＝(k×λ)/(2×n ₃)

In the case, between reflected light 8 and reflected light 9, produce the interference that weakens mutually, the result reduces to minimum from the reflected light of thin layer 4, and this is because the catoptrical phase deviation pi/2 on the interface of reflected light on the interface on one side of thin layer 4 and another side.And this is n ₁＞n ₃, n ₂＞n ₃Situation.

At n ₁＞n ₃＞n ₂Situation under, at T=((2k-1) * λ)/(4 * n ₃) situation under, it is minimum that reflected light is reduced to.

That is to say, at n ₁＞n ₃, n ₂＞n ₃Situation under, thickness T is T ≠ (k * λ)/(2 * n ₃), at n ₁＞n ₃＞n ₂Situation under, can be T ≠ ((2k-1) * λ)/(4 * n ₃).

And especially, the thickness T of ridge optical waveguide 4 is according to T=(2k-1) * λ)/(4-n ₃) ± 30nm with interior situation under, can be reduced to below 5% from maximal value from the intensity of reflected light of thin layer 4.So, the thickness T of thin layer 4 is set in this scope, observe interference stripes easily, so, wish in this scope, to carry out film thickness monitoring.And, under the very little situation of the intensity of reflected light 8 or reflected light 9,, also be less from the intensity of reflected light of thin layer 4 even reflected light 8 and reflected light 9 strengthen mutually by disturbing.But, experimental results show that: n ₁And n ₃Refringence or n ₂And n ₃Refringence in, if at least one side is not less than 0.05, so, can observe interference stripes.

In the 2nd embodiment, understand that for example thin layer 4 adopts with Ta ₂O ₅Dielectric monofilm for principal ingredient.The material of thin layer 4 is not limited only to this.And thin layer 4 is also set up same principle about the situation of multilayer film.For example, thin layer 4 adopts under the situation of the multilayer film that is made of the different multilayer of refractive index, as general known, according to the refractive index and the layer thickness of each layer, can obtain and hang down conditioned reflex or high conditioned reflex.

For example, as mentioned above, on the waveguide substrate 1 of MgO:LN crystal (refractive index to wavelength 632.8nm light is 2.17), utilize refractive index to wavelength 632.8nm light be 2.05 and 2.10 2 kinds with Ta ₂O ₅For the film of principal ingredient forms multilayer film.At this moment, to adopt refractive index be 2.05 layer to the layer that is connected with substrate 2 of waveguide substrate 1.And, refractive index be 2.05 the layer thickness be decided to be 77nm; Refractive index be 2.10 the layer thickness be decided to be 75nm, make it alternately carry out film forming.The reflectivity of the thin layer 4 of the employing 9 layer multi-layer films of Gou Chenging is 2.3% like this.The reflectivity that adopts the thin layer 4 of 19 layer multi-layer films is 7.1%.Like this, control, can control reflectivity by refractive index and thickness to each layer of multilayer film.

And so-called low conditioned reflex is meant between the reflected light on each bed interface cancels each other the condition that intensity of reflected light is reduced because of phase place is different.And so-called high conditioned reflex is meant between the reflected light on each bed interface on the contrary and synthesizes, the condition that catoptrical intensity is increased.Come design of thin rete 4 according to high conditioned reflex, can make the reflection light quantity of thin layer 4 integral body reach maximum like this.

And, in the 2nd embodiment, narrated the situation that the optical source wavelength λ of interference stripes observation usefulness is decided to be 632.8nm.But, general as the optical source wavelength of measuring purposes, 380nm, 410nm, 441.6nm, 488nm, 532nm etc. are arranged.No matter, can both calculate the thickness of best thin layer 4, can increase from the reflection light quantity of thin layer 4 with same computing method to which wavelength.

[the 3rd embodiment]

Below utilize accompanying drawing, describe the optical element that relates to the present invention the 3rd embodiment in detail.At this, it is example that optical element adopts the optical-waveguide-type element of making by direct joint, as 2 substrates of direct joint, adopts the LiNbO of strong dielectric crystal ₃The LiNbO of crystal (being designated hereinafter simply as the LN crystal) substrate and doped with Mg O ₃Crystal (hereinafter to be referred as the MgO:LN crystal) substrate is that example is illustrated with this situation.But the present invention is not limited only to this structure.

The optical element of the 3rd embodiment, its structure are in the optical element of assembling substrates (two one group the substrate that finger closes) of 2 substrates after adopting optical grinding, have the disengaged zone as the gap in the zone of the part on composition surface.

The optical element of the 3rd embodiment is to engaging with kind substrate or variety classes substrate, forms under the situation of optical element, and gap (disengaged zone) is set on the part on composition surface.Like this, it is poor to obtain the refractive index step (highly) of substrate thickness direction.Therefore, for example, one side to assembling substrates carry out carry out ridged processing after the sheet, form optical waveguide, like this, no matter the refractive index of substrate how, all can be produced the optical-waveguide-type optical element.

Below utilize accompanying drawing, describe the optical element that relates to the present invention the 3rd embodiment in detail.Fig. 8 is the oblique view that expression relates to the optical element structure of the present invention the 3rd embodiment.The structure of the 3rd embodiment is, do not use the thin layer 4 of the 1st and the 2nd embodiment, but is provided with disengaged regionally 24, obtains refractive index platform price differential like this near the composition surface of substrate 22 and waveguide substrate 21.Therefore, no matter be the waveguide substrate 21 that adopts what material, can both form optical waveguide, improve guide properties.So can improve the selectivity of substrate material.

For example, waveguide substrate 21 adopts the MgO:LN crystal substrates of X cutting.And substrate 22 adopts the LN crystal substrates of X cutting.Moreover waveguide substrate 21 carries out ridged processing, forms ridge optical waveguide 23.And optical waveguide 23 is not connected with substrate 22, between substrate 22 and optical waveguide 23, is provided as disengaged regional 24 gap (being designated hereinafter simply as the gap).Each interarea to waveguide substrate 21 and substrate 22 carries out optical grinding.Moreover the face of waveguide substrate 21 sides of substrate 22 has and is processed into the disengaged regional 24 of concavity, and under the situation that substrate 22 and waveguide substrate 21 are engaged, disengaged regional 24 become the gap.Disengaged regional 24 after engaging waveguide substrate 21 and substrate 22, becomes the gap that it is separated.

Below the method for the optical element of the 3rd embodiment is made in explanation.At first, on substrate 22, form disengaged regional 24.Forming disengaged regional 24 method has a lot.For example can adopt dry etching.On the interarea on one side of substrate 22, utilize RF sputter or EB evaporation deposition method to form the Cr film of 200nm, utilize photoetching and wet etching method to carry out graphic making as disengaged regional 24 zone.Then, Cr as etching mask, is carried out dry etching on substrate 22, forming the degree of depth is that 100nm is an erosion grooves to disengaged regional 24 of 300nm.Then, utilize the wet etching method to remove the Cr that uses as mask.And, also can form substrate 22 with the method beyond above-mentioned.

To as the formation of the interarea on direct one side of the waveguide substrate 21 on composition surface and substrate 22 disengaged regional 24 interarea carry out water wettability and handle.Specifically, the interarea that waveguide substrate 21 and substrate 22 are directly engaged respectively carries out the acetone ultrasonic cleaning, then, be immersed in ammoniacal liquor: aquae hydrogenii dioxidi: in the mixed solution (being designated hereinafter simply as the ammonia hydrogen peroxide) of pure water=1: 1: 6 more than 15 minutes, carry out dried after cleaning with pure water.And the ammonia aquae hydrogenii dioxidi can use general concentration, promptly 20%～40%.The concentration of ammonia aquae hydrogenii dioxidi is preferably 30%.

Then, the crystal axis of waveguide substrate 21 and substrate 22 to aiming at, is made it and respectively carried out the interarea that water wettability handles and contact, pressurization slightly, like this, formed except disengaged regional 24 the position, made waveguide substrate 21 and substrate 22 form the state that is adjacent to.

Moreover, heat-treat by waveguide substrate 21 and substrate 22 that this is adjacent to, can obtain direct assembling substrates.Stove is used in thermal treatment, for preventing that assembling substrates from peeling off and heating rapidly and cause breakage, programming rate is set at 50～500 ℃/hour, carries out under 350～800 ℃.

In order on the direct assembling substrates that obtains like this, to form optical waveguide 23, waveguide substrate 21 is carried out surface grinding and sheet, finally the thickness of waveguide substrate 21 is reduced to 3～4 μ m.Then, utilize photoetching to carry out and optical waveguide 23 corresponding graphic makings,, promptly form the step of 1.5～2 μ m on the waveguide substrate 21 by dry etching, form ridge optical waveguide 23 like this at the MgO:LN of sheet crystal substrates.And the both ends of the surface of optical waveguide 23 are carried out mirror ultrafinish after ridged forms.

And assembling substrates can not form ridge waveguide, for example as diffraction grating, and the optical element of modulator, deflector etc.

Below further describe disengaged regional 24.Generally in the optical-waveguide-type element, adequate closure light and low-loss optically waveguide are most important characteristics in optical waveguide.And, for the transport property uniformity in the overall optical waveguide that makes optical waveguide, and improve the qualification rate of making, must guarantee homogeneity aspect the control of optical waveguide shape.Even in optical waveguide shape control, also be to carry out sheet at substrate to one side of assembling substrates, form under the situation of optical waveguide, especially the thickness evenness of the substrate of sheet (waveguide substrate 21) is well necessary condition.

Composition surface 25 is the face that engages with substrate 22 in the interarea of waveguide substrate 21.In composition surface 25, waveguide substrate 21 and substrate 22, some engages.This is because the optical element of the 3rd embodiment between waveguide substrate 21 and substrate 22, has as disengaged regional 24 gap.So, in composition surface 25, in the scope that forms this interstitial area, form optical waveguide 23, like this, can between optical waveguide 23 and gap, produce the refractive index step discrepancy in elevation.Obtain the sufficient light blocking effect on the substrate thickness direction of optical waveguide 23 like this, easily.At this moment, if in the zone of optical waveguide 23 projection on composition surface 25, have the zone that engages with substrate 22, then the light blocking effect of optical waveguide 23 is insufficient, and the loss of waveguide light increases.That is to say that disengaged regional 24 zones that comprise optical waveguide 23 projection on composition surface 25 are interior, it is very important becoming the zone bigger than this view field.Like this, can fully obtain the light blocking effect that the refractive index step discrepancy in elevation is produced.

After the technology of formation optical waveguide 23 is the sheet of waveguide substrate 21.Disengaged regional 24 by being provided with, when forming optical waveguide 23 by photoetching and carry out graphic making, optical waveguide 23 and disengaged regional 24 position alignment disengaged regional 24 to be benchmark, are easy to carry out.And it is disengaged regional 24 for example to be with the crystal axis of substrate 22 that benchmark forms, and can aim at the crystal axis of substrate 22, forms optical waveguide 23.Like this, can control waveguide loss.

Moreover, the following formation interval of the Width of the optical waveguide 23 between disengaged regional 23 of the explanation direction identical width and each disengaged regional 24 with the Width of optical waveguide 23.Forming under a plurality of disengaged situations of regional 24, in order to obtain sufficient joint strength to adapt to the technology behind the direct joint, to between disengaged regional 24, obtain enough intervals, interval between disengaged regional 24 the center is being set under the situation that is not less than 1mm and forms, verified by actual measurement, if the width in disengaged zone is 1 μ m～500 μ m, can obtain enough direct bond strengths so.And, prove that by actual measurement be spaced apart 30 μ m～1mm between disengaged regional 24 the center, disengaged regional 24 width is not more than 30 μ m, can obtain sufficient direct bond strength.Moreover, for example,, then adapt with it if the width of optical waveguide 23 is 5 μ m, wish that disengaged regional 24 width is 10～30 μ m.And disengaged regional 24 width is 30 μ m, and the interval between disengaged regional 24 the center preferably is not less than 100 μ m.

The characteristic of the qualification rate when making optical element and a large amount of production and optical waveguide 23 as if consideration, then for example under the situation of the optical waveguide 23 that forms width 3 μ m, wish disengaged regional 24 width setup to be 5～10 μ m, disengaged regional 24 formation is set at several 10 μ m at interval.

And, if not engaging zones 24 only forms, then when the machining (for example cut off and grind) of assembling substrates, the load of substrate is depended on disengaged regional 24 formation direction on a direction on the composition surface, have the skew tendency.Like this, for example breakage that when cutting off and grind, can produce optical element.For preventing this phenomenon, disengaged regional 24 as shown in Figure 9, wishes to make clathrate.

Fig. 9 is the figure of disengaged regional 24 the position of expression, is the orthograph that adopts the third quadrant method.Shown in the vertical view of Fig. 9, not only along optical waveguide 23, and with optical waveguide 23 vertical direction on also arrange disengaged regional 24.And the interval of this grid all is uniformly-spaced.That is to say that disengaged regional 24 form equally spaced clathrate.Use this structure, can disperse to alleviate the load when cutting off and grinding, so the bond strength height.At this moment, change the rare close degree of engaging zones, anti-machining intensity has been carried out practical measurement, its result proves the physical strength height.By graphic making, in direct composition surface, be arranged to equally spaced clathrate to disengaged regional 24, can improve the physical strength of direct assembling substrates.

The below explanation and corresponding disengaged regional 24 the degree of depth of substrate thickness direction (gap depth).As mentioned above, because optical waveguide 23 is ridge structures, so the light blocking effect of the opposition side of the Width of optical waveguide 23 and substrate 22 is very abundant.And, waveguide light is not leaked from disengaged regional 24 sides of optical waveguide 23.That is to say that disengaged regional 24 gap depth, promptly the size light that oozes out that must reach in optical waveguide 23 the waveguide light of propagating does not exist in substrate 22.

Therefore, gap depth is decided to be 0.005 μ m～0.5 μ m, makes the optical element of the 3rd embodiment, when the characteristic of each element is estimated, is to be not less than under the situation of 0.01 μ m in gap depth, and worsening does not appear in the thickness direction light blocking effect of optical waveguide 23.So, be full of under the air state disengaged regional 24, if disengaged regional 24 gap depth is not less than 0.01 μ m, so, waveguide light can fully be propagated in optical waveguide 23.And, as mentioned above, utilize dry etching to carry out disengaged regional 24 formation, can make the high precision that the control of gap depth is reached several percentage points.

And waveguide substrate 21 and substrate 22 adopts the substrate of the high specification of the depth of parallelisms (thickness evenness), also can make THICKNESS CONTROL reach high precision in the grinding of waveguide substrate 21, sheet.For example, the thickness thin slice thickness evenness that turns to the waveguide substrate 21 of 3 μ m in 3 inches wafer face, can reach ± below the 50nm.

And when coming waveguide substrate 21 and substrate 22 engaged with direct bonding method, the flatness of the face of joint is very important.For example, the surface smoothness of the face of joint then is difficult to engage if be not less than 5nm.So before the direct joining process of waveguide substrate 21 and substrate 22, the flatness of carrying out the face that engages under the situation of technologies such as film forming and corrosion degenerates and causes concern.But, passing through above-mentioned Cr sputter, in the substrate 22 of technologies such as photoetching, wet etching, dry etching, proved that by actual measurement the flatness of interarea does not degenerate, easy and waveguide substrate 21 directly engages.

And, in the grinding of waveguide substrate 21, sheet operation, clearance part (disengaged regional 24) damaged and, also cause concern because of the disengaged regional 24 bond strengths declines that cause, peeling off etc. when being attrition process are arranged.But, waveguide substrate 21 after directly engaging and substrate 22 substrates, in the technology (the sheet grinding of waveguide substrate 21, photoetching, dry etching, end surface grinding etc.) after directly engaging, do not find to peel off and deterioration, proved that engagement state keeps very well yet.

Have, also confirm, the guide properties of the optical waveguide 23 in the optical element of the 3rd embodiment is good, can make sufficient light blocking effect and the low optical waveguide of propagating loss.

And waveguide substrate 21 and substrate 22 directly engage, and have in the structure example of disengaged regional 24 optical element, and substrate 22 is processed into concavity, have formed disengaged regional 24.But also can be processed into concavity to waveguide substrate 21, form disengaged regionally 24, this structure also realizes having effect same easily.

And, waveguide substrate 21 and substrate 22 used materials also are not limited in this, but, do not limit the refractive index of each substrate by disengaged zone is set, can utilize between the variety classes substrate or the direct joint between the identical type substrate obtains optical element.And, also can adopt direct joint joint in addition when between substrate, engaging.

And Figure 10 is the oblique view of another kind of structure that expression relates to the optical element of the 3rd embodiment.As shown in figure 10, also can in disengaged regional 34, optical waveguide 33 be set.This structure is prepared the waveguide substrate 31 that has formed ridge optical waveguide 33 in advance and is had disengaged regional 34 the substrate 32 that is processed to form concavity, for example adopts the MgO:LN crystal substrates of X cutting as waveguide substrate 31.And substrate adopts the LN crystal substrates of X cutting.Each interarea of waveguide substrate 31 and substrate 32 carries out optical grinding.Substrate 32 is processed into concavity, form disengaged regional 34 in, have optical waveguide 33, and have the gap that optical waveguide 33 and substrate 33 are separated.The guide properties that also is direct engagement state and optical waveguide 33 in this structure is good.

And the optical element of the 3rd embodiment describes as the optical-waveguide-type element.But be not limited only to the optical-waveguide-type element.For example also can on the part on composition surface, form periodic disengaged zone, as diffraction optical element.

[the 4th embodiment]

Below utilize accompanying drawing, describe the optical element that relates to the present invention the 4th embodiment in detail.

Figure 11 is the oblique view of the optical element of expression the 4th embodiment.The optical element of the 4th embodiment is the filling material different with the material of assembling substrates in the disengaged zone of the optical element of the 3rd embodiment, ultraviolet curable resin for example, like this, the bond strength except between the substrate of direct joint, the bonding force of ultraviolet curable resin can also be obtained, joint can be strengthened.Like this, can improve anti-machining intensity in the technology (adopting the sheet of the direct assembling substrates that grinds etc.) behind the joint more.

In Figure 11, constitute by engaging as the waveguide substrate 41 of the MgO:LN crystal substrates of X cutting and as the substrate 42 of the LN crystal substrates of X cutting.On substrate 42, form and to be processed into the disengaged regional 44 of concavity, ultraviolet curable resin 47 is write in filling.And, each interarea of waveguide substrate 41 and substrate 42 is carried out optical grinding.In Figure 11, form a plurality of disengaged regional 44.Its quantity is not only to be defined in this.And this optical element also can make the refractive index of waveguide substrate 41 be higher than to be filled in ultraviolet curable resin 47 and substrate 42 in disengaged regional 44, as waveguide, and can change each refringence to waveguide substrate 41, carries out waveguide selectively.Moreover, also can carry out ridged processing to waveguide substrate 41, use as ridge waveguide.

The manufacture method of the optical element of the 4th embodiment was identical with the manufacture method of the optical element of the 3rd embodiment before halfway.That is to say that identical operation is: on substrate 42, for example carry out the Cr film forming, carry out the Cr graphic making, carry out dry etching, form disengaged regional 44 with photoetching and wet etching method with RF sputter or EB evaporation method.Then, on waveguide substrate 41 and substrate 42, carry out water wettability and handle, form and be adjacent to state, directly engage by heat treated.Later operation is different with the 3rd embodiment.

In the gap direct assembling substrates made from above-mentioned manufacture method, that form as disengaged regional 44, filling ultraviolet curable resin 47.

At this moment ultraviolet curable resin 47 utilizes capillarity and is inhaled in the direct assembling substrates inner formed disengaged regional 44, especially ultraviolet curable resin 47 adopts lower (roughly below the 60cp) of viscosity, the speed of carrying out of capillarity is significantly accelerated, can make filling easier, the time is shorter.Then, carry out the ultraviolet ray irradiation from direct assembling substrates surface.Like this, the ultraviolet curable resin 47 of filling can obtain very strong bonding force through overcuring between waveguide substrate 41 and substrate 22.Then, also can for example carry out ridged processing, make optical waveguide this optical element.And, in addition, carry out other processing again according to purposes, perhaps directly use.

Moreover, the optical element of the 4th embodiment, when machining, ultraviolet curable resin 47 becomes padded coaming, also has the effect of disperseing and alleviating the load that bears on the substrate.Like this, for example in the possibility of waveguide substrate 41 being ground, thin slice also can reduce substrate breakage when magnificent and peel off direct bonding part.And, for example be used as under the situation of optical-waveguide-type optical element at the 4th embodiment optical element, owing to have compaction material in disengaged regional 44, so, can not invade foreign matter in the gap and be connected with waveguide substrate 41, guide properties can not degenerate.

And in the optical element of the 4th embodiment, other structure example are shown in Figure 12.As shown in figure 12, waveguide substrate 41 and substrate 42 are engaged again by thin layer 45.Can critically control the thickness evenness of film.Especially when using dielectric,, can reach various refractive indexes and absorption coefficient by selecting material as film.

The manufacture method of optical element shown in Figure 12, the same with the manufacture method of optical element shown in Figure 11, formed disengaged regional 44 substrate 42 and waveguide substrate 41 and engaged.At this, for example the method with the formation optical element thin layer 4 shown in the 1st, the 2nd embodiment is the same on waveguide substrate 41, is pre-formed thin layer 45.And the refractive index of wishing thin layer 45 for example adopts with Ta less than waveguide substrate 41 and substrate 42 ₂O ₅Monofilm for principal ingredient.

Have disengaged regional 44 substrate 42 and waveguide substrate 41, directly engage with a side of the formation of thin layer 45 and substrate 42 disengaged regional 44 with thin layer 45.Then, filling ultraviolet curable resin 47 in disengaged regional 44.Moreover, carry out the ultraviolet ray irradiation from direct assembling substrates surface, the ultraviolet curable resin 47 of filling is cured.

And in the optical element of the 4th embodiment, another structure example is shown in Figure 13.As shown in figure 13, also can adopt such structure, promptly on substrate 42, on identical layer, form thin layer 45 and disengaged regional 44 selectively, form waveguide substrate 41 more in the above.Said structure is to form thin layer 45 with methods such as sputters on waveguide substrate 41 or substrate 42, utilizes photoetching and dry etching to carry out graphic making, and the part of thin layer 45 is removed and can be finished.The position that thin layer 45 is removed becomes disengaged regional 44.After waveguide substrate 41 and substrate 42 directly engaged, filling ultraviolet curable resin 47 in disengaged regional 44.

As mentioned above, even under situation about engaging by 45 pairs of waveguide substrates 41 of thin layer and substrate 42, also can partly remove thin layer 45, be provided with disengaged regionally 44, filling ultraviolet curable resin 47 is cured, thereby improves bond strength.

And the material that is filled in disengaged regional 44 has adopted ultraviolet curable resin, but is not limited only to this.

[the 5th embodiment]

Below utilize accompanying drawing, describe the optical element that relates to the present invention the 5th embodiment in detail.

Figure 14 (a)～Figure 14 (d) is a front elevation of representing the optical element of the 5th embodiment by the order of manufacturing process.The optical element of the 5th embodiment, its structure are to form dielectric layer on the disengaged zone of the optical element of the 3rd embodiment.

Figure 14 (d) is the front elevation of the state of the optical element made.Among Figure 14 (d), by constituting as the waveguide substrate 51 of the MgO:LN crystal substrates of X cutting and as the substrate 52 mutual Colaesces of the LN crystal substrates of X cutting.On substrate 52, be processed in the zone of concavity and formed thin layer 55.Thin layer 55 for example is with Ta ₂O ₅Monofilm for principal ingredient.

The manufacture method of the optical element of the 5th embodiment below is described.At first, as forming disengaged regional 54 on Figure 14 (a) institute substrate that is shown in 52.Then, shown in Figure 14 (b), on the surface of substrate 52, come deposit thin rete 55 by sputter.On substrate 52, form thin layer 55, so, under this state,, also be that bond strength is low for example even directly engage, the film strength deficiency of anti-machining.Therefore, shown in Figure 14 (c), form the only state of deposit thin rete 55 on disengaged regional 54.Specifically, utilize CMP (cmp) equipment,, make the surfacing of the substrate 52 that comprises thin layer 55 by grinding the thin layer of removing beyond disengaged regional 54 55.And known CMP equipment is the very high milling apparatus of precision, can reach the abrasive surface flatness of following amount of grinding absolute value control of sub-micron and the following precision of number 10nm.

Disengaged regional 54 the degree of depth is 100nm～300nm, and the thickness of the thin layer 55 of deposit is 150nm～350nm.And CMP handles the interarea that can control to substrate 52 and is ground about 50nm.Like this, the surface of substrate 52 is exposed fully, and the surface of the surface of thin layer 55 and substrate 52 is all very smooth.And, be not less than the deposit thin rete 55 of disengaged regional 54 the degree of depth, handle by CMP, can make the surface of the surface of thin layer 55 and substrate 52 all very smooth.

Utilize CMP equipment, when grinding, can carry out mirror ultrafinish abrasive surface.So do not need to carry out mirror ultrafinish for directly engaging in addition.

Shown in Figure 14 (d), to the crystal axis of substrate 52 and waveguide substrate 51 to aiming at, make substrate 52 formation disengaged regional 55 interarea, and the interarea of waveguide substrate 51 contacts, pressurization makes its formation be adjacent to state slightly, directly engages by heat treated.Carry out the substrate 52 of milled processed by CMP equipment, with direct joint of waveguide substrate 51 in can realize with to common substrate between the roughly the same state that is adjacent to and direct engagement state when directly engaging.

In the assembling substrates that obtains like this, also be to fit by the high precision substrate that obtains directly to engage, compare when only thin layer directly engages with substrate shown in the 1st embodiment, can realize following two purposes simultaneously: the one, because of having the direct engagement state of substrate 52 and waveguide substrate 51, thereby increased substantially anti-machining property; The 2nd, owing to have thin dielectric film, so improved the function (low-loss, high function) of optical element.

And, even only being formed on disengaged regional 54 the part, thin layer 55 also can.For example, shown in Figure 15 (a) and (b), in the optical element that has formed optical waveguide 53, thin layer 55 is formed on the waveguide substrate 51, is formed on optical waveguide 53 at least and gets final product on the projecting plane of vertical direction.If this structure, then waveguide luminous energy by adequate closure in waveguide.Like this, can reduce the volume of thin layer 55, so, can reduce cost.

Method for manufacturing optical waveguide shown in Figure 15 (a) and (b) below is described.At first, on the opposing face of the face of the optical waveguide 53 that forms waveguide substrate 51, form thin layer 55.Then, utilize photoetching, dry etching to come thin layer 55 is made figures, at least optical waveguide 53 just below formation thin layer 55.At last, waveguide substrate 51 and substrate 52 are directly engaged.Like this, do not carry out milled processed, can make optical element.And, also can be in the space 54a in disengaged regional 54 potting resin etc.Like this, the intensity on composition surface will be improved.

[the 6th embodiment]

Below with accompanying drawing the optical element of the present invention the 6th embodiment is described.The optical element of the 6th embodiment is that a plurality of substrates of optical grinding are carried out lamination, for example to engaging with direct bonding method respectively between each substrate.On each substrate, periodically form disengaged zone again.

Figure 16 is the oblique view of the optical element of expression the present invention the 6th embodiment.The optical element of the 6th embodiment is, other substrates are directly engaged having on the substrate in disengaged zone, the substrate after this is directly engaged carries out sheet, forms disengaged zone, these operations are carried out repeatedly, can form the optical element of lamination structure.Substrate 62a has abreast by the groove that uniformly-spaced forms, is disengaged regional 64a.On substrate 62a, by forming a plurality of bar-shaped substrate 62b at interval by the time, make it vertical abreast with disengaged regional 64a.Between each bar-shaped substrate 62b, form the disengaged regional 64b of channel form.Again on substrate 62b abreast by uniformly-spaced forming a plurality of bar-shaped substrate 62c, make it vertical with disengaged regional 64b.Between each bar-shaped substrate 62c, form the disengaged regional 64c of channel form.

The manufacture method of the optical element of the 6th embodiment below is described.Specifically, at first, on the substrate 62a of LN crystal substrates, for example utilizing with the Cr sputtered film is that the dry etching method of etching mask forms disengaged regional 64a.Behind the Cr graphic making, be that etching mask carries out dry etching on substrate 62a with Cr, according to the strip etching tank that uniformly-spaced forms the degree of depth 3 μ m (disengaged zone).And, make figure with the photoetching legal system, can produce the figure of arbitrary shape with high precision.For example, also can form disengaged zone with the polygon figure of cycle shape.Specifically, can form optical element shown in Figure 17.That is to say, also can form such optical element, promptly periodically have between substrate 62d, the 62e of 6 dihedral etching tanks (disengaged regional 64d, 64e), the mode that engages is the period migration semiperiod of 6 dihedrals.

On the other hand, identical with above-mentioned situation, on the interarea on one side of the substrate 62b of LN crystal substrates, form the etching tank of 3 μ m, promptly disengaged regional 64b.And, the direction of the etching tank of substrate 62b, vertical respectively for the direction that makes substrate 62a and each etching tank of substrate 62b, after taking in, the joint to substrate 62a and substrate 62b determines.Then, utilize wet etching to remove Cr as mask, to as the formation of the direct substrate 62a on composition surface the interarea of disengaged regional 64a and substrate 62b formation the interarea of disengaged regional 64b carry out water wettability and handle.Then, to the crystal axis of substrate 62a and substrate 62b to aiming at, the interarea that comprises disengaged regional 64a of substrate 62a and the interarea that comprises disengaged regional 64b of substrate 62b are contacted, form the state that is adjacent to of substrate 62a and substrate 62b.Further this is adjacent to substrate and heat-treats, can directly engage, obtain direct assembling substrates substrate 62a and substrate 62b.

In the direct assembling substrates that obtains like this, substrate 62b is carried out surface grinding, sheet, the thickness of substrate 62b is reduced to 2.5 μ m till.Like this, substrate 62b is not a substrate, but a plurality of bar-shaped substrate.Further, utilize and above-mentioned identical method, adopt substrate 62c and a plurality of bar-shaped substrate 62b of the disengaged regional 64c of etching tank directly to engage having formed, and make disengaged regional 64b vertical with disengaged regional 64c, carry out surface grinding and sheet then.And, repeat this operation, substrate is carried out lamination.That is to say on substrate to form disengaged zone, the disengaged area surface of the substrate that is provided with disengaged zone is directly engaged to assembling substrates, make substrate sheet behind the direct joint, form a plurality of bar-shaped substrates by grinding.

In above-mentioned operation, can form crystal substrates with cycle shape lamination structure.This is a kind of dielectric, and it is called as photonic crystal, has the structure of refractive index cycle variation, can control light wave.Photonic crystal has and a kind of light wave is had the characteristic of band structure, can realize distinctive optical waveguide control, so noticeable.Generally, photonic crystal adopts the electron beam exposure method to make, and cycle shape ground is arranged and formed the room of diameter for number 100nm～hundreds of μ m in crystal.Therefore, the making of photonic crystal needs meticulous processing, so very difficult.

The manufacture method of the optical element of the 6th embodiment by form disengaged zone with dry etching, can form the disengaged zone of cycle shape.And the size in disengaged zone and forming at interval or the thickness direction degree of depth of substrate can be fabricated into from submicron order to tens micron.So, adopt the manufacture method of the optical element of the 6th embodiment, also can make photonic crystal.And general, the polycrystalline material of necessary strict control composition and crystal structure is adopted in the formation of photonic crystal.If adopt the 6th embodiment, then also can make of the monocrystal material of even structure.

And, the material and the structure thereof of the formation optical element shown in concrete among the embodiment, an example just after all, the present invention is not limited only to these object lessons.And the method for assembling substrates also is not limited only to direct joint.

Claims

1, a kind of manufacture method of optical element, it is characterized in that: on the interarea of at least one substrate of waveguide substrate and substrate, form recess as disengaged zone, above-mentioned disengaged zone is clamped in the mode between above-mentioned waveguide substrate and the above-mentioned substrate, above-mentioned waveguide substrate is engaged with substrate.

2, the manufacture method of optical element as claimed in claim 1 is characterized in that: to the interarea of any substrate in above-mentioned waveguide substrate and the above-mentioned substrate, carry out concavity processing on the thickness direction of substrate, to form above-mentioned disengaged zone.

3, the manufacture method of optical element as claimed in claim 1, it is characterized in that: by on the interarea of any substrate of above-mentioned substrate and above-mentioned waveguide substrate, forming film, on thickness direction, this film is carried out concavity processing, to form above-mentioned disengaged zone.

4, the manufacture method of optical element as claimed in claim 1 is characterized in that:

On the face that has carried out concavity processing, form film,

The face that has formed above-mentioned film is carried out CMP processing, makes it smooth,

Above-mentioned disengaged zone being clamped in the mode between above-mentioned waveguide substrate and the substrate, the interarea of above-mentioned waveguide substrate and above-mentioned substrate is directly engaged.

5, the manufacture method of optical element as claimed in claim 1 is characterized in that:

On above-mentioned substrate, form above-mentioned recess,

On the interarea of above-mentioned waveguide substrate, form film,

So that above-mentioned film is formed on the mode in the above-mentioned disengaged zone, above-mentioned waveguide substrate and substrate are engaged.

6, the manufacture method of optical element as claimed in claim 1, it is characterized in that: after above-mentioned waveguide substrate and above-mentioned substrate are engaged, between above-mentioned waveguide substrate and above-mentioned substrate, in the gap that forms by above-mentioned recess, the compaction material that the above-mentioned waveguide substrate of filling refractive index ratio is little.

7, the manufacture method of optical element as claimed in claim 1 is characterized in that: the joint of above-mentioned waveguide substrate and above-mentioned substrate is direct joint.