JP2003014965A - Waveguide for direct laser drawing and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a new waveguide by direct drawing with laser and a method for manufacturing the waveguide having low scattering loss comparable with a glass waveguide and having excellent optical characteristics. SOLUTION: Patterning is carried out without using a conventional photolithographic method or the like but by focusing a UV laser beam B to a polymer layer 3 for photo-bleaching coated with a low refractive index layer 2 to irradiate the layer while either a substrate 1 side or the laser beam B is relatively moved so as to form a core layer 5 as a light propagation layer and side clad layers 6 to guide the light. By this method, the side faces of the core layer 5 are not roughened but the obtained polymer waveguide has low scattering loss comparable with a glass waveguide and has excellent optical characteristics.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polymer waveguide for optical transmission between electric and electronic devices, and more particularly to a laser direct writing waveguide whose transmission line pattern is formed by using an ultraviolet laser beam, and the same. The present invention relates to a manufacturing method.

[0002]

2. Description of the Related Art With the recent development of optical interconnection technology, a method of parallel optical transmission between devices by means of fiber is in the practical stage.
A method of parallel transmission of optical signals between SI chips has been studied in earnest.

In order to realize this method, a waveguide is used instead of a fiber as a transmission line. As this waveguide, a waveguide using a glass material that has been widely used in the past (hereinafter referred to as a glass waveguide) is used. Instead, the one using a polymer material (hereinafter referred to as a polymer waveguide) is considered to be promising. That is, the polymer waveguide can be easily manufactured by a low temperature process as compared with the glass waveguide, and therefore, it can be expected to be superior to the glass waveguide in terms of cost reduction and large size. is there.

As a method of manufacturing this polymer waveguide, first, a polymer solution dissolved in an organic solvent is applied onto various substrates by, for example, a spin coating method or an extrusion coating method, and then this is heated to 300 ° C. or lower. The film-like polymer layer is formed by heating at a low temperature. Next, a photolithography or etching process is applied to this polymer layer to obtain a high-refractive-index core pattern having a substantially rectangular cross section, and then a low-refractive-index polymer is coated to cover the core pattern. A clad having a refractive index is formed.

As one of the techniques for patterning a photoresist film, a method has also been developed in which a photoresist film is exposed to a desired pattern by directly irradiating the photoresist film with an ultraviolet laser beam without using a photomask. ing.

[0006]

By the way, the conventional polymer waveguide thus obtained has some problems which hinder its practical use as shown below.

1): 0.1 dB / cm has been reported as the top data of scattering loss of polymer waveguides up to now, but this value is still larger than that of glass waveguides. It is not a substitute candidate. That is, with the conventional polymer waveguide structure and manufacturing method, it is difficult to reduce the loss to 0.1 dB / cm or less, which is comparable to that of a glass waveguide.

The reason for this is that the scattering loss due to the roughness of the side surface of the core is extremely large among the losses of the polymer waveguide. As a countermeasure against this, it is conceivable to apply a method of directly irradiating the photoresist film with an ultraviolet laser beam to expose the photoresist film in a desired pattern without using a photomask as a technique for patterning the photoresist film. However, in this method, since the pattern must be used as a mask for etching after that, side surface roughness is caused by the etching, and as a result, it is difficult to reduce the loss.

The next possible reason is that there is an absorption loss depending on the absorption group (CH group, OH group) peculiar to the polymer material. As a measure to reduce this absorption loss, attempts have been made to fluorinate or deuterate polymers, but there are problems such as deterioration in heat resistance and difficulty in film formation. Has not been done.

2): The obtained polymer waveguide is then used for electronic components necessary on the front surface or the back surface, and further inside.
Electronic circuits, optical components, and optical circuits will be hybrid-mounted by soldering. However, the polymer waveguide, which can be expected to have a low loss characteristic (about 0.2 dB / cm) at present, has poor heat resistance, so that the solder reflow temperature (Au / Sn solder reflow temperature:>
It is difficult to withstand 280 ℃, and when mounted and processed at the above temperature, the refractive index of the polymer used in the waveguide changes, and the optical characteristics of the waveguide change significantly, making it unusable. It may become. Therefore, it is possible to use a waveguide using a polymer material having excellent heat resistance characteristics, but such a waveguide has a large loss and polarization dependency, which poses a practical problem.

Therefore, the present invention has been devised to solve the above problems, and its main purpose is to provide a novel laser direct laser having a low scattering loss similar to that of a glass waveguide and excellent optical characteristics. An object of the present invention is to provide a drawing waveguide and a manufacturing method thereof.

[0012]

In order to solve the above problems, the present invention provides an ultraviolet laser on a photobleaching polymer layer covered with a low refractive index layer without using conventional photolithography and etching processes. Focus the beam,
While irradiating, either the object to be irradiated or the laser beam is relatively moved to perform patterning to form a core layer to be a light propagation layer and a side clad layer for guiding the core layer. As a result, it is possible to realize a waveguide having a low scattering loss with almost no roughness on the side surface of the core layer. Further, since the interface between the core layer and the cladding layer on the side surface thereof can be formed to have a continuous refractive index distribution, it is possible to further reduce the scattering loss and improve the light confinement within the core layer.

Since the ultraviolet laser beam can be narrowed down to a beam spot diameter of 1 μm and is coherent light, it is possible to draw and form a core layer and side clad layer pattern with very high dimensional accuracy. Especially, as in the waveguide type directional coupler, the distance between two core layers is several μm.
The method of the present invention is an effective method for realizing a structure in which m is connected in parallel over the bond length L. The smaller the gap between the core layers, the shorter the bond length L can be.
In the conventional method using the etching process and the buried waveguide structure in which the rectangular core layer is filled with the cladding layer, it was difficult to set the distance to 4 μm or less, but in the present invention, the distance between the core layers is narrowed to about 1 μm. Therefore, the coupling length can be easily shortened and a small waveguide circuit can be realized. In addition to the above-mentioned waveguide type directional coupler, ring resonator circuits, filter circuits, etc. can be made smaller and have higher performance.

As the photobleaching polymer for forming the polymer layer, a polysilane compound, a polysilane compound containing a silicone compound, or a silicone compound and a photo-acid generator added thereto is used.
Since the heat treatment can be performed at a temperature higher than 00 ° C. to promote the mineralization, the absorption loss depending on the absorption group (CH group, OH group) specific to the polymer material can be reduced. In addition, the Au / Sn solder reflow temperature (Au
/ Sn solder reflow temperature:> 280 ° C), so that electronic parts, electronic circuits, optical parts, optical circuits, etc. can be hybrid-mounted on the front surface or the back surface of the waveguide, and further inside. .

Furthermore, if a pulsed laser beam is used as the ultraviolet laser beam, the refractive index of the polymer layer can be lowered with a low average output laser beam power without being thermally damaged by the irradiated polymer layer.
In addition, by using a pulse compared to a continuous wave, the average intensity is low while having a high light intensity momentarily, so that even for a thick polymer layer, the change in the refractive index can be made uniform in the depth direction. It can be generated, and a waveguide can be realized in a short time. The degree of the change in the refractive index in the depth direction can be controlled by adjusting the power of the laser beam and the moving speed of the workpiece (or the laser beam). Further, the same position may be irradiated with the laser beam a plurality of times.

Further, the widths of the core layer and the side clad layer can be easily controlled by adjusting the beam spot diameter of the ultraviolet laser beam. For example, increasing the width of the side cladding layer can be easily achieved by increasing the laser beam spot diameter for irradiation, or by irradiating in a defocused state.

The wavelength of this ultraviolet laser is a wavelength band (250n) which is absorbed by the polymer layer and changes its refractive index.
m-445 nm), but it is preferable to select the maximum absorption wavelength. When using a laser having a wavelength deviated from the maximum absorption wavelength, an excessive power is required to compensate for the deviation.

Since the photomask is not used in the manufacturing method of the present invention, the waveguide manufacturing cost can be significantly reduced. In particular, the cost for producing various optical circuits having different optical circuit patterns can be drastically reduced and can be produced in a short time, so that the total cost performance can be drastically improved.

Further, the characteristics of the optical circuit can be changed by irradiating the laser beam while in-line monitoring, and the optical characteristics can be improved by trimming. Further, since the polymer layer having a change in refractive index has a flat surface, even if an upper clad layer is formed on the polymer layer, the surface can also have a flat surface. As a result, electronic components, electronic circuits, optical components, optical circuits, etc. can be mounted on the upper surface with high dimensional accuracy.

Further, an ultrashort pulsed laser beam having a wavelength far deviated from the absorption wavelength of the polymer is collected and irradiated on the surface or inside of the core layer not irradiated with the ultraviolet laser beam, and the core is irradiated with the ultrashort pulsed laser beam. The refractive index of the layer may be increased.

The wavelength of the ultrashort pulsed laser beam is selected from the range of 600 nm to 1600 nm, the pulse width is selected from the range of several thousand fs to several tens of fs, and the pulse repetition is selected from the range of 10 Hz to 200 KHz. The average output is preferably selected from the range of several tens mw to several hundred mw. Increasing the refractive index of the core layer in this way improves the confinement of light in the core layer, and the organic matter in the core layer is further removed by the irradiation of the ultrashort pulsed laser beam to be inorganicized, Moreover, the core layer can be modified to have a high density and a small number of light scattering centers.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION Next, an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

1 (1) to 1 (4) show an embodiment of a laser direct writing waveguide (hereinafter referred to as a laser waveguide) according to the present invention. FIG. 1 (1) shows A sectional view on the input (or output) side of the laser waveguide, FIG. 2B is a refractive index distribution in the section AA of FIG. 1A, and FIG. 3C is a sectional view of BB of FIG. The refractive index distribution in the cross section, FIG. 4 (4) shows the structure in the BB cross section of FIG. 1 (1), respectively.

As shown in the figure, this laser waveguide has a low refractive index layer 2 formed on a rectangular substrate 1, and a high refractive index for photobleaching is formed on the low refractive index layer 2. A polymer layer 3 made of a polymer is formed, and an upper clad layer 4 having a lower refractive index than the polymer layer 3 is formed on the polymer layer 3.

This substrate 1 is made of a known material such as glass,
It is made of ceramics, plastics, semiconductors, ferroelectrics or composite materials of glass and plastics, and also a combination of the above materials, and also has a low refractive index layer 2
And the upper clad layer 4 is made of SiO ₂ , SiO ₂
e, P, Ti, B, Zn, Sn, Ta, F, etc. to which at least one kind of refractive index controlling dopant is added, or a polymer material or an organic-inorganic composite material.

On the other hand, the polymer layer 3 has an unirradiated region 5 having a width Wc which is not irradiated with the ultraviolet laser beam and an irradiated region having a width Ws in which the refractive index is lowered by being irradiated with the ultraviolet laser beam along both side surfaces thereof. 6 and 6 and regions 7 and 7 outside the regions 6 and 6 which are not irradiated with the ultraviolet laser beam, and the unirradiated region 5 at the center is the core layer 5 serving as the light propagation region. And the irradiation regions 6 and 6 on both sides thereof form the low-refractive-index side cladding layers 6 and 6 located so as to sandwich the core layer 5, respectively.

The polymer layer 3 is formed of a photobleaching polymer. As the photobleaching polymer, a material that can be heat treated at a temperature higher than 300 ° C. to promote mineralization, for example, a polysilane compound. A silicone compound, a silicone compound and a photo-acid generator added to a polysilane compound, a silicone compound to which nitrone is added, and the like are used. Each of these compounds will be described in detail below.

As the polysilane compound applicable to the present invention, linear type and branched type can be used. The branched type and the linear type are distinguished by the bonding state of Si atoms contained in polysilane. That is, with the branched polysilane, the number (bond number) bonded to the adjacent Si atoms is
It is a polysilane containing 3 or 4 Si atoms. On the other hand, in linear polysilane, the number of Si atoms bonded to adjacent Si atoms is two. Usually, it is bonded to a hydrocarbon group, an alkoxy group or a hydrogen atom in addition to the Si atom. Such a hydrocarbon group has 1 to 1 carbon atoms.
An aliphatic hydrocarbon group which may be substituted with 10 halogens and an aromatic hydrocarbon group having 6 to 14 carbon atoms are preferable. Specific examples of the aliphatic hydrocarbon group include a methyl group, a propyl group, a butyl group, a hexyl group, an octyl group, a decyl group, a trifluoropropyl group, a nonafluorohexyl group and the like, and a cyclohexyl group and methylcyclohexyl group. Examples thereof include alicyclic ones such as groups. Further, specific examples of the aromatic hydrocarbon group include a phenyl group, a p-tolyl group, a biphenyl group and an anthracyl group. Examples of the alkoxy group include those having 1 to 8 carbon atoms. Specific examples include a methoxy group, an ethoxy group, a phenoxy group and an octyloxy group. Of these, a methyl group and a phenyl group are particularly preferable in view of ease of synthesis.

In the case of a branched polysilane, the adjacent S
The number of Si atoms having 3 or 4 bonds with i atoms is more preferably 2% or more of the total number of Si atoms in the branched polysilane. If less than 2% or linear polysilane has high crystallinity, microcrystals are easily generated in the film, which causes light scattering, and light transparency is easily deteriorated.

The polysilane used in the present invention is produced by a polycondensation reaction by heating a halogenated silane compound to 80 ° C. or higher in the presence of an alkali metal such as sodium in an organic solvent such as n-decane or toluene. be able to. It can also be synthesized by an electrolytic polymerization method or a method using metal magnesium and metal chloride.

The branched polysilane is composed of an organotrihalosilane compound, a tetrahalosilane compound, and a diorganodihalosilane compound, and the organotrihalosilane compound and the tetrahalosilane compound account for 2 mol% or more of the total amount. The desired branched polysilane is obtained by heating and polycondensing the halosilane mixture. Here, the organotrihalosilane compound serves as a Si atom source having a bond number of 3 with an adjacent Si atom, and one tetrahalosilane compound has a Si atom source having a bond number of 4 with an adjacent Si atom. Become. The network structure can be confirmed by measuring an ultraviolet absorption spectrum and a nuclear magnetic resonance spectrum of silicon.

The halogen atom contained in each of the organotrihalosilane compound, the tetrahalosilane compound, and the diorganodihalosilane compound used as the raw material of polysilane is preferably a chlorine atom. Examples of the substituent other than the halogen atom contained in the organotrihalosilane compound and the diorganohalosilane compound include the above hydrocarbon group, alkoxy group or hydrogen atom.

As the silicone compound added to the polysilane compound of the present invention, those represented by the following chemical formulas are used.

[0034]

[Chemical 1]

However, in the chemical formula, R1 to R12 are aliphatic hydrocarbon groups which may be substituted with halogen or glycidyloxy groups having 1 to 10 carbon atoms, and 6 to 12 carbon atoms.
Of aromatic hydrocarbon groups and alkoxy groups having 1 to 8 carbon atoms, which may be the same or different. a, b, c and d are integers including 0, and a +
b + c + d ≧ 1 is satisfied.

Specific examples of the aliphatic hydrocarbon group contained in this silicone compound include methyl group, propyl group, butyl group, hexyl group, octyl group, decyl group, trifluoropropyl group, glycidyloxypropyl group and the like. Alicyclic ones are mentioned. Further, specific examples of the alkoxy group include a methoxy group, an ethoxy group, a phenoxy group, an octyloxy group, a ter-butoxy group and the like.
The types of R1 to R12 and the values of a, b, c and d are not particularly important and are compatible with polysilane and an organic solvent.
The film is not particularly limited as long as it is transparent. In consideration of compatibility, it is preferable that the polysilane used has the same group as the hydrocarbon group. For example, when a phenylmethyl type polysilane is used as the polysilane, it is preferable to use the same phenylmethyl type or diphenyl type silicone compound. Further, a silicone compound having two or more alkoxy groups in one molecule such that at least two of R1 to R12 are carbon-based alkoxy groups having 1 to 8 carbon atoms can be used as a crosslinking agent. Examples thereof include methylphenyl methoxy silicone and phenyl methoxy silicone containing 15 to 35 wt% of alkoxy groups. The molecular weight is 10,000 or less, preferably 30.
Those of 00 or less are preferable. The CH groups and OH in the film
In order to reduce the light absorption by the group, if polysilane compound or silicone compound is deuterated, or partially or entirely halogenated, especially fluorinated one, the light loss by the above-mentioned absorbing group can be significantly reduced. You can As a result, it is possible to realize a polymer film having low wavelength loss and low optical loss, and it is possible to expand the application to a wide range for high-performance waveguide type optical components and optical devices.

Further, by using a crosslinkable or alkoxy group-containing silicone compound, it can be uniformly added to the branched polysilane compound.
Moreover, it is easily soluble in an organic solvent such as toluene to form a nanometer level ultrafine particle solution, and by using the above polymer solution, a uniform structure or film without light scattering centers can be formed.

Next, a method for forming the polymer layer 3 and a specific method for forming the core layer 5 and the side cladding layers 6 and 6 will be described.

First, the polymer compound is dissolved in an organic solvent to prepare a polymer solution, and the solution is applied onto the low refractive index layer 2 by a spin coating method or an extrusion coating method, and then at 80 ° C. to 200 ° C. 2 in the temperature range
Pre-bake for 0 to 40 minutes. After that, 250 ℃ ~
Post-baking is performed for about 20 to 60 minutes in the temperature range of 300 ° C. to form the polymer layer 3. The pre-baking and post-baking may be carried out continuously in the program-type temperature control type electric furnace by continuously performing the temperature raising, constant temperature holding, temperature raising, constant temperature holding, and temperature lowering steps.

The organic solvent used in this example includes
It is a hydrocarbon type having 5 to 12 carbon atoms, a halogenated hydrocarbon type, an ether type and the like. As examples of hydrocarbons, pentane, hexane, heptane, cyclohexane, n-decane, n-dodecane, benzene, toluene, xylene, methoxybenzene and the like can be used. Examples of halogenated hydrocarbons include carbon tetrachloride, chloroform,
1,2-dichloroethane, dichloromethane, chlorobenzene and the like can be used. As examples of ether type, diethyl ether, dibutyl ether, tetrahydrofuran, etc. can be used. Further, as a polymer material for photobleaching, as an organic solvent for a silicone compound containing a nitrone compound, as described above,
Pegmia may be used. The photobleaching polymer material must be a material that is soluble in the organic solvent.

Next, the polymer layer 3 formed by the above method is irradiated with an ultraviolet laser beam to form side cladding layers 6 and 6 having a low refractive index. Examples of the ultraviolet laser used here include He-Cd lasers of 266 nm and 325 nm that use the third harmonic with an oscillation wavelength of 800 nm, third harmonic lasers of a YAG laser with an oscillation wavelength of 355 nm, and semiconductor lasers with an oscillation wavelength of 400 nm. A He—Cd laser or the like having an oscillation wavelength of 442 nm can be used. The oscillation output may be continuous wave or pulse oscillation.

As an example of the polymer layer 3, the branching degree is 2
A polymer obtained by adding 50 wt% of a silicone compound to a branched polymethylphenylsilane compound of 0% was dissolved in an organic solvent toluene, and a polymer solution for photobleaching was used. This solution had a low refractive index on a substrate 1 (quartz glass substrate). Applied on layer 2 (SiO2 layer, film thickness about 10 μm),
After pre-baking at 0 ° C. for 20 minutes and post-baking at 250 ° C. for 30 minutes to obtain a polymer layer 3 having a thickness of about 10 μm, an H wavelength having an oscillation wavelength of 442 nm is formed on the polymer layer 3.
e-Cd laser (continuous wave power value on the polymer layer surface: about 2
mw) is maintained at a laser beam spot diameter of about 1 μm,
Length 5 while moving the substrate 1 at a speed of 100 μm / s
Irradiation was performed on a straight part of 0 mm. And a width of 10 μm
The irradiation position is gradually shifted (by 1 μm) for about 10 times, and irradiation is performed by scanning about 10 times, and the refractive index of the polymer layer 3 is lowered from the value before irradiation to 1.64 to 1.625. It was possible to obtain the region (refractive index value at a wavelength of 632.8 nm). By performing the same operation, a low refractive index layer could be obtained.

Continuing as another example, as a result of changing the moving speed of the substrate 1 to 50 μm / s to lower the refractive index, the refractive index is lowered to 1.618, and still another example. As an example, of the above conditions, the continuous wave power on the polymer layer surface of the He—Cd laser was increased to about 5 mw, and the refractive index was reduced as a result of lowering the refractive index only at the moving speed of the substrate 1 of 50 μm / s. I was able to lower it to 1.608.

From these results, it was found that lowering the refractive index can be promoted by increasing the energy at the laser beam irradiation portion. Further, by using a He-Cd laser having an oscillation wavelength of 325 nm, which is close to the maximum absorption wavelength range of ultraviolet rays of the polysilane compound, further lowering of the refractive index can be promoted.

Then, the same layer as the low refractive index layer 2, that is, the upper clad layer 4 was formed on the polymer layer 3 having the above-mentioned change in the refractive index to form a waveguide. The irradiation of the ultraviolet laser beam may be performed by forming a laser beam on the polymer layer and irradiating the polymer layer after forming the upper clad layer 4.

Further, the low refractive index layer 2 and the upper cladding layer 4
May be configured using the following materials.
That is, a polymer obtained by adding 50 wt% of a silicone compound to a branched polymethylphenylsilane compound having a branching degree of 20% is dissolved in an organic solvent toluene to prepare a polymer solution for photobleaching, and an ultraviolet ray (15
The light emitted from the 0w mercury-xenon lamp is propagated through the image fiber bundle having a diameter of 20 mm and output, and the light is emitted at a distance of about 10 cm. The output is about 1200 mw / cm.
By irradiating 2) for 135 minutes, the refractive index is lowered (the refractive index at a wavelength of 632.8 nm is lowered from 1.645 to 1.62 before ultraviolet irradiation), and this solution is applied onto the substrate 1 to obtain 150 After prebaking at ℃ for 20 minutes,
This is a method of post-baking at 250 ° C. for 20 minutes to form a polymer layer for the low refractive index layer 2. The upper clad layer 4 is also formed by the same method.

The refractive index distribution of the waveguide prepared by the above method has the characteristics shown in FIGS. 1 (2) and 1 (3).

In the AA cross section of FIG.
As shown in (2), the refractive index distribution is almost step-like, but within the BB cross section of FIG. 1A, as shown in FIG. It was found that the refractive index distribution has a refractive index distribution and that the refractive index changes continuously at the interface between the laser beam irradiated portions 6 and 6 and the non-irradiated portion 5. This continuous change in the refractive index is very effective in greatly reducing the scattering loss at the interface, and also improves the confinement of light in the core layer 5.

The waveguide structure of FIG. 1 (4) shows a core layer 5 having a linear pattern with a length of 50 mm, side clad layers 6 and 6 on the side surfaces thereof, and refractive index unchanged regions 7 and 7. Is. In addition, in FIG. 1A, the laser beam may be irradiated also on the laser beam non-irradiated portions 7, 7. Here, the value of the width (Ws) of the side cladding layers 6 and 6 is preferably at least a value larger than 5 μm in the case of a single mode waveguide, and larger than 10 μm in the case of a multimode waveguide. . The value of the width (Wc) of the core layer 5 is at least 3 in the case of a single mode waveguide.
A value larger than 10 μm is preferable in the case of a multimode waveguide.

The polymer waveguide of FIG. 1 (Wc: 8 μm, W
As a result of evaluating the optical propagation loss of (s: 15 μm) at a wavelength of 1550 nm, 0.09 dB / cm could be realized. Further, the post-baking temperature was 300 when the post-baking temperature was changed by changing the post-baking temperature of the laser direct writing waveguide.
As the temperature increases to ℃, 350 ℃, and 400 ℃, wavelength 1
The optical propagation loss at 550 nm is 0.08 dB / cm, 0.
The loss could be reduced to 06 dB / cm and 0.05 dB / cm.

Next, as another example, a waveguide using the polymer layer 3 in which the branching degree of the polysilane compound was changed from 2% to 48% was prepared, and the optical propagation loss was evaluated. As a result, the branching degree was high. Indeed, long wavelength band (1300 nm band, 1550
An extremely low loss value (0.04 dB / cm) could be realized in the (nm band).

As still another example, a polymer layer obtained by adding 2% to 5% of a photoacid generator (paramethoxystytiltriazine having a melting point of 192 ° C. and a maximum absorption wavelength of 177 nm) to a polysilane compound to which the above silicone compound has been added is used. A polymer waveguide as shown in FIG. 1 was examined by using it. Although the loss tended to increase to some extent, the uniformity of the pattern in the depth direction of the low refractive index change region due to the irradiation of the ultraviolet laser beam was further improved, and it was possible to realize a rectangular core layer with higher dimensional accuracy. . It was found that the photoacid generator is preferably a triazine-based photoacid generator.

An ultraviolet blocking layer may be provided on the upper clad layer 4 so that the refractive index of the core layer 5 does not change over a long period of time.

Next, another embodiment of the laser waveguide according to the present invention will be described.

First, FIG. 2 shows a second embodiment of the laser waveguide of the present invention. FIG. 2A is a sectional view of the waveguide input (or output) side, and FIG. ) Shows the AA sectional view of the same figure (1). This laser waveguide is an example of a directional coupler, and according to the present embodiment, the coupling interval G between the two core layers 5 and 5 can be realized to be about 1 μm, which is a feature of the method of the present invention. It is also one of That is, the beam spot diameter of the ultraviolet laser beam is 1 μm
Such an optical circuit can be realized because it can be made as small as 1. By narrowing the coupling interval G of the coupling portion, it becomes possible to reduce the size of the directional coupler to nearly half of the conventional size.

Next, FIG. 3 shows a third embodiment of the laser waveguide according to the present invention. FIG. 3A is a sectional view on the input (or output) side of the waveguide. (2) is a cross-sectional view taken along the line AA of (1) in the same figure. This is an embodiment of the ring type resonator, and in this case as well, a narrow resonance characteristic can be obtained by narrowing the interval of the coupling portion G.
As described above, it can be widely applied to an optical circuit having an extremely narrow coupling interval.

Further, as shown in FIG. 4, an optical circuit such as a grating filter in which a thin layer 8 having a low refractive index and a thin layer 9 having a high refractive index are periodically formed in the core layer 5 in the light propagation direction, etc. Can also be applied to. Incidentally, FIG. 1A is a sectional view on the input (or output) side of the waveguide, and FIG. 2B is a sectional view taken along the line AA of FIG. 1A.

Instead of FIG. 1C, a refractive index distribution structure as shown in FIG. 5 may be used. The refractive index in the region of the side cladding layers 3b, 3b in this refractive index distribution can be realized by slightly weakening the irradiation amount of the ultraviolet laser beam.

The present invention can also be applied to a laminated structure type waveguide. That is, as shown in FIG. 6, first, the ultraviolet laser beam B is applied to the surface of the first polymer layer 3A.
The substrate 1 is indicated by an arrow 1 while the light is condensed and irradiated by the lens 10.
The polymer layer 3A having a low refractive index is formed by moving it in the 2 or 11 direction at a desired speed, and then the lens 10 is moved in the direction of the arrow 13 to focus and irradiate the surface of the second polymer layer 3B. While moving the substrate 1 in the same manner as described above, the polymer layer 3B having a low refractive index is formed. in this way,
A region having a low refractive index can be formed by moving the substrate 1 while focusing and irradiating the laser beam B on or inside the respective polymer layers 3A and 3B. Further, in FIG. 6, the refractive index distribution in the depth direction may be controlled while changing the focal position of the laser beam in the depth direction in the polymer layers 3A and 3B.

The present invention is not limited to the above embodiment. That is, a polysilane compound, a silicone compound,
Various compounds can be applied to the triazine-based compound, the photoacid generator, and the like. For example, a branched polysilane compound having a branching degree of 2% or more is preferable as the polysilane compound from the viewpoint of optical transparency. The photoacid generator is preferably a triazine-based one, and among them, those having high light transparency at long wavelengths and those having a high melting point are preferable. The silicone compound is also preferably one having a high light transparency and a high melting point.

In the polymer waveguides shown in FIGS. 1 to 5, the wavelengths on the surface or inside of the core layer 5 which is the light propagation layer not irradiated with the ultraviolet laser beam are much different from the absorption wavelength of the polymer. It is also possible to collect and irradiate the ultrashort pulsed laser beam to increase the refractive index of the core layer 5 as shown in FIG. Here, the wavelength of the ultrashort pulse laser beam is 600 nm to 1600.
nm range (preferably 800 nm wavelength),
As the pulse width, select from the range of several thousand fs to several tens fs,
The pulse repetition is selected from the range of 10 Hz to 200 KHZ. The average output is preferably selected from the range of several tens mw to several hundreds mw. Increasing the refractive index of the core layer 5 in this way further strengthens the confinement of light in the core layer 5, and
By the irradiation with the ultrashort pulsed laser beam, the organic substances in the core layer 5 are further removed to be made inorganic, and the core layer 5 can be modified into a highly homogeneous core layer 5 having a high density and a small number of light scattering centers. The narrower the pulse width of the laser beam, the higher the energy within the pulse width, and the higher refractive index can be realized without any thermal damage. If the low refractive index ultraviolet laser and the high refractive index ultra-short pulse laser are covered by a single wavelength tunable laser, both steps can be performed simply by changing the wavelength, output, pulse width, etc. It will be possible.

[0062]

In summary, the present invention exerts the following excellent effects.

1) In the present invention, the photo-bleaching polymer layer covered with the low refractive index layer is condensed and irradiated with an ultraviolet laser beam without using the conventional photolithography and etching processes, and the above-mentioned target is irradiated. Patterning is performed by relatively moving either the irradiation object or the laser beam to form the core layer that will be the light propagation layer and the side clad layer that guides it. It is possible to realize a waveguide with little scattering and low scattering loss.

2) Since the interface between the core layer and the cladding layer on the side surface thereof can be formed to have a continuous refractive index distribution, it is possible to further reduce the scattering loss and improve the light confinement within the core layer. be able to.

3) Since the beam spot diameter of the ultraviolet laser beam can be narrowed down to 1 μm, it is possible to draw and form a core layer and side clad layer pattern with extremely high dimensional accuracy. In particular, the method of the present invention is an effective method for realizing a structure in which two cores have a width of several μm and are parallel-coupled over a coupling length L, such as a waveguide type directional coupler. The smaller the core width is, the shorter the coupling length can be made, but it is difficult to set the core width to 4 μm or less in the conventional method using the etching process and the buried waveguide structure in which the rectangular core layer is filled with the cladding layer. However, in the present invention, since it can be narrowed to about 1 μm, the bond length can be shortened. That is, a small waveguide circuit can be realized. In addition to the waveguide type directional coupler, it is possible to reduce the size and performance of ring resonator circuits, filter circuits, and the like.

4) Polysilane compound for the photobleaching polymer layer, silicone compound for the polysilane compound,
Alternatively, by using a silicone compound and a photo-acid generator added, heat treatment at a temperature higher than 300 ° C. can be carried out to promote mineralization, and therefore absorption groups (CH group, OH group) peculiar to the polymer material can be promoted. ) Dependent absorption loss can be reduced.

5) By heat treatment at a temperature higher than 300 ° C., a waveguide with lower loss can be obtained, and Au /
Since it can withstand the Sn solder reflow temperature (Au / Sn solder reflow temperature:> 280 ° C.), electronic parts, electronic circuits,
It becomes possible to hybrid-mount optical components, optical circuits, etc.

6) If a pulsed laser beam is used as the ultraviolet laser beam, the refractive index of the polymer layer can be lowered with a low average output laser beam power without being thermally damaged by the irradiated polymer layer. . In addition, by using pulses compared to continuous waves, the average intensity is low while having a high light intensity momentarily, so even for a thick polymer layer, the change in refractive index can be made uniform in the depth direction. And can be realized as a waveguide in a short time. The degree of the change in the refractive index in the depth direction can be controlled by adjusting the power of the laser beam and the moving speed of the workpiece (or the laser beam).

7) By adjusting the beam spot diameter of the laser beam, the widths of the core layer and the side cladding layer can be easily controlled.

8) Since no photomask is used,
The waveguide fabrication cost can be significantly reduced. In particular, the cost for producing various optical circuits having different optical circuit patterns can be drastically reduced and can be produced in a short time, so that the total cost performance can be drastically improved.

9) The characteristics of the optical circuit can be changed by irradiating the laser beam while monitoring in-line, and the optical characteristics can be improved by trimming, so that the production yield of optical parts can be greatly improved.

10) Since the polymer layer having a change in refractive index has a flat surface, even if an upper clad layer is formed thereon, the surface can also have a flat surface. As a result, electronic parts, electronic circuits, optical parts, optical circuits, etc. can be mounted on the upper surface with high dimensional accuracy.

11) Since a waveguide having a laminated structure can also be easily produced, a more highly functional and highly integrated waveguide device can be realized.

12) Since the refractive index of the core layer can be easily increased, the confinement of light in the core layer is further improved, and the organic matter in the core layer is further improved by the irradiation with the ultrashort pulsed laser beam. It can be removed and mineralized, and can be modified into a homogeneous core layer with high density and few light scattering centers.
As a result, a waveguide with even lower loss can be realized.

[0075]

[Brief description of drawings]

FIG. 1A is an input (or output) side sectional view showing an embodiment of a laser direct writing waveguide according to the present invention. (2) is a refractive index distribution diagram in the AA line cross section in FIG. 1 (1). (3) is a refractive index distribution diagram in the BB line cross section in FIG. 1 (1). (4) is B- in FIG.
It is a B line sectional view.

FIG. 2A is an input (or output) side sectional view showing a second embodiment of a laser direct writing waveguide according to the present invention. 2B is a sectional view taken along the line AA in FIG.

FIG. 3 (1) is an input (or output) side sectional view showing a third embodiment of a laser direct writing waveguide according to the present invention. FIG. 2B is a sectional view taken along the line AA in FIG.

FIG. 4A is an input (or output) side sectional view showing a fourth embodiment of a laser direct writing waveguide according to the present invention. (2) is a sectional view taken along the line AA in FIG. 4 (1).

FIG. 5 is a refractive index distribution diagram of a laser direct writing waveguide according to the present invention.

FIG. 6 is an explanatory view showing an embodiment in which the method of the present invention is applied to a laminated structure type waveguide.

FIG. 7 is a refractive index distribution diagram of a laser direct writing waveguide according to the present invention.

[Explanation of symbols]

1 substrate 2 Low refractive index layer 3 polymer layers 4 Upper clad layer 5 core layers 6 Side clad layer 7 Laser non-irradiation area 8 Thin layer with low refractive index 9 Thin layer with high refractive index 10 lenses 11,12 Movement direction on the board side 13 Lens movement direction B UV laser beam

Claims (15)

[Claims] 1. A low refractive index layer, a polymer layer made of a photobleaching polymer having a higher refractive index, and an upper clad layer having a lower refractive index than the polymer layer are sequentially laminated on a substrate. In the polymer waveguide, the polymer layer is a core layer that is a light propagation region not irradiated with an ultraviolet laser beam, and side cladding layers on both sides of the core layer whose refractive index is lowered by irradiation with an ultraviolet laser beam. And a refractive index of the interface between the core layer and the side cladding layer is continuously changed, and a laser direct writing waveguide. 2. A plurality of polymer layers are formed, and each polymer layer has a core layer serving as a light propagation region not irradiated with an ultraviolet laser beam, and an ultraviolet laser beam on both sides of the core layer. 2. The laser according to claim 1, wherein the laser has a side cladding layer whose refractive index is lowered by irradiation, and the refractive index at the interface between the core layer and the side cladding layer is continuously changed. Direct writing waveguide. 3. The laser direct writing waveguide according to claim 1, wherein the width (Wc) of the core layer is 1 μm or more. 4. The laser direct writing waveguide according to claim 1, wherein the width (Ws) of each of the side cladding layers is 1 μm or more. 5. The refraction index of the core layer is further increased by irradiation with an ultrashort pulsed laser beam having a wavelength longer than the absorption wavelength of the photobleaching polymer. The laser direct writing waveguide according to any one of 1. 6. The polymer layer comprises a polysilane compound, a polysilane compound containing a silicone compound, a silicone compound containing a photo-acid generator, or a nitrone-containing silicone compound. The laser direct writing waveguide according to any one of 1 to 5. 7. A low refractive index layer formed on a substrate,
After forming a polymer layer made of a polymer for photobleaching having a higher refractive index than this, an ultraviolet laser beam is focused and irradiated at a constant interval so as to sandwich the core layer, which is a light propagation region, in the polymer layer. By directly lowering the refractive index of the polymer on both sides of the core layer to form side cladding layers, and then forming an upper cladding layer having a lower refractive index on the polymer layer. Method of manufacturing drawing waveguide. 8. A low refractive index layer formed on a substrate,
A polymer layer made of a photobleaching polymer having a higher refractive index than this is formed, and an upper clad layer having a lower refractive index is formed on the polymer layer. The UV laser beam is focused and irradiated at regular intervals so that the core layer, which is the light propagation region, is sandwiched between the layers, and the refractive index of the polymer on both sides of the core layer is reduced to reduce the side clad layers. A method of manufacturing a laser direct writing waveguide, which is characterized by forming the same. 9. The laser direct writing waveguide according to claim 7, wherein two or more polymer layers are formed, and the core layer and the side clad layer are formed on each polymer layer. Production method. 10. The method for manufacturing a laser direct writing waveguide according to claim 7, wherein a pulsed laser beam is used as the ultraviolet laser beam. 11. The method of manufacturing a laser direct writing waveguide according to claim 7, wherein the ultraviolet laser beam having a wavelength of 250 nm to 445 nm and a laser output of 20 mw or more is used. 12. A high refractive index of the core layer is obtained by condensing and irradiating a long-short pulse laser beam having a wavelength longer than the absorption wavelength of the polymer on or in the core layer. The method for manufacturing a laser direct writing waveguide according to any one of claims 7 to 11, which is characterized in that. 13. The polymer for forming the polymer layer is selected from the group consisting of a polysilane compound, a polysilane compound containing a silicone compound, a silicone compound plus a photoacid generator, and a nitrone-containing silicone compound. The method for manufacturing a laser direct writing waveguide according to any one of claims 7 to 12. 14. The method of manufacturing a laser direct writing waveguide according to claim 7, wherein after the polymer layer is formed, the polymer layer is heat-treated at a temperature of 300 ° C. or higher. 15. The laser direct writing waveguide according to claim 7, wherein the side clad layer is formed to have an arbitrary width by a plurality of ultraviolet laser beam irradiation scans. Method.