JP3292031B2 - Waveguide-type grating, method of manufacturing the same, optical filter and wavelength-division multiplexed optical transmission system using the waveguide-type grating - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a quartz- based waveguide for forming an optical multiplexer / demultiplexer, a directional coupler, an optical filter, etc., which are important components in the field of optical communication, especially in wavelength division multiplex transmission and frequency division multiplex transmission. The present invention relates to a waveguide grating, a method of manufacturing the same, an optical filter using the grating, and a wavelength division multiplexing optical transmission system.

[0002]

2. Description of the Related Art There is a wavelength division multiplexing technique as a system for efficiently transmitting a plurality of pieces of information over a single optical fiber.
Wavelength division multiplexing technology is a new multiplexing method in the optical domain, which assigns (divides) a plurality of signals to optical signals having different wavelengths, multiplexes them, and transmits the signals bidirectionally through a single optical fiber. is there. On the transmitting side, optical signals from light sources having different wavelengths are combined by an optical multiplexer / demultiplexer, and on the receiving side, the optical signals are demultiplexed into optical signals of each wavelength by an optical multiplexer / demultiplexer, and are converted into electric signals by a light receiving element. Wavelength division multiplex transmission has the advantages of (1) transmission of large-capacity information, (2) simultaneous transmission of heterogeneous signals such as digital and analog, and (3) bidirectional transmission over a single fiber. It is expected as a large capacity communication technology in the future. Regarding this wavelength division multiplexing method, see "Optical Communication Handbook" (editor: Hiroshi Hirayama)
Others, Kagaku Shimbun, p. 636, 1984) and "Ultrafast Optical Switching Technology" (author: Takeshi Kamiya, Baifukan,
p. 190, 1993).

[0003]

[0004]

[0005]

In recent years, a light-induced refractive index change phenomenon in which the refractive index of the core increases when an optical fiber is irradiated with excimer laser light has been discovered, and by utilizing this phenomenon, a Bragg grating is formed in the optical fiber to form a narrow-band reflection filter. Many applications are being studied, such as dispersion compensation filters, optical filters, and stress / temperature sensors. Also, IEICE Technical Report OPE94-5, p. 25 and the magazine OPTONIC
S Vol. 1, p. 135 (1995) details a fiber laser or fiber sensor.

As an application to an optical filter, there is a narrow band transmission filter using a Michelson interferometer as shown in FIG. In the figure, 47 and 48 are ports, 49 is 3
A dB fiber coupler, 50 is a grating, and is a narrow band transmission filter using a Michelson interferometer having a Bragg grating 50 equivalent to the ports 47 and 48 of the fiber coupler 49 (OPTONICS, V
ol. 1, p. 135, 1995).

However, the optical filter using the fiber coupler 49 has many problems such as a method for fixing a fiber or a Michelson interferometer and a method for managing a surplus fiber, and is not suitable for a case where the number of practical wavelength multiplexes is large. Not. On the other hand, an optical filter using an optical waveguide made of quartz has also been reported.

[0009] FIG. 15, Mach Tse with a wavelength-selective
Is a schematic diagram showing the emission Zehnder interference type optical filter (OPTO
NICS, Vol. 1, p. 135, 1995),
(Optics Letter, Vol. 18, No.
12, p. 953, 1993), (IEEE Pho
tonics Technology. Lett. Vol.
5, no. 2, p. 191, 1993). In the figure, a waveguide type optical filter 51 forms an equivalent grating 50 between two 3 dB couplers 49a and 49b of a Mach-Zehnder interferometer. The optical waveguide is composed of a high refractive index core layer that confines light and a low refractive index cladding layer surrounding the core layer on a silicon substrate, and is fabricated using semiconductor technology, enabling miniaturization and integration. Therefore, it is suitable for mass-produced products and manufacture of complex optical filters having a large number of wavelength multiplexes. However, it is difficult to obtain a large photoinduced refractive index change, and there is a problem that high pressure hydrogen treatment or the like is required before light irradiation.

[0010] The method of manufacturing the quartz optical waveguide shown in FIG. 15 is based on the flame deposition method. FIG. 16 is a schematic view showing a flame deposition method. As shown in the figure, argon gas is supplied from a carrier gas inlet 12 and SiCl ₄ 52, BC
Starting materials such as l ₃ 53, PCl ₃ 54, and GeCl ₄ 55 are used as oxy-hydrogen burners 5 using hydrogen gas 56.
7 and hydrolyzed in a flame to produce fine powder B, P
To prepare a SiO ₂ containing, deposited by spraying it onto the substrate 1 on the turntable 58. The refractive index distribution in the thickness direction of the optical waveguide film is formed by controlling the composition of glass. That is, at the beginning of the flame deposition, SiO ₂ containing B and P
Only to form a lower cladding layer, and then dope Ge by about 10% according to the refractive index to form a core film. However, after depositing the fine particle film of SiO ₂ , it is necessary to perform a heat treatment for transparency at a temperature of 1000 to 1200 ° C.

After the transparency treatment, a metal chromium film is formed on the core film by a sputtering method or a vapor deposition method, and a metal chromium film having a desired waveguide pattern is formed by a photoengraving method.
Thereafter, the core film is etched by RIE (reactive ion etching) to remove the core film that is not covered with the metal chromium film, thereby forming a core layer having a predetermined width. Then, again with a SiO ₂ composition containing B and P and not containing Ge,
Fine particles are deposited by a flame deposition method, and a high-temperature heat treatment is performed to form an upper cladding layer, thereby producing an optical waveguide.

As an example of the optical waveguide produced as described above, the refractive index of the cladding layer is 1.4585, the refractive index of the core layer is 1.4885, and the refractive index difference between the core layer and the cladding layer is 0. 0.75%. The core size at the time of manufacturing the waveguide is related to this difference in the refractive index. In the case of 0.75%, a 6 μm × 6 μm square is the core size through which single mode light propagates. The basic characteristics of the optical waveguide made of quartz manufactured by this process are described in the paper NTT, R & D (vo
l. 40, no. 2, p. 199), the propagation loss is 0.1 dB / cm, the relative refractive index difference is 0.75%, and the allowable bending radius is 5 mm. Quartz waveguide 5 of this configuration
Is made of the same silica-based material as the quartz optical fiber used in optical communications, and the core size is close to that of the optical fiber, so the loss of the optical waveguide itself and the connection loss between the optical waveguide and the optical fiber Has the advantage of being extremely small.

A strong ultraviolet light (excimer laser, KrF: wavelength 248 n) is applied to the core layer of the Ge-containing optical waveguide as described above.
When m) is irradiated, the refractive index of the portion irradiated with the laser beam increases. The refractive index after the rise is about 1.4692. The increase in refractive index is referred to as a photo-induced refractive index change, as described by K. K. of Canada. O. Hill is a phenomenon in which the refractive index changes in a color center created by strong light energy.

FIG. 17 is a schematic view showing a typical method of manufacturing a grating in a conventional example. To manufacture the grating, a phase mask 59 made of quartz glass is
a, 60 c and a core layer (waveguide core) 60 b are placed on a waveguide film 60, and an excimer laser beam 61 is irradiated via a phase mask 59. The phase mask 61 has a relief-shaped diffraction grating formed on the surface thereof, as shown in an enlarged sectional view 62 of a portion A. The excimer laser light 61 is applied to the waveguide film 6 so that the grooves of the diffraction grating are perpendicular to the waveguide.
Diffracted by the phase mask 59 placed on the waveguide core 6
A grating having a −1st order, 0th order, and + 1st order diffraction pattern (B part enlarged view) 63 is formed on 9b. The diffraction pattern of the grating changes to a higher refractive index.
The irradiation condition of the excimer laser beam 61 is 200 mJ / cm
² / pulse energy density, frequency 60Hz,
The irradiation time was 30 minutes. The Bragg reflection wavelength of the grating is expressed by the following equation (1).

Λ _B = 2nP (1) where λ _B is the Bragg wavelength, n is the effective refractive index for the propagation mode, and P is the grating pitch.

The reflectance of the grating is expressed by the following equation (2).

R _B = tanh (πLΔn / λ _B ) (2) where L represents the grating length and Δn represents the modulation width of the refractive index.

FIG. 18 shows a reflection spectrum of a typical grating formed by the above-described manufacturing method. The horizontal axis is
The wavelength (nm) and the vertical axis indicate light intensity (dB). When the grating length was 1 mm, the reflection characteristics of the obtained grating were a Bragg wavelength of 1530.8 nm and a reflectivity of 8%.

The mechanism of the photoinduced refractive index change is described in, for example, IEICE Technical Report OPE94-5,
p. As described at 25, it is described as follows.

An absorption band of a Ge—Si bond generated as an oxygen vacancy of the glass to which Ge is added exists in the glass to which Ge is added. This bond is broken by the energy of ultraviolet light, and the bound electron is released. This released electron is
Once again captured by Ge atoms, a new absorption band (color center) is formed, and the absorption spectrum changes. This change in the absorption spectrum causes a change in the refractive index through the Kramers-Kronig relationship. In addition, a dipole moment is formed between electrons captured by Ge atoms. Since the dipole moment is oriented along the axis of the optical electric field and a DC electric field is formed in the glass, a change in the refractive index also occurs due to the electro-optic effect. The photoinduced refractive index change in the core layer to which Ge is added is due to the change in the absorption spectrum and the electro-optic effect. Therefore, the amount of change in the refractive index depends on the amount of Ge in the glass material and the amount of oxygen deficiency. It is considered that a large change in the refractive index can be realized by adding a high concentration of Ge and increasing the amount of oxygen defects.

Further, by diffusing the hydrogen molecules into the core layer 60b, the hydrogen molecules are dissociated by the energy of the excimer laser, and Ge and Si atoms in the core layer 60b and new Ge-H, Ge-OH, Si- OH or Si-H bonds can be formed to change the refractive index.

Before forming the grating, the substrate is treated in a high-pressure hydrogen (H ₂ ) gas at 140 atm for about one week at room temperature. Immediately after the treatment, an excimer laser (wavelength: 248 nm) is phased as shown in FIG. When irradiated through a mask, the high-pressure hydrogen treatment causes the photo-induced refractive index change to be at least 10 times larger than that of no treatment.

However, since the generation of OH groups leads to absorption in the 1.5 μm band used in optical communication, the propagation loss of the waveguide increases. When a 5 mm grating is manufactured by applying a high pressure treatment to a 20 mm long waveguide, a propagation loss of about 1 to 3 dB increases.

In place of the high-pressure hydrogen treatment, 140
Treatment is performed at room temperature for about one week in high-pressure deuterium gas (D ₂ ) at atmospheric pressure to diffuse deuterium molecules into the waveguide core 17b, and dissociate the deuterium molecules with the energy of the excimer laser to make Ge, Si Atoms and new Ge-D, Ge-OD, S
By making an i-OD or Si-D bond and changing the refractive index, the light-induced refractive index change is 1
It can be made 0 times or more. The generation of the OD group is different from that of the OH group in the absorption wavelength band.
The propagation loss of the waveguide in the m band does not change much.

However, since a high-pressure deuterium treatment at 100 atm and a long period of several days to several weeks is required, the production cost is high, and when the device size becomes large, it is difficult to procure a pressure-resistant container for performing the high-pressure treatment.

Further, the diffusion of hydrogen molecules into the core layer 60b is accelerated by heat to shorten the processing time. Before forming the grating, a hydrogen gas is supplied at a rate of 400 ° C. while flowing 3 liters per minute. , The photo-induced refractive index change can be increased about eight times.

However, it is difficult to control the change in the refractive index due to the heat treatment, it is difficult to produce a device having the same refractive index with good reproducibility, and the loss of the waveguide is large. When a 5 mm grating is manufactured by performing a high temperature hydrogen treatment on a 20 mm long waveguide, a propagation loss of about 2 to 4 dB occurs. Further, when the processing temperature is high, there is a problem that the elements in the core layer 60b are reduced and the characteristics of the waveguide are changed.

The refractive index of the core layer 60b can be increased by increasing the addition amount of Ge to 50%. With 10% Ge addition, the refractive index is 1.46.
It is about 70, but it becomes about 1.500 when 50% is added. Thereby, the refractive index of the cladding layer (1.4585)
The difference between the two is about 3%, and the confinement of light in the core layer 60b is increased, and the curvature of the curved portion can be increased.

However, in order to obtain a waveguide of single mode propagation, it is necessary to reduce the core size of the core layer 60b to about 3 to 4 μm square. In the method of increasing the amount of Ge added, the propagation loss of the waveguide itself is 1 mm for a length of 20 mm.
dB or less, but due to the small size of the waveguide core,
Coupling with an optical fiber is difficult, and the coupling loss between the waveguide and the fiber is as large as 4 dB.

The core layer 60b is thinned by etching by RIE to expose the upper and lower portions of the core layer 60b, and the refractive indices of the upper and lower portions of the core layer are measured. The lower core layer has substantially the same refractive index as 1.4682, but separately has a core layer 60b of 6 μm
A clad layer is formed on the formed sample, and then irradiated with weak ultraviolet light (excimer laser, KrF: wavelength 248 nm, energy density: ² mJ / cm ² / pulse, 10 minutes). When the upper clad layer was thinned by etching and the refractive indexes of the upper and lower portions of the core layer were measured, the refractive index of the upper portion of the core layer was 1.469.
1. In the lower part of the core layer, it can be seen that there is a difference in refractive index change from 1.4687. That is, it can be understood that the energy is not enough to change the refractive index of the core layer uniformly in the light-induced refractive index change due to weak ultraviolet light.

Next, a conventional wavelength multiplexing system will be described. In a submarine system, an optical branch circuit that branches an optical cable coming from one direction into two directions has been required. Until now, optical branch circuits having a two-core optical cable for each destination have been used. However, this two-core optical cable requires a four-core line including an up line and a down line. This has led to higher costs. On the other hand, the fact that the number of core wires can be reduced to half by using the WDM technology is described in Noboru Oyama, et al., "Optical Submarine Cable Communication" (KEP, pp. 141-151, 1991).
Year).

FIG. 19 shows an optical branching circuit using the WDM technique. Here, 64 is an optical branching circuit, 65a, 65b, 6
5c is an optical filter for separating wavelengths, 66a, 66b, 6
An optical filter 6c multiplexes wavelengths. For example, the wavelengths λ ₁ and λ ₂ incident from the cable A are
λ ₁ goes to the cable C via the optical filter 66c, and λ ₂ goes to the cable B via the optical filter 66b. On the other hand, the wavelength λ ₁
And λ ₂ are separated by an optical filter 65b, λ ₁ goes to the cable A via the optical filter 66a, and λ ₂ goes to the cable C via the optical filter 66c. Thus ,
The use of two different wavelengths allows for branching of the optical cable in two directions.

As the optical filters 65a, 65b and 65c which play an important role in the optical branch circuit 64, the dielectric multilayer filter shown in FIG. 20 has been widely used. In FIG. 20, the WDM light incident from the terminal 68 is
The light is collimated by a and reaches the dielectric multilayer film 69. The dielectric multilayer film 69, for example to reflect wavelengths lambda _1, is designed to transmit the wavelength lambda ₅ otherwise. Reflected wavelength
λ ₁ is condensed by the lens 67 b and emitted to the terminal 70,
The signal is output to the receiver 71b connected to the terminal 70. On the other hand, the wavelength λ ₅ is transmitted by the transmitter 72 a, the terminal 73, and the lens 67.
c, The light passes through the dielectric multilayer film 69 and is output to the terminal 68.

As a conventional example of a ring network, for example, M.I. J. Chawki, V .; Tholey, et
c, "Wavelength reuse scheme"
ein a WDM undirectional
ring networking a prop
r fobber grating add / drop
multiplexer "(Electron Let
ters, vol. 31, No. 6, p. 476-4
77, 1995). Add / Drop Multiplexer: AD by WDM
M) There is a network. The ADM is a multiplexing / branching device that drops (Add) a signal addressed to its own station and inserts (Add) a signal addressed to its own station to multiple stations. One network connected by a ring-shaped optical fiber is connected to another network via an optical cross-connect device. For example, station 1 is assigned a unique wavelength λ ₁ . Of the WDM signal arriving on the station 1, only the wavelength lambda ₁ is received by the branch receiver by an optical filter. On the other hand, the optical signal transmitted from the station 1 transmitter can also use the wavelength lambda _1. Therefore, it is possible to identify to which station the signal is addressed by the wavelength. In this ring network,
An important function is the optical filter. FIG. 21 shows a proposed optical filter.

In FIG. 21, 220a and 220b are fiber gratings, and 222a and 222b are 2 × 2.
, A reference numeral 203b denotes an optical transmitter, and reference numeral 204b denotes an optical receiver. Reference numerals 221a and 221b denote a refractive index adjustment unit;
3a and 223b are terminals at the previous stage of the 3dB coupler 222a,
223c and 223d are terminals at the subsequent stage of the 3dB coupler 222a, 224a and 224b are terminals at the previous stage of the 3dB coupler 222b, and 224c and 224d are terminals at the subsequent stage of the 3dB coupler 222b. Here, the Bragg wavelengths (wavelengths of reflected waves) of the fiber gratings 220a and 220b are
It is set to λ _5. Fiber grating 220a, 2
20b, in which alone does not function only as a reflector merely wavelength selectivity, by connecting the 3dB coupler 222a in front, of the WDM light incident from the terminal 223a, only the lambda ₅ is the fiber grating 220a, 22
The light is reflected at 0b and can be extracted from the terminal 223b of the 3 dB coupler.

The light incident from the terminal 223a is split into two and output to the terminals 223c and 223d, reflected by the fiber gratings 220a and 220b, respectively, and returned to the 3dB coupler 222a. Terminal 223a
To return to the terminal 223a from the terminal 223a and the terminal 2
23c, fiber grating 220a (reflection), terminal 223c, light following the first route of terminal 223a, terminal 223a, terminal 223d, fiber grating 220b (reflection), terminal 223d, second of terminal 223a.
Are combined and output from the terminal 223a. In the 3 dB coupler, a phase difference of π / 2 occurs between the transmitted light and the combined light. Assuming that the phase difference is 0 for transmitted light and π / 2 for coupled light, the terminals 223a and 223c of the first route
Terminal 223c and terminal 223a are transmitted light, terminal 223a of the second route, terminal 223d (π / 2) and terminal 223
d, the terminal 223a (π / 2) is the coupled light, and the total phase difference is π / 2 + π / 2 (= π). Therefore, the first
And the second route light have opposite phases and are canceled by interference.

When returning from the terminal 223a to the terminal 223b, the light following the first route of the terminal 223a, the terminal 223c, the fiber grating 220a (reflection), the terminal 223c, the terminal 223b, the terminal 223a, and the terminal 223
d, fiber grating 220b (reflection), terminal 2
Light that has followed the second route of 23d and terminal 223b is combined and output from terminal 223b. Terminals 223a and 223c of the first route are terminals 223c and 223a that are transmitted light and coupled light (π / 2), and a terminal 2 of the second route.
The terminal 23a and the terminal 223d are coupled light, the terminal 223d and the terminal 223b (π / 2) are transmitted light, and the phase difference is π / 2 for both the first and second terminals.
Output from 3d.

The wavelengths other than the wavelength λ ₅ are
0b is reached. When the light is emitted from the terminal 223a to the terminal 224c, the terminal 223a, the terminal 223c, the fiber grating 220b (transmission), the terminal 224a, the terminal 2
24c, a first route and terminals 223a, 223d,
Fiber grating 220b (transmission), terminal 224
b, light of the second route of the terminal 224c is combined and output from the terminal 224c. Terminal 223 of the first route
a, the terminal 223c and the terminal 224a, the terminal 224c is the passing light, the terminal 223a of the second route, the terminal 223d and the terminal 224b, and the terminal 224c are the coupling light, and the total phase difference is π / 2 + π / 2 (= π). . Therefore, the first route light and the second route light have opposite phases and are canceled by interference.

When output from the terminal 223a to the terminal 224d, the terminal 223a, the terminal 223c, the fiber grating 220a (pass), the terminal 224a, the terminal 224
d, the light following the first route and the terminals 223a and 22
3d, the fiber grating 220b (passing), the light following the second route of the terminal 224b, and the terminal 224d are combined and output from the terminal 224d. Terminals 223a and 223c of the first route are terminals 224a and 224a by passing light.
The terminal 224d is coupled light (π / 2), the terminals 223a and 223d of the second route are coupled light, the terminals 224b and 224d (π / 2) are transmitted light, and the phase difference of both the first and second is π. / 2, and as a result of in-phase, constructive by interference, terminal 2
Output from 24d.

The signal of wavelength λ ₅ to be inserted is supplied to terminal 224.
c transmitted from the optical transmitter 203b connected to terminal c.
d. This operation is the same as the signal wavelength lambda ₅ entering from the terminal 223a is outputted to the terminal 223b. The refractive index adjusting unit 221a is a 3 dB coupler 2
22a to each fiber grating 220a, 220
The refractive index is adjusted so that the optical path length up to b is the same. Similarly, the refractive index adjuster 221b sends the 3 dB coupler 222b to each of the fiber gratings 220a,
The refractive index is adjusted so that the optical path length up to 20b is the same. The refractive index adjusting unit 221b changes the refractive index by irradiating ultraviolet light in the same manner as in the method of manufacturing a fiber grating. This technology is disclosed in
98702.

[0041]

The reflectivity that affects the performance of the waveguide grating is related to the magnitude of the change in the refractive index. The greater the change in the refractive index, the greater the reflectivity.
The band of the optical filter also widens. This change in the refractive index relates to the amount of Ge and Si bonded in the core layer 60b made of quartz .

In order to increase the amount of change in the refractive index, as described above, high-pressure hydrogen treatment or high-temperature hydrogen treatment is performed, and an OH group or an OD group is introduced to increase the change in the refractive index. But,
High-pressure and high-temperature hydrogen treatment increases the propagation loss.
And the characteristics of the waveguide are changed, and there are problems such as the length of processing time and the price of gas. In addition, the method of increasing the amount of Ge added has a problem that the size of the core layer 60b is reduced and the coupling loss between the optical waveguide and the fiber is increased.

When the refractive index is changed by irradiating the light, if the energy of the irradiating light is weak, there is a problem that a refractive index distribution occurs in the depth direction or in the plane of the core layer 60b. The cause of this problem is that due to insufficient energy of the irradiation light, even if the oxygen vacancy or the amount of Ge—Si bonded is sufficient, the change in the refractive index does not occur uniformly. When the refractive index distribution occurs in the optical waveguide, there is a problem that the wavelength cutoff characteristic, which is a feature of the optical filter using the waveguide grating, is deteriorated and the band is widened.

[0044]

[0045]

[0046]

The present invention has been made in order to solve the above-mentioned problems, and it is intended that the core layer be bent in the depth direction or in the plane.
Index distribution is prevented from occurring, and the refractive index change is uniform.
Provided is a waveguide-type grating and a method for manufacturing the same.
The porpose is to do. Also prevents deterioration of wavelength cutoff characteristics
High-performance optical filter and high-performance WDM optical transmission
The purpose is to provide a system .

[0048]

[0049]

[0050]

[0051]

The invention according to claim 1 is
Substrate, on the substrate, Ge the main component as SiO _2, T
forming a film of quartz containing at least one or more doping elements of i, B, P, and Tn by a CVD (chemical vapor deposition) method;
Light is applied to an optical waveguide including a core layer formed to have a predetermined waveguide width and a clad layer surrounding the core layer and formed by depositing quartz whose main component is SiO ₂ by a CVD method. In the waveguide type grating in which the grating is formed by changing the refractive index of the core layer,
The contained doping element, in the thickness direction of the core layer,
Change the incident side of the irradiation light so that it is smaller than the exit side.
This is a waveguide-type grating.

[0052]

[0053]

According to a second aspect of the present invention, an organic metal compound of Si is used as a raw material or a main raw material on a substrate, and an ozone gas, an oxygen gas, a nitrous oxide gas (N ₂
Supplying at least one gas O), at atmospheric pressure or under reduced pressure in, by CVD (chemical vapor deposition) method of depositing an oxide film of the elements in said raw material, Si O ₂ component or primary Step (a) of forming a cladding layer made of quartz as a component, and the above-mentioned CVD method using at least one or more organometallic compounds of Ge, Ti, B, P and Sn and an organometallic compound of Si as doping raw materials. by, Si O ₂ step of forming a core layer made of quartz as a main component and (b), (c) forming a core layer by patterning the core layer to a predetermined waveguide width, Si Using the organometallic compound as a raw material or a main raw material so as to surround the core layer,
Step (d) of forming a cladding layer made of quartz containing SiO ₂ as a component or a main component by VD to form an optical waveguide, and irradiating the core layer with light through a phase mask. the manufacturing method of a waveguide grating that includes a step (e) to form a grating with varying refractive index
In the step (b), the dope material is added to the core
In the thickness direction of the film, the incident side of the irradiation light is smaller than the exit side.
This is a method of manufacturing a waveguide type grating for forming a film so as to eliminate it .

[0055]

[0056]

[0057]

[0058]

According to a third aspect of the present invention , n sets (where n is 1 or more) of gratings (n is 1 or more) in which gratings having a reflection center wavelength are formed on optical signals having predetermined wavelengths λ _{1 to} λ _n , respectively . n) a waveguide grating, and four n ₁ , n ₂ , n ₃ and n ₄ for inputting and outputting the optical signal provided corresponding to each of the (1) to (n) -th waveguide gratings
And a terminal, enter the optical signal of wavelength lambda _n to n ₁ terminal n
Output to _two terminals, and outputs an optical signal other than the wavelength lambda _n to n ₄ terminals, the Symbol wavelength input from n ₃ terminal lambda _n or lambda _n
Λ (λ _n ′ is within the reflection wavelength band of the (n) th waveguide grating) to an optical filter that outputs an optical signal to the n ₄ terminal .
And the (1) to (n) th waveguide gratings
Is an optical filter that is the waveguide grating according to claim 1 .

[0060]

[0061]

[0062]

[0063]

[0064]

[0065]

According to a fourth aspect of the present invention, there are provided n (n is 3 or more) sets of (1) to (n) waveguide types in which a grating having a reflection center wavelength is formed on an optical signal having a predetermined wavelength λ _1. A grating, directional couplers connected to the front and rear of each of the (1) to (n) waveguide gratings, and the rear of the (1) to (n) waveguide gratings Are connected to two (n) ₁ and (n) ₂ terminals for inputting / outputting an optical signal provided in each of the directional couplers connected to the (n−2) th waveguide type grating (n−2).
2) ₁ terminal and (n-1) ₂ terminal of the (n-1) th waveguide grating, (n-1) ₁ terminal of the (n-1) th waveguide grating and ₁ terminal and the (n-1) th waveguide grating n ₂ terminals, and n ₁ terminal and the n-th waveguide grating (n-2) waveguide grating (n-2) ₂ terminal and the wavelength-multiplexed optical Den formed so as to be connected
In the transmission system, the above-mentioned waveguide grating is contracted.
A wavelength division multiplexing optical transmission system, which is the waveguide grating according to claim 1 .

According to a fifth aspect of the present invention, there are provided n sets (where n is 1 or more) of a (1) to (n) th waveguide type in which a grating having a reflection center wavelength is formed on an optical signal having a predetermined wavelength λ _1. A grating and a directional coupler for connecting the (1)-(n) -th waveguide grating are formed on the output side and the input side of each of the (1)-(n) -th waveguide grating. and the directions of the optical transmitter and connected to the output side of the first (n) a waveguide grating that outputs light wavelength multiplex signal consisting of a predetermined wavelength lambda ₁ of the optical signal and the wavelength lambda ₁ except the optical signal By connecting the optical receiver connected to the directional coupler and inputting the optical signal of the predetermined wavelength λ ₁ to the directional coupler connected to the input side of the (1) waveguide grating, After being input to the first (1) waveguide type grating, The predetermined wavelength lambda ₁ of the optical signal of the serial optical wavelength-multiplexed signal inputted to the optical receiver, the first (n) optical wavelength-multiplexed signal other than the wavelength λ1 outputted from the waveguide grating and the light transmitting Wavelength multiplexing optical transmission system that multiplexes and transmits the optical wavelength multiplexing signal output from the transmitter.
In the stem, the waveguide-type grating is claimed.
1. A wavelength division multiplexing optical transmission system which is the waveguide type grating according to 1 .

[0068]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view showing a waveguide grating according to the present invention. In the drawing, reference numeral 1 denotes a substrate made of a silicon substrate or the like;
_The lower clad layer formed by depositing quartz of ₂ by a CVD (chemical vapor deposition) method, 3 is mainly composed of SiO ₂ , Ge, T
A core layer formed by depositing quartz containing at least one or more doping elements of i, B, P, and Sn by a CVD method and having a predetermined waveguide width, 4 is a core layer together with the lower cladding layer 2. An upper cladding layer formed by depositing quartz of which main component is SiO ₂ by a CVD method and surrounding the layers, a grating 5 formed by irradiating light to change a refractive index of the core layer 3, and a lower cladding layer 6 This is an optical waveguide composed of a layer 2, a core layer 3, and an upper cladding layer 4.

In the waveguide grating of the present invention shown in FIG. 1, the optical waveguide 6 is formed by the CVD method.
Even at a relatively low substrate temperature of 00 ° C. or less, the transparent waveguide 6
And does not require high-temperature clarification.
The oxygen defect density in the core layer 3 increases, and the change in the refractive index during light irradiation increases.

Further, by changing the doping element contained in the core layer 3 in the thickness direction of the core layer 3 by the CVD method, the above doping element is particularly formed on the incident side of the irradiation light in the thickness direction of the core layer 3. By reducing the number and increasing the amount on the output side, even if the irradiation light is irradiated on the optical waveguide and the absorption starts, the absorption amount becomes equal on the incident side and the output side of the irradiation light, and the grating 5 having a uniform refractive index change. Is obtained.

[0071]

On a substrate, at least one gas of ozone gas, oxygen gas, nitrous oxide gas (N ₂ O) is supplied along with the raw material vapor using an organometallic compound of Si as a raw material or a main raw material. Alternatively, CVD (chemical vapor deposition) for depositing an oxide film of the element in the above raw material under reduced pressure
(A) forming a cladding layer made of quartz containing SiO ₂ as a component or a main component by a method, Ge, Ti,
B, P, at least one or more organometallic compounds and Si organometallic compounds of Sn as raw materials, the step of forming by the CVD method, the core layer a Si O ₂ made of quartz as a main component (b) (C) patterning the core film into a predetermined waveguide width to form a core layer, and using the organometallic compound of Si as a raw material or a main raw material by the CVD method so as to surround the core layer. (D) forming a cladding layer made of quartz containing SiO ₂ as a component or a main component to form an optical waveguide, and irradiating the core layer with light through a phase mask to reduce the refractive index. And (e) forming a changed grating.

FIG. 2 shows an ozone oxidation type CVD film forming apparatus used for manufacturing the waveguide type grating of the present invention.

As shown in FIG. 2, a plurality of source containers 8 are provided, and a plurality of types of CVD source vapors are simultaneously supplied to the substrate 1.
Can be supplied above. Si, G
The alkoxides of e, Ti, B, P and Sn are used.
The carrier gas such as high-purity Ar gas introduced from the carrier gas inlet 12 and discharged from the outlet 13 can independently control the flow rate of the vapor of each raw material by the flow controller 7 attached to each raw material container 8. Therefore, a plurality of types of alkoxide raw materials can be transported onto the substrate 1 in the reaction tube 9 at an arbitrary ratio. Oxygen gas containing 8% of ozone generated by introducing into the ozonizer 11 from the oxygen gas inlet 10 is introduced into the reaction tube 9, and the temperature of the substrate 1 is set to 800
When the temperature is set to ° C., the decomposition and reaction of the raw materials are promoted, and a film is formed on the substrate 1 installed in the reaction tube 9. The substrate 1 uses a silicon substrate. The degree of vacuum is 50 Torr, and the deposition rate is 10
μm / hour.

As the Si alkoxide, TEOS (S
i (OC ₂ H ₅ ) ₄ ), Si (OCH ₃ ) ₄ , Si (O
_{C 3 H 7) 4, Si} (OC 4 H 9) ₄ can be used like.

As an alkoxide of Ge, TEG is used.
In addition to (Ge (OC ₂ H ₅ ) ₄ ), Ge (OC ₃ H ₇ ) _{4 and the} like can be used.

As the alkoxide of P, TEP
(P (OCH ₃ ) ₃ )), P (OCH ₃ ) ₃ and PO (O
CH ₃ ) ₃ , PO (OC ₂ H ₅ ) _{3 and the} like can be used.

In the alkoxide of B, TEB(B
(OC _Three H ₇ ) _Three ), And B (OC _Two H _Five ) _Three , B (OC
_Three H ₇ ) _Three , B (OC _Four H ₉ ) _Three etcCan be used.

As alkoxides of Ti or Sn, TET (Ti ( OiC ₃ H ₇ ) ₄ ), Sn (C
_{H 3) 4, Sn (C} 2 H 5) 4 or Sn (C ₃ H _{7) 4} can be used like <br/>.

In addition to the above-mentioned alkoxides, it can be easily expected that alkoxides capable of transporting vapor by piping with a suitable carrier gas can achieve the same effect.

FIGS. 3A to 3E are cross-sectional views showing the steps of manufacturing the waveguide grating of the present invention. First, only the vapor of the alkoxide of Si and B is supplied onto the silicon substrate 1 to form a lower cladding layer 14 made of quartz containing SiO ₂ containing B (boron) as shown in FIG.

Next, alkoxides of Si and Ge are simultaneously supplied onto the substrate 1 to form a core film 15 made of quartz containing SiO ₂ containing Ge (FIG. 3B).

Next, a waveguide pattern 16 is formed on the core film 15 using a metal mask (FIG. 3C) , and is etched by RIE to pattern the core layer 3 having a predetermined waveguide width ( FIG. 3D) . )).

Next, an upper clad layer 17 containing B in SiO ₂ is formed of TEOS + TEB material so as to surround the core layer 3 ( FIG. 3E), and an optical waveguide is manufactured.

Next, a grating was formed on the optical waveguide 6 by the same method as in the prior art. That is, in manufacturing the grating, a phase mask made of quartz glass is placed in contact with the waveguide film, and an excimer laser beam is irradiated through the phase mask (see FIG. 17). The irradiation conditions of the excimer laser beam were an energy density of 400 mJ / cm ² / pulse, a frequency of 60 Hz, and an irradiation time of 1 hour.

The ultraviolet light to be irradiated is KrF of excimer laser at 248 nm, but may be excimer laser ArF of lower wavelength, 193 nm or argon laser of longer wavelength of 488 nm.

The CVD method is an ozone oxidation type CVD.
(Chemical vapor deposition) method, plasma CVD method, thermal decomposition C
It can be applied by any one or more of the methods of VD method or a photo CVD method.

Further, a substrate made of quartz can be used as the substrate 1 and the step of forming the lower cladding layer 14 can be omitted.

[0089]

Further, the phase mask is brought into contact with the optical waveguide or placed at a distance of less than 5 mm to irradiate light.
Next, ± 2 orders, ± n orders occur, but the diffraction angle of the irradiation light is
The angles are 0 degree, θ degree, 2θ degree, and nθ degree, respectively. If the distance from the phase mask is less than 5 mm, the third-order or higher-order light is irrelevant. Modulation can be applied to the grating period using the diffraction pattern.

A high-performance optical filter can be obtained by applying the waveguide grating shown in FIG.

The optical filter shown in FIG. 6 has a waveguide grating 1 having a set of optical signals having a wavelength λ ₁ and having a reflection center wavelength.
9, an optical wavelength multiplexed signal is input from a port 20, an optical signal having a wavelength λ ₁ is output to a port 21, and an optical signal other than the wavelength λ ₁ is output to a port 23.

FIGS. 8 and 10 show a case where a grating having a reflection center wavelength is formed on an optical signal having one or more predetermined wavelengths λ, and a grating having a reflection center wavelength is formed on optical signals having wavelengths λ _{1 to} λ _n . n sets (where n is 1 or more) of the (1) to (n) waveguide gratings and the optical signals provided corresponding to the (1) to (n) waveguide gratings are input. The four n ₁ , n ₂ ,
It has n ₃ and n ₄ terminals, one or more waveguide gratings, and four n ₁ , n ₂ , and n ₃ input and output optical signals provided for each of the waveguide gratings.
And n ₄ and a terminal, and outputs the n ₂ terminal by inputting a light signal of wavelength lambda _n to n ₁ terminal, an optical signal other than the wavelength lambda _n n
₄ and outputs to the terminal, n ₃ said wavelength inputted from the terminal lambda _n or λ _n '(λ _n' is the (n) waveguides grating in the reflection wavelength band of) the light output optical signals of the n ₄ terminal Filter.

An optical wavelength-division multiplexed signal is input to each of the (n) -th waveguide gratings from the n ₁ or n ₃ terminal, and λ
_n optical signals are output from the n ₃ or n ₁ terminals, respectively, and λ _n
Can output light signals from the n ₂ or n ₄ terminals each other.

FIG. 11 is a principle diagram for explaining the relationship between the angle θ of the waveguide and the grating pitch x _{1 on} the curve.
From the figure, the relationship of the angle θ and the grating pitch x ₁ of the waveguide is expressed by the following equation (3). a ₁ represents the original grating pitch.

A grating pitch x ₁ = a ₁ / cos (θ) on a curve (3)

The original grating pitch a _{1 is set} to 107
Assuming 8 nm, grating period x tilted 5 degrees
₁ becomes 1082.1 nm from the equation (3). Thus, the two optical filters 24a and 24b having different curvatures are
A grating can be manufactured using a phase mask having the same pitch, and a device capable of dropping and inserting two kinds of wavelengths such as 1078 nm and 1082.1 nm can be manufactured.

Therefore, each of the first to n-th waveguide gratings has at least one waveguide grating composed of an optical waveguide of a straight waveguide or a curved waveguide, and has different curvatures.
By forming a grating of the same pitch in the optical waveguide of the song ray waveguide that, the wavelength lambda ₁ to [lambda] _n n sets having a grating having a reflection center wavelength in the optical signal of the (n is 1 or more) first (1 ) To (n) th waveguide grating can be formed.

Also, by forming gratings having different pitches in the optical waveguide of the linear waveguide, the wavelength λ ₁
N sets (where n is 1 or more) of the (1) to (n) th waveguide gratings in which gratings having a reflection center wavelength are formed on optical signals of λ _n can be formed.

[0100] Further, in n is 2 or more, connected in the (n-1) waveguide grating (n-1) ₄ terminal and optical connection member and the n ₁ terminal of the (n) waveguide grating By doing so, the optical signals of the wavelengths λ _{1 to} λ _n can be sequentially demultiplexed.

The optical connecting member may be a plurality of optical fibers or a multi-core fiber array. Further, the optical connecting member may be a waveguide formed on a substrate, so that the processing of the extra-long fiber can be performed. It can be unnecessary.

By applying the waveguide grating shown in FIG. 1, a high-performance wavelength multiplexing optical transmission system can be obtained.

FIG. 12 shows directional couplings connected to the front and rear portions of three sets of waveguide type gratings 19a, 19b and 19c in which a grating having a reflection center wavelength is formed on an optical signal having a predetermined wavelength λ _1. The optical waveguide 32 and two terminals 35a and 35b for inputting and outputting optical signals provided in the directional couplers 32 connected to the rear portions of the waveguide gratings 19a, 19b and 19c, respectively, are connected to a first waveguide grating. The 35a terminal 19a and the 35b terminal of the second waveguide grating 19b, the 35a terminal of the second waveguide grating 19b and the 35b terminal of the third waveguide grating 19c, and the 35a terminal of the third waveguide grating 19c. A wavelength division multiplexing optical transmission system formed so as to be connected to the 36b terminal of the first waveguide grating. It is a system.

FIG. 12 shows an example in which three sets of waveguide type gratings 19a, 19b and 19c are used. However, n sets (n) in which an optical signal having a predetermined wavelength λ ₁ is formed with a grating having a reflection center wavelength. (3) or more) (1) to (n) waveguide gratings, and directional couplers connected to the front and rear portions of the (1) to (n) waveguide gratings, respectively. The above (1) to (n)
Two (n) ₁ and (n) ₂ terminals for inputting and outputting an optical signal provided in each of the directional couplers connected to the rear part of the waveguide type grating are connected to the (n-2) th waveguide type. (N-2) ₁ terminal of the grating and (n-1) ₂ terminal of the (n-1) th waveguide grating, and (n-1) ₁ terminal and the nth terminal of the (n-1) th waveguide grating wavelength waveguide grating n ₂ terminal, and the n-waveguide grating n ₁ terminal and the (n-2) of the waveguide of the grating (n-2) and the _second terminal is formed so as to be connected A multiplex optical transmission system can be configured to obtain a wavelength multiplex optical transmission system that branches wavelength multiplexed light coming from one direction into two directions.

FIG. 13 shows two sets of waveguide gratings 19a and 19b in which a grating having a reflection center wavelength is formed on an optical signal having a predetermined wavelength λ ₁ , and output and input sides of each of the waveguide gratings 19a and 19b. waveguide grating 19a, the directional coupler 32a which connects 19b, 32b, 32c, to form a 32d, an optical wavelength multiplexed signal comprising a predetermined wavelength lambda ₁ of the optical signal and the wavelength lambda ₁ except the optical signal The output optical transmitter 39 is connected to the directional coupler 32d connected to the output side of the waveguide grating 18b, and the optical receiver 40 for inputting the optical signal of the predetermined wavelength λ ₁ is connected to the waveguide type grating 18b. By connecting to the directional coupler 32a connected to the input side of the grating 19a, the optical wavelength multiplexed signal input to the waveguide type grating 19a is connected. The optical signal of the predetermined wavelength λ ₁ is input to the optical receiver 40 and the waveguide type
It has been a wavelength division multiplexing optical transmission system for transmitting an optical wavelength-multiplexed signal multiplexes output from the optical wavelength-multiplexed signal other than the wavelength lambda ₁ and the optical transmitter 39 outputted from.

As in FIG. 13, n sets (where n is 1 or more) of the (1)-(n) -th waveguide-type grating and the output of each of the (1)-(n) -th waveguide-type grating are provided. the side and the input side, from those in the first (1) to the (n) waveguide grating to form the directional coupler for connecting a predetermined wavelength lambda ₁ of the optical signal and the wavelength lambda ₁ except the optical signal An optical transmitter for outputting an optical wavelength-division multiplexed signal is connected to a directional coupler connected to the output side of the (n) th waveguide grating, and the optical signal having the predetermined wavelength λ ₁ is input. By connecting the receiver to a directional coupler connected to the input side of the (1) first waveguide grating,
The first (1) above a predetermined wavelength lambda ₁ of the optical signal in waveguide grating-entered the optical wavelength-multiplexed signal inputted to the optical receiver, output from the first (n) waveguide grating By forming a wavelength division multiplexing optical transmission system for multiplexing and transmitting the optical wavelength division multiplexing signal other than the wavelength λ1 and the optical wavelength division multiplexing signal output from the optical transmitter, when the branch wavelength and the insertion wavelength are the same, The occurrence of talk can be reduced.

[0107]

EXAMPLES Reference Example 1 . FIG. 1 is a sectional view of a waveguide grating cut in a waveguide direction. In FIG. 1 , reference numeral 6 denotes an optical waveguide, and the optical waveguide 6 is formed and formed on a substrate 1 made of a silicon substrate by a CVD (vapor phase growth) method. Reference numeral 2 denotes a lower cladding layer formed by depositing quartz whose main component is SiO ₂ by a CVD method, and 3 denotes quartz whose main component is SiO ₂ and which is doped with about 10% of Ge.
A core layer 4 formed by a CVD method and having a predetermined waveguide width, 4 is a quartz whose main component is SiO ₂ , an upper clad layer formed by a CVD method, 5 is an excimer This is a grating formed by irradiating a laser.

FIG. 2 is a schematic view showing an apparatus for forming a quartz film by an ozone oxidation type CVD method used for manufacturing the optical waveguide 6.

In the apparatus shown in FIG. 2, four source containers 8 are provided, and four types of CVD source vapors can be supplied onto the substrate 1 at the same time. The raw material used was TEOS (Si (OC ₂ H ₅ )
₄ ), TEB (B (OC ₃ H ₇ ) ₃ ), TEG (Ge (OC
It was ₂ H _{5) 4).} The carrier gas introduced from the carrier gas inlet 12 and discharged from the outlet 13 is high purity A
r gas was used. A flow controller 7 is attached to each raw material container 8, and the flow rate of steam of each raw material can be controlled independently. Therefore, four types of alkoxide raw materials can be transported onto the substrate 1 in the reaction tube 9 at an arbitrary ratio. Oxygen gas containing 8% ozone generated by introducing into the ozonizer 11 from the oxygen gas inlet 10 is introduced into the reaction tube 9, and the temperature of the substrate 1 is set to 800 ° C. to promote decomposition and reaction of the raw material. Then, a film is formed on the substrate 1 installed in the reaction tube 9.
As the substrate 1, a silicon substrate having a diameter of 3 inches was used. The degree of vacuum was 50 Torr, and the deposition rate was 10 μm / hour.

FIGS. 3A to 3E are process diagrams showing a manufacturing process of the optical waveguide 6. FIG. First, using the film deposition apparatus shown in FIG. 2, TEOS on the silicon substrate 1, only supplies the steam TEB, the SiO ₂ as shown in FIG. 3 (a) B
A lower cladding layer 14 made of quartz containing (boron) was formed. The thickness of the lower cladding layer 14 was about 20 μm. At this time, the refractive index of the lower cladding layer 14 is 1.458.
It was 2.

Next, TEOS and an alkoxide such as TEG were simultaneously supplied onto the substrate 1 to form a high refractive index core film 15 made of quartz containing SiO ₂ and Ge to a thickness of 6 μm .

In the formation of the core film 15, Ge oxide is contained.
So that the amount is about 10%.
The flow rate was adjusted. The temperature of the substrate 1 is controlled by the lower cladding layer 14.
Was the same as in the case of the film formation.

Next, the core film 15 is guided by a metal mask.
Create a road pattern 16 and etch it by RIE
Is patterned on the core layer 3 having a waveguide width of (FIG.
(C), (d)).

Next, the SiO 2 is surrounded so as to surround the core layer 3._TwoTo
B containing upper cladding layer 17 (refractive index n2)
Formed about 20μm thick with S + TEB raw material (FIG.
(E)) An optical waveguide was produced.

The refractive index of the upper cladding layer 17 is 1.45.
82, which was 1.4688 for the core layer 3 doped with Ge, and the refractive index difference was about 0.8%.

The quartz optical waveguide 6 manufactured as described above is used.
Is a slightly higher value when the light loss in a straight line is 0.05 dB / cm (wavelength = 1.55 μm) as compared with the loss of a waveguide of 0.01 dB / cm by the conventional flame deposition method. When used as a waveguide device having a cm length, the waveguide loss is about 0.3 dB, which is a loss that can be used without any problem.

Further, the waveguide 6 of the present reference example was exposed to
After heat treatment at 0 ° C. for 4 hours, the loss of the waveguide becomes 0.01
dB / cm, which was exactly the same as the conventional flame deposition method.

Unlike the flame deposition method, the CVD method does not have a heat treatment process at a high temperature (around 1000 ° C.), so that a very small amount of OH groups and the like may remain. Is 0.05 to 0.1 dB / c
Not so large as to be problematic with m.

Next, a grating was formed on the optical waveguide 6 by the same method as in the related art. That is, in manufacturing a grating, a phase mask made of quartz glass is placed in contact with the waveguide film, and excimer laser light is irradiated through the phase mask. Excimer laser light irradiation conditions are 4
The irradiation was performed at an energy density of 00 mJ / cm ² / pulse at a frequency of 60 Hz and an irradiation time of 1 hour. The phase mask used a grating pitch of 1078 nm.

FIG. 4 is a graph showing the measurement results of typical transmission wavelength characteristics of the grating of the linear waveguide in the present reference example. FIG. 4 shows that the resulting grating has a Bragg wavelength of 1567 nm and a reflectivity of 99.9.
%, The band is 1.8 nm.

FIG. 5 shows the result of examining the effect of excimer laser irradiation. Irradiation conditions were 200 mJ / cm ² / pu
At an energy density of 1 s, the frequency was changed to 60 Hz, and the irradiation time was changed to 15 minutes, 30 minutes, 45 minutes, and 60 minutes, and the refractive index change of the core film 15 was measured each time.

In FIG. 5, (a) is a core film 15 of the present embodiment , (A) is a core film 15 of the present embodiment subjected to high-pressure hydrogen treatment, (b) is a conventional quartz film, and (B) is It is obtained by subjecting a conventional quartz film to high-pressure hydrogen treatment.

As is clear from FIG. 5, the core film 15
In both (a) and the conventional quartz film (b), the change in the refractive index increased substantially in proportion to the laser irradiation time. Conventional quartz film (b) without high pressure hydrogen treatment,
Even for 60 minutes irradiation, the change was about 0.0002,
The high-pressure hydrogen-treated (B) significantly changed to 0.0018. The core film 15 of the present invention is 0.0018 (refractive index, 1.470) even when the high-pressure hydrogen treatment is not performed (a).
6) and a change substantially equivalent to that obtained by subjecting the conventional quartz film to high-pressure hydrogen treatment (B) was obtained. Further, the core film 15 of the present invention
Was subjected to high-pressure hydrogen treatment (A), and a much larger change in refractive index was obtained at 0.0025.

From the results shown in FIG. 5, the core film 15 of the present invention is
It is clear that the film has a high sensitivity to the change in refractive index caused by light, and it can be understood that the high-pressure hydrogen treatment can obtain a larger change in the refractive index than can be obtained conventionally.

Reference Example 2 The present reference example is an example using a plurality of doped elements, and a waveguide was manufactured through the same steps as in FIG. 3 using the film forming apparatus shown in FIG.

As the substrate 1 for producing the waveguide, a synthetic quartz substrate was used, and the temperature of the substrate 1 was set to 750 ° C. The refractive index of the synthetic quartz substrate is 1.4585, which is equal to the refractive index of pure quartz. Therefore, there is no need of forming a lower clad layer (see FIG. 3) to form a core layer 3 and the Ueku Rudd layer 17 on the substrate 1. The concentration of the ozone gas in the oxygen gas was set to 12% using a high output ozonizer.

The raw material alkoxide includes TEOS, TEOS
B, TEG, and other alkoxides such as TEP ((P (OCH ₃ ) ₃ )) are used and the alkoxides whose flow rates have been adjusted are simultaneously supplied onto the substrate 1 to contain Ge oxides. About 1
A high-refractive-index core film 15 having a thickness of 6 μm having a content of 2%, a content of B oxide of about 4%, and a content of P oxide of about 7%, and further forming an upper cladding layer did. The refractive index of the core film 15 was 1.4692.

The core film 15 is patterned in the same manner as in Reference Example 1 to form the core layer 3, and thereafter, TEOS, TEOS
The alkoxides of B and TEP were simultaneously supplied onto the substrate 1 to form the upper clad layer 17 of the optical waveguide to a thickness of about 20 μm.

In forming the upper cladding layer 17, the flow rate of alkoxide vapor such as Si, B, P is adjusted so that the content of B oxide is about 6% and the content of P oxide is about 9%. went. The refractive index of the upper cladding layer 17 was 1.4581.

The core layer 3 of the manufactured optical waveguide was provided with the reference example 1.
Similarly to the above, upon irradiation with an excimer laser, the core layer 3 has a refractive index of 1.4704, a core layer containing no B and P,
It shows almost the same change in refractive index.

Reference Example 3 In the formation of the core film 15 of Reference Example 2, the Si content was set to about 20%, the B oxide content to about 5%, and the P oxide content to about 8%. When the flow rate of alkoxide vapors of Ge, B, and P is adjusted, the refractive index of the manufactured core film 15 is increased due to an increase in the content of Ge oxide.
It is slightly higher at 1.4782.

A grating was formed on the optical waveguide in which a linear waveguide was formed using the core film 15 in the same manner as in Reference Example 1. That is, a phase mask made of quartz glass is placed in contact with the waveguide film, and excimer laser light is irradiated through the phase mask. The excimer laser beam was irradiated at an energy density of 400 mJ / cm ² / pulse, a frequency of 60 Hz, and an irradiation time of 1 hour. The reflection characteristics of the fabricated linear waveguide grating were such that the Bragg wavelength was 1564 nm and the reflectivity was 99.9%.
Met.

Reference Example 4 This reference example is obtained by carrying out the deposition of the quartz film by plasma CVD. The plasma CVD apparatus includes four source containers 8 as in the CVD apparatus of Reference Example 1 (see FIG. 2), and can supply four types of CVD source vapor onto the substrate 1 in the reaction tube 9 at the same time. . Each raw material is filled in a temperature-controllable closed container, and the flow rate of each vapor can be controlled independently by a flow controller that can accurately control the flow rate of the raw material vapor, and four types of alkoxide raw materials can react at an arbitrary ratio. It can be transported onto the substrate 1 in the tube 9.

The raw materials used were TEOS, TEB, TEB
In G and TEP, each raw material considers its vapor pressure,
75 ° C for TEOS, 45 ° C for TEB, 65 ° C for TEG,
The TEP was heated to 60 ° C. The flow rate of the raw material steam is
For the formation of the cladding layer , TEOS was set at 5 cc / min.
EB was set to 1 cc / min, and TEO
S was 5 cc / min, TEB was 0.3 cc / min, TEG was 0.5 cc / min, and TEP was 0.5 cc / min.

An oxygen gas is introduced into the reaction tube 9 to generate a high-frequency plasma and to reduce the temperature of the substrate 1 by 50%.
At 0 ° C., the decomposition and reaction of the raw materials are promoted, and a film is formed on the substrate 1 provided. As the substrate 1, a silicon substrate having a diameter of 3 inches was used. The degree of vacuum was 0.3 Torr, the high-frequency output was 350 W, the flow rate of oxygen gas was 200 cc / min, and the deposition rate was 8 μm / hour.

As in Reference Example 1, an optical waveguide was manufactured through the steps shown in FIG. The refractive index of each quartz film is 1.4590 for the cladding layers 14 and 17 and 1.4691 for the core film 15 doped with Ge, and the refractive index difference is about 0.7%.
Met.

As in Reference Example 1, strong ultraviolet light (excimer laser, KrF: wavelength 248) was applied to the core layer 3 of the optical waveguide.
nm) to form a refractive index change in the core layer 3 induced by light. After the excimer laser irradiation, the upper cladding layer 17 was removed by etching by the RIE method, and the refractive index was measured using the core layer 3 as the surface. As a result, a large change in the refractive index was found to be 1.4710.

A linear waveguide grating was manufactured, and its reflectance and band were measured.
%, A band of 3.0 nm, and a waveguide loss of 2 dB, which are characteristics that can be used as an optical filter.

Reference Example 5 In the present embodiment , a quartz film is formed by the thermal decomposition CVD method in the embodiment 4. San thermal decomposition CVD apparatus
Remarks Example 4 and provided with four material container 8 as well, it can be supplied onto the substrate 1 at the same time four types of CVD material vapor. Each raw material is filled in a temperature-controllable closed container, and the flow rate of each vapor can be controlled independently by a flow controller that can accurately control the flow rate of the raw material vapor, and four types of alkoxide raw materials can react at an arbitrary ratio. It is possible to transport onto the substrate 1 in the tube 9.

To the reaction tube 9, nitrous oxide gas (N ₂ O)
Is introduced, the temperature of the substrate 1 is set to 950 ° C.,
The reaction is promoted, and a film is formed on the placed substrate 1. Substrate 1
Used a silicon substrate having a diameter of 3 inches. The deposition rate was 4 μm / hour. The thermal decomposition CVD method has a lower film formation rate than the ozone oxidation CVD method, the plasma CVD method, or the like.

The refractive index of each quartz film produced in the same manner as in Reference Example 4 was 1.4585 for the cladding layer and 1.4687 for the core film 15 doped with Ge, and the refractive index difference was about 0.8.
%Met.

As in Reference Example 4, strong ultraviolet light (excimer laser, KrF: wavelength 248) was formed on the core layer 3 of the optical waveguide.
nm), a light-induced change in the refractive index was formed in the core film of the waveguide, and the refractive index of the core layer was measured.
The refractive index change was 1.4698. However, the change in the refractive index was larger than that of the conventional flame deposition method, but was smaller than that of Reference Examples 1 to 4.

Reference Example 6 In this reference example , a quartz film was formed by using a light CV
It was carried out by method D. Even in the photo CVD method, four source containers are provided, and four types of CVD source vapors can be simultaneously supplied onto the substrate. Each raw material is filled in a temperature-controllable closed container, and the flow rate of each vapor can be controlled independently by a flow controller that can accurately control the flow rate of the raw material vapor, and four types of alkoxide raw materials can react at an arbitrary ratio. It is possible to transport onto the substrate in the tube.

An oxygen gas was introduced into the reaction tube, and ultraviolet rays were applied to the vicinity of the substrate in the reaction tube in order to promote the decomposition of the raw material and the synthesis of SiO ₂ . The temperature of the substrate is set to 850 ° C. to promote the decomposition and reaction of the raw materials, and a film is formed on the substrate placed in the reaction tube. As the substrate, a silicon substrate having a diameter of 3 inches was used. The deposition rate was 4 μm / hour.

The refractive index of each quartz film produced in the same manner as in Reference Example 4 was 1.4595 for the cladding layer and 1.4725 for the Ge-doped core film.

As in Reference Example 4, strong ultraviolet light (excimer laser, KrF: wavelength 248) was formed on the core layer 3 of the optical waveguide.
nm), a refractive index change induced by light was formed on the core film of the waveguide, and the refractive index of the core layer was measured.
The refractive index changed to 1.4741.

In the reference examples 1 to 6, the number of raw material containers is four, but this number is not particularly limited and depends on the type of element to be added.

Reference Example 7 This reference example, the ozone oxidized CVD method of Reference Example 1, 1 Torr vacuum degree (Reference Example 1 50 Torr) in which a film is formed on. As a result, the deposition rate is 1
From 0 μm / hour to 5 μm / hour, the refractive index of the core film slightly changed to 1.4680 (1.4682 in Reference Example 1).

[0149] The core layer of the waveguide of the present embodiment was irradiated with excimer laser irradiation conditions of Reference Example 1, the refractive index change, the larger value as compared with 0.0018 0.0025 Reference Example 1 Indicated. This large change in the refractive index is considered to be because the concentration of oxygen defects in the core film was increased by increasing the degree of vacuum, and the change in the refractive index caused by the oxygen defects was increased.

Reference Example 8 In the present reference example, after forming a film by the ozone oxidation type CVD method (the degree of vacuum is 50 Torr) of the reference example 1, the substrate temperature is 500 ° C., the treatment is performed at a degree of vacuum of 1 mTorr for 2 hours, and then the temperature is lowered to room temperature. . As a result, the refractive index of the core film was 1.4679, which was slightly lower than that of Reference Example 1.

[0151] The core layer of the waveguide of the present embodiment was irradiated with an excimer laser under the same irradiation conditions as in Reference Example 1, the refractive index change, showed a large value as 0.0026. This large change in the refractive index causes the vacuum heat treatment after the film formation to increase the oxygen defect concentration in the core film, as in Reference Example 6.
As a result, it is considered that the change in the refractive index caused by the oxygen deficiency increased.

[0152]Embodiment 1 FIG.  In this embodiment, even with weak ultraviolet light irradiation, a uniform change in the refractive index is obtained.
That can produce a grating with a plasma CV
The formation of the quartz film by the method D will be described below.

The raw materials used were TEOS, TEB, TEB
G, TEP. Considering the vapor pressure of each raw material, TEOS is 75 ° C, TEB is 45 ° C, and TEG is 6
5 ° C, TEP was heated to 60 ° C.

The flow rates of the raw material vapor were 5 cc / min for TEOS and 1 cc for TEB for forming the upper and lower cladding layers.
/ Min, TEO for forming the high refractive index layer of the core film.
S is 5 cc / min, TEB is 0.3 cc / min, and TEG
From 0.5 to 0.3 cc / min and TEP from 0.2 to 0.3 cc / min.
It was changed to 6 cc / min.

When forming the high refractive index layer of the core film by the plasma CVD method, the amount of Ge added is initially 0.5 cc.
/ Min (at a thickness of 0 μm), lastly 0.3 cc / min (at a thickness of 8 μm), the amount of P added was 0.2 cc / min (at a thickness of 0 μm) at the beginning, and 0.6 cc / min at the end (at a thickness of 8 μm). ) And in the thickness direction of the core film.

The refractive index of each manufactured quartz film was 1.4590 for the cladding layer and 1.46 for the core film doped with Ge.
90, and the refractive index difference was about 0.7%.

A weak ultraviolet light (excimer laser, KrF: wavelength 248 nm, energy density: 2 mJ) was applied to an optical waveguide in which a core layer having a predetermined width was formed on the core film of the waveguide of this embodiment.
/ cm ² / pulse) to form a refractive index change induced by light on the core layer, and the refractive indices of the surface side and the substrate side of the core layer were measured.
The refractive index was almost the same as 702.

The photo-induced refractive index change mainly depends on the concentrations of Ge and oxygen vacancies. Therefore, the intensity of the ultraviolet light to be irradiated is weak, and the light of about several mJ / cm ² / pulse cannot sufficiently change the refractive index of the core layer. For this reason, there is a case where a difference occurs between the refractive index change near the surface of the core layer and the refractive index change on the substrate surface side.

When Ge and P are added to the core film, the refractive index increases due to both elements, but the increase rate is greater when Ge is added than when P is added. According to the present embodiment, by changing the addition amounts of Ge and P in the thickness direction of the core film, it is possible to produce a waveguide type grating having a uniform refractive index change even with weak ultraviolet light irradiation.

[0160]

[0161]

[0162] In addition, Reference Examples 1 to 8, Oite in Example 1,
The ultraviolet light to be irradiated is KrF of excimer laser, 248n
m, but a lower wavelength excimer laser Ar
The same effect can be obtained with F, 193 nm or a long wavelength argon laser of 488 nm.

It is also possible to use a mass flow controller capable of accurately controlling the flow rate of the raw material vapor by placing the raw material in a temperature-controlled closed container without using a carrier gas.

Embodiment 2 FIG. In this embodiment, an example in which a grating is manufactured by strongly pressing a phase mask against a waveguide will be described. When irradiating light to a waveguide through a phase mask, the grating pattern is normally 0th-order, ±
A diffraction pattern is formed by interference of the first order, ± 2 order, ± n order, and the like. The diffraction angles of these lights are respectively 0θ
Degrees, θ degrees, 2θ degrees, and nθ degrees, and if the distance between the phase mask and the waveguide is several millimeters, higher-order light of the third order or higher does not matter.

However, when the distance is set to about several 100 μm, the 0th order, ± 1st order, and ± 2nd order light participate in the diffraction pattern. Usually, in order to obtain a desired periodic pattern, +1 order and −1 order interference and 0 order and ± 1 order interference are often used. In the +1 order and −1 order interference, a diffraction pattern having the same period as the period of the phase mask is formed in the waveguide, and the 0 order and ±
In the first-order interference, a diffraction pattern having a half period of the phase mask is formed on the waveguide. 0 order, ± 1 order, ± 2
The intensity of the next diffracted light can be preset according to the shape of the phase mask. For example, if the phase difference of the phase mask is π, the zero-order light can be reduced to several percent or less. If the shape of the diffraction grating of the phase mask is changed from a rectangular shape to a sin curve, the ± 2 order can be suppressed.

In the present embodiment, a grating pattern having the same period as that of the phase mask is formed in the waveguide using a phase mask utilizing the +1 order and −1 order interference. The phase mask had a period of 1068 nm, and the relief used was a rectangular mask. The irradiation light was 248 nm light from an excimer laser, and the irradiation conditions were the same as in Example 1. At that time, the distance between the phase mask and the waveguide was 1 cm,
It was manufactured by changing to 5 mm, 1 mm, and 0 mm.

Table 1 shows the result of normalizing the intensity of the primary light of the reflected light of the optical filter manufactured by changing the interval between the phase mask and the waveguide by the peak intensity. From the table, when the interval is 5 mm or more, since there is no higher-order diffracted light at the time of light irradiation, a grating having a simple interval is formed in the waveguide, and as a result, in the manufactured optical filter, the primary reflected light intensity remains largely. I will. When the interval is smaller than 5 mm, particularly, the interval is 1 m
At m or less, the second-order diffracted light also exists in the waveguide, and the grating period is not simple, but becomes a complicated grating including a plurality of periods having different intensities. The reflected light intensity decreases to 7% or less.

[0168]

[Table 1]

[0169]Reference Example 9.  FIG.Reference Example 1Applied linear waveguideOptical filter
so,Two 3 dB couplers 18, 18 in a 6 μm wide waveguide
A 5 mm long waveguide grating 19 was formed between them.
MachZenderIt is a type optical filter.

The wavelength characteristics of the produced Mach-Zehnder optical filter were measured using a broadband light source of an erbium-doped fiber amplifier. As shown in FIG. 6, when a wavelength-multiplexed optical signal is input from the port 20, an optical signal having a wavelength not reflected by the waveguide grating 19 is output from the port 23 and has a wavelength reflected by the waveguide grating 19. An optical signal is output from the port 21.

When an optical signal having a wavelength reflected by the waveguide type grating 19 is input from the port 22, it is multiplexed from the port 23 with the optical signal of the port 20 and output.
Such an optical filter is an optical signal multiplexer / demultiplexer or ADM (Add Drop Multipump) in wavelength division multiplexing communication.
lexer).

FIG. 7 is a diagram showing the multiplexing / demultiplexing characteristics of the Mach-Zehnder type optical filter manufactured as described above . In the figure,
The horizontal axis is the wavelength (nm), the vertical axis is the light intensity (dB), and the transmission characteristic is that the center wavelength is 1567 nm and the band is 1.8 n.
m, the transmission loss was 25 dB, and the reflection characteristics were a central wavelength of 1567 nm, a band of 2 nm, and a reflectivity of 25 dB.

[0173]Reference example 10.  FIG.Is the otherOptical filter, width 10mm, length 30mm
Of different grating pitches on a silicon substrate
Waveguide type grating 19a to eighth waveguide type gray
From the first optical filter 24a having the
An integrated optical filter incorporating the optical filter 24h.
You.

Each of the optical filters 24a to 24h had a waveguide width of 6 μm, a waveguide interval of 250 μm, and a difference in refractive index between the core layer and the cladding layer of 0.7%.

[0175] Figure 9 is a process diagram showing the manufacturing process of the integrated optical filter. As shown in FIG. 9, Reference Example 1
8 optical filter waveguides 2
9 (process (a)), the first optical filter 24a
A window of the metal mask 30 having a window is placed on the linear portion (step (b)), and light is irradiated to form a diffraction pattern according to the pitch of the phase mask on the linear portion by the phase mask.
Is manufactured. The metal mask 30 is sequentially placed so as to have a window in the linear portion of the second to eighth optical filters, and is irradiated with light to form a diffraction pattern corresponding to the pitch of the phase mask by the phase mask.
The second waveguide type grating 19b to the eighth waveguide type grating 19h are manufactured, and each of the optical filters 24a to 24h is manufactured.
24h is connected to a 16-core ribbon fiber.

Table 2 shows the reflection center band and the reflection wavelength bandwidth of these individual optical filters.

[0177]

[Table 2]

A narrow-band DFB laser is prepared according to the center wavelength of the optical filter shown in Table 2 and wavelength-division multiplexed.
Then, as shown in FIG. 8, when wavelength-multiplexed light is incident from 25a, the first optical filter 24a causes the center wavelength 1
Reflected in the band of 510.3 nm and 1.5 nm, the terminal 2
6a output a laser beam corresponding to this wavelength. Light of other wavelengths was output from 28a. Next, when the terminal 28a and the terminal 27b are connected, the center wavelength 152
The light is reflected in the band of 0.1 nm and 1.6 nm,
Output a laser beam corresponding to this wavelength. The other wavelength light was output from the terminal 26b. Similarly,
When the terminals were connected and eight optical filters were connected in tandem, wavelength branching was performed according to the wavelength characteristics of each optical filter.

Similarly, the center wavelength 151 is connected to the terminal 27a.
When a DFB laser beam of 0.3 nm and a band of 1.0 nm was input, it was multiplexed from the terminal 28a and output. From this, it was confirmed that eight wavelength multiplexed lights were dropped and inserted. In addition, this ginseng
The considered example, the wavelength lambda ₁ that has been inserted with the wavelength lambda ₁ that has branched from the optical filter is the same, the same effect is obtained even by inserting a different wavelength.

[0180] In this reference example, it was connected by a fiber, a similar effect can be interconnected using the waveguide. in this case,
The loss at the connection portion can be reduced as compared with the connection of the fiber.
However, since the curvature of the curve of the connecting waveguide cannot be reduced, the dimensions are equal to or slightly larger than those of the fiber connection.

Reference Example 11 FIG. 10 shows another optical filter having a width of 10 mm and a length of 30 m.
This is an integrated optical filter in which a first optical filter 24a and a second optical filter 4b having curved waveguides having different curvatures are formed on an m silicon substrate. Each optical filter 24
a and 24b have a waveguide width of 6 μm and a waveguide interval of 250 μm.
μm, and the refractive index difference between the core layer and the cladding layer was 0.7%. Waveguide grating 1 of first optical filter 24a
9a was formed in a straight waveguide (θ = 0 °, θ: inclination angle of the grating from a direction perpendicular to the waveguide). The waveguide-type grating 19b of the second optical filter 24b has θ
Was formed in a curved waveguide having a curvature determined to be 5 degrees.

FIG. 11 is a principle diagram for explaining the relationship between the angle θ of the waveguide and the grating pitch x _{1 on} the curve.
From the figure, the relationship of the angle θ and the grating pitch x ₁ of the waveguide is expressed by the following equation (3). a ₁ represents the original grating pitch.

The grating pitch x ₁ = a ₁ / cos (θ) on the curve (3)

The original grating pitch a _{1 is set} to 107
Assuming 8 nm, grating period x tilted 5 degrees
₁ becomes 1082.1 nm from the equation (3). Thus, the two optical filters 24a and 24b having different curvatures
Can fabricate a grating using phase masks of the same pitch to produce a device that can add and drop two types of wavelengths, such as 1078 nm and 1082.1 nm.

Embodiment 3 FIG. This embodiment is an embodiment of a wavelength division multiplexing optical transmission system in which an optical branch circuit for branching a wavelength division multiplexed light coming from one direction into two directions is realized by using a wavelength selective coupler and a directional coupler. It is. Wavelength-selective coupler and directional coupler are reference examples
1 to 11 were manufactured using the same technology as in Example 1 .

FIG. 12 is a block diagram showing the present embodiment.
In the figure, 31 is an optical branching circuit, 24a, 24b, 24
c is an optical filter, and optical filters 24a, 24b, 24c
Is a 3 dB coupler 32 as a directional coupler, and the waveguide type grating 19 of the present invention as a wavelength selective reflector.
a, 19b, 19c and a refractive index adjusting unit 33. 3
4a and 34b are terminals at the previous stage of the 3 dB coupler 32;
a and 35b are terminals at the subsequent stage of the 3dB coupler 32. 3
3dB of one of the two optical filters 24a, 24b, 24c
The coupler 32 is connected to the 3 dB coupler 32 of the adjacent optical filter.

Terminal 35a of optical filter 24a, terminal 35b of optical filter 24b, terminal 35a of optical filter 24b
And the terminal 35b of the optical filter 24c, and the terminal 35a of the optical filter 24c and the terminal 35b of the optical filter 24a are connected to each other. Also, three optical filters 24a,
Terminal 34 at the previous stage of 3 dB coupler 32 of 24b, 24c
a, 34b are input / output fibers 36a, 36b, 37a, 37b, 38 to / from the optical branch circuit 31, as shown in FIG.
a, 38b. Optical filters 24a, 24b,
24c waveguide gratings 19a, 19b, 19
Bragg wavelength of c are all λ _1.

The wavelength input from the input / output fiber 36a
λ ₁ enters from the terminal 34a of the optical filter 24a, is reflected by the waveguide grating 19a, and exits through the terminal 34b to the input / output fiber 38b. That is, the route setting from the input / output fiber 36a to the input / output fiber 38b is automatically determined by the wavelength λ. Wavelength other than the wavelength lambda ₁ that has entered from the terminal 34a of the optical filter 24a is outputted to the terminal 35b is transmitted through the waveguide grating 19a. Next, the light enters the terminal 35a of the optical filter 24c, passes through the waveguide grating 19c, and is output to the input / output fiber 37b via the terminal 34b. That is, the wavelengths other than the wavelength λ ₁
To 37b.

[0189] Similarly, the wavelength lambda ₁ that has entered from the input and output fiber 37a is reflected by the optical filter 24b outputs the output fiber 36b, a wavelength other than the wavelength lambda ₁ that has entered from the input and output fiber 37a is input fiber 38b Output to Further, the wavelength λ incident from the input / output fiber 38a
Reference numeral ₁ denotes an input / output fiber 37b reflected by the optical filter 24c.
And the wavelength λ ₁ incident from the input / output fiber 38a.
Other wavelengths are output to the input / output fiber 36b. Of the wavelength lambda ₁ that has entered from the input and output fibers 36a, minor component passing through without being completely reflected by the waveguide type grating 19a are all directed to the optical filter 24c. Therefore,
Most of the light is reflected toward the optical filter 24b. Further, most of the light is reflected and returns to the optical filter 24a. In fact, the loss does not result in crosstalk due to the waveguide loss.

[0190] On the other hand, of the wavelength other than the wavelength lambda ₁ that has entered from the input and output fibers 36a, although components exiting the terminal 35a is slightly, this is the optical filter 24b terminal 34b
Head to. Since the direction is opposite to the traveling direction of the input / output fiber 37a, crosstalk of other signals does not occur.

As described above, the two 3 dB couplers 32 and the two waveguide gratings 19a, 19b, 19c
By connecting three optical filters 24a, 24b and 24c in a star configuration, a highly reliable wavelength multiplexing optical transmission system with small insertion loss and small crosstalk can be constructed.

In this embodiment, the wavelength λ ₁ branched from the optical filter and the inserted wavelength λ ₁ are the same, but the same effect can be obtained by inserting another wavelength.

Embodiment 4 FIG. In the present embodiment, when the branch wavelength and the insertion wavelength are the same, the occurrence of crosstalk is reduced by connecting two waveguide gratings of the present invention in cascade via a 3 dB coupler.

FIG. 13 is a block diagram of the present embodiment. In the figure, 39 is a transmitter, 40 is an optical receiver, 32a, 32
b, 32c, 32d are 3dB couplers, 19a, 19b in the waveguide type grating having the same Bragg wavelength lambda _2, for example, those described in Reference Example 1. 33a1,
33a2, 33b1, and 33b2 are refractive index adjusting units.
41 is an optical transmission line input terminal, 42 is a branch terminal, 43a, 4
3b a subsequent stage of the terminals of the 3dB coupler 32 b, 44a, 44
b denotes a terminal at the previous stage of the 3 dB coupler 32c, 45 denotes an optical transmission line output terminal, and 46 denotes an insertion terminal.

WDM incident from optical transmission line input terminal 41
Of the light, only lambda ₂ is reflected by a waveguide grating 19a, it can be taken out from the branch terminal 42 of the 3dB coupler 32a. At this time, the refractive index adjusting unit 33a1 is provided so that the optical path length from the 3dB coupler 32a to the waveguide type grating 19a is the same. light of wavelengths other than lambda ₂ is transmitted through the waveguide grating 19a,
Although the light reaches the 3 dB coupler 32b, a refractive index adjuster 32a2 is provided so that the phase difference here is reversed. As a result, light of wavelengths other than lambda ₂ are all output from the terminal 43b.

The outputted light having a wavelength other than λ _{2 is} supplied to the terminal 44.
b branches into two through a 3 dB coupler 32c. The 3 dB coupler 3 is provided by the refractive index adjusters 33b1 and 33b2.
Since the optical path lengths of 2c and 32d are adjusted to be equal, all the light passes through the optical transmission line output terminal 45. On the other hand, the insertion light is output to the terminal 45 by transmitting from the optical transmitter 39 connected to the insertion terminal 46. The operation is the same as that when λ ₂ input from the optical transmission line input terminal 41 is output to the branch terminal 42. Here, since the reflectivity of the waveguide grating 19b is not 100%, the transmitted slight light reaches the 3dB coupler 32d, but most of the light is output from the terminal 44a.

As described above, the two waveguide gratings 19a, 19b are connected to the 3 dB couplers 32a, 32b, 3b.
By cascade-connecting via 2c and 32d to form an optical add / drop circuit, crosstalk between the inserted light and the branched light can be reduced.

In this embodiment, the wavelength λ ₁ branched from the optical filter and the inserted wavelength λ ₁ are the same, but the same effect can be obtained by inserting another wavelength.

[0199]

Effects of the Invention] According to the engaging Ru invention in claims 1 and 2, C
Since the optical waveguide is formed by the VD method, a transparent waveguide can be obtained even at a relatively low substrate temperature of 900 ° C. or less, and the transparentization treatment at a high temperature is not required. And the change in refractive index during light irradiation is large .
And a grating having a uniform refractive index change is obtained.
You.

[0200]

[0201]

[0202]

[0203]

According to the third aspect of the present invention, a high-performance optical filter can be obtained by applying the waveguide grating of the present invention.

[0205]

[0206]

[0207]

[0208]

[0209]

[0210]

According to the fourth and fifth aspects of the present invention, a high-performance wavelength multiplexing optical transmission system can be obtained by applying the waveguide grating of the present invention. And a wavelength division multiplexing optical transmission system can be obtained.

[0212]

[Brief description of the drawings]

FIG. 1 is a sectional view showing a waveguide grating according to an embodiment of the present invention.

FIG. 2 is a configuration diagram of a film forming apparatus for manufacturing a waveguide grating according to one embodiment of the present invention.

FIG. 3 is a process chart for manufacturing an optical waveguide for forming a waveguide grating according to one embodiment of the present invention.

FIG. 4 is a diagram illustrating wavelength characteristics of a waveguide grating according to a reference example of the present invention.

FIG. 5 is a diagram showing a relationship between a photo-induced refractive index change in an optical waveguide and excimer laser irradiation.

FIG. 6 is a configuration diagram showing a Mach- Zehnder optical filter according to a reference example of the present invention.

FIG. 7 is a diagram illustrating a wavelength characteristic of a Mach- Zehnder optical filter according to a reference example of the present invention.

FIG. 8 is a configuration diagram showing an integrated optical filter according to a reference example of the present invention.

FIG. 9 is a process chart for manufacturing an integrated optical filter according to a reference example of the present invention.

FIG. 10 is a configuration diagram showing an integrated optical filter according to a reference example of the present invention.

FIG. 11 is a diagram illustrating the principle of an integrated optical filter according to a reference example of the present invention.

FIG. 12 is an optical branch circuit of a wavelength division multiplexing optical transmission system according to an embodiment of the present invention.

FIG. 13 is an optical branch circuit of a wavelength division multiplexing optical transmission system according to another embodiment of the present invention.

FIG. 14 is a configuration diagram showing a conventional fiber type narrow band transmission filter.

FIG. 15 is a configuration diagram showing a conventional waveguide-type narrow band transmission filter.

FIG. 16 is a schematic view showing a conventional quartz film forming apparatus using a flame deposition method.

FIG. 17 is a schematic view showing a method for producing a grating by optically induced refractive index modulation.

FIG. 18 is a diagram illustrating wavelength characteristics of a conventional waveguide grating.

FIG. 19 is an optical branch circuit diagram in a conventional wavelength division multiplexing optical transmission system.

FIG. 20 is a configuration diagram showing a conventional dielectric multilayer optical filter.

FIG. 21 is a configuration diagram showing an optical filter in a conventional ring network.

[Explanation of symbols]

1 substrate, 2 the lower clad layer, 3 the core layer, 4 the upper cladding layer, 5 a grating, 6,19,19A～19
h, 50 waveguide grating, 7 flow controller,
8 raw material container, 9 reaction tube, 10 oxygen gas inlet, 11
Ozonizer, 12 carrier gas inlet, 13 outlet, 14 lower cladding layer , 15 core film, 16 waveguide pattern, 17 upper cladding layer , 18, 49, 49a,
49b3dB coupler, 20, 21, 22, 23, 47,
47a-47d, 48 ports, 24a-24h, 65
a-65c, 66a-66c Optical filter, 25a-2
5h, 26a-26h, 27a-27h, 28a-28
h, 68, 70, 73 terminals, 29, 51, 60 optical waveguide, 30 metal mask, 31, 64 optical branch circuit, 32
3 dB coupler as directional coupler, 33 refractive index adjustment unit, 34a, 34b, 44a, 44b
35a, 35b, 43a, 43b Subsequent terminals, 36
a, 36b, 37a, 37b, 38a, 38b Input / output fiber, 39 optical transmitter, 40 optical receiver, 41 optical transmission line input terminal, 42 branch terminal, 45 optical transmission line output terminal, 46 insertion terminal, 52 to 55 Liquid raw material, 56
Hydrogen gas, 57 burner, 58 turntable, 59
Phase mask, 60a, 60c Cladding layer, 60b
Waveguide core (core layer), 61 excimer laser, 62 relief diffraction grating, 63 grating, 67a-6
7c lens, 71b, 203b Optical transmitter, 204b
Optical receiver, 72a, 220a, 220b Fiber grating, 221a, 221b Refractive index adjuster, 22
2a, 222b 2 × 2 3 dB coupler, 223a, 2
23b Terminal in front of 3 dB coupler 222a, 223
c, 223d Terminal at the subsequent stage of 3dB coupler 222a, 2
24a, 224b Terminal at the preceding stage of the 3dB coupler 222b, 224c, 224d Terminal at the subsequent stage of the 3dB coupler 222b .

──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Hideko Uchikawa 2-3-2 Marunouchi, Chiyoda-ku, Tokyo Mitsubishi Electric Corporation (56) References JP-A-7-281016 (JP, A) JP-A Heihei 5-241035 (JP, A) JP-A-7-77620 (JP, A) JP-A-8-86929 (JP, A) JP-A 8-220317 (JP, A) JP-A-1-202702 (JP, A) A) JP-A-63-303305 (JP, A) JP-A-5-273426 (JP, A) WO 96/9563 (WO, A1) WO 94/784 (WO, A1) Svalgard et. a l. , Electronics Letters, August 18, 1994, Vol. 17, pp. 1401-1403 G.C. D. Maxwell et. a l. , Electronics Letters, March 4, 1993, Vol. 29 No. 5, pp. 425-426 p. J. Lemaire et. a l. , Electronics Letters, June 24, 1993, Vol. 13, pp. 1191-1194 M.P. J. Chawki et. a l. , Electronics Letters, March 16, 1995, Vol. 31 No. 6, pp. 476-477 Maki Inai et. al. , 1994 IEICE Autumn Conference, Society 1 Preliminary Conference Papers, Electronics 1, September 5, 1994, p. 209 Yoshishinki-shi et. al. Proceedings of the 1996 IEICE General Conference, Communications 2, March 11, 1996, pp. 743-744 B.A. Malo et. al. , Eltronics, Letters, May 25, 1995, Vol. 31 No. 11, p. 879-880 R.C. M. Atkins et. a l. , Electronics, Letters, July 8, 1997, Vo. 29 No. 14, pp. 1234-1235 Poulsen, C.I. V et. a l. , Conference on Lasers and Electro-Optics Europe 1994, p. 45 (58) Fields surveyed (Int.Cl. ⁷ , DB name) G02B 6/12-6/14 G02B 6/10 G02B 5/18

Claims (5)

(57) [Claims] 1. A substrate, on which a main component is SiO ₂
A core layer formed by depositing quartz containing at least one or more doping elements of Ge, Ti, B, P, and Sn by a CVD (chemical vapor deposition) method and forming a predetermined waveguide width. Irradiating light to an optical waveguide having a cladding layer formed by depositing quartz whose main component is SiO ₂ by CVD and surrounding the core layer to change the refractive index of the core layer .
Oscillation of waveguide type grating with rating
The doping element contained in the core layer,
In the thickness direction of the layer, the incident side of the irradiation light is smaller than the output side.
A waveguide-type grating characterized by being changed in a manner as described above . 2. A method in which an organometallic compound of Si is used as a raw material on a substrate.
Or as the main raw material, ozone gas,
At least one of oxygen gas and nitrous oxide gas (N ₂ O)
The above gas is supplied, and the above
CVD (chemical vapor deposition) to deposit oxide films of elements
Quartz containing SiO ₂ as a component or main component by the film) method
(A) for forming a cladding layer made of Ge, T
at least one or more organometallic compounds of i, B, P, Sn
The above-mentioned C
By the VD method, a core made of quartz containing SiO ₂ as a main component is used.
Step (b) of forming a film,
Step (c) of forming a core layer by patterning to a path width
And an organometallic compound of Si as a raw material or a main raw material,
In order to surround the core layer, S is formed by the CVD method.
Cladding made of quartz containing iO ₂ as a component or main component
Forming a layer to form an optical waveguide (d);
A layer is irradiated with light through a phase mask to change the refractive index
(E) forming a grating that has been subjected to
In the method of manufacturing a waveguide grating, the above-described steps
In (b), the above-mentioned dope material is added in the thickness direction of the above-mentioned core film.
So that the incidence side of the irradiation light is smaller than the emission side.
Waveguide grating characterized by forming a film
Manufacturing method. Wherein each optical signal having a predetermined wavelength lambda ₁ to [lambda] _n
N sets of gratings having a reflection center wavelength
(N is 1 or more) (1)-(n) th waveguide type grating
And the (1)-(n) th waveguide type grating
Input and output the optical signal provided for each
4 n _1, n _2, n ₃ and n ₄ and a terminal, the n ₁ terminal
An optical signal of wavelength λ _n is input and output to n ₂ terminal,
Outputs optical signals other than λ _n to n ₄ terminal and inputs from n ₃ terminal
Wavelength λ _n or λ _n ′ (where λ _n ′ is the (n) th waveguide
The optical signal n ₄ end in the reflection wavelength band) of the road-type grating
In the optical filter for outputting to the
(N) The waveguide type grating according to claim 1,
Optical filter characterized by being a waveguide grating
Ta. 4. An optical signal having a predetermined wavelength λ ₁ has a reflection center wavelength.
Sets (n is 3 or more) forming a grating having
(1)-(n) th waveguide type grating, and
Each of the (1) to (n) th waveguide gratings
A directional coupler connected to the front and rear portions;
(1) to the (n) th waveguide type grating
Input / output optical signals provided for each connected directional coupler
The two (n) ₁ and (n) ₂ terminals to be
2) (n-2) ₁ terminal of waveguide type grating
(N-1) _Two ends of (n-1) waveguide grating
(N-1) of the (n-1) th waveguide grating
₁ terminal and n ₂ terminal of the n-th waveguide grating , and
n ₁ terminal of the n-waveguide grating and the (n-2) guide
(N-2) ₂ terminals of waveguide grating
WDM optical transmission system formed to be connected
Wherein the waveguide grating is of the type described in claim 1.
Wavelength multiplexing characterized by being a waveguide grating
Heavy light transmission system. 5. An optical signal having a predetermined wavelength λ ₁ has a reflection center wavelength.
Sets (n is 1 or more) forming a grating having
(1)-(n) th waveguide type grating, and
Each of the (1) to (n) th waveguide gratings
On the output side and the input side, the (1)-(n) th waveguide type
Forming a directional coupler for connecting the gratings,
Consisting of a constant wavelength lambda ₁ of the optical signal and the wavelength lambda ₁ except the optical signal
An optical transmitter for outputting an optical wavelength division multiplexed signal is connected to the (n) th optical transmitter.
Directional connection connected to the output side of the waveguide grating
Connect to engager, and inputs the optical signal of the predetermined wavelength lambda ₁
Write the optical receiver on the (1) waveguide grating
By connecting to a directional coupler connected to the force side.
Input to the (1) waveguide type grating.
Above the predetermined wavelength lambda ₁ of the optical signal of the optical wavelength multiplex signal
Input to the optical receiver, the (n) th waveguide type grating
Light wavelength multiplex signal other than the wavelength λ1 outputted from the ring
And the optical wavelength multiplexed signal output from the optical transmitter.
In a wavelength division multiplexing optical transmission system for transmitting
The waveguide type gray according to claim 1, wherein the waveguide type grating is a waveguide type gray.
Wavelength division multiplexing optical transmission system characterized by
M