JPH0335203A - Glass waveguide added with rare earth element and production thereof and glass waveguide laser and device using this waveguide - Google Patents

Abstract

PURPOSE:To attain a smaller size, smaller loss and multipler functions by constituting a core waveguide of a hybrid film composed of fine particles of SiO2 and fine particles contg. rare earth elements. CONSTITUTION:A low-refractive index glass film 2 is formed on a substrate 1 consisting of LiNbO3, etc., and the core waveguide 3 is formed of the hybrid film consisting of the fine particles of the SiO2 contg. at least one kind of additives for refractive index control, such as B and F, and the fine particles contg. at least one kind of the rare earth elements, such as Er and Nd. The amt. of the rare earth elements to be added can be extremely increased to a range from several thousands ppm to several % and the controllability thereof is good. The smaller size, the smaller loss and the multiplier functions are attained in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a glass waveguide doped with a rare earth element, a method for manufacturing the same, and a glass waveguide laser and device using the same.

[Prior Art] Research into optical fiber amplifiers and lasers in which rare earth elements are added to the core of an optical fiber has been actively conducted, and these have attracted attention as amplifiers and lasers for light wave communications.

Conventionally, as an optical fiber amplifier, as shown in Fig. 8,
A signal light is propagated in an optical fiber doped with a rare earth element, a signal light is propagated in a pumping optical fiber in the propagation direction of the signal light, and an optical fiber coupler is used to convert the pumping light in the propagation direction of the signal light. A method of amplifying the signal and light by forming a population inversion state and separating the pumping light from the output side with an optical fiber coupler is being considered (Kiku, Nakazawa: Oscillation characteristics of optical fiber lasers and Its application to optical communication, Laser Society Research Group, RTM-87
-16, PP, 31-37. January 1988).

[Problems to be Solved by the Invention] Such optical fiber amplifiers and lasers have the following characteristics: (1) The core diameter is as small as about 10 μm, which increases the pumping power density and increases the pumping efficiency; and (2) The ability to increase the interaction length. ■In the case of quartz fiber, it has features such as extremely low loss.

However, when trying to configure a system that includes semiconductor lasers, photodetectors, optical modulation circuits, optical branching, coupling circuits, optical switch circuits, optical multiplexing/demultiplexing circuits, etc., each component is an individual component, making it more compact and less expensive. There was a problem in that it was difficult to convert the losses into losses.

In addition, since the optical axes of individual components must be adjusted and arranged individually, there are problems such as an enormous amount of adjustment time, high costs, and problems with reliability.

The present invention has been made to solve the problems of the prior art described above, and includes a glass waveguide that can realize miniaturization, low loss, and multifunctionality, a method for manufacturing the same, and a glass waveguide using the same. The purpose is to provide waveguide lasers and devices.

[Means and effects for solving the problems] In order to solve the above problems, the present invention is based on the premise that a Brener structure waveguide structure is used in place of the conventional optical fiber structure.
The waveguide structure is a glass waveguide in which a core waveguide doped with a rare earth element and having a substantially rectangular cross section is formed on a substrate, and these are coated with a material having a refractive index lower than that of the core waveguide. , the core waveguide is made of at least SiO2
By constructing a hybrid film consisting of fine particles and rare earth element-containing fine particles, the amount of rare earth elements added to the core waveguide is dramatically increased, thereby realizing miniaturization, low loss, and multifunctionality. It is.

In addition, as a method for manufacturing such a glass waveguide, a composite film consisting of at least SiO2 fine particles and rare earth element-containing fine particles is formed on a substrate, a metal film and a photoresist film are formed on the film, and photolithography is performed. After patterning, the hybrid film is dry-etched and processed into a substantially rectangular cross-section to form a core waveguide.The metal film and photoresist film are removed, and the surfaces of the core waveguide and substrate are shaped to have the refractive index of the core waveguide. It is coated with a material with a lower refractive index.

In forming the hybrid film in this case, an electron beam evaporation device having at least two evaporation sources is used, and S io 2 fine particles are evaporated from one evaporation source and rare earth element fine particles are evaporated from the other evaporation source almost simultaneously. By depositing the rare earth element in the core waveguide, it is possible to manufacture the core waveguide while arbitrarily adjusting the content of the rare earth element.

Note that the core waveguide may be one in which S I O 2 fine particles and rare earth element-containing fine particles are fused by high-temperature heat treatment, and the rare earth element is diffused substantially uniformly into the core waveguide.

The SiO2 fine particles constituting the core waveguide can contain at least one type of additive for controlling the refractive index. The additives for controlling the refractive index include Ti, Ge,
P, Sn, Zn, B, F, Ajl
.

At least one of Na, Na, etc. can be used.

The rare earth element-containing fine particles are, for example, rare earth element oxide fine particles or rare earth element fluoride fine particles, and the rare earth element is Er.

At least one of Nd, Yb, Ce, Ho, Tm, etc. can be used.

In addition, the dimensions of the core waveguide are: in the case of a single mode waveguide, the thickness and width are from several μm to 10-odd μm, and in the case of a multi-mode waveguide, the thickness and width are from 10-odd μm to 10 μm.
It can be done to a certain extent.

It is also possible to configure a glass waveguide laser by providing laser mirrors on both end faces of at least the core waveguide of the glass waveguide of the present invention, and allowing excitation light to enter from one mirror and output light from the other mirror. . Moreover, optical multiplexer/demultiplexer, optical star coupler,
Optical devices comprising at least one kind of optical passive circuit elements such as optical switches, optical filters, optical modulators, optical deflectors, etc., and in which excitation light is superimposed on signal light from the input side, as well as semiconductor lasers and light emitting diodes. , photodetector, semiconductor device for optical amplifier, semiconductor device for optical modulation, bistable optical device,
It is also possible to apply stress to an optical device or the like in which at least one type of optical gate or the like is coupled to the input or output side of the glass waveguide of the present invention.

[Example] Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 shows a schematic diagram of an embodiment of the rare earth element-doped glass waveguide of the present invention. A low refractive index glass film 2 (refractive index nb) is formed on a substrate 1 made of S i , S I O 2 glass, multicomponent glass, L I N b Os, or the like. This film 2 is made of, for example, pure SiO2 glass, B, P,
The SiO2 glass containing a refractive index controlling additive such as Ti or the above SiO2 glass containing a rare earth element is used. In this example, the core waveguide 3 (refractive index n
v, nv > nb) is B, F, Ti, P, Ge, Ajl
, SiO2 fine particles containing at least one kind of refractive index controlling additive such as Sn, Er, Nd, Yb, Ce, Ho, T
It consists of a hybrid film made of fine particles containing at least one kind of rare earth element such as m. In the case of a unit mode waveguide, this core waveguide 3 has a width and thickness of several μm to several tens of μm.
m1 refractive index difference v is selected. For multimode waveguides, the width and thickness are 10
A few μm to 100 μm 1 refractive index difference is 0. Selected as a few percent to 2 percent.

The amount of rare earth element added is selected from a range of several thousand ppm to several percent.

The cladding film 4 (refractive index nc) is made of the same material as the low refractive index glass film 2. However, the refractive index nc does not necessarily have to be equal to nb.

The inventors constructed the core waveguide 3 in a rare earth element glass waveguide with a composite film composed of two types of fine particles, the main component of which is SiO2, which does not contain a rare earth element and the fine particles which contain a rare earth element. It has been found that it is possible to add a very large amount of , and that the controllability is also good. Therefore, by using this glass waveguide, it is possible to efficiently oscillate a laser with a short length g, and it is also possible to realize various optical devices with an amplification function and a high gain.

FIG. 2 shows another embodiment of the rare earth element-doped glass waveguide of the present invention, which has a thinner cladding film 4 than the buried type glass waveguide shown in FIG. It is.

FIG. 3 shows an example of a glass waveguide laser constructed using the rare earth element-doped glass waveguide of the present invention, in which (a) is a left side view, and (b) is an A in (a). -A' cross-sectional view is shown. An optical resonator was constructed by providing laser mirrors 5 and 6 on both end faces of a core waveguide 3 constructed of a composite film of two fine particles. Excitation light 7 is made to enter from the input mirror side, and continuously oscillated output light 8 is taken out from the output mirror 6. The excitation light is A'ion laser light (wavelength 514.5 nm).

Dye laser light (wavelength: 650 nm), semiconductor laser light (wavelength: 830 nm, 1.48 μm), etc. are used. For example, when the core waveguide 3 is doped with Nd, using an excitation light Ar ion laser beam, and using a manual mirror 5 with a reflectance of 99% and an output mirror 6 with a reflectance of 98%, approximately 1.0
Continuous oscillation is possible over a wavelength of 6 μm to 1.1 μm.

FIG. 4 shows an embodiment of a star coupler with optical amplification function constructed using the rare earth element glass waveguide of the present invention. This is constructed using Y branch waveguides 11-1 to 11-4, and the signal light 9 incident from the input waveguide 12-1 is connected to the excitation light 7 incident from the other input waveguide 12-2. Propagates while being amplified and passes through the output waveguide 13-
Output light 10-1 of signal light amplified to 1 to 13-4 respectively
~10-4 is output. In addition to the four branches of this embodiment, it is also possible to have multiple ports such as eight branches, 166 branches, and 322 branches.

FIG. 5 shows an embodiment of a duplexer with an optical amplifier function constructed using the glass waveguide of the present invention. That is, the wavelength λ1. which is incident on the input waveguide 12-1. λ2. λ3
..., λn is amplified by the excitation light 7 as it propagates within the core waveguide 3. and the wavelength λ1
The optical signal resonates by the ring resonance 615-1 and is extracted from the output waveguide 16-1. Similarly, optical signals of wavelengths λ2 and λ3 are transmitted to ring resonators 15-2 and 15-
3, and are extracted from output waveguides 16-2 and 16-3, respectively. Wavelength λ4 that did not cause resonance.
λ5. ..., λn are emitted from the output waveguide 16-4. Since the optical demultiplexer with this configuration has an optical amplification function using the core waveguide 3, the ring resonator 15-1.1
It becomes possible to compensate for absorption loss, scattering loss, demultiplexing loss, etc. in 5-2.15-3.

Next, a method for manufacturing the rare earth element-doped glass waveguide of the present invention will be explained.

FIG. 6 shows a process diagram of the method for manufacturing the glass waveguide of the present invention as shown in FIG. First, to give an overview,
In (a), a low refractive index glass film 2 is formed on a substrate 1, and then a hybrid film 30 consisting of at least SiO2 fine particles and rare earth element-containing fine particles is formed thereon.

This hybrid 1130 is the electron beam evaporator 2 shown in FIG.
It is formed using 0. That is, the dome-shaped substrate holder 2 is placed inside the vapor deposition apparatus 20 which is evacuated by the vacuum evacuation system 22.
1 is provided, and the substrate 1 is attached to this holder 21. Next, by introducing oxygen gas 23 into the vapor deposition apparatus 20 and heating the respective evaporation sources 24 and 25, desired materials are evaporated to form a film. Pure Si is used as the evaporation source 24.
O□ or S containing at least one kind of additive for controlling the refractive index
An iO2 tablet is inserted. Further, a tablet containing at least one kind of rare earth element is inserted into the evaporation source 25. Then, while controlling the current flowing through each evaporation source, fine particles mainly containing 5IO2 and fine particles containing rare earth elements are evaporated from the two evaporation sources and simultaneously deposited on the substrate. Note that 26 is a shield plate for shielding the evaporation sources 24 and 25. The substrate l is kept at a low temperature (for example, about 350°C
) Film formation is performed under heating conditions. Next, as shown in FIG. 6(b), a metal film 17 is formed on the composite film 30 using, for example, a sputtering device. At this time, the substrate is heated to a high temperature (for example, 120℃) before the metal film 17 is formed.
The films 2 and 30 may be densified by heating in advance in an oxygen atmosphere at a temperature of 0°C. Next, as shown in (C), a photoresist film 18 is formed on the metal film 17, and the photoresist film 18 is patterned by photolithography. Using this photoresist film as a mask, the metal film 17 is
Then, using the photoresist film and metal film as a mask, the composite film 30 is dry-etched to pattern it into a substantially rectangular cross-section (d). Thereafter, the photoresist film and metal film are removed, and a porous glass film 19 is formed thereon. (e).

Next, the substrate on which the film 19 is formed is sintered at a high temperature of 1000° C. or higher, thereby converting it into a transparent rad film 4, as shown in (5).

Next, a specific example of the case shown in FIG. 6 will be explained.

A quartz substrate with a diameter of 3 inches and a thickness of 1 inch was used as the substrate 1, and a low refractive index glass film made of SiO2 doped with P and B was formed thereon to a thickness of 5 μm.

The amounts of P and B added were controlled so that the refractive index of this film was equal to that of SiO2. Next, a seventh layer is placed on top of the above film.
Hybrid 830 using an electron beam evaporator as shown in the figure.
A thickness of approximately 8 μm was formed. This composite film 30 was formed as follows. That is, the evaporation source 24 contains SiO2 and T.
Mix io2 in a powder state, press it to solidify it, then sinter it into a rod-shaped tablet. Put E203 in the form of a tablet into evaporation source 2, and heat the two evaporation sources at the same time. and evaporate it as fine particles to form a composite film 30.
formed. Thereafter, after heating the substrate at about 1000'C, a WSi film 17 with a thickness of about 1 μm was formed on the composite film 3o. Next, a photoresist was applied to form a film, a photomask was placed on top of the film, and photolithography was performed to form a desired pattern. Next, the WSi film was etched by dry etching using the pattern of the photoresist film as a mask to pattern the WSi film. Next, the composite film 30 was patterned by dry etching using the patterns of the photoresist film and WSi film as masks. After that, after removing the photoresist film and the WSi film, a porous glass film 1 of S H O2 containing B and P was removed.
9 was coated with Vt and sintered at high temperature to obtain a transparent LAD film 4.

In this way, it was confirmed that the amount of E'' added in the core waveguide 3 could be controlled within the range of several thousand ppm to several tens of percent. The refractive index nw of 3 becomes high, making it difficult to construct a single mode waveguide.In that case, the evaporation source 24 is SiO2 containing B or F as an additive to lower the refractive index.
or use E r in the evaporation source 25.
Fs.

It is preferable to use a tablet of a rare earth element containing F, such as NdF3, and to suppress an increase in the refractive index of the core waveguide by adding B or F. However, if the above-mentioned additive is contained only in the core waveguide, the coefficient of thermal expansion there will increase, and the softening temperature will decrease, causing structural mismatch with the cladding film, which may deteriorate the temperature characteristics. be. Therefore, it is desirable to match the thermal expansion coefficient and softening temperature by adding a certain additive to the cladding, for example, an additive that increases the refractive index of SiO2.

The core waveguide is composed of a composite film consisting of at least SIO2 fine particles and rare earth element-containing fine particles, but in the high temperature sintering process shown in FIGS. These microparticles can be fused by treatment. As a result, the rare earth element can be diffused substantially uniformly into the core waveguide. The degree of this diffusion depends on the temperature and time during sintering.

The invention is not limited to the above embodiments. For example, by connecting or integrating FIG. 3 and FIG. 4, it is possible to realize a glass waveguide laser having a configuration in which the oscillation light is divided into four parts. Also, each output waveguide 13-1, 13-2 in FIG.
．． By sintering the circuits shown in FIG. 5 in 13-3 and 13-4, the wavelength-multiplexed signal light (wavelengths λ1, λ2, ..., λn) incident on the human-powered waveguide 12-1 shown in FIG. After dividing the signal into four parts, the optical signal of each wavelength can be separated and extracted using the demultiplexer shown in FIG. Other optical devices such as optical switches, optical filters, optical modulators, and optical deflectors can also be easily realized, and semiconductor lasers,
Light receiving elements, semiconductor elements for optical amplification, semiconductor elements for optical modulation,
It is also possible to mount an optical gate element or the like on the input end or output side of the glass waveguide.

[Effects of the Invention] As described above, the rare earth element-doped glass waveguide of the present invention has the following effects:
A planar waveguide structure is used instead of the optical fiber structure, and the waveguide structure is at least S102.
By adopting a core waveguide composed of a hybrid film made of fine particles and rare earth element-containing fine particles, the amount of rare earth elements added in the core waveguide can be increased with good control, resulting in smaller size, lower loss, and Multifunctionality can be realized.

[Brief explanation of drawings]

FIGS. 1 and 2 are schematic diagrams showing an embodiment of the rare earth element-doped glass waveguide of the present invention, and FIG. 3 is a diagram showing an embodiment of the glass waveguide laser of the present invention. FIG. 4 is a left side view, (b) is a sectional view taken along line AA' in (a), and FIG. (b) is a cross-sectional view taken along the line AA' in (a), FIG. 5 is a cross-sectional view showing an embodiment of the duplexer with optical amplification function of the present invention, and FIG. 6 is a rare-earth element-doped glass guide of the present invention. FIG. 7 is a schematic diagram showing an embodiment of an electron beam evaporation apparatus for forming a hybrid film of the present invention, and FIG. 8 is a schematic diagram of a conventional optical fiber amplifier. be. 1: Substrate, 2: Low refractive index glass film, 3: Core waveguide, 4: Clad film, 5.6 = Laser mirror 11-1 to 11-2: Y branch waveguide, 15-1 to 15-3: Ring resonator, 17: Metal film, 24°: Photoresist film, : Electron beam evaporator, : Evaporation source, : Hybrid film. ＼Heeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeulyssssssssssssssssssssssof ofwofofofofsssssssof of of the 6th st.

Claims (1)

[Scope of Claims] 1. Glass formed by forming a core waveguide doped with a rare earth element and having a substantially rectangular cross section on a substrate, and covering the core waveguide with a material having a refractive index lower than that of the core waveguide. In the waveguide,
A rare earth element-doped glass waveguide, characterized in that the core waveguide is constituted by a composite film consisting of at least SiO_2 fine particles and rare earth element-containing fine particles. 2. The rare earth element-doped glass waveguide according to claim 1, wherein the SiO_2 fine particles constituting the core waveguide contain at least one type of additive for controlling the refractive index. 3. The rare earth element-doped glass waveguide according to claim 2, wherein the refractive index controlling additive is an additive that lowers the refractive index of SiO_2. 4. Claims 1 to 3, wherein the rare earth element-containing fine particles constituting the core waveguide are fine particles of a rare earth element oxide or rare earth element fluoride particles.
The rare earth element-doped glass waveguide described above. 5. Claims 1 to 4, characterized in that the core waveguide is subjected to high-temperature heat treatment to fuse at least the SiO_2 fine particles and the rare earth element-containing fine particles, thereby substantially uniformly diffusing the rare earth element into the core waveguide. Rare earth element doped glass waveguide. 6. Form a hybrid film made of at least SiO_2 fine particles and rare earth element-containing fine particles on the substrate, form a metal film and a photoresist film on the hybrid film, perform photolithography to pattern it, and then dry-etch the hybrid film. The core waveguide is processed into a substantially rectangular cross-section, the metal film and the photoresist film are removed, and the surfaces of the core waveguide and the substrate are coated with a material having a refractive index lower than that of the core waveguide. A method for manufacturing a rare earth element glass waveguide, characterized by: 7. When forming a hybrid film consisting of at least SiO_2 fine particles and rare earth element-containing fine particles on the substrate, using an electron beam evaporation device having at least two evaporation sources,
7. The method of manufacturing a rare earth element-doped glass waveguide according to claim 6, wherein the SiO_2 fine particles are evaporated from one evaporation source and the rare earth element-containing fine particles are evaporated from the other evaporation source substantially simultaneously and deposited on the substrate. 8. Laser mirrors are provided on both end faces of at least the core waveguide of the glass waveguide according to claims 1 to 5, and excitation light is made to enter from one mirror and output light is taken out from the other mirror. glass waveguide laser. 9. A glass waveguide device comprising at least one type of optical passive circuit element using the glass waveguide according to any one of claims 1 to 5, wherein excitation light is superimposed on signal light from the input side.