JPH10300957A - Optical waveguide and optical device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To optically couple a bulk type optical element, an optical fiber, an optical active element such as a semiconductor laser and other waveguide type parts simply with a low loss by specifying a gap width by a specified inequality. SOLUTION: An optical waveguide K2 is provided with one and more gap parts in which an optical element is packaged in the direction crossing a waveguide core 2 between a light entrance end part 2a and a light exit end part 2b. The gap width G of the gap part satisfys G<0.32πnω<2> /λ, where, λ: the wavelength of a waveguide length, n: refractive index of optical element, ω: the mode field radius of waveguide light. Otherwise, at least one of the gap parts satisfys 0.975<(1+((λG)/(2πnω<2> ))<2> )<-1> , where, λ: the wavelength of a waveguide length, G: gap width, n: the refractive index of the gap part, ω: the mode field radius of waveguide light. By arranging plural gap parts, the coupling loss is suitably decreased compared with the case that one gap width equal to the sum of the plural gap widths is provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hybrid mounting of a bulk type optical element used for an optical communication device, an optical recording device, an optical sensor, and the like, and a laser diode, an optical waveguide, an optical fiber, and the like. In particular, the present invention relates to an optical waveguide such as a hybrid mounting waveguide which can be suitably used for a laser module used in an optical communication device, and an optical device using the same.

[0002]

2. Description of the Related Art Hitherto, optical elements such as optical isolators, polarizers, various filters, and attenuators have been known. Recently, in addition to such bulk-type conventional components, there have been many waveguide-type components. Has appeared. However, since the dimensional tolerance for forming the waveguide is strict and the wavelength dependency is large, many of them have not been put to practical use. At present, optical components such as bulk components and some waveguide components, optical fibers, and semiconductor lasers are mixed.

FIG. 5 is a sectional view of a pigtail type bulk component J1 which is a conventional optical device having optical fibers connected to both ends. As shown in FIG. 5, an optical element 52 such as an optical isolator, a filter, an attenuator, and a polarizer is housed inside the package 51. The light emitted from the optical fiber 53a is collimated by the lens 54a, passes through the optical element 52, is collected again by the lens 55b, and is incident on the optical fiber 53b.

Further, as shown in FIG. 6B, the mode field diameter at the end faces of the optical fibers 61a and 61b is enlarged without using a lens as in a bulk part J2 as an optical device similar to that in FIG. It has been proposed to sandwich the component 62. This is because, as shown in FIG. 6 (a), the optical fiber 61 is heated to diffuse the dopant such as Ge doped in the core 61c of the optical fiber 61, so that the diffusion region of the dopant is widened and the refractive index difference is increased. Is reduced. As a result, the mode field diameter is increased while maintaining the single mode. Then, as shown in FIG. 6B, the optical fiber 61 is cut, that is, the optical fiber (core expanded fiber) 61 is formed.
The optical element 62 is inserted after fixing a and 61b to the V-groove 63 and forming an opening 65 in which a part of the V-groove 63 is cut at the center of the core enlarged portion 64.

FIG. 7 shows an example of a conventional semiconductor laser module J3 as an optical device. A semiconductor laser 72, lenses 73a and 73b, an end of an optical fiber 74, and the like are housed in a package 71. Semiconductor laser 7
The light emitted from 2 is collimated by a lens 73a, passes through an optical isolator 77 and other optical elements (not shown), is condensed by a lens 73b, and enters a fiber 74.

[0006] The photodiode 75 is provided with an optical fiber 74 for monitoring the emission intensity of the semiconductor laser 72.
And installed in the opposite position. The whole is housed in a package 71 for shielding from an external environment. In the drawing, reference numeral 76 denotes a rubber boot for protecting the extra length portion 74a of the optical fiber, and reference numeral 78 denotes a substrate on which electrodes are formed, which is fixed on the electronic cooling element 79.

[0007]

However, in the conventional pigtail type component as shown in FIG. 5, the position adjustment between the lens and the optical fiber is very precise and time-consuming. Also,
As the optical path length increases, the difficulty of adjustment increases, so that the thickness of the optical element to be inserted and the number of optical elements are limited. Further, since each optical element is fixed to a package after being attached to a fixing holder, the number of components is very large, which also increases the cost and the complexity of assembly.

[0008] Although the core-expanded fiber fixed in the V-groove in FIG. 6 does not cause axial misalignment between the fibers, it is difficult to uniformly heat the enlarged-core portion, and it is not possible to produce a long region in the traveling direction. Since the enlarged core portion is local and short, it is not suitable for inserting a thick element or a plurality of elements, and if the position where the opening is formed is shifted, the core is deviated from the core enlarged region, so that the opening position tolerance is small. Furthermore, the core-expanded fiber once manufactured is not versatile with respect to design changes such as an increase in the thickness and the number of elements to be inserted. Particularly, there is a problem in mounting a thick element and a plurality of elements.

In a semiconductor laser module, both the optical isolator and the lens are aligned as independent parts after being fixed to a holder for assembly, so that the number of parts becomes very large, and the assembly process is complicated and takes a long time. I was

Therefore, the present invention solves the above-mentioned conventional problems, and makes it possible to easily and bulk-type optical elements, optical fibers, optical active elements such as semiconductor lasers, and other waveguide-type parts with low loss. It is an object of the present invention to provide a waveguide body and an optical device capable of optical coupling.

[0011]

In order to solve the above-mentioned problems, an optical waveguide according to the present invention comprises an optical waveguide between a light input end and a light output end of a waveguide core in a direction crossing the waveguide core. It is characterized by comprising one or more gaps where the element is mounted, wherein the gap width G of the gaps satisfies the following equation. G <0.32πnω ² / λ (where λ: wavelength of guided light, n: refractive index of optical element,
ω: mode field radius of guided light).

Further, in the optical device of the present invention, an optical element is mounted in the gap of the optical waveguide body, and an optical fiber is provided at the light input end and / or the light output end of the waveguide core. The device is characterized in that the core diameter of the light input end and / or the light output end of the waveguide core matches the mode field diameter of the optical fiber to be provided.

Alternatively, at least one gap for mounting an optical element across the waveguide core is provided between the light input end and the light output end of the waveguide core, and at least one of the gaps is provided. One is 0.975 <(1 + ((λG) / (2πnω ² )) ² )
^-1 (where, λ: wavelength of guided light, G: gap width, n: refractive index of gap, ω: mode field radius of guided light). Here, by providing a plurality of the gaps and arranging the optical elements in the respective gaps, one gap having a gap width equal to the sum of the plurality of gap widths is provided, and the optical element is provided in the gap. This is preferable because the coupling loss is reduced as compared with the case of disposing. This is because, as is clear from the graph of FIG. 4, the loss increases sharply as the gap width increases, so that the total coupling loss can be reduced to one gap by providing a plurality of small gap widths. Therefore, it is possible to keep it lower than in the case where a part is provided.

Alternatively, the optical device according to the present invention is characterized in that an optical element is mounted on at least one of the gaps crossing the waveguide core.

Specifically, when the mode field radius is 20
A hybrid mounting waveguide having a region of 1 μm or more in the traveling direction of light is used. Here, a region having a mode field radius of 20 μm or more is a waveguide for mounting a bulk element. A gap (opening) is formed so as to cross the waveguide for mounting a bulk element, so that the bulk optical element can be mounted. Even if the thickness and the number of optical elements to be inserted into the hybrid mounting waveguide are not predetermined, they can be universally used because of the length of the mounting portion.

The light input / output end of the hybrid mounting waveguide is matched to the mode field diameter of the optical fiber. Further, one end may be matched with the mode field diameter of the optical fiber, and the other end may be matched with the mode field diameter of an optically active element such as a semiconductor laser. Thus, a plurality of bulk optical elements having an arbitrary thickness can be easily coupled to an optical fiber or an optical active element.

[0017]

Embodiments of the present invention will be described below in detail with reference to the drawings. An optical waveguide according to the present invention and an optical device using the same will be described with reference to FIG. As shown in FIG. 1, an optical waveguide body K1 is provided with a waveguide layer (cladding) 3 which is an upper part of a base where a waveguide core 2 is formed on a substrate 1 which is a lower part of the base. The waveguide core 2 is located between the end 2a and the light emitting end 2b.
Is provided with at least one gap 4 for mounting an optical element, and at least one of the gaps 4 is 0.975 <(1 + ((λG) / (2πnω ² )) ² ) ^-1. (A) (where, λ: wavelength of guided light, G: gap width, n: refractive index of gap, ω: mode field radius of guided light). Here, 0.975 on the left side of the above equation is a numerical value corresponding to 1 dB of the diffraction loss, and is a value obtained by converting the power transmission coefficient into dB. The above equation (A) is G <0.32.
πnω ² / λ (where λ: wavelength of guided light, n: refractive index of optical element, ω: mode field radius of guided light).

In such an optical waveguide body K1, the light input end 2a and / or the light output end 2b of the waveguide core 2 are provided.
Alternatively, an optical device may be configured by optically coupling the optical fiber with the mode field diameter of the optical fiber to be provided.

Further, the optical device may be configured by mounting an optical element 5 such as an optical isolator, a polarizer, various filters, and an attenuator on at least one of the gaps 4 crossing the waveguide core 2.

According to the optical waveguide body K1 and the optical device having the above-described configuration, the components for holding the optical elements for optical alignment are not required, and the number of components and the volume can be reduced.
The size can be reduced. In addition, as long as the length of the bulk component mounting waveguide portion provided in the waveguide core permits, it is possible to form gap grooves of any thickness and number. Therefore, it is possible to cope with hybrid mounting of various thicknesses and numbers with a simple design (product).

[0021]

EXAMPLES Next, specific examples will be described.

Example 1 FIG. 1 shows an optical waveguide body K according to the present invention.
1 is shown. As shown in FIG. 1, a waveguide layer (cladding) 3 whose refractive index is higher than that of the substrate 1 by 0.3% is formed on a quartz substrate 1. Next, for a total length of 7 mm, a bulk element mounting waveguide 6 having a core diameter of 36 μm is 3 mm, and tapered portions 7 on both sides thereof.
The waveguide core 2 is formed by CVD, etching, or the like so that a and 7b are provided by 1.5 mm each, and the light incident end 2a and the light output end 2b having a core diameter of 9 μm are 0.5 mm at both ends. . The light incident end 4a and the light output end 4b are set to have a relative refractive index difference of 0.3% with respect to the substrate 1, and the bulk element mounting waveguide 6 is set to have a relative refractive index difference of 0.019%. Note that the single mode is used with a core radius of 4.5 μm and a relative refractive index difference of 3%. However, if the core radius is r and the relative refractive index difference is D, r × D ^1/2 is a numerical value proportional to the normalized frequency. . If this is constant, the single mode condition is similarly maintained and the higher mode is not excited.

A quartz cladding layer 3 is formed on the waveguide core 2 by a CVD method or the like. Since the mode field diameter is about 1.1 times the core diameter, the mode field diameter is about 40 μm (radius 2
0 μm), and the mode field diameter is about 10 μm (radius 5 μm) at the light incident end 2a and the light exit end 2b.

A gap 4 having a predetermined interval G is formed in the bulk element mounting waveguide section 6 by dicing or the like, so that an arbitrary thickness and an arbitrary number of elements can be mounted. A large number of elements may be integrated and the gap 4 may be formed in one place, but the number of the gaps 4 may be increased according to the number of elements and mounted.
The gap 4 may be formed by etching or the like.

FIG. 4 shows the coupling loss of light when two waveguide cores 2 are opposed to each other. The horizontal axis is the distance between the two waveguide cores 2 facing each other, and corresponds to the distance between the gaps 4 (gap width G) in the present invention, and the vertical axis is the diffraction loss, that is, the coupling loss caused by separating the waveguide cores 2. Is shown. In the drawing, w is a mode field radius. A normal silica-based waveguide having a mode field radius of 5 μm is shown.
The solid curve shows the case where the mode field radius is enlarged to 20 μm. The wavelength is 1.31 μm, and the refractive index in the gap is air (n = 1). In order to suppress the diffraction loss to about 1 dB (1 dB corresponds to about 0.975 in the formula (A)), a mode field radius of at least 20 μm is required at a distance of 1 mm between the facing sides. When a plurality of elements are inserted, for example, the mode field radius is 20 μm.
m, two elements having a thickness of 200 μm are put together at 400
When inserted into a waveguide with a thickness of μm, the loss is 0.185
However, if a gap is provided at another place and elements having a thickness of 200 μm are separately inserted, the total loss is 0.094 dB, and the loss can be further reduced. This is not possible with a lens system, but is possible because the waveguide for mounting the bulk element is provided in a long section.

Example 2 Next, an optical waveguide K2 and an optical device S2 according to another embodiment will be described with reference to FIG. A waveguide layer 3 having a refractive index 0.3% higher than that of a substrate 1 on a quartz substrate 1
To form Next, for a total length of 7 mm, a core diameter of 36 μm
The bulk element mounting waveguide 6 is 3 mm, the tapered portions 7a and 7b are 1.5 mm on both sides, and the light incident end 2a and the light output end 2b having a core diameter of 9 μm are 0.5 mm at both ends. The core shape is formed by CVD and etching.

The light input / output ends 2a and 2b have a relative refractive index difference of 0.3% with respect to the substrate 1, and the bulk element mounting waveguide 6 has a relative refractive index difference of 0.019%. Since the mode field diameter is about 1.1 times the core diameter, the mode field diameter of the waveguide section 6 for mounting a bulk element is about 40 μm.
(Radius 20 μm), and the mode field diameter becomes approximately 10 μm (radius 5 μm) at the light input / output ends 2a and 2b.

Optical fibers 8a, 8b are connected to the light input / output ends 2a, 2b by butt joints. Reference numeral 9 denotes a V-grooved substrate for aligning and fixing the hybrid mounting waveguide 10 and the optical fibers 8a and 8b.
V-groove 1 for positioning and holding optical fibers 8a and 8b
One.

In the waveguide 6 for mounting a bulk element, the gap 4a is cut with a width of about 500 μm and the gap 4b is cut with a width of 800 μm, and the wavelength filter 12 and the optical isolator 13 are inserted and fixed therein. . The optical isolator 13 is previously provided with a garnet 14 and two polarizers 15 in total.
Although the two optical elements are bonded and integrated, three openings (gap portions) may be provided and separately inserted and fixed to reduce coupling loss.

In this example, the optical element is bonded and fixed using a photocurable resin. Since the refractive index of the photocurable resin can be finely adjusted, the cores of the optical input / output ends 2a and 2b of the hybrid mounting waveguide 10 and the cores of the optical fibers 8a and 8b have the same refractive index. ing.
The surfaces of the wavelength filter 12 and the optical isolator 13 are provided with an AR coating for an adhesive.

The fixing may be performed by soldering or the like, but in this case, it is necessary to provide both surfaces of the wavelength filter 12 and the optical isolator 13 with an AR coat for air and to provide an air gap. Further, the fixing may be performed by soldering, the both surfaces of the wavelength filter 12 may be coated with an AR coating for an adhesive, and the gap at the time of inserting the wavelength filter 12 and the optical isolator 13 may be filled with the above-described photocurable resin. Although not shown in FIG. 2, it is finally sealed in a package.

Also in this example, the total diffraction loss of the gaps 4a and 4b was 1 dB or less.

Example 3 Next, another example of the optical waveguide body K3 and the optical device S3 will be described with reference to FIG. As shown in FIG. 3, a total length of 7 mm
In contrast, a bulk element mounting waveguide 6 having a mode field radius of 20 μm is 6 mm, and tapered portions 7 a and 7 b are provided on both sides thereof.
The light incident end 2a having a mode field radius of 3 μm and the light emitting end 2b having a mode field radius of 5 μm are formed to be 0.5 mm at both ends. Reference numeral 14 denotes a platform for aligning and fixing the hybrid mounting waveguide 10, the optical fiber 8, and the semiconductor laser 16.

The light incident end 2a is optically coupled to a semiconductor laser 16 fixed on a platform 14,
An optical fiber 8 is connected to the light emitting end 2b by a butt joint. The gap 4a is cut to a width of about 800 μm and the gap 4b is cut to a width of about 800 μm in the bulk element mounting waveguide section 6.
a and 13b are inserted and fixed. Thus, a two-stage optical isolator can be easily realized. It goes without saying that the polarization planes of the two optical isolators 13a and 13b are matched. Furthermore, the optical isolators 13a, 1
3b is formed of garnet and two polarizers, respectively, but a total of six gaps may be formed and arranged separately. In this case, the loss can be reduced. Without considering the refractive index of the element, simply considering the width of the gap, and assuming a garnet thickness of 400 μm and a polarizer thickness of 200 μm, and two isolators simply bonded to each other with a thickness of 800 μm, the diffraction loss is 1.4 dB. When the elements are installed separately, the total diffraction loss is 0.56 dB. The wavelength is 1.31 μm.

In this embodiment, as in the first embodiment, each of them is bonded and fixed by using a photocurable resin.

When assembling an optical module, the most complicated and most likely process to cause a problem is the process of aligning and fixing the semiconductor laser. Before forming the gap for mounting the optical element, the semiconductor laser and the optical fiber are aligned with the waveguide for hybrid mounting of the present invention, and if the defect is removed at this time, the man-hour for forming the gap and the waste of the optical element are eliminated. Can be prevented. This is due to the structure that enables optimal alignment between the semiconductor laser and the optical fiber regardless of the presence or absence of the optical element.

[0037]

As described above, according to the optical waveguide of the present invention and the optical device using the same, the following excellent effects can be obtained.

Parts for holding optical elements for optical alignment are not required, and the number of parts and the volume can be reduced. That is, assembling is easy and miniaturization is possible.

As long as the length of the waveguide for mounting a bulk component formed on the waveguide core is allowed, the gap groove having an arbitrary thickness and number can be formed. Therefore, a single design (product) can support various thicknesses and numbers of hybrid mountings. In particular, it is preferable because a plurality of elements can be easily and simultaneously mounted. Further, by dividing the mounting position of the optical element, the loss at the time of mounting can be reduced, and the tolerance of the forming position of the gap (groove) is very large.

By the butt joint between the hybrid mounting waveguide and the optical fiber, optical coupling can be minimized with a waveguide type component whose mode field is matched. Therefore, it is easy and easy to hybridize the bulk component and other waveguide components.

Since there is almost no space propagating part in the air at the light passing part, a change in characteristics due to a change in environment is unlikely to occur.

The waveguide for hybrid mounting, the optical fiber, the LD, and the like may be connected first, a gap may be formed later, and the bulk optical element may be mounted. In consideration of the above, an optimal assembly order can be adopted.

[Brief description of the drawings]

FIG. 1 is a perspective view illustrating an optical waveguide body for hybrid mounting according to the present invention.

FIG. 2 is a perspective view illustrating another optical waveguide body and an optical device for hybrid mounting according to the present invention.

FIG. 3 is a perspective view illustrating another optical waveguide body and an optical device for hybrid mounting according to the present invention.

FIG. 4 is a graph illustrating a relationship among a mode field radius, a facing distance, and a diffraction loss.

FIG. 5 is a sectional view showing a conventional pigtail type component.

6A and 6B are partial cross-sectional views illustrating a mounting method using a conventional core-enlarged fiber.

FIG. 7 is a partial sectional view showing a conventional semiconductor laser module.

[Explanation of symbols]

 1: substrate 2: waveguide core 2a: light incident end 2b: light exit end 3: waveguide layer (clad layer) 4, 4a, 4b: gap K1, K2, K3: optical waveguide S, S2 S3: Optical device

Claims (2)

[Claims] 1. A waveguide core comprising at least one gap between a light input end and a light output end of a waveguide core in which an optical element is mounted in a direction crossing the waveguide core. An optical waveguide having a width G satisfying the following expression. G <0.32πnω ² / λ (where λ: wavelength of guided light, n: refractive index of optical element,
ω: mode field radius of guided light) 2. An optical device in which an optical element is mounted in a gap of the optical waveguide body according to claim 1, and an optical fiber is additionally provided at a light input end and / or a light output end of the waveguide core. An optical device, wherein a core diameter of a light incident end and / or a light output end of the waveguide core is matched with a mode field diameter of an optical fiber to be provided.