JPH08194195A - Optical waveguide element - Google Patents

Abstract

PURPOSE: To improve a yield and to reduce a cost with a simple structure. CONSTITUTION: This optical waveguide element 10 has optical waveguides 12, 14A, 14B, 17 capable of propagating light waves, properly selects output light 18 propagated in these optical waveguides and used for subsequent processing after emission outside from an exit end face 11A and leaking light 19 leaked outside the optical waveguides in a substrate 11 and emitted outside from the exit end face 11A at the position where is off the optical waveguides and emits the light outside from the exit end face 11A. The exit position of the output light 18 at the exit end face 11A and the exit position of the leaking light 19 are parted to the extent that the respective light waves do not affect each other. The optical waveguides are formed by bending the optical waveguides between the leaking out part of the leaking light 19 and the exit end face 11A for the purpose described above and the optical axes of the optical waveguides in the leaking part of the leaking light 19 are misaligned.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical waveguide device used for optical communication and optical measurement, and more particularly to an optical waveguide device having improved output light characteristics.

[0002]

2. Description of the Related Art Generally, an optical waveguide device having a Mach-Zehnder (MZ) type optical modulator utilizing the electro-optical effect is constructed as shown in FIGS. Specifically, the substrate 1, the incident side single mode waveguide 2 provided on the substrate 1 and connected to an external optical fiber (not shown), and the light wave from the incident side single mode waveguide 2 A bifurcating section 3 that bifurcates, bifurcating waveguide sections 4A and 4B bifurcated by the bifurcating section 3, and bifurcating waveguide sections 4
Electrodes 5A and 5B which are respectively provided in A and 4B to form an electric field to control the light waves propagating in the respective branch waveguide portions 4A and 4B, and a combining unit 6 which combines the branched light waves again. It is configured to include a multiplexing unit 6 for connecting the light waves synthesized by the multiplexing unit 6 to the emission side single mode waveguide 7 that guides the light waves to the emission end face 1A of the substrate 1.

By appropriately controlling the voltage applied to the electrodes 5A and 5B, a phase difference is generated between the light waves propagating through the branching waveguide sections 4A and 4B. Electrode 5A,
When the phase difference of each light wave becomes the same phase by the control of 5B, the combined light wave is the output side single mode waveguide 7
And is emitted as output light A from the emission end face 1A to the outside. When the phases are opposite to each other, the light waves cannot cancel each other in the combining unit 6 and cannot propagate in the emission side single mode waveguide 7, and a radiation mode leaks to the outside from the combining unit 6. In this radiation mode, the light wave leaked from the combining unit 6 to the outside is emitted as the leaked light B from the emission end face 1A to the outside.

The light wave emitted from this optical waveguide device is
As shown in FIG. 9, when collimated by the lens 8 and used for spatial radiation, the output light A in the same phase and the leaked light B in the opposite phase are too close to each other, so that an overlapping portion occurs. It is impossible to clearly separate these two light waves. For this reason, the slit 9 may be provided so as to transmit only the output light A in the same phase, but in this case, since the leaked light B is located on both sides so as to sandwich the slit 9, a part of this leaked light B is generated. It leaks into the slit 9.
That is, the leaked light B in the radiation mode cannot be completely cut, and the extinction ratio of the output light A deteriorates.

Further, when the outgoing side single mode waveguide 7 is connected to an external optical fiber (not shown) by using an optical power meter, the leaked light B in the radiation mode is detected, so these connections are made. Was difficult.

In order to solve this problem, a method of forming a groove or an absorption layer for removing the leaked light B in the vicinity of the emitting end facet 1A of the emitting side single mode waveguide 7 (JP-A-6-18).
6451) or a method of providing a light reflecting film or the like (JP-A-5-1).
96823) is known. Further, a method (Japanese Patent Laid-Open No. 3-145623) in which the leaked light B is used as feedback light in order to prevent the fluctuation of the operating point is also known.

[0007]

However, in the optical waveguide device having the above structure, a step of providing radiation mode removing means such as a groove, an absorption layer or a light reflection film is required,
There is a problem that the yield at the time of manufacturing this element is reduced and the cost is increased accordingly.

Further, when the leaked light B is used as feedback light, the control is performed after the operating point changes,
Poor responsiveness. Also, an optical fiber for feedback control, an optical detector, a signal processing control circuit, etc. are required,
There is a problem that the device becomes complicated and the cost increases.

The present invention has been made to solve the above problems, and an object of the present invention is to provide an optical waveguide device having a simple structure, improved yield and reduced cost.

[0010]

In order to solve the above-mentioned problems, an optical waveguide device according to a first invention has an optical waveguide capable of propagating a light wave, and propagates in this optical waveguide to the outside from an emitting end face. Output light that is emitted and used for subsequent processing, and leaked light that leaks out of the optical waveguide and is emitted from the emission end face to the outside at a position deviated from the optical waveguide are appropriately selected from the emission end face to the outside. In the optical waveguide element to be emitted, the emission position of the output light and the emission position of the leaked light on the emission end face are separated from each other so that the respective light waves do not influence each other.

In the optical waveguide element according to the second aspect of the present invention, the optical waveguide is formed by bending a portion of the optical waveguide between the leaked light leakage portion and the emission end face so that the output light and the leaked light do not affect each other. It is characterized by being separated from each other.

In the optical waveguide element according to the third aspect of the present invention, the optical axis of the optical waveguide in the leaked light leak portion is shifted, and the leaked light leaks from the leaked portion to the outside of the optical waveguide and is emitted to the outside from the emission end face. The output light propagating in the optical waveguide and emitted to the outside from the emission end face is separated from each other to the extent that they do not affect each other.

[0013]

In the first aspect of the invention, since the output positions of the output light and the leaked light on the exit end face are sufficiently separated from each other, the light waves of the output light and the leaked light do not influence each other. That is, the spatial light intensity distribution of the output light and the spatial light intensity distribution of the leaked light do not overlap with each other, the output light and the leaked light are clearly distinguished and emitted, and it is possible to reliably prevent a malfunction such as a malfunction. it can.

In the second aspect of the invention, since the optical waveguide located between the leaking portion and the emitting end face is bent and shaped, the output light propagates in the curved optical waveguide and is separated from the leaking light at the emitting end face. Emit from the position. As a result, the spatial light intensity distribution of the output light and the spatial light intensity distribution of the leaked light do not overlap with each other and do not affect each other.

In the third invention, since the optical axis of the optical waveguide in the leakage portion is shifted, the leakage light leaked from the leakage portion to the outside of the optical waveguide is emitted at a position apart from the output light propagating in the optical waveguide. Emitted from the end face to the outside. As a result, the spatial light intensity distribution of the output light and the spatial light intensity distribution of the leaked light do not overlap with each other and do not influence each other.

[0016]

Embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[First Embodiment] In this embodiment, helium neon laser light having a wavelength of 633 nm is used as a light source. When this light source is used, the spread of the leaked light 19 on the emission end face 11A of the optical waveguide element 10 described later has a radius of 200 μm.
Became.

FIG. 1 is a plan view showing an optical waveguide device 10 having an MZ type optical modulator 10A, and FIG. 2 is a side view of the optical waveguide device 10 shown in FIG.

The optical waveguide device 10 of this embodiment also includes an MZ type optical modulator 10A. The overall structure of the optical waveguide device 10 is almost the same as that of the conventional optical waveguide device. In the figure, 11 is a substrate, 12 is an incident side single mode waveguide, 1
3 is a branch portion, 14A and 14B are branch waveguide portions, 15A,
Reference numeral 15B is an electrode, 16 is a multiplexing portion, 17 is an exit side single mode waveguide, 18 is output light, and 19 is leakage light in a radiation mode. The substrate 11 is lithium tantalate (LiTaO
It is molded in ₃ ). The optical waveguides 12, 14A, 14B and 17 are formed on the substrate 11 by the proton exchange method. In addition, the electrode 15A for controlling the output light 18,
15B is produced by the photolithography technique.

In the MZ type optical modulator 10A, the electrodes 15A,
The substrate 11 is controlled by controlling the voltage applied to 15B.
The ON state in which the output light 18 is emitted from the emission end surface 11A and the OFF state which is a radiation mode in which the leakage light 19 is emitted from the emission end surface 11A can be appropriately switched and set. The leaked light 19 at the time of OFF is the light that cannot propagate from the combining unit 16 into the emission side single mode waveguide 17 and leaks to the outside at the combining unit 16 portion,
It spreads with a divergence angle of about 3 degrees centering on the multiplexing section 16.

Emitting end face 11A of the substrate 11 from the combining portion 16
Output side single mode waveguide 17 which is an optical waveguide up to
Is bent and molded twice. Specifically, it is formed by bending it into an S shape in FIG. The bent portion of the exit side single mode waveguide 17 is shaped according to the shape expressed by the following equation.

Y = 150 (1-COS (πZ / 7000)) where π is the circular constant, Z is the distance from the starting point of the exit side single mode waveguide 17, and y is the lateral shift amount.

Due to the emission-side single-mode waveguide 17 bent according to the value of this equation, the emission position of the output light 18 is shifted laterally by 300 μm from the center position of the adjacent leaked light 19, and the leakage spread to a radius of 200 μm. It is completely separated from the light 19.

This prevents the output light 18 and the leaked light 19 from affecting each other. These output light 18
Also, when collimating the leaked light 19 with the lens 21,
As shown in FIG. 3, the spatial light intensity distribution of the output light 18 and the spatial light intensity distribution of the leaked light 19 do not overlap with each other, and inconveniences such as malfunctions are surely prevented and deterioration of the characteristics of the output light 18 is prevented. To do.

Further, since the position of the output light 18 can be accurately specified, the output end position of the output side single mode waveguide 17 can be accurately specified and the connection of the optical fiber from the outside becomes easy.

Since the conventional step of providing the radiation mode removing means can be omitted, the element manufacturing step can be simplified. By simplifying the element manufacturing process and the structure, it is possible to improve the manufacturing yield and reduce the cost.

Further, in order to prevent the operating point of the element from fluctuating, the leaked light 19 in the radiation mode emitted from the substrate of the element.
Can be used.

[Second Embodiment] The optical waveguide device 2 of the present embodiment.
As shown in FIG. 4 and FIG.
It is almost the same as the embodiment and has the same function.

In this embodiment, the MZ type optical modulator 25A is formed by tilting. Specifically, it is inclined by 5 degrees from the normal line direction on the emission end face 11A of the substrate 11. The exit side single mode waveguide 26 is formed in an arc shape having a curvature radius of 40 mm. The length of the exit side single mode waveguide 26 is 3.4 mm. In FIG. 4, the waveguide portion from the branch waveguide portions 27A and 27B to the multiplexing portion 28 seems to have a large angle, but this is because it is easy to understand in the drawing. Actually the multiplexing section 2
The angle between the branching waveguide portions 27A and 27B in 8 is 1
It is about the degree.

As a result, the center positions of the output light 30 and the leaked light 31 could be shifted by 350 μm. Also in spatial radiation, as shown in FIG. 6, the spatial light intensity distribution of the output light 30 and the spatial light intensity distribution of the leaked light 31 do not overlap and can be clearly separated.

Further, in order to prevent the spatial light intensity distributions of the output light 30 and the leaked light 31 from overlapping with each other, the length of the curved waveguide portion of the emission side single mode waveguide 26 is shortened and its curvature is reduced. Can be made small, and the size of the optical waveguide element 25 can be made small while the propagation loss of the output light propagating through the curved waveguide portion is kept low. As a result, the number of materials can be reduced and the cost can be reduced.

[Modification] (1) In each of the above embodiments, the light source has a wavelength of 633 nm.
The case of using the helium-neon laser light of 1 is described as an example.
It is also applicable to the semiconductor laser light of m and other laser light. Also in this case, the same effect as each of the above-described embodiments can be obtained.

(2) In the first embodiment, the bending degree of the exit side single mode waveguide 17, that is, the waveguide shape is determined by the COS function, but another waveguide shape, for example, S
An IN function type or an arc may be used. Also by this, the same effect as each of the above-described embodiments can be obtained.

(3) As the substrate 11, other than lithium tantalate (LiTaO ₃ ), lithium niobate (L
iNbO ₃ ) or a glass substrate such as quartz on which a thin film having an electro-optical element is formed may be used.

(4) In each of the above embodiments, a modulator using an electro-optical element has been described as an example, but in the case where another light wave control means such as a thermo-optic effect or a magneto-optic effect is used, each of the embodiments is also described. The same effect can be achieved.

(5) In each of the above embodiments, the Mach-Zehnder type optical modulator has been described as an example. However, the present invention can be applied to any optical waveguide element such as a waveguide type polarizer that produces a radiation mode. The same effects as those of the above-described respective embodiments can be obtained. The present invention can be applied not only to one channel but also to multiple channels, and even in this case, it is possible to obtain the same effects as those of the above-described embodiments.

[0037]

As described above, according to the laser device of the present invention, the following effects can be obtained.

(1) The emission position of the output light and the emission position of the leaked light on the emission end face are formed by bending between the leaked light leakage portion and the emission end face of the optical waveguide or by forming the leakage light. By shifting the optical axes of the optical waveguides in the leaking section, the light waves were set so that they did not affect each other, so the spatial light intensity distribution of the output light and the spatial light intensity distribution of the leaked light overlap. Therefore, inconvenience such as malfunction is surely prevented, and deterioration of characteristics of output light is prevented.

(2) Since only the optical waveguide is bent or the optical axis of the optical waveguide is shifted, the structure is simple and the manufacturing yield can be improved and the cost can be reduced.

[Brief description of drawings]

FIG. 1 is a plan view showing an optical waveguide device according to a first embodiment of the present invention.

FIG. 2 is a side view of the optical waveguide device shown in FIG. 1 as viewed from the output end face side.

FIG. 3 is a schematic diagram showing states of output light and leakage light emitted from an optical waveguide device.

FIG. 4 is a plan view showing an optical waveguide device according to a second embodiment of the present invention.

5 is a side view of the optical waveguide device shown in FIG. 4 as viewed from the output end face side.

FIG. 6 is a schematic diagram showing states of output light and leaked light emitted from the optical waveguide device.

FIG. 7 is a plan view showing a conventional optical waveguide device.

FIG. 8 is a side view of the optical waveguide device shown in FIG. 6 viewed from the output end face side.

FIG. 9 is a schematic diagram showing states of output light and leaked light emitted from the optical waveguide device.

[Explanation of symbols]

Reference numeral 10 ... Optical waveguide element, 10A ... MZ type optical modulator, 11 ...
Substrate, 11A ... Emitting end face, 12 ... Incident side single mode waveguide, 13 ... Branching part, 14A, 14B ... Branching waveguide part, 15A, 15B ... Electrode, 16 ... Multiplexing part, 17 ... Exiting side single mode waveguide , 18 ... Output light, 19 ... Leakage light, 21 ... Lens.

Claims (3)

[Claims] 1. An output light having an optical waveguide capable of propagating a light wave, propagating in the optical waveguide, emitted from an emitting end face to the outside, and used for subsequent processing, and leaking out to the outside of the optical waveguide. In an optical waveguide element that appropriately selects leaked light to be emitted to the outside from the emission end face at a position deviated from the optical waveguide and emits the light to the outside from the emission end face, the emission position of the output light and the emission position of the leakage light at the emission end face The optical waveguide element is characterized in that and are separated from each other to such an extent that the respective light waves do not affect each other. 2. The optical waveguide element according to claim 1, wherein a portion of the optical waveguide between the leakage light leakage portion and the emission end face is bent and molded, and the output light and the leakage light influence each other. An optical waveguide device characterized in that they are separated to a certain extent. 3. The optical waveguide element according to claim 1, wherein the optical axis of the optical waveguide in the leaked light leak portion is shifted.
The leaked light that leaks out of the optical waveguide from the leaked portion and is emitted to the outside from the emission end face is separated from the output light that propagates in the optical waveguide and is emitted to the outside from the emission end face. An optical waveguide device characterized by: