JP2000081522A - Waveguide type optical element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a ridge from breaking by pressure from a preventing plate against intrusion of a dielectric film by forming a part of equal height to or higher than an electrode in the region where a ridge optical waveguide is held. SOLUTION: An n-InP clad 5, InGaAlAs/InAlAs multiple quantum well core 4, p-InP clad 3, and p+-InGaAs gap 2 are laminated on a semi-insulating InP substrate 10. This multilayer structure is etched into a pattern having a ridge optical waveguide and the region which interposes the ridge and which has a part to stably hold a preventing plate 9 against intrusion of a dielectric film, and the center electrode 1 and ground electrodes 11 are formed. Then the plate 9 is disposed on the upper face of the optical element, and an antireflection film is vapor deposited only on the end face of the optical element. In this method, even when the plate 9 is pressed on the upper face, the lower face of the plate 9 does not touch the upper face of the center electrode 1 so that no pressure is added to the ridge of the optical waveguide.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a small-sized semiconductor waveguide type optical device having good manufacturability. More specifically, the present invention relates to a waveguide-type optical device capable of efficiently and easily depositing an antireflection film on an end face of the waveguide-type optical device.

[0002]

2. Description of the Related Art As an example of a conventional waveguide type optical element, an electroabsorption optical modulator having a traveling wave electrode of a conventional structure (broadband electroabsorption semiconductor optical modulator: Japanese Patent Application No. 9-280211).
4 is shown in FIG. 4, and a cross-sectional view taken along line AA ′ is shown in FIG. Here, 1 is a center electrode, 2 is p ⁺ -InGaAs
Cap, 3 is p-InP clad, 4 is InGaAlAs (1
3 nm) / InAlAs (5 nm) multiple quantum well (MQW) core, 5 is an n-InP clad, 6 is an n ⁺ -InP substrate,
7 is a ground electrode, 8 is polyimide, I is an input part of an electric signal (microwave), and II is an output part of an electric signal. In this conventional example, light modulation is performed by running an electric signal and light in parallel. As can be seen from the figure, p + -InGa
As cap 2, p-Inp clad 3, InGaAlAs / InAl
As MQW core 4 has a ridge structure and a width of 2 μm.
From about 3 μm, which is generally called a high-mesa optical waveguide.

The refractive index of the semiconductor optical modulator with respect to incident light is about 3.2. In order to reduce the insertion loss of light due to Fresnel reflection and the reflected return light, the light must be incident on the light incident end face and the light exit end face. It is indispensable to form a dielectric anti-reflection film such as SiO ₂ . This anti-reflection film is generally deposited on the end face of the waveguide in a vacuum device. In this case, if a dielectric film is deposited on the upper portion of the electrode, conduction with an external electrical connector cannot be taken in a subsequent electrode process, which is preferable. Absent. Therefore, in an actual vapor deposition, as shown in FIG. 6, a vapor deposition is performed from the front to the end face of the waveguide in a state where a dielectric film wraparound prevention plate 9 such as an antireflection film is covered from above the element to a semiconductor substrate or the like. I have.

[0004]

However, as can be seen from FIG. 6, in this conventional example, a dielectric wraparound preventing plate 9 is provided.
Is pressed from above, a force from the lower surface of the dielectric wraparound preventing plate 9 is applied to the ridge of the optical waveguide through the upper surface of the center electrode 1 to the ridge of the optical waveguide. However, as described above, the width of the ridge is as narrow as about 2 μm to about 3 μm, so that the ridge is mechanically fragile, and the ridge is broken by the pressure from the dielectric film wraparound prevention plate 9. As a result, light is no longer guided. There was a problem that would.

[0005]

In order to solve the above-mentioned problems, according to the present invention, a light guiding core is disposed between a lower cladding and an upper cladding, and an electrode is provided above the upper cladding. In a waveguide type optical device having a shaped optical waveguide, a portion which is the same as or higher in height than the electrode is provided in a region sandwiching the ridge shaped optical waveguide.

It is preferable that the electrode of the waveguide type optical element forms the center electrode of the traveling wave electrode. Further, it is preferable that a portion which is the same as or higher in height than the electrode of the waveguide type optical element of the present invention forms the ground electrode of the traveling wave electrode.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail.

A waveguide type optical device according to the present invention includes an optical waveguide having a ridge structure, and a portion sandwiching the ridge type optical waveguide has a portion which is the same as or higher in height than the ridge type optical waveguide. Is provided. Specifically, a portion is provided which is higher than the ridge-shaped optical waveguide by 0 to several tens of microns. Preferably, a portion higher than the ridge-shaped optical waveguide is provided. By providing a portion that is the same as or higher in height than this ridge-type optical waveguide, when the waveguide-type optical element is suppressed from above with a plate-like medium as a dielectric wraparound preventing plate, the plate-like The medium does not contact the ridge-shaped optical waveguide, or even if it does, only a small force is applied to the ridge. However, if the portion higher than the ridge-shaped optical waveguide is too high than the ridge-shaped optical waveguide, the vapor-deposited film wraps around the electrode when the antireflection film is vapor-deposited on the end face of the waveguide-type optical element.

In this ridge type optical waveguide, a core for guiding light is disposed between a lower clad and an upper clad, and an electrode is provided above the upper clad.

The materials such as electrodes, claddings and cores used in the waveguide type optical element of the present invention are commonly used and are not particularly limited. Examples of the electrodes include coplanar waveguide type (Coplanar-waveguide: CP
W) electrodes and asymmetric coplanar strip electrodes. As the core of the optical waveguide, for example, InGa
There are MQW materials other than AlAs / InAlAs MQW and InGaAlAs / InAlAs, and bulk materials such as InGaAsP.

Preferably, the electrode of the ridge-shaped optical waveguide forms the center electrode of the traveling wave electrode.

Further, in the waveguide type optical element of the present invention,
It is preferable that the same or higher portion as the electrode on the ridge type optical waveguide be the ground electrode of the traveling wave electrode, but a block of solder, polyimide, etc. is partially formed on the ground type electrode. It may be provided, or a block of solder, polyimide, or the like may be provided without providing the ground electrode. Further, the ground electrode may be made entirely higher or partially higher.

According to the present invention, for example, in the case of a traveling waveform optical modulator, the height of the ground electrode is equal to or higher than that of the center electrode above the ridge, so that a waveguide type optical modulator such as an optical modulator is used. When an antireflection film is deposited on the end face of the element in a vacuum device, a large pressure is not applied to the ridge even if it is suppressed from above by a plate such as a semiconductor substrate. As a result, there is no fear that the ridge is destroyed.

Further, the waveguide type optical element of the present invention can be applied not only to an optical modulator but also to other waveguide type optical elements such as a semiconductor photodetector.

[0015]

Embodiment 1 FIG. 1 is a view for explaining Embodiment 1, and is a cross-sectional view showing a state in which a dielectric film wraparound preventing plate is arranged on a traveling wave electrode type electro-absorption light modulator.

First, a traveling wave electrode type electro-absorption optical modulator was manufactured as follows. A semi-insulating InP substrate 10 is used as a substrate, an n-InP cladding 5 is laminated thereon, and then an InGaAlAs (13 nm) / InAlAs (5 nm) multiple quantum well (MQW) core 4 and a p-InP cladding 3 , P
⁺ -InGaAs cap 2 was laminated. On top of this, a desired pattern, that is, a pattern having a portion that can stably hold the ridge-shaped optical waveguide and a region sandwiching the ridge-shaped optical waveguide when the dielectric film wraparound prevention plate is later placed on the upper portion thereof Was etched by a conventional method. afterwards,
An electrode composed of the center electrode 1 and the ground electrode 11 was formed.

Further, an electrode of 2 μm may be further stacked on the ground electrode 11 with the ridge-shaped optical waveguide interposed therebetween. Here, the 2 μm electrode laminated later does not need to cover the entire pattern sandwiching the ridge-shaped optical waveguide, and when the dielectric wraparound preventing plate is later placed on the ridge-shaped optical waveguide, the dielectric film wraparound prevention plate becomes ridged. Only the portion that does not come into contact with the upper part of the shaped optical waveguide and that can be stably held may be used.

Thus, a desired traveling-wave electrode type electro-absorption light modulator was manufactured.

Next, as shown in FIG. 1, a dielectric film wraparound prevention plate 9 is disposed on the upper surface of the optical element, and the antireflection film is pressed only from above on the end face of the optical element. Evaporated. At this time, even if the dielectric film wraparound prevention plate 9 is pressed from above, the lower surface of the dielectric film wraparound prevention plate 9 does not contact the upper surface of the center electrode 1 and no pressure is applied to the ridge of the optical waveguide, and Was not destroyed. Further, no anti-reflection film was deposited on the center electrode 1.

If the upper surface of the ground electrode 11 of the CPW electrode and the upper surface of the center electrode 1 are equal in height, the dielectric film wraparound prevention plate 9 also contacts the upper surface of the center electrode 1. Although the effect cannot be expected to be as high as in the case of No. 1, the pressure is dispersed not only on the ridge but also on the ground electrode 11 of the CPW electrode, so that protection of the ridge which was impossible in the conventional embodiment shown in FIG. Needless to say, this is possible.

Embodiment 2 FIG. 2 is a view for explaining Embodiment 2, and is a cross-sectional view showing a state in which a dielectric film wraparound prevention plate is arranged on a traveling wave electrode type electroabsorption light modulator.

The height of the upper surface of the center electrode 1, which is the electrode of the ridge-shaped optical waveguide of the first embodiment, and the height of the upper surface of the ground electrode 11, which is the electrode of the CPW electrode sandwiching the ridge-shaped optical waveguide, remain the same. A traveling wave electrode type electro-absorption optical modulator was manufactured in the same manner as in Example 1, except that a polyimide block having a height of 2 μm was provided on the upper surface of the ground electrode 11. At this time, the polyimide block does not need to cover the entire length of the upper surface of the ground electrode 11, and when the dielectric wraparound prevention plate is later disposed on the dielectric block, the dielectric wraparound prevention plate does not contact the upper part of the ridge-type optical waveguide, and Only a portion that can be stably held may be used.

Next, in the same manner as in Example 1, an antireflection film was deposited only on the end face of the optical waveguide. At this time, the lower surface of the dielectric film wraparound prevention plate 9 did not contact the upper surface of the center electrode 1, and no breakage of the ridge type optical waveguide was observed. Also,
No anti-reflection coating was deposited on the center electrode.

Even if a gap is formed between the dielectric film wraparound prevention plate 9 and the ground electrode 11 as in this embodiment, if the gap is small, it is needless to say that the influence of the deposited film wraparound is small.

Embodiment 3 FIG. 3 shows the concept of Embodiment 2 of the present invention applied to the conventional example of FIG. FIG. 3 is a cross-sectional view showing a state in which a dielectric film wraparound prevention plate is arranged on a traveling wave electrode type electroabsorption light modulator according to a third embodiment.

The n ⁺ -InP substrate 6 was used instead of the semi-insulating InP substrate 10 shown in FIG. 2, the polyimide block 12 was provided without providing the ground electrode 11, and the ground electrode 7 was provided on the back surface of the substrate. A traveling wave electrode type electro-absorption optical modulator was manufactured in the same manner as in Example 2 except for the above. Here, the difference between the upper surface of the ridge-shaped optical waveguide and the upper surface of the polyimide block was 3 μm.

Next, in the same manner as in Example 1, an antireflection film was deposited only on the end face of the optical waveguide. At this time, the lower surface of the dielectric film wraparound prevention plate 9 did not contact the upper surface of the center electrode 1, and no breakage of the ridge type optical waveguide was observed. Also,
No anti-reflection coating was deposited on the center electrode.

[0028]

As described above, according to the present invention, since there is a portion higher than the center electrode above the ridge, the end face of the waveguide type optical element such as an optical modulator or a light receiver is provided. Even when the antireflection film is deposited in a vacuum apparatus, a large pressure is not applied to the ridge even if it is suppressed from above by a plate such as a semiconductor substrate, so that the ridge is not broken.

[Brief description of the drawings]

FIG. 1 is a view for explaining Example 1 of the present invention, and is a cross-sectional view showing a state in which a dielectric film wraparound prevention plate is arranged on a traveling wave electrode type electroabsorption optical modulator.

FIG. 2 is a view for explaining Example 2 of the present invention, and is a cross-sectional view showing a state where a dielectric film wraparound prevention plate is disposed on a traveling wave electrode type electro-absorption optical modulator.

FIG. 3 is a view for explaining Example 3 of the present invention, and is a cross-sectional view showing a state in which a dielectric film wraparound prevention plate is arranged on a traveling wave electrode type electroabsorption optical modulator.

FIG. 4 is a perspective view of a conventional electrode type electroabsorption light modulator.

FIG. 5 is a cross-sectional view taken along line AA ′ of FIG. 4 shown as a conventional example.

FIG. 6 is a view for explaining a problem in the conventional example, and is a cross-sectional view showing a state in which a dielectric film wraparound prevention plate is arranged on the conventional electrode type electric field light modulator.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 center electrode 2 p ⁺ -InGaAs cap 3 p-InP cladding 4 InGaAlAs / InAlAs multiple quantum well (MQW) core 5 n-InP cladding 6 n ⁺ -InP substrate 7 ground electrode 8 polyimide 9 dielectric film surrounding prevention plate 10 Semi-insulating InP substrate 11 Ground electrode for CPW electrode

Claims (3)

[Claims] 1. A waveguide type optical device comprising a ridge type optical waveguide having a core for guiding light disposed between a lower clad and an upper clad and an electrode provided above the upper clad, A waveguide type optical element, wherein a portion having the same height or a higher height as the electrode is provided in a region sandwiching the ridge type optical waveguide. 2. The waveguide type optical element according to claim 1, wherein said electrode forms a center electrode of a traveling wave electrode. 3. The waveguide type optical device according to claim 2, wherein a portion which is the same as or higher in height than said electrode forms an earth electrode of said traveling wave electrode. element.