JP2000075254A - Array type waveguide element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an array type waveguide element which enables high-speed operation without being limited by the inductance of bonding wires and is small in electrical crosstalks. SOLUTION: The array type waveguide element has central electrodes 17 (17a, 17b, 17c) arranged to an array form as an optical function part on a semiconductor substrate and a grounding electrode 18 holding these electrodes. Central conductors 5, 7 of a co-plane waveguide formed to operate this optical function part are connected to the central electrodes 17 which are the central conductors of the array type waveguide element by gold ribbons 19.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an arrayed waveguide device, and more particularly to an arrayed waveguide device which is small in size, has low electric crosstalk, and operates at high speed.

[0002]

2. Description of the Related Art As an example of a conventional array type waveguide device, an array type optical modulator in which three optical modulators are arranged side by side is taken as an example.
FIG. 6 is a top view and FIG. 7 is a sectional view taken along the line AA 'in FIG. Here, 1 is an n ⁺ -InP substrate, 2 is a center electrode, 3 is a pad electrode, 4 is a dielectric substrate made of alumina or aluminum nitride, and 5 is a coplanar waveguide (CPW) electrode on the electric signal input side. A center electrode, 6 is a ground electrode of the CPW electrode, 7 is a center electrode of the CPW electrode on the electric signal output side, 8 is a terminating resistor, and 9 is a bonding wire. In FIG. 7, 10 is a p ⁺ -InGaAs cap, and 11 is a p-
InP clad. 12 is i-InGaAlAs /
InAlAs multiple quantum well (MQW) core, 13 is n-
InP clad, 14 is an n-side electrode, and 15 is polyimide.

As shown in FIGS. 6 and 7, in this array type optical modulator, three center electrodes 2 are provided in parallel on an n ⁺ -InP substrate 1 as an optical function part. The pad electrode 3 is provided so as to protrude laterally, and its cross-sectional structure is such that an n-InP clad 1
3, i-InGaAlAs / InAlAs multiple quantum well (MQW) core 12, p-InP cladding 11, p ⁺ −
An InGaAs cap 10 is sequentially formed, a center electrode 2 and a pad electrode 3 are placed thereon, and n
In this configuration, a side electrode 14 is provided, and a polyimide 15 is provided on the side of the core / cladding portion in order to reduce the parasitic capacitance of the pad electrode 3. Here, i-InGaAlAs / InA
If, for example, the exciton peak wavelength is set near 1.50 μm, the lAs multiple quantum well (MQW) core 12 operates as an absorption type optical modulator near 1.55 μm by the electroabsorption effect. The CPW electrode portion is formed on a dielectric substrate 4 made of alumina, aluminum nitride, or the like, on which a central electrode 5 of the CPW electrode on the electric signal input side, a ground electrode 6 of the CPW electrode,
The center electrode 7 and the terminating resistor 8 of the CPW electrode on the electric signal output side
Is provided. Reference numeral 9 denotes a bonding wire, which connects each pad electrode 3 of the light modulation unit to the center electrode 5 on the electric signal input side and the center electrode on the electric signal output side of the coplanar waveguide electrode unit.

As can be seen from FIG. 6, an electric signal propagating through the center electrode 5 of the CPW electrode on the electric signal input side is input to the optical modulator through the bonding wire 9 and then output through the bonding wire 9. It is sent to the terminating resistor 8.

However, when the number of optical functional parts in the arrayed waveguide element increases, the length of the bonding wire 9 becomes longer, and the high-frequency characteristics are significantly deteriorated due to the influence of the inductance. Further, as shown in FIG. 6, since the bonding wires 9 are wired in the air, electric crosstalk occurs.

[0006]

As described above,
In the conventional example of the array type waveguide element, a bonding wire is used to apply an electric signal to each functional unit such as an optical modulator, so that high-speed operation is difficult due to the influence of the inductance of the bonding wire. In addition, there is a problem that electric crosstalk is large.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an arrayed waveguide element which enables high-speed operation without being limited by the inductance of a bonding wire and has small electric crosstalk.

[0008]

According to a first aspect of the present invention, there is provided an arrayed waveguide device comprising at least two optical function units formed on a semiconductor substrate and the optical function unit. An arrayed waveguide element having a center electrode formed for operation, wherein a center conductor of a coplanar waveguide formed on the substrate and a center conductor of the arrayed waveguide element are connected. I do.

According to a second aspect of the present invention, in the array type waveguide element according to the first aspect, the center conductor of the coplanar waveguide is arranged on a dielectric layer on the semiconductor substrate. Features.

According to a third aspect of the present invention, in the array type waveguide device according to the first aspect, a semi-insulating semiconductor substrate is used as the semiconductor substrate, and a center conductor of the coplanar waveguide is the semiconductor. It is characterized by being arranged in contact with a substrate.

According to a fourth aspect of the present invention, in the array type waveguide element according to the first, second or third aspect, at least a part of the ground conductor of the coplanar waveguide is formed on the semiconductor substrate. A conductive semiconductor layer.

According to a fifth aspect of the present invention, there is provided an array type waveguide element having two or more optical function parts formed on a semiconductor substrate and a center electrode formed for operating the optical function part. The center conductor of the microstrip waveguide formed on the substrate is connected to the center conductor of the arrayed waveguide element.

According to a sixth aspect of the present invention, there is provided an arrayed waveguide device according to the fifth aspect, wherein at least a part of a ground conductor of the microstrip waveguide is formed on a semiconductor substrate. It is characterized by forming a layer.

According to a seventh aspect of the present invention, in the array type waveguide element according to the fifth aspect, the center conductor of the coplanar waveguide is arranged on a dielectric layer on the semiconductor substrate. Features.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An arrayed waveguide device according to the present invention comprises:
An array-shaped optical function unit formed on a semiconductor substrate; and a control unit for operating the optical function unit. A center electrode formed to operate the array-type optical function unit as the control unit, and the array type The center conductor of the waveguide element is arranged close to the conductor, and these are connected by a conductor having a small inductance such as a gold ribbon. With this configuration, according to the present invention, an electric signal can be transmitted to each functional unit of the arrayed waveguide element without using a bonding having a large inductance. In contrast, high-speed operation is possible without being limited by inductance. Furthermore, particularly when a CPW electrode is used, a common ground electrode is provided on the upper surface of the substrate, so that electrical crosstalk can be reduced.

[0016]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples.

FIG. 1 is a top view of an arrayed waveguide device according to a first embodiment of the present invention. In FIG. 1, I is an optical function unit, II is a control unit for operating the optical function, 4 is a dielectric substrate made of alumina or aluminum nitride,
5 is a center conductor (center electrode) of the CPW electrode on the electric signal input side, 6 is a ground conductor (earth electrode) of the CPW electrode, 7 is a center conductor (center electrode) of the CPW electrode on the electric signal output side,
8 is a terminating resistor, 17 is the center electrode of the CPW electrode, 18 is C
The ground conductor (earth electrode) of the PW electrode, 19 is a gold ribbon,
Reference numeral 20 denotes an electric separation groove. As shown in FIG. 1, in the present embodiment, the central electrode 17 (1
7a, 17b, 17c) are provided, and these central electrodes 1
7a, 17b, and 17c have one ends (21a, 21a,
21b, 21c) are formed so as to be closely opposed to the center electrode 5 of the CPW electrode on the electric signal input side of the control unit formed to operate the optical function unit, and the other end (2
2a, 22b, 22c) is the C on the electric signal output side of the control unit.
It is formed so as to be closely opposed to the center electrode 7 of the PW electrode,
Furthermore, the end portions 21 of the center electrodes 17a, 17b, 17c
a, 21b and 21c and the center electrode 5 facing them, and the ends 22a, 22b and 22c and the center electrode 7 facing them are connected by a gold ribbon 19, respectively. Since the gold ribbon 19 is wider and shorter than the bonding wire, the inductance is small. Each center electrode 17a, 17
The portions where b and 17c are arranged are separated from the remaining portions by electric separation grooves 20, respectively. The configuration of the control unit is such that a central electrode 5 of the CPW electrode on the electric signal input side, a central electrode 7 of the CPW electrode on the electric signal output side, 7, a ground electrode 6 of a CPW electrode sandwiching each of the electrodes 7 and a terminating resistor 8 formed between the center electrode 7 and the ground electrode 6 are provided.

FIG. 2 is a sectional view taken along the line BB 'of FIG.
And FIG. 2 and 3, 10 is p
⁺ -InGaAs cap, 11 is a p-InP cladding. 12 is an i-InGaAlAs / InAlAs multiple quantum well (MQW) core, 13 is an n-InP clad, 15 is a polyimide used to reduce the parasitic capacitance of the pad electrode 3, and 16 is a semi-insulating InP substrate. In the example shown in FIG. 2, the cross-sectional structure is such that an n-InP clad 13 and an i-InGaAlAs / I
nAlAs MQW core 12, p-InP clad 11,
A p ⁺ -InGaAs cap 10 is sequentially formed, and a ridge having a core / clad structure is formed by pattern formation and etching by photolithography. The portion other than the ridge is etched until it reaches the substrate, the polyimide 15 is provided on the side of the ridge structure, and the center conductor 17 is provided on the ridge structure and the polyimide 15 and on the exposed substrate. Here, i-InGaAlA
The s / InAlAs multiple quantum well (MQW) core 12
For example, if the exciton peak wavelength is set near 1.50 μm, the absorption type optical modulator operates by the electro-absorption effect near 1.55 μm. As mentioned above, CPW
Where the center conductor 17 (17a, 17b, 17c) of the electrode is arranged, the n-InP cladding 13 is removed. On the other hand, in the example shown in FIG. 3, a ridge structure is formed as in the example of FIG.
Since the P clad 13 remains, the central conductor 17 of the CPW electrode is formed via the polyimide 15 to ensure insulation. These lines are designed to be approximately 50Ω system. The central conductor side of the CPW electrode may have any of the structures shown in FIGS.
Next, the ground electrode side of the CPW electrode will be described with reference to FIG. FIG. 4 is a sectional view taken along line CC 'of FIG. An n-InP clad 13, an i-InGaAlAs / InAlAs MQW core 12, a p-InP clad 11, and a p ⁺ -InGaAs cap 10 are sequentially formed on a semi-insulating InP substrate 16, and portions other than the ridge of the core / clad structure are n. The ground electrode 18 of the CPW electrode is formed on the remaining n-InP clad 13 by etching until reaching the -InP clad 13. n-I
Since the conductivity of the nP cladding 13 is high, the ground electrode of the CPW electrode is not necessarily provided, but the ground electrode 18 is used here to further improve the characteristics.

(Example 2) An arrayed waveguide element was manufactured in the same manner as in Example 1 except that the n ⁺ -InP substrate 1 was used instead of the semi-insulating substrate 16 in the structure shown in FIG.

(Embodiment 3) C of Embodiments 1 and 2
This is an example in which a microstrip electrode is used instead of the PW electrode. FIG. 5 shows a cross-sectional view of a joint between the center electrode of the arrayed waveguide element and the center electrode of the microstrip electrode. The layer structure is the same as that of the first embodiment shown in FIG.
GaAlAs / InAlAs MQW core 12, p-In
A P-clad 11 and ap ⁺ -InGaAs cap 10 are sequentially formed, and a ridge having a core-clad structure is formed by pattern formation and etching by photolithography. The portion other than the ridge is etched until it reaches the n-InP cladding 13, a polyimide 15 is provided on the side of the ridge structure, and the center conductor 17 is formed on the ridge structure and the polyimide 15 and on the remaining n-InP cladding 13.
Is provided. The earth electrode (ground conductor) 18 of the microstrip electrode is in contact with the highly conductive n-InP clad 13 which is in contact with the semiconductor substrate 16, and the center electrode of the microstrip electrode is disposed on polyimide on the semiconductor substrate. As the ground conductor, an n-InP clad can be used.

In each of the above-described embodiments, no bonding wire having a large inductance is used.
Since the gold ribbon used here is short and thick, the inductance is smaller than that of the bonding wire, and high-speed operation is possible. In the case where the CPW structure is used, since the ground electrode is provided between the plurality of center electrodes, electric crosstalk can be reduced.

The present invention is applicable not only to CPW electrodes but also to asymmetric coplanar strip electrodes. Materials other than those described here may be used as the core material of the semiconductor. Further, it goes without saying that the present invention is applicable not only to the array type optical modulator but also to the array type light receiver.

[0023]

As described above, according to the present invention,
Since an electric signal can be transmitted to each functional portion of the arrayed waveguide element without using a bonding wire, high-speed operation can be performed without being limited by the inductance of the bonding wire.

Furthermore, when a CPW electrode is used, a common ground electrode is provided on the upper surface of the substrate, so that there is an advantage that electrical crosstalk can be reduced.

[Brief description of the drawings]

FIG. 1 is a top view of an arrayed waveguide device according to a first embodiment of the present invention.

FIG. 2 is a sectional view taken along the line BB 'of FIG.

FIG. 3 is a sectional view taken along the line BB 'of FIG.

FIG. 4 is a sectional view taken along line CC ′ of FIG. 1;

FIG. 5 is a cross-sectional view of a joint between a center electrode of an arrayed waveguide element and a center electrode of a microstrip electrode.

FIG. 6 is a top view of a conventional array type optical modulator.

FIG. 7 is a sectional view taken along line AA ′ of FIG. 6;

[Explanation of symbols]

Reference Signs List 1 n ⁺ -InP substrate 2 Center conductor (center electrode) 3 Pad electrode 4 Dielectric substrate 5 Center conductor (center electrode) of coplanar waveguide (CPW) electrode on electric signal input side 6 Ground conductor (ground electrode) of CPW electrode 7) Central conductor (center electrode) of CPW electrode on electric signal output side 8 Terminating resistor 9 Bonding wire 10 p ⁺ -InGaAs cap 11 p-InP clad 12 i-InGaAlAs / InAlAs multiple quantum well (MQW) core 13 n-InP Cladding 14 n-side electrode 15 Polyimide 16 Semi-insulating InP substrate 17, 17 a, 17 b, 17 c Center conductor of CPW electrode (center electrode) 18 Ground conductor of CPW or microstrip electrode (earth electrode) 19 Gold ribbon 20 Electrical separation groove 21 a , 21b, 21c One end of the center conductor (center electrode) 22 , 22b, the other end portion of the 22c central conductor (central electrode)

Claims (7)

[Claims] 1. An array-type waveguide device having two or more optical function parts formed on a semiconductor substrate and a center electrode formed to operate the optical function part, wherein a coplanar surface formed on the substrate is provided. An arrayed waveguide element, wherein a center conductor of the waveguide is connected to a center conductor of the arrayed waveguide element. 2. The arrayed waveguide device according to claim 1, wherein a center conductor of said coplanar waveguide is disposed on a dielectric layer on said semiconductor substrate. 3. The arrayed waveguide device according to claim 1, wherein a semi-insulating semiconductor substrate is used as said semiconductor substrate, and a center conductor of said coplanar waveguide is arranged in contact with said semiconductor substrate. 4. An arrayed waveguide according to claim 1, wherein at least a part of a ground conductor of said coplanar waveguide is a conductive semiconductor layer formed on said semiconductor substrate. element. 5. An array-type waveguide device having two or more optical function units formed on a semiconductor substrate and a center electrode formed for operating the optical function units, wherein the microstrip formed on the substrate is provided. An arrayed waveguide element, wherein a center conductor of the waveguide is connected to a center conductor of the arrayed waveguide element. 6. The array-type waveguide element according to claim 5, wherein at least a part of the ground conductor of the microstrip waveguide is a conductive semiconductor layer formed on a semiconductor substrate. 7. An arrayed waveguide device according to claim 5, wherein a center conductor of said coplanar waveguide is arranged on a dielectric layer on said semiconductor substrate.