JP3240301B2 - Semiconductor optical integrated circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor optical integrated circuit in which various optical elements are integrated with a semiconductor crystal as a substrate.

[0002]

2. Description of the Related Art In recent years, with the background of the development of next-generation optical communication technology, the development of next-generation large-capacity storage technology, and the spread of networks such as commercial connection services using the Internet, the age of full-scale multimedia is increasing. We are about to enter the age.

[0003] Regarding next-generation optical communication technology,
1: ultra high speed / ultra long distance transmission technology, 2: light wave communication technology,
Each technology of 3: optical signal processing technology, 4: optical component / optical integrated circuit technology is a basic technology.

In particular, many researches and developments have been made on the above-mentioned 3: optical signal processing technology and 4: optical component / optical integrated circuit technology. Among them, a typical example in which a device in which optical components are mechanically coupled and integrated is developed is a device in which an optical isolator element is integrated with a semiconductor laser (for example, Japanese Patent Application Laid-Open No. 60-219787). JP-A-63-
65419, JP-A-62-62324, JP-A-1-
No. 74524, JP-A-1-175785, JP-A-1-175
175786, JP-A-2-135416, JP-A-3
-106092 and JP-A-6-125146).

However, these devices merely incorporate an optical isolator element and a semiconductor laser device in one device, and are required to be further miniaturized in order to enter a full-scale multimedia era. Research and development progressed. The result of the recent significant technological progress is optical integrated circuits.

[0006] This optical integrated circuit is capable of integrating micro optics by confining light in a waveguide, and is excellent in compatibility with conventional semiconductor integration techniques and the like. In this optical integrated circuit, the light source and the photodetector are generally made of a semiconductor, whereas the light control element is often made of a dielectric material. There are two main types. That is, there are two types: a hybrid type in which a dielectric and a semiconductor are integrated, and a monolithic type composed of only a semiconductor. In principle, the latter monolithic type is more suitable for achieving high integration and miniaturization.

Examples of the hybrid type include, for example, JP-A-58-169106, JP-A-59-74526,
A combination of an oxide single crystal and a semiconductor has been developed as disclosed in Japanese Patent Laid-Open Publication No. 2-139502. Examples of the monolithic type include, for example, JP-A-2-281777 and JP-A-4-93815.
JP-A-4-97118, JP-A-6-260726
As disclosed in each of the publications, a combination of a magnetic semiconductor and a III-V semiconductor has been developed, and recently, for example, Japanese Patent Application Laid-Open Nos. 8-278423 and 9-269516. Non-reciprocal optical integrated circuits using only non-magnetic semiconductors have been developed as disclosed in each of the publications.

In these optical integrated circuits, in order to control light waves, an electro-optic effect (for example, see Japanese Patent Application Laid-Open No. 5-61002) that is induced by an electric field or current is used, and mechanical distortion is applied. The acousto-optic effect is utilized, and further, the magneto-optic effect is utilized. As the electro-optic effect, the Pockels effect is mainly used for dielectrics and the electric field absorption effect is mainly used for semiconductors, while the magneto-optic effect is mainly used for oxides and magnetic semiconductors. Uses a bulk permanent magnet.

[0009]

However, among the above-mentioned conventional optical integrated circuits, it is difficult to reduce the size of the permanent magnet in the semiconductor optical integrated circuit that performs light wave control by the magneto-optical effect. Cannot be integrated
This has been a major obstacle in reducing the size of the semiconductor optical integrated circuit.

[0010] The present invention has been proposed in view of the above,
It is an object of the present invention to provide a semiconductor optical integrated circuit capable of realizing a significant miniaturization.

[0011]

In order to achieve the above object, the present invention provides a semiconductor optical integrated circuit in which a semiconductor crystal is used as a substrate and various optical elements are integrated.
The magnetic effect can be arbitrarily controlled by bonding to the above semiconductor crystal
A thin ferromagnetic metal thin film and an optical waveguide formed inside the semiconductor crystal and passing through a region where the magnetic effect of the ferromagnetic metal thin film is exerted.

[0012]

Embodiments of the present invention will be described below in detail with reference to the drawings. First, a first embodiment will be described with reference to FIGS.

FIG. 1 is a plan view showing the configuration of a semiconductor optical integrated circuit according to the present invention, and FIG. 2 is a sectional view taken along line XX of FIG. In these figures, a semiconductor optical integrated circuit 1 of the present invention is configured by integrally integrating various optical elements on a substrate 2 made of gallium arsenide (GaAs) semiconductor crystal.
This is an interference type optical waveguide modulator. The semiconductor optical integrated circuit 1 is formed so as to pass through the ferromagnetic metals 3a and 3b bonded to the substrate 2 and the region inside the substrate 2 where the magnetic effect of the ferromagnetic metals 3a and 3b is exerted. Optical waveguide 4
(4a, 4b).

The substrate 2 is bonded to the substrate body 2a and formed on the substrate body 2a by changing the additive composition so that the refractive index of the substrate body 2a is different from that of the substrate body 2a. And a rate control layer 2b.

The ferromagnetic metals 3a and 3b are thin films of manganese antimony (MnSb) grown on the refractive index control layer 2b at 50 ° C. by molecular beam epitaxy.

A sample for measuring the magnetic properties of the ferromagnetic metals 3a and 3b was prepared on a GaAs substrate under the same conditions as the ferromagnetic metals 3a and 3b, and the magnetic properties were measured at room temperature using the samples. Was measured. FIG. 3 is a magnetization hysteresis curve showing the measurement results. In FIG. 3, the bold line indicates G
This is a measurement result of a sample in which the surface of an aAs substrate was formed into a (4 × 6) rearranged structure and a thin film was formed on the substrate surface.
It is a measurement result of a sample in which the surface of an aAs substrate has a (2 × 4) rearranged structure and a thin film is formed on the substrate surface. The magnetic field at the time of magnetization measurement was respectively applied to the inside of the thin film. FIG.
From the above data, it is possible to produce a very good ferromagnetic thin film on a GaAs substrate, and the coercive force and the value of the remanent magnetization can be controlled by, for example, the most-arranged structure on the substrate surface. I understand.

Like the refractive index control layer 2b, the optical waveguide 4 is formed so that the refractive index of the substrate main body 2a is slightly larger than that of the substrate main body 2a by changing the additive composition. As shown in FIGS. 1 and 2, the upper end of the optical waveguide is formed in the substrate main body 2a so as to be in contact with the refractive index control layer 2b, and the gap between the light input end 8 and the light output end 9 is formed. It is divided into two branch waveguides 4a and 4b along the way. The ferromagnetic metals 3a and 3b are provided above the branch waveguides 4a and 4b via a refractive index control layer 2b.

Above the substrate 2, one metal wire 5 is disposed so as to be orthogonal to the branch waveguides 4a and 4b, and two metal wires 6a and 6b are arranged along the branch waveguides 4a and 4b. The metal wire 5 and the metal wire 6a are connected to the ferromagnetic metal 3
a, and the metal wire 5 and the metal wire 6b cross each other above the ferromagnetic metal 3b.

In the semiconductor optical integrated circuit 1 having the above configuration,
The magnitude and direction of the magnetization of the ferromagnetic metal 3a depend on the magnitude and direction of the control current I1 applied to the metal line 5, and
a can be arbitrarily changed by a combination of the magnitude and the direction of the control current I21 supplied to a. Similarly, the magnitude and direction of the magnetization of the ferromagnetic metal 3b are arbitrary depending on the combination of the magnitude and direction of the control current I1 applied to the metal wire 5 and the magnitude and direction of the control current I22 applied to the metal wire 6b. Can be changed to The control currents I1, I21 and I22 magnetize the ferromagnetic metals 3a and 3b, respectively, and apply a magnetic field to the branch waveguides 4a and 4b by the magnetization. The light passing from the input end 8 to the output end 9 of the optical waveguide 4 is affected by the magnetic field applied to the branch waveguides 4a and 4b when passing through the branch waveguides 4a and 4b, Is modulated based on the magneto-optic effect. The modulated light is combined after passing through the branch waveguides 4a and 4b, and emitted from the output end 9 as modulated light.

Thereafter, the power is turned off and the control currents I1, I
21 and I22 are turned off, the ferromagnetic metals 3a, 3b
Holds its magnetization, so that the modulation of the output light with respect to the input light can be held as it is.

The magnetization of the ferromagnetic metals 3a and 3b will be further described with reference to FIG.

FIGS. 4A and 4B are diagrams for explaining the magnetization of the ferromagnetic metal. FIG. 4A shows the case where the control current is applied, and FIG. 4B shows the case where the control current is off. The control current I1 is applied to the metal wire 5 and the control current 21 is applied to the metal wire 6a.
When the current is supplied, a magnetic field is generated around the metal wires 5 and 6a by the current, and the resultant magnetic field acts on the ferromagnetic metal 3a. Here, the control current I21 applied to the metal wire 6a is applied to the ferromagnetic metal 3a. Only the magnetic field based on the control current I21 will be described. When the control current I21 is applied to the metal wire 6a, a magnetic field H is generated around the metal wire 6a as shown in FIG. 4A, and the magnetic field H magnetizes the ferromagnetic metal 3a in a certain direction. Due to the magnetization of the ferromagnetic metal 3a, a magnetic field J is generated around the ferromagnetic metal 3a, and the magnetic field J is applied to the branch waveguide 4a to modulate light passing through the inside.

Thereafter, even if the control current I21 is turned off, as shown in FIG. 4B, the ferromagnetic metal 3a retains its magnetization, and the control current I21 flows around the ferromagnetic metal 3a.
A magnetic field J is generated in the same manner as in the case where is supplied with electric current, and this magnetic field J is applied to the branch waveguide 4a and modulates light passing therethrough.

FIG. 5 is a time chart for explaining the relationship between the control current and the output light modulation. In the figure, when the control currents I1, I21, I22 turn on at time t1,
The ferromagnetic metals 3a and 3b are magnetized, and the input light L1 turned on at time t1 is modulated by the magnetization, and an output light modulation ΔL2 shown in the upper part of FIG. 5 appears in the output light. Thereafter, at time t2, the control currents I1, I21,
Even if I22 is turned off, the magnetization of the ferromagnetic metals 3a and 3b is maintained, so that the output light modulation amount ΔL2 is continuously output as it is. At time t3, when the control currents I1 and I22 are applied in a combination that just cancels the output light modulation ΔL2, the output light modulation Δ
L2 becomes zero. Thereafter, at time t4, the control current I
Even if 1, I22 is turned off, the magnetization of the ferromagnetic metals 3a, 3b is maintained, and the state where the output light modulation amount ΔL2 is zero continues.

As described above, in the first embodiment, in the semiconductor optical integrated circuit 1, the ferromagnetic metals 3a and 3b are formed in a thin film instead of the permanent magnet conventionally used. The semiconductor optical integrated circuit 1 can be highly integrated, and can be significantly reduced in size.

Further, since the control current is applied in two directions perpendicular to each other above the ferromagnetic metals 3a and 3b, the ferromagnetic metals 3a and 3b can be magnetized in desired sizes and directions. Therefore, the modulation of the input light can be freely performed, and desired light wave control can be performed.

Further, even if the control currents I1, I21, I22 are turned off, the magnetization of the ferromagnetic metals 3a, 3b is maintained as it is, so that the control of the light wave can be continued without supplying external energy. Power consumption can be reduced.

Next, a second embodiment will be described with reference to FIGS.

FIG. 6 is a perspective view schematically showing a semiconductor optical integrated circuit according to the second embodiment of the present invention. 1, a semiconductor optical integrated circuit 10 of the present invention is a quasi-monolithic integrated circuit in which various optical elements are integrally integrated on a substrate 20 made of gallium arsenide (GaAs) semiconductor crystal. A) A substrate 20 made of a semiconductor crystal has a row configuration A in which a semiconductor laser 50, an optical modulator 60 as a control element, and a ferromagnetic metal 30 also as a control element are arranged in a row.
In FIG. 6, the column configuration B is arranged adjacent to the column configuration A for one column. However, since the column configuration A and the column configuration B are substantially the same, each component of the column configuration B will be described. Means that b is added to the end of the reference numeral assigned to each component of the column configuration A, and the description is omitted. In FIG. 6, the row configuration is two rows, but in an actual semiconductor optical integrated circuit, a large number of the row configurations are arranged.

The ferromagnetic metal 30 is, like the ferromagnetic metals 3a and 3b in the first embodiment, supplied with a current through a metal wire disposed above the ferromagnetic metal 3a and 3b, and is then magnetized once. And a magnetic field is formed around it based on the residual magnetization.

The above-described semiconductor laser 50 is formed at one end side inside the substrate 20 and includes a semiconductor laser body 51 and an electrode 5.
2 and 53. From the semiconductor laser main body 51 to the other end of the substrate 20, two layers of a refractive index control layer 41 and a buried optical waveguide 40 are formed.
Is on the same plane as the upper end of the substrate 20. In the refractive index control layer 41, the gold electrode 60 and the ferromagnetic metal 30 are formed in a thin film shape, respectively.
Constitutes an optical modulator together with the lower optical waveguide 40, and this optical modulator turns on the optical waveguide 4 by energizing the gold electrode 60.
It has the function of changing the phase of light passing through zero.

The ferromagnetic metal 30 is a nickel (Ni) thin film grown and bonded by an electrodeposition method.
Is formed at the upper end on the other end side. This ferromagnetic metal 30
A sample for measuring the magnetic properties of
When the magnetic characteristics are measured using the sample formed on the s substrate, the sample is the ferromagnetic metal 3 in the first embodiment.
Magnetization hysteresis similar to a and 3b was shown.

The semiconductor optical integrated circuit 10 shown in FIG.
In the above, the light guided in the optical waveguide 40 is incident on the ferromagnetic metal 30 from the refractive index control layer 41 side (back side). In this case, the ferromagnetic metal 30 acts as a polarizer. In order to measure the magnetic properties of the ferromagnetic metal 30, the magneto-optical effect was measured from the surface side of the ferromagnetic metal 30, and a spectrum as shown in FIG. 7 was obtained.
That is, it was found that the thin-film ferromagnetic metal 30 directly bonded to the substrate 20 exhibited a remarkable magneto-optical Kerr effect similar to that of a bulk, and it was found that it could be used as a polarizer.

Semiconductor optical integrated circuit 1 configured as described above
0, when the ferromagnetic metal 30 is used as a polarizer, a part of the light passing through the optical waveguide 40 below the ferromagnetic metal 30 is transmitted through the refractive index control layer 41 to the ferromagnetic metal 30. The ferromagnetic metal 30 exudes to the lower surface, and exhibits the magneto-optical Kerr effect shown in FIG. 7 for the light, and functions as a polarizer.

FIGS. 8A and 8B are diagrams showing the rotation angle of the polarization plane at each part of the light emitted from the semiconductor laser. FIG. 8A shows the rotation angle of the polarization plane at each part of the column structure A in FIG.
Indicates the rotation angle of the polarization plane in each part of the adjacent row configuration B.
Note that, in this figure, reference numerals 60 and 60b actually represent the modulator 6
0, 60b correspond to the optical waveguides 40, 40b present below, and 30, 30b are the ferromagnetic metals 30, 3,
It corresponds to the optical waveguides 40 and 40b that exist below 0b.

As shown in the figure, the laser light emitted from the semiconductor laser 50 having the row configuration A is modulated by the modulator 60, and the polarization plane thereof is rotated by a predetermined angle by the ferromagnetic metal 30. Out of the fiber. On the other hand, the laser light emitted from the semiconductor laser 50b in the row configuration B is
The light is modulated by the modulator 60b and has a phase that is temporally advanced with respect to the light in the row configuration A. Then, the plane of polarization is rotated in the opposite direction to the light in the row configuration A by the ferromagnetic metal 30b. The light is emitted to the downstream fiber. in this way,
When the semiconductor optical integrated circuit 10 is used, the polarization plane and phase of light can be arbitrarily controlled, and various light controls can be performed. Further, an isolator function can be provided by utilizing the rotation of the polarization plane.

As described above, also in the second embodiment,
Since the ferromagnetic metal 30 is directly bonded to the semiconductor substrate 20, all of the components constituting the semiconductor optical integrated circuit 10 can be integrated, and therefore, the semiconductor optical integrated circuit 10 can be significantly reduced in size. Can be realized.

Further, since the residual magnetization of the ferromagnetic metal 30 is maintained as it is, the control of the light wave can be continued without supplying energy from the outside. Therefore, in this embodiment, a large number of column arrangements A are provided. In this case, the power consumption is greatly reduced.

In each of the above embodiments, the substrates 2, 2
Although the semiconductor device is configured to use a gallium arsenide (GaAs) semiconductor as the semiconductor device, other semiconductors, for example, Si, SiC, Ge
Group IV semiconductors such as AlAs, InAs, GaS
Any material may be used as long as an optical integrated circuit can be manufactured, such as b, InP, or a III-V semiconductor represented by a mixed crystal thereof. Since a semiconductor can change its energy gap freely, it is a magneto-optical material corresponding to any wavelength region.

In the first embodiment, the ferromagnetic metals 3a and 3b are formed of manganese antimony (MnSb). In the second embodiment, the ferromagnetic metal 30 is formed of nickel (Ni). However, other materials such as MnAs, Mn2Sb, MnGa, MnAl, and MnB
A ferromagnetic compound such as i or a ferromagnetic element such as Fe or Co and a compound thereof may be used.

Further, in each of the above embodiments, the ferromagnetic metal is formed as a single layer. However, the ferromagnetic metal may be formed as a multi-layer structure, or the ferromagnetic metal may be present in a semiconductor in a cluster. It may be formed.

In order to control the magnetic properties such as the magnetic transition temperature and the saturation magnetic field, the ferromagnetic metal may be a mixture of any of the various materials described above in an appropriate combination, or Al, Si, or the like. Ti, V, Cr, Cu, Zn, Zr,
Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, I
n, Sn, Te, Hf, Ta, W, Re, Os, Ir,
At least one of Pt, Au, Hg, Tl, Pb, and Bi may be appropriately added.

As a method of forming a ferromagnetic metal, the molecular beam epitaxy is used in the first embodiment and the electrodeposition method is used in the second embodiment. Any material may be used as long as it forms a ferromagnetic material, such as a phase growth method, a sputtering method, a laser ablation method, or a combination thereof with heat treatment, laser treatment, and electron beam treatment. Preferably, among them, molecular beam epitaxy, vapor deposition, sputtering,
Vacuum evaporation such as laser ablation is preferred. The deposition temperature is from -80 ° C to 400 ° C, preferably from room temperature to 2 ° C.
Desirably, the temperature is 50 ° C. If the ferromagnetic material is joined in this temperature range, the structure of the element made of a semiconductor will not be destroyed.

[0044]

As described above, according to the semiconductor optical integrated circuit of the present invention, a ferromagnetic metal is formed in a thin film on a substrate in place of a conventionally used permanent magnet. The semiconductor optical integrated circuit can be highly integrated, and can be significantly reduced in size.

Further, since the ferromagnetic metal can maintain its magnetization even when the control current is turned off, the control of the light wave can be continued without supplying energy from the outside, and the power consumption can be reduced. it can.

[Brief description of the drawings]

FIG. 1 is a plan view showing a configuration of a semiconductor optical integrated circuit of the present invention.

FIG. 2 is a sectional view taken along line XX of FIG.

FIG. 3 is a magnetization hysteresis curve showing measurement results of a sample.

FIG. 4 is a diagram for explaining magnetization of a ferromagnetic metal.

FIG. 5 is a time chart for explaining a relationship between a control current and an output light modulation amount.

FIG. 6 is a perspective view schematically showing a semiconductor optical integrated circuit according to a second embodiment of the present invention.

FIG. 7 is a diagram showing a measurement result of a magneto-optical Kerr effect of a ferromagnetic metal.

8A and 8B are diagrams showing the rotation angle of the polarization plane at each part of the light emitted from the semiconductor laser. FIG. 8A shows the rotation angle of the polarization plane at each part of the column configuration A in FIG. 6, and FIG. The rotation angle of the polarization plane in each part of the row configuration B is shown.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Semiconductor optical integrated circuit 2 Substrate 2a Substrate main body 2b Refractive index control layer 3a Ferromagnetic metal 3b Ferromagnetic metal 4 Optical waveguide 4a Branch waveguide 4b Branch waveguide 5 Metal wire 6a Metal wire 6b Metal wire 8 Input end 9 Output end 10 Semiconductor optical integrated circuit 20 Substrate 30 Ferromagnetic metal 30b Ferromagnetic metal 40 Optical waveguide 40b Optical waveguide 41 Refractive index control layer 50 Semiconductor laser 50b Semiconductor laser 51 Semiconductor laser main body 51b Semiconductor laser main body 52 Electrode 53 Electrode 60 Modulator 60b Modulator A row configuration B row configuration H Magnetic field I1, I21, I22 Control current J Magnetic field L1 Input light ΔL2 Output light modulation

──────────────────────────────────────────────────続 き Continued on the front page Examiner Takashi Hinatsuta (56) References JP-A-9-139539 (JP, A) JP-A-6-186514 (JP, A) US Patent 5598492 (US, A) (58) Field surveyed (Int.Cl. ⁷ , DB name) G02F 1/09-1/095 G02F 1/015-1/025 JICST file (JOIS)

Claims (3)

(57) [Claims] 1. A semiconductor optical integrated circuit in which a semiconductor crystal is used as a substrate and various optical elements are integrated, and the magnetic effect can be arbitrarily controlled by bonding to the semiconductor crystal.
A thin ferromagnetic metal thin film, and an optical waveguide formed so as to pass through a region within the semiconductor crystal where the magnetic effect of the ferromagnetic metal thin film is exerted. Semiconductor optical integrated circuit. 2. A magnetic effect of the ferromagnetic metal thin film is generated arbitrarily control a ferromagnetic metal thin film on the basis of the induced magnetic field by energizing the ferromagnetic metal above the wire
The semiconductor optical integrated circuit according to claim 1, wherein the effect is caused by a possible magnetic field. 3. A magnetic effect of the ferromagnetic metal thin film, ferromagnetic metal thin when energization of the said wires
3. The semiconductor optical integrated circuit according to claim 2, wherein the effect is caused by a magnetic field generated from the ferromagnetic metal thin film due to residual magnetization of the film .