JPH05275808A - Optical device - Google Patents

Abstract

PURPOSE:To obtain a waveguide type optical device such as semiconductor laser, semiconductor optical amplifier and optical modulator which ensure low loss and good productivity. CONSTITUTION:A first and a second core layers 5, 102 are laminated in the thickness direction and the width of the second core layer 102 is formed narrower than the width of the first core layer 5 in view of generating difference of refractive index. Simultaneously, the periphery of the ridged clad consisting of conductive medium is buried within at least a kind of half- insulating, n type, p type or non-doped clad layer 107, leaving the first core layer 5 and a guide layer 6 as the optical functioning part.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical device having at least a clad layer and a core layer on a substrate and using at least a part of the clad layer as a conductive medium.

[0002]

2. Description of the Related Art A ridge type semiconductor laser is taken as an example of a conventional optical waveguide device, its sectional view is shown in FIG. 13, and its perspective view is also shown in FIG. Here, 1 is a p-side electrode, 2 is a p ⁺ -InGaAs cap, 3 is p-InP
Clad, 4 is p-InP side clad, 5 is i-M
QW active layer, 6 is n-InGaAsP guide layer, 7 is n
-InP clad, 8 is an n-side electrode. By applying a forward bias between the p-side electrode 1 and the n-side electrode 8, it oscillates as a ridge type laser and emits light.

[0003]

In this ridge type semiconductor laser, the mesa width W of the mesa formed by the electrode 1, the cap 2 and the cladding 3 and the thickness D of the p-InP side cladding 4 influence the single mode oscillation. If the mesa width W and the thickness D of the side clad 4 are larger than a predetermined value, the condition for single mode oscillation is broken and multimode oscillation occurs. Generally, mesa width W and side clad 4
The thickness D of the p-InP clad layer 3 is defined by wet etching or dry etching.
Thickness (about 1.5 μm), the etching amount is large, and processing variations in the mesa width W and the thickness D of the side cladding 4 are large. As a result, the yield of this ridge-shaped semiconductor laser for single-mode oscillation is deteriorated. In addition, the propagation loss of light increases due to the roughness of the side surface of the ridge during processing.

Therefore, an object of the present invention is to solve the above problems and provide a waveguide type optical device such as a semiconductor laser, a semiconductor optical amplifier, and an optical modulator, which has low loss and is easily manufactured. ..

[0005]

In order to achieve such an object, the present invention according to claim 1 has at least a clad layer and a core layer on a substrate, and at least a part of the clad layer is made conductive. In the optical device using the medium, the core layer has at least first and second core layers stacked in the thickness direction, and the width of the second core layer is smaller than the width of the first core layer. And also the second core layer is arranged on at least one of the upper side and the lower side of the first core layer to generate a refractive index difference in the lateral direction so that it can be regarded as a single optical waveguide in the lateral direction. In addition, at least one kind of semi-insulating, n-type, p-type, and non-doped clad layer is embedded around the clad layer made of a conductive medium, and the clad layer of the first core layer and the second core layer is further embedded. Characterized in that the one with the optical function layer even without.

According to a second aspect of the present invention, in the optical device according to the first aspect, at least one core layer of the first and second core layers is composed of a quantum well or a multiple quantum well. And

According to a third aspect of the present invention, in the optical device according to the first or second aspect, the width of the conductive medium layer is made wider than the width of the second core layer.

According to a fourth aspect of the present invention, in the optical device according to any one of the first to third aspects, the substrate is an n-type doped substrate.

The present invention according to claim 5 is the optical device according to any one of claims 1 to 3, wherein the substrate is a p-type doped substrate.

According to a sixth aspect of the present invention, in the optical device according to any one of the first to third aspects, the substrate is a semi-insulating substrate.

The present invention according to claim 7 is characterized in that the optical device according to any one of claims 1 to 6 is configured as a part of a semiconductor optical integrated device.

[0012]

According to the present invention, the core layer is formed by laminating at least the first and second core layers in the thickness direction, and the width of the second core layer is equal to that of the first core layer. By making the width narrower than the width, a difference in refractive index is generated, and at least one kind of semi-insulating, n-type, p-type or non-doped clad surrounds the periphery of the ridge-shaped clad made of a conductive medium. By using at least one of the core layer and the second core layer as an optical functional layer for optical amplification or the like, a thin second core layer with high processing accuracy is used, and the second core layer is embedded. Since the refractive index difference in the lateral direction is defined and realized by, the single mode operation becomes easy. Furthermore, since the present invention has a buried structure, the propagation loss is small. Moreover, the optical device of the present invention has an advantage that it can be formed in a part of an optical integrated circuit together with other optical functional circuits such as an optical switch.

[0013]

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

As an embodiment of the present invention, the wavelength used is 1.5.
Taking the case of a 5 μm semiconductor laser or semiconductor amplifier as an example, the manufacturing procedure thereof will be described, and the structure of the present invention will be described in the description.

As shown in FIG. 1, the n-InGaAsP guide layer 6 is arranged on the n ⁺ -InP substrate 7, and the MQW layer 5 and InGa as the first core layer are formed on the guide layer 6.
An AsP (bandgap wavelength 1.3 μm) etch stop layer 100, an InP etch stop layer 101, and an InGaAsP layer 102 for forming a second core are deposited.
Then, a photoresist layer 8 is placed on the layer 102 and the photoresist layer 8 is patterned to form the photoresist 8 as shown in FIG. This photoresist pattern 8 is used to perform a second wet etching.
The core 102 is formed. At this time, the InP layer 101 serves as an etch stop layer. In the case of dry etching, the etch stop layer 101 is unnecessary.

As shown in FIG. 2, on the layers 101 and 102, p-InP layers 103 and p ⁺ forming a conductive medium layer are formed.
After depositing the InGaAs cap layer 104, a SiO ₂ layer 105 is further deposited, a photoresist 106 is applied, and then patterned as shown in FIG. 2 to form a SiO ₂ mask 105.

Using the photoresist 106 as a mask,
As shown in FIG. 3, the p-InP layer 103 is dry-etched and wet-etched to form a ridge shape. At this time, the InGaAsP layer 100 becomes an etch stop layer.

As shown in FIG. 4, the photoresist 106 is removed, and then the SiO ₂ mask 105 is used as a mask.
A ridge-shaped p− as a clad layer made of a conductive medium
The periphery of the InP layer 103 is filled with a semi-insulating medium 107 such as Fe-doped InP or non-doped InP.

While removing the SiO ₂ mask 105, as shown in the sectional view of FIG. 5 and the perspective view of FIG. 6, the p-side electrode 1 is provided on the cap layer 104, and the n-side electrode 8 is formed on the substrate 7.
Provided on the bottom surface of. In FIG. 6, the active layer 5 and the guide layer 6 are left only in the optical function part and the other parts are removed, and i-InGaA having a band gap wavelength of 1.3 μm is removed.
The sP layer 108 has a butt joint.

Here, if a forward bias is applied between the p-side electrode 1 and the n-side electrode 8, it operates as a semiconductor laser or a semiconductor amplifier switch. On the other hand, if a reverse bias is applied, it operates as a light intensity or optical phase modulator.

In the structure of this embodiment, the width of the p-side electrode 1, that is, the width W of the p ⁺ -InGaAs cap layer 104 is made wider than the width w of the second core 102 to improve the efficiency.

7 and 8 are a sectional view and a perspective view, respectively, showing a second embodiment of the present invention. In this embodiment, the second core 102 is provided below the i-MQW layer 5 and the guide layer 6, which are common cores.

Although the n-InP substrate is used as the substrate 7 in the above embodiments, a p-InP substrate may be used. In this case, the upper conductive clad and the cap layer are n-type doped, and the lower conductive clad is p-type doped.

9 and 10 are sectional views showing a third embodiment in which a semi-insulating InP substrate 111 is used instead of the n-InP substrate 7 in the first embodiment shown in FIG. 5, respectively. FIG. Here, 103 is p-I
nP clad layer, 109 is an n-InP clad layer, 11
Reference numeral 0 is a non-doped InP buffer layer. The rest of the configuration is the same as in the first embodiment.

11 and 12 are sectional views showing a fourth embodiment in which a semi-insulating InP substrate 111 is used instead of the n-InP substrate 7 in the second embodiment shown in FIG. FIG. Other configurations are the same as those in the second embodiment.

Furthermore, in the third or fourth embodiment, the upper clad is p-type and the lower clad is n-type, but conversely the upper clad may be n-type and the lower clad is p-type. ..

Alternatively, in the present invention, for example, i-InGaAs / InP, i-InG is used as the first core layer 5.
MQW layers such as aAs / InAlAs can be used, but MQW layers or bulk materials of other compositions may also be used.

Furthermore, although the present invention can be realized as a single optical device, it can also be applied as an amplifier for compensating for optical propagation loss in an optical device such as an optical switch.

[0029]

As described above, according to the present invention, the core layer is constituted by laminating at least the first and second core layers in the thickness direction, and the width of the second core layer is ,
By making the width narrower than the width of the first core layer, a refractive index difference is generated, and at least one kind of semi-insulating, n-type, p-type or non-doped clad around the ridge-shaped clad made of a conductive medium. By using a thin second core layer having a high processing accuracy by embedding by means of the above, and at least one of the first core layer and the second core layer is an optical functional layer for optical amplification or the like. Since the second core layer is embedded and the lateral refractive index difference is defined and realized, single mode operation is facilitated. Moreover, the optical device of the present invention has an advantage that it can be formed in a part of an optical integrated circuit together with other optical functional circuits such as an optical switch. Furthermore, since the present invention is a buried structure,
There is also an advantage that the propagation loss is small.

[Brief description of drawings]

FIG. 1 is a diagram illustrating a manufacturing process according to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating a manufacturing process according to the first embodiment of the present invention.

FIG. 3 is a diagram illustrating a manufacturing process according to the first embodiment of the present invention.

FIG. 4 is a diagram illustrating a manufacturing process according to the first embodiment of the present invention.

FIG. 5 is a cross-sectional view of the first embodiment of the present invention.

FIG. 6 is a perspective view of the first embodiment of the present invention.

FIG. 7 is a sectional view of a second embodiment of the present invention.

FIG. 8 is a perspective view of a second embodiment of the present invention.

FIG. 9 is a sectional view of a third embodiment of the present invention.

FIG. 10 is a perspective view of a third embodiment of the present invention.

FIG. 11 is a sectional view of a fourth embodiment of the present invention.

FIG. 12 is a perspective view of a fourth embodiment of the present invention.

FIG. 13 is a sectional view of a conventional example.

FIG. 14 is a perspective view of a conventional example.

[Explanation of symbols]

1 p-side electrode 2 p ⁺ -InGaAs cap 3 p-InP clad 4 p-InP side clad 5 i-MQW active layer (first core layer) 6 n-InGAAsP guide layer 7 n-InP clad 8 n-side electrode 100 InGaAsP etch stop layer 101 InP etch stop layer 102 InGaAsP second core layer 103 p-InP clad layer 104 p-InGaAs cap layer 105 SiO ₂ mask 106 photoresist 107 InP buried layer 108 InGaAsP core layer

Claims (7)

[Claims] 1. An optical device having at least a clad layer and a core layer on a substrate, wherein at least a part of the clad layer is a conductive medium, wherein the core layer is at least a first layer and a first layer laminated in the thickness direction. Has two core layers,
The width of the second core layer is made narrower than the width of the first core layer and the second core layer is arranged on at least one of the upper side and the lower side of the first core layer so that In the same direction, a refractive index difference is generated in the lateral direction so that it can be regarded as a single optical waveguide, and at least one kind of clad layer of semi-insulating, n-type, p-type, and non-doped is provided around the clad layer made of a conductive medium. Embedded by
Furthermore, at least one of said 1st core layer and said 2nd core layer was made into the optical functional layer, The optical device characterized by the above-mentioned. 2. The optical device according to claim 1, wherein at least one core layer of the first and second core layers comprises a quantum well or a multiple quantum well. 3. The optical device according to claim 1, wherein the width of the conductive medium layer is wider than the width of the second core layer. 4. The optical device according to any one of claims 1 to 3, wherein the substrate is an n-type doped substrate. 5. The optical device according to any one of claims 1 to 3, wherein the substrate is a p-type doped substrate. 6. The optical device according to claim 1, wherein the substrate is a semi-insulating substrate. 7. A semiconductor optical integrated optical device comprising the optical device according to claim 1 as a part of a semiconductor optical integrated device.