JP2007220930A - Optical semiconductor integrated device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the separation length between optical elements in an optical semiconductor integrated device wherein the optical elements sharing an embedded mesa stripe including an optical waveguide are monolithically integrated. <P>SOLUTION: This optical semiconductor integrated device comprises a mesa stripe 6 including an upper clad layer 5 laminated on the optical waveguide 4 and having side faces insulated by a high resistance embedded layer 7, and first and second electrodes 12a, 12b provided on the upper surface of the mesa stripe 6 via a separating zone 10. The minimum width of the mesa strip 6 in the separating zone 10 is smaller than the maximum width thereof under the first electrode 12a, and the maximum width thereof under the second electrode 12b. The width of the upper clad layer 5 in the separating zone 10 is small, so that the interference from the adjacent electrode is suppressed. On the other hand, the degradation of the device characteristics is reduced because the width of the optical waveguide 4 can be made larger under the electrode. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an optical semiconductor integrated device in which optical semiconductor devices sharing a mesa stripe including an optical waveguide are integrated, and more particularly, to an optical semiconductor integrated device that suppresses interference between electrodes provided adjacently on a mesa stripe.

  An optical semiconductor integrated device that monolithically integrates multiple optical devices with various functions has been developed because it can realize high-performance optical devices that can be used for advanced and complex optical communication systems used for wavelength division multiplexing (WDM) communications. Is underway.

  For example, a modulator integrated semiconductor laser in which a DFB laser as an optical communication light source and an optical modulator are integrated, a wavelength tunable semiconductor laser in which a laser light emitting unit, a phase control element, and a wavelength tunable DBR waveguide are integrated, or in an optical waveguide direction A TDA-DFB tunable semiconductor laser has been developed in which active layers and wavelength control layers are alternately arranged and currents are independently injected.

  In these monolithic optical semiconductor integrated devices, each optical device shares one mesa stripe including an optical waveguide (for example, a buried mesa stripe in which a side surface of the mesa stripe is buried by a high-resistance buried layer), and the mesa stripe. The electrode of each element is arrange | positioned on the top. The optical waveguide of the present specification refers to a path provided for propagating light. In addition to an optical transmission path for simply transmitting light, an active layer having an amplification gain of light, and a refractive index And an optical transmission line composed of layers whose absorption coefficient or absorption edge wavelength can be controlled by applied voltage or injection current.

  Such a buried mesa stripe has a laminated structure in which an upper clad layer is laminated on an optical waveguide, and the electrode of each optical element sharing the buried mesa stripe is on the upper clad layer constituting the upper part of the mesa stripe. The mesa stripes are arranged in a line along the extending direction.

  However, since the electrodes of each optical element are provided on the upper clad layer having high electrical conductivity, the insulation separation between the adjacent optical elements is insufficient, and the influence of the current or voltage applied to the electrodes of the adjacent optical elements is affected. In response, the characteristics of the optical element may deteriorate. In order to reduce the interference caused by the current or voltage applied to the electrodes of the adjacent optical elements, it is necessary to sufficiently increase the interval between the optical elements. For this reason, it is difficult to reduce the size of an optical semiconductor integrated device in which these elements are integrated.

  Further, the optical waveguide under the electrodes constituting the optical element cannot be made too narrow from the viewpoint of avoiding deterioration of element characteristics. For this reason, the method of reducing the width of the upper cladding layer having conductivity by narrowing the mesa stripe width (that is, the width of the optical waveguide) and increasing the resistance of the upper cladding layer to improve the isolation between the elements is the optical waveguide. It is difficult to achieve sufficient isolation between elements due to width restrictions. The structure and problems of these conventional optical semiconductor integrated devices will be described below with reference to specific examples.

  FIG. 10 is an explanatory view of a conventional optical semiconductor integrated device, showing a mesa stripe structure including a waveguide and an electrode arrangement. 10A is a plan view of the optical semiconductor integrated device, and FIGS. 10B to 10E are a QR sectional view, a KL sectional view, a MN sectional view, and an OP sectional view of FIG. 10A, respectively. .

  Referring to FIG. 10, in the optical semiconductor collector, a semiconductor laser 16 and an optical modulator 15 are integrated on a substrate 1 with a separation band 10 therebetween. This optical semiconductor integrated device has a mesa stripe 6 of a certain width formed on a substrate 1, and the side surface of the mesa stripe 6 is buried with a high resistance buried layer 7. The mesa stripe 6 is formed by processing a laminated structure including the layers constituting the optical waveguide 4 and the upper contact layer 5 into a mesa stripe shape. Therefore, the optical waveguide 4 and the upper contact layer 5 have the same width as the mesa stripe 6. Defined. A diffraction grating layer 2 is provided under the optical waveguide 4 via a buffer layer 3, and this diffraction grating layer 2 constitutes a diffraction grating 2 a of a DFB laser in the formation region of the semiconductor laser 16.

  The optical waveguide 4 includes an active layer 4a having an optical amplification factor in the semiconductor laser 16 formation region, a modulation layer 4b whose absorption wavelength end is controlled by voltage in the modulator 15 formation region, and loss of transmitted light in the separation region. The light transmission layer 4c is small. In the light transmission layer 4c, the modulator 10 side is made of the same layer as the modulation layer 4b, and the semiconductor laser 16 side is made of the same layer as the active layer 4a.

  The semiconductor laser 16 and the electrodes 12 a and 12 b of the modulator 15 are disposed on the mesa stripe 6 on both sides of the separation band 10. These electrodes 12a and 12b are provided on the upper surface of the upper cladding layer 5 constituting the mesa stripe via the contact layer 11.

  Interference between the electrodes 12a and 12b occurs mainly through the upper cladding layer 5 constituting the mesa stripe 6, and the degree of the interference strongly depends on the electrical resistance between the electrodes 12a and 12b of the upper cladding 5 of the separation band 10. To do. The electrical resistance between the electrodes 12 a and 12 b of the upper cladding 5 of the separation band 10 is proportional to the length of the separation band 10 and inversely proportional to the width of the upper cladding layer 5 (that is, the width of the mesa stripe 6). Therefore, interference can be reduced (that is, element isolation can be made more complete) by increasing the length of the separation band 10 and reducing the width of the mesa stripe 6.

  However, in the conventional optical semiconductor integrated device, the width of the mesa stripe 6 is the same through the semiconductor laser 16, the modulator 15, and the separation band 10. In such an element, it is necessary to determine the width of the mesa stripe 6 according to the element having the maximum width of the optical waveguide 4 (that is, the width of the mesa stripe 6) required from the viewpoint of element characteristics. As a result, the width of the mesa stripe 6 of the separation band 10 must be wider than the necessary width of the separation band 10, and the electrical resistance of the upper clad layer 5 of the separation band 10 is reduced, resulting in insufficient isolation between elements. Prone. For this reason, in the conventional optical semiconductor integrated device, it is necessary to perform separation between the elements by making the separation band 10 sufficiently long. Since such a long separation band 10 is provided, the element length of the optical semiconductor integrated device becomes long. It was.

  In order to avoid the problem of the separation band 10 of the conventional optical semiconductor integrated device described above and shorten the device size, a groove is formed on the surface of the upper cladding layer to prevent the influence from adjacent electrodes, and between the optical devices. A method of shortening the interval has been devised. (For example, see Patent Document 1).

  In this method, a groove is formed on the surface of the upper cladding layer exposed between the electrodes, and insulation separation is performed by utilizing the fact that the upper cladding layer is thinned and the resistance is increased at the groove portion. Interference between the electrodes disposed in the is prevented.

  Also, a method has been devised in which a high resistance ion implantation layer is formed in the upper clad layer to insulate and separate the electrodes. (For example, refer to Patent Document 2).

  In this method, H is ion-implanted into an upper clad layer exposed between adjacent electrodes, the upper clad layer is converted into a high resistance layer, and interference between electrodes arranged on both sides of the upper clad layer is achieved. To prevent.

In the method by forming these grooves or ion-implanted layers, the electric resistance of the upper cladding layer in which the grooves or ion-implanted layers are formed increases, so that sufficient element isolation can be achieved even if the distance between the electrodes is shortened.
JP-A-62-032680 JP 2001-326424 A

  As described above, in a conventional optical semiconductor integrated device that uses a mesa stripe of uniform width in common for each optical element, it is difficult to shorten the distance between the electrodes of each element due to the isolation between the elements. There has been a problem that the element length of the apparatus becomes long. Further, in the method of separating elements by narrowing the mesa stripe width, it is necessary to maintain the mesa stripe width necessary for avoiding deterioration of element characteristics, and it is difficult to sufficiently shorten the element length.

  Furthermore, in the isolation using the groove or ion implantation described above, there is a problem that a groove forming process or an ion implantation process must be added in addition to the normal manufacturing process, and the number of processes is increased.

  The present invention can be manufactured without adding a special manufacturing process for forming isolation between elements, and insulates the electrodes of each element provided on the mesa stripe at a short distance. An object of the present invention is to provide an optical semiconductor integrated circuit that can be used.

  In an optical semiconductor integrated device according to the present invention for solving the above-mentioned problems, a mesa stripe including an upper cladding layer laminated on an optical waveguide, the side of which is insulated by a high resistance layer, and an upper surface of the mesa stripe In the optical semiconductor integrated device having the first and second electrodes provided separately, the minimum width of the mesa stripe between the electrodes is larger than the maximum width under the first electrode and the maximum width under the second electrode. Configure narrowly.

  That is, the width of the mesa stripe is made narrower between the electrodes than the maximum width under any adjacent electrode. In other words, the minimum width Wi of the mesa stripe between the electrodes is set such that Wi <W1 and Wi <W2 with respect to the maximum widths W1 and W2 of the respective mesa stripes below the first and second electrodes.

  In the configuration of the present invention, the distance between the elements can be shortened because the electrical resistance between the electrodes increases as the mesa stripe width between the electrodes is narrowed, that is, the width of the upper cladding layer is narrowed. . Therefore, the element length of the optical semiconductor integrated element can be shortened.

  On the other hand, the mesa stripe width under the electrode can be set to a sufficiently wide width irrespective of element isolation, so that deterioration of element characteristics due to narrowing of the width of the optical waveguide is avoided. Therefore, the element length can be shortened without deteriorating element characteristics.

  Furthermore, the optical semiconductor integrated device of the present invention can be manufactured in the same process as that of a normal optical semiconductor integrated device, except that mesa stripes having different widths are formed under and between the electrodes. The mesa stripes having different widths only need to change the mask pattern of a mask for forming a mesa stripe, for example, an etching mask for forming a mesa, and this does not involve an increase or a change in the manufacturing process. Therefore, the optical semiconductor integrated device of the present invention can be manufactured by substantially the same process as a normal manufacturing process.

  In the above-described optical semiconductor integrated device of the present invention, a buried mesa stripe in which the side surface of the mesa stripe is buried with a high resistance buried layer can be formed. Thereby, it is possible to realize an optical semiconductor integrated device having excellent element characteristics of the embedded mesa stripe type device and less interference between electrodes. Note that a mesa stripe using air as an insulating material may be used instead of the buried layer.

  In the optical semiconductor integrated device of the present invention, the minimum width of the mesa stripe between the electrodes is made wider than half of the maximum width of the mesa stripe under each electrode, that is, W1 / 2 <Wi and W1 / 2 <Wi. It is preferable that Thereby, the optical coupling loss between electrodes can be suppressed within -0.5 db.

  According to the present invention, it is possible to provide an optical semiconductor integrated device having a short element length that can be manufactured without adding a special manufacturing process and has a short element isolation length.

  The first embodiment of the present invention relates to an optical semiconductor integrated device in which a DFB semiconductor laser and an electroabsorption modulator are integrated.

  FIG. 1 is a plan view of an optical semiconductor integrated device according to a first embodiment of the present invention, and shows the mesa stripe and electrode planar shape of the optical semiconductor integrated device. FIG. 2 is a cross-sectional view of the optical semiconductor integrated device according to the first embodiment of the present invention, and represents a cross section AB shown in FIG. 3 is a cross-sectional view showing the mesa stripe structure of the optical semiconductor integrated device according to the first embodiment of the present invention. FIGS. 3A, 3B, and 3C are a CD cross-section and an EF, respectively, shown in FIG. A cross section and a GH cross section are shown.

  1, 2 and 3, in the optical semiconductor integrated device of the first embodiment, a modulator 15 and a semiconductor laser 16 are monolithically integrated on the same substrate 1 with a separation band 10 interposed therebetween. .

  In the first embodiment, a mesa stripe 6 is formed on the n-type InP substrate 1 on which a buffer layer (not shown) is deposited, with both sides buried by a high resistance buried layer 7. The mesa stripe 6 is formed on an n-type InP substrate 1 in order from the bottom, a diffraction grating layer 2 made of n-type InGaAsP, a buffer layer 3 made of n-type InP, a layer constituting the optical waveguide 4, and a p-type InP. A laminated structure is formed by laminating the upper clad layer 5 made of the above, and the laminated structure is formed in a mesa stripe shape. In this etching for forming the mesa stripe, the upper layer of the substrate 1 is included in the mesa stripe 6 so that the upper cladding layer 5 is the uppermost layer and the layer constituting the optical waveguide 4, the buffer layer 3, and the diffraction grating layer 2 are included. It is formed by etching to a depth including. Accordingly, the upper cladding layer 5 and the optical waveguide 4 are both formed to have the same width as the mesa stripe 6. When the mesa stripe 6 has a trapezoidal cross section, the width of the waveguide 4 is the same as the width of the mesa stripe 6 at the height where the waveguide 4 is located. The buried layer 7 is made of Fe-doped InP and electrically insulates the side surface of the mesa stripe 6.

  The mesa stripe in the first embodiment described above is formed by processing a laminated structure into a mesa stripe and then embedding with a high-resistance InP buried layer 7.

  In the first embodiment, the width of the mesa stripe 6 is formed so that the width of the optical waveguide 4 is 1.6 μm in the formation region of the semiconductor laser 16 and the modulator 15 and 0.8 μm in the separation band 10. The length of the separation band 10, that is, the distance between the formation regions of the semiconductor laser 16 and the modulator 15 (separation length) was 10 μm.

  In the region where the semiconductor laser 16 is formed, the optical waveguide 4 is formed by a 50 nm thick SCH layer above and below a 100 nm thick strained MQW layer (multiple quantum well layer) having a luminescence light wavelength of 1.55 μm band. An active layer 4a having a sandwiched structure and having an optical amplification function is configured. Also, in the region where the modulator 15 is formed, a structure in which the upper and lower sides of a 100 nm thick MQW layer (multiple quantum well layer) having a luminescence light wavelength of 1.50 μm band are sandwiched between 50 nm thick SCH layers, respectively. Thus, the modulation layer 4b for controlling the light absorption rate is configured. The optical waveguide 4 in the separation band 10 is the same as the optical waveguide 4 in the region where the semiconductor laser 16 is formed only in the vicinity of the semiconductor laser 16, and the remaining region on the modulator 15 side is the optical waveguide 4 in the region where the modulator 15 is formed. Are the same. However, since no electrode is provided in the separation band 10 and the optical waveguide 4 in the separation band 10 is not excited, it simply functions as a light transmission layer 4c that transmits light with low loss.

  The diffraction grating layer 2 is processed into a diffraction grating 2 a in the region where the semiconductor laser 16 is formed, and constitutes the diffraction grating 2 a of the DFB semiconductor laser 16.

  On the upper surface of the upper cladding layer 5 constituting the uppermost layer of the mesa stripe 6, an electrode 12 a for applying a current for exciting the semiconductor laser 16 and an electrode 12 b for applying a current for modulation to the modulator 15 are provided. These electrodes 12a and 12b are disposed with a separation length of 10 μm across the separation band 10. A contact layer 11 composed of two layers, a p-type InGaAsP layer and a p-type InGaAs layer, is provided under the electrodes 12a and 12b. Furthermore, an electrode 13 that is the opposite electrode of the electrodes 12a and 12b is formed on the back surface of the substrate 1 (the main surface opposite to the mesa stripe 6 formation surface).

  The optical loss of the optical waveguide whose width becomes narrower in the separation band was calculated. FIG. 4 is a diagram showing the optical loss of the separation band, and shows the influence of the optical waveguide width and the separation length of the separation band on the optical loss in the separation band. FIG. 5 is a plan view of the optical waveguide used in the calculation of FIG.

  Referring to FIG. 5, the optical loss of the separation band is as follows. The optical waveguide has the width Wi in the separation band having the separation length of 1 and the widths W1 and W2 (W1 = W2) under the electrodes on both sides. Calculated. The optical waveguide is made of InGaP with a thickness of 200 nm, and this optical waveguide is embedded in InP. In addition, calculation was performed assuming that W1 = W2 = 1.6 μm. The vertical axis in FIG. 5 represents the optical waveguide width Wi of the separation band normalized by the optical waveguide width W1 = W2 below the electrode.

  Referring to FIG. 4, the optical loss in the separation band increases as the optical waveguide width Wi of the separation band becomes narrower and the separation length becomes shorter. However, when the optical waveguide width Wi in the separation band is about 0.5 times the optical waveguide width W1 = W2 below the electrode, for example, about 0.4 to 0.6 times, the optical loss in the separation band is about -0.5 db. Can be suppressed. In the above-described optical semiconductor integrated device according to the first embodiment, the loss of the separation band is calculated to be −0.5 db from the result of FIG. This level of light loss is in a range that can be tolerated as light loss in the separation band of a normal optical semiconductor integrated device.

  The above-described optical semiconductor integrated device according to the first embodiment outputs a single-mode laser beam having a wavelength of 1.55 μm generated by the DFB semiconductor laser 16 after optical intensity modulation, for example, pulse modulation, by the modulator 15. In this optical semiconductor integrated device, interference between the semiconductor laser 16 and the modulator 15 could be suppressed to the same extent with a half separation length l as compared with the same conventional optical semiconductor integrated device shown in FIG. .

  The second embodiment of the present invention relates to a variable wavelength DBR semiconductor laser having a phase control unit.

  FIG. 6 is a plan view of an optical semiconductor integrated device according to the second embodiment of the present invention, and FIG. 7 is a cross-sectional view of the optical semiconductor integrated device according to the second embodiment of the present invention, showing a DBR semiconductor laser.

  6 and 7, in the optical semiconductor integrated device of the second embodiment, the active layer electrode 12c, the phase control electrode 12d, and the DBR electrode 12e are arranged in a line on the optical waveguide 4 in this order. The optical waveguide 4 includes an active layer 4a that emits light when a drive current is injected from the active layer electrode immediately below the active layer electrode 12c. Further, immediately below the phase control electrode 12d and the DBR electrode 12e, a refractive index control layer 4d whose refractive index is controlled by the respective electrodes 12d and 12e is formed. The current applied to the DBR electrode 12e controls the refractive index of the refractive index control layer 4d immediately below it, and controls the oscillation wavelength of the DBR semiconductor laser together with the diffraction grating 2a provided under the refractive index control layer 4d. The current applied to the phase control electrode 12d is controlled so that the phases of the laser beams that reciprocate between the active layer 4a and the diffraction grating match.

  Similar to the first embodiment, a mesa stripe 6 formed on the substrate 1 and a high-resistance buried layer 7 for embedding the mesa stripe 6 are formed. The layer structure included in the mesa stripe 6 is the same as that of the optical waveguide 4 of the first embodiment described above.

  The width of the mesa stripe 6 was 1.6 μm when the width of the optical waveguide 4 was just below the electrodes 12c, 12d, and 12e, and 0.8 μm at each of the separation bands 10-1 and 10-2. The length (separation length) of each of the separation bands 10-1 and 10-2 was 10 μm.

  In the optical semiconductor integrated device of the second embodiment, the length of the separation bands 10-1 and 10-2 can be reduced to half that of the conventional one, and interference between the electrodes can be suppressed equally.

  The third embodiment of the present invention relates to an optical semiconductor integrated device in which the width of the mesa stripe is gradually narrowed under the electrode.

  FIG. 8 is a plan view of an optical semiconductor integrated device according to the third embodiment of the present invention, and shows the planar shape of the mesa stripe and electrode of the optical semiconductor integrated device in which the DFB semiconductor laser and the modulator are integrated.

  Referring to FIG. 8, the width of the mesa stripe 6 is constant in the separation band 10, and gradually increases to a predetermined width under the electrode 12a of the semiconductor laser and the electrode 12b of the modulator 15, for example, widens in a tapered shape. To do. In one embodiment, the separation band 10 has a width of 0.8 μm, expands from the bottom of the electrodes 12a and 12b to a taper of 1.6 μm, and then extends below the electrodes 12a and 12b with a predetermined width of 1.6 μm. To do. Except for the width of the mesa stripe 6, it is the same as in the first embodiment.

  In the third embodiment, since the width of the mesa stripe 6, that is, the width of the optical waveguide 4 changes gently, the optical loss in the separation band 10 is small.

  The fourth embodiment of the present invention relates to an optical semiconductor integrated device in which the width of the mesa stripe is gradually narrowed in the separation band.

  FIG. 9 is a plan view of an optical semiconductor integrated device according to the fourth embodiment of the present invention, and shows a planar shape of a mesa stripe and electrode of an optical semiconductor integrated device in which a DFB semiconductor laser and a modulator are integrated.

  Referring to FIG. 9, the width of the mesa stripe 6 has a constant width under the electrodes 12 a and 12 b, for example, a width of 1.6 μm, and a minimum width at the center of the separation band 10, for example, 0.8 μm. It gradually becomes narrower toward the center, for example, in a tapered shape. Other configurations are the same as those of the third embodiment.

  In the fourth embodiment, the same effects as in the third embodiment can be obtained, and the characteristics of the semiconductor laser 16 and the modulator 15 can be easily controlled because the width of the optical waveguide 4 under the electrodes 12a and 12b is constant.

  In the third and fourth embodiments described above, the mesa stripe width is not limited to the tapered shape, and the mesa stripe width may be gently widened or narrowed. Also, in the optical semiconductor integrated device of the present invention, a groove is formed on the surface of the upper cladding layer of the separation band, or a high resistance ion implantation layer is formed on the surface of the upper cladding layer of the separation band, so that insulation isolation is achieved. It can also be done more fully.

The invention described in the following supplementary notes is disclosed in the present specification.
(Supplementary note 1) A mesa stripe including an upper clad layer laminated on an optical waveguide and having a side surface insulated by a high resistance layer;
In an optical semiconductor integrated device having first and second electrodes provided on the top surface of the mesa stripe so as to be separated in the extending direction of the mesa stripe,
The minimum width of the mesa stripe between the first and second electrodes is narrower than the maximum width of the mesa stripe under the first electrode and the maximum width of the mesa stripe under the second electrode. An optical semiconductor integrated device.
(Supplementary note 2) The optical semiconductor integrated device according to supplementary note 1, wherein the mesa stripe is a mesa mesa stripe whose side surface is buried by a high-resistance buried layer.
(Supplementary Note 3) The minimum width of the mesa stripe between the first and second electrodes is ½ of the maximum width of the mesa stripe under the first electrode and the mesa stripe under the second electrode. 3. The optical semiconductor integrated device according to appendix 1 or 2, wherein the optical semiconductor integrated device is wider than ½ of the maximum width.
(Supplementary Note 4) The mesa stripe has first, second, and third widths under the first electrode, under the second electrode, and between the first and second electrodes, respectively. The optical semiconductor integrated device according to appendix 1, 2, or 3.
(Supplementary note 5) The mesa stripe under the electrode is gradually narrowed in the vicinity of the electrode end and connected to the mesa stripe between the first and second electrodes. The optical semiconductor integrated device described.
(Appendix 6) The mesa stripe between the first and second electrodes is gradually widened from the center between the first and second electrodes in the direction of the first and second electrodes. 4. The optical semiconductor integrated device according to claim 1, 2, or 3.

  By applying the present invention to an optical semiconductor integrated device in which a plurality of electrodes are provided on an optical waveguide, an optical semiconductor integrated device having excellent characteristics with less interference between electrodes can be provided.

1 is a plan view of an optical semiconductor integrated device according to a first embodiment of the present invention. Sectional drawing of the optical semiconductor integrated device of 1st Embodiment of this invention Sectional drawing showing the stripe structure of the optical semiconductor integrated device of 1st Embodiment of this invention Diagram showing optical loss of separation band Plan view of the optical waveguide used in the calculation of FIG. Optical semiconductor integrated device plan view of the second embodiment of the present invention Sectional drawing of the optical semiconductor integrated device of 2nd Embodiment of this invention Optical semiconductor integrated device plan view of the third embodiment of the present invention Optical semiconductor integrated device plan view of the fourth embodiment of the present invention Illustration of a conventional optical semiconductor integrated device

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Substrate 2 Diffraction grating layer 2a Diffraction grating 3 Buffer layer 4 Optical waveguide 4a Active layer 4b Modulation layer 4c Light transmission layer 4d Refractive index control layer 5 Upper clad layer 6 Mesa stripe 10, 10-1, 10-2 Separation zone 11 Contact Layer 12a, 12b, 13 Electrode 12c Active layer electrode 12d Phase control electrode 12e DBR electrode 15 Modulator 16 Semiconductor laser

Claims (5)

A mesa stripe including an upper clad layer laminated on an optical waveguide and having a side surface insulated by a high-resistance layer;
In an optical semiconductor integrated device having first and second electrodes provided on the top surface of the mesa stripe so as to be separated in the extending direction of the mesa stripe,
The minimum width of the mesa stripe between the first and second electrodes is narrower than the maximum width of the mesa stripe under the first electrode and the maximum width of the mesa stripe under the second electrode. An optical semiconductor integrated device.   The minimum width of the mesa stripe between the first and second electrodes is one half of the maximum width of the mesa stripe under the first electrode and 1 of the maximum width of the mesa stripe under the second electrode. 2. The optical semiconductor integrated device according to claim 1, wherein the optical semiconductor integrated device is wider than / 2.   2. The mesa stripe has first, second, and third widths under the first electrode, under the second electrode, and between the first and second electrodes, respectively. Or the optical semiconductor integrated device of 2.   3. The optical semiconductor integrated device according to claim 1, wherein the mesa stripe under the electrode is gradually narrowed in the vicinity of the electrode end and is connected to the mesa stripe between the first and second electrodes. .   The mesa stripe between the first and second electrodes gradually widens from a central portion between the first and second electrodes in the direction of the first and second electrodes. Item 3. The optical semiconductor integrated device according to Item 1 or 2.

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