US4408330A
Expired / Lapsed
US
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Field effect semiconductor laser, method of modulation thereof
Assignee: TOWA GIKEN A CORP OF JAPAN KK
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Filing: 1980-12-05
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Granted: 1983-10-04
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Expires: 2000-12-05
Abstract
Abstract A field effect semiconductor laser has two clad layers and an active layer therebetween, formed by an epitaxial growth on a semiconductor substrate, which is mesa-etched to form a stripe-shaped mesa part of a double heterostructure on the semiconductor substrate. The laser further includes first and second buried layers of conductivity types opposite to each other and formed on both sides of the mesa-etched part, respectively. Gate electrodes G are formed on at least one of the top faces of the buried layers, and a drain electrode D is formed on the mesa-etched double heterostructure part. Depletion layers are produced at the junction interfaces between the first and the second buried layers when a reverse-bias voltage is applied across pairs of these buried layers. The thickness of the depletion layers, and thus a refractive index of a part of the buried layer neighboring outside the active layer, can be controlled by changing the external voltage applied to the gate electrode G, and the laser oscillation can be directly controlled by a voltage signal thereby enabling effective and high speed modulation of the laser.
Inventors
- 👤 Seiji An
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 21:33
CPC Classifications
H; H10; H10H; H10H20/00; H10H20/062; H01; H01S; H01S5/00; H01S5/06; H01S5/062; H01S5/06203; H01S5/20; H01S5/22; H01S5/227; H01S5/2205; H01S5/2275
Claims Analysis
Total Claims: 35
Claim 1
Independent Claim
270 words
A field effect semiconductor laser comprising: a semiconductor substrate, a stripe-shaped mesa part of a double heterostructure including a first clad layer, an active layer, and a second clad layer on the top face of said semiconductor substrate in this order, both of said first and said second clad layers having lower refractive indices than that of said active layer, buried layers buried in both side parts of said stripe-shaped mesa part on said semiconductor substrate, electrodes provided on the bottom surface of said semiconductor substrate and on said second clad layer, characterized in that said active layer has the same conductivity type as that of said first clad layer, light reflecting faces at both ends thereof being cleavage planes of (011), that each of said buried layers comprises a first buried layer formed on said semiconductor substrate and a second buried layer thereon where said first and said second buried layers have conductivity types different from each other so that these buried layers are reverse-biased when a voltage of the same direction as the forward direction of a voltage to be applied to said stripe-shaped mesa part is applied to said second buried layer, that a carrier concentration of said second buried layers is lower than that of said first buried layers, that said first buried layers are formed in a manner that junction interfaces between said first and said second buried layers are disposed lower by a predetermined level difference than a junction place between said first clad layer and said active layer, and that an electrode is formed on at least one of said second buried layers.
Claim 2
Dependent Claim
270 words
A field effect semiconductor laser comprising: a semiconductor substrate, a stripe-shaped mesa part of a double heterostructure including a first clad layer, an active layer, and a second clad layer on the top face of said semiconductor substrate in this order, both of said first and said second clad layers having lower refractive indices than that of said active layer, buried layers buried in both side parts of said stripe-shaped mesa part on said semiconductor substrate, electrodes provided on the bottom surface of said semiconductor substrate and on said second clad layer, characterized in that said active layer has the same conductivity type as that of said first clad layer, light reflecting faces at both ends thereof being cleavage planes of (011), that each of said buried layers comprises a first buried layer formed on said semiconductor substrate and a second buried layer thereon where said first and said second buried layers have conductivity types different from each other so that these buried layers are reverse-biased when a voltage of the same direction as the forward direction of a voltage to be applied to said stripe-shaped mesa part is applied to said second buried layer, that a carrier concentration of said second buried layers is lower than that of said first buried layers, that said first buried layers are formed in a manner that junction interfaces between said first and said second buried layers are disposed lower by a predetermined level difference than a junction place between said first clad layer and said active layer, and that an electrode is formed on at least one of said second buried layers.
Claim 3
Dependent Claim
30 words
A field effect semiconductor laser in accordance with claim 1, further comprising a cap layer formed between said second clad layer and said electrode above said second clad layer thereon.
Claim 4
Dependent Claim
49 words
A field effect semiconductor laser in accordance with claim 1 or 2, wherein said active layer is formed by GaAs, and said first and said second clad layers are formed by Ga 1-x Al x As (x=0.3 to 0.5) and Ga 1-y Al y As (y=0.3 to 0.5), respectively.
Claim 5
Dependent Claim
44 words
A field effect semiconductor laser in accordance with claim 1 or 2, wherein said semiconductor substrate, said first clad layer, said active layer and said second buried layers are of n-type, and said second clad layer and said first buried layers are of p-type.
Claim 6
Dependent Claim
27 words
A field effect semiconductor laser in accordance with claim 4, wherein a carrier concentration of said active layer is lower than that of said second buried layers.
Claim 7
Dependent Claim
34 words
A field effect semiconductor laser in accordance with claim 5, wherein a carrier concentration of said active layer is selected to be within a range of 5×10 15 to 5×10 16 cm -3 .
Claim 8
Dependent Claim
35 words
A field effect semiconductor laser in accordance with claim 5, wherein a carrier concentration of said first buried layers is selected to be within a range of 1×10 17 to 5×10 18 cm -3 .
Claim 9
Dependent Claim
35 words
A field effect semiconductor laser in accordance with claim 5, wherein a carrier concentration of said second buried layers is selected to be within a range of 1×10 16 to 5×10 17 cm -3 .
Claim 10
Dependent Claim
62 words
A field effect semiconductor laser in accordance with claim 1 or 2, wherein proton-bombarded layers are provided in said first and said second buried layers in a manner to be separated from said stripe-shaped mesa part with a predetermined gap therebetween, the depth of said proton-bombarded layers being deeper than that of the junction plane between said first and second buried layers.
Claim 11
Dependent Claim
270 words
A field effect semiconductor laser comprising: a semiconductor substrate, a stripe-shaped mesa part of a double heterostructure including a first clad layer, an active layer, and a second clad layer on the top face of said semiconductor substrate in this order, both of said first and said second clad layers having lower refractive indices than that of said active layer, buried layers buried in both side parts of said stripe-shaped mesa part on said semiconductor substrate, electrodes provided on the bottom surface of said semiconductor substrate and on said second clad layer, characterized in that said active layer has the opposite conductivity type to that of said first clad layer, light reflecting faces at both ends thereof being cleavage planes of (011), that each of said buried layers comprises a first buried layer formed on said semiconductor substrate and a second buried layer thereon where said first and said second buried layers have conductivity types different from each other so that these buried layers are reverse-biased when a voltage of the same direction as the forward direction of a voltage to be applied to said stripe-shaped mesa part is applied to said second buried layers, that a carrier concentration of said second buried layers is higher than that of said first buried layers, that said first buried layers are formed in a manner that junction interfaces between said first and said second buried layers are disposed higher by a predetermined level difference than a junction plane between said second clad layer and said active layer, and that an electrode is formed on at least one of said second buried layers.
Claim 12
Dependent Claim
270 words
A field effect semiconductor laser comprising: a semiconductor substrate, a stripe-shaped mesa part of a double heterostructure including a first clad layer, an active layer, and a second clad layer on the top face of said semiconductor substrate in this order, both of said first and said second clad layers having lower refractive indices than that of said active layer, buried layers buried in both side parts of said stripe-shaped mesa part on said semiconductor substrate, electrodes provided on the bottom surface of said semiconductor substrate and on said second clad layer, characterized in that said active layer has the opposite conductivity type to that of said first clad layer, light reflecting faces at both ends thereof being cleavage planes of (011), that each of said buried layers comprises a first buried layer formed on said semiconductor substrate and a second buried layer thereon where said first and said second buried layers have conductivity types different from each other so that these buried layers are reverse-biased when a voltage of the same direction as the forward direction of a voltage to be applied to said stripe-shaped mesa part is applied to said second buried layers, that a carrier concentration of said second buried layers is higher than that of said first buried layers, that said first buried layers are formed in a manner that junction interfaces between said first and said second buried layers are disposed higher by a predetermined level difference than a junction plane between said second clad layer and said active layer, and that an electrode is formed on at least one of said second buried layers.
Claim 13
Dependent Claim
30 words
A field effect semiconductor laser in accordance with claim 10, further comprising a cap layer formed between said second clad layer and said electrode above said second clad layer thereon.
Claim 14
Dependent Claim
49 words
A field effect semiconductor laser in accordance with claim 10 or 11, wherein said active layer is formed by GaAs, and said first and said second clad layers are formed by Ga 1-x Al x As (x=0.3 to 0.5) and Ga 1-y Al y As (y=0.3 to 0.5), respectively.
Claim 15
Dependent Claim
44 words
A field effect semiconductor laser in accordance with claim 10 or 11, wherein said semiconductor substrate, said first clad layer and said second buried layers are of n-type, and said active layer, said second clad layer and said first buried layers are of p-type.
Claim 16
Dependent Claim
27 words
A field effect semiconductor laser in accordance with claim 13, wherein a carrier concentration of said active layer is higher than that of said first buried layers.
Claim 17
Dependent Claim
34 words
A field effect semiconductor laser in accordance with claim 14, wherein a carrier concentration of said active layer is selected to be within a range of 1×10 17 to 5×10 18 cm -3 .
Claim 18
Dependent Claim
35 words
A field effect semiconductor laser in accordance with claim 14, wherein a carrier concentration of said first buried layers is selected to be within a range of 1×10 16 to 5×10 17 cm -3 .
Claim 19
Dependent Claim
35 words
A field effect semiconductor laser in accordance with claim 14, wherein a carrier concentration of said second buried layers is selected to be within a range of 1×10 17 to 5×10 18 cm -3 .
Claim 20
Dependent Claim
57 words
A field effect semiconductor laser in accordance with claim 10 or 11, wherein proton-bombarded layers are provided in said first and said second buried layers in a manner to be separated from said stripe-shaped mesa part with a predetermined gap therebetween, the depth of said proton-bombarded layers being deeper than the highest face of said active layer.
Claim 21
Dependent Claim
423 words
A field effect semiconductor laser comprising: a semiconductor substrate, a stripe-shaped mesa part of a double heterostructure including a first clad layer, an active layer, a second clad layer and a cap layer on the top face of said semiconductor substrate in this order, both of said first and said second clad layers having lower refractive indexes than that of said active layer, buried layers buried in both side parts of said stripe-shaped mesa part on said semiconductor substrate, each of said buried layers comprising a first buried layer formed on said semiconductor substrate and a second buried layer thereon where said first and said second buried layers have conductivity types different from each other so that these buried layers are reverse-biased when a voltage of the same direction as the forward direction of a voltage to be impressed across said stripe-shaped mesa part, is impressed across said second buried layer and said semiconductor substrate, an anode electrode, a cathode electrode and at least one gate electrode provided respectively on said cap layer, the bottom surface of said semiconductor substrate and said second buried layers, characterized in that said active layer has the same conductivity type as that of said first clad layer, light reflecting faces at both ends thereof being cleavage planes of (011), that each of said second buried layers disposed on both sides of said active layer completely covers both light reflecting side faces of said active layer in a manner that junction interfaces between said first and said second buried layers are disposed nearer to said semiconductor substrate by a predetermined level difference than the junction interface between said first clad layer and said active layer, that a carrier concentration in said second buried layers is same as or higher than that of said active layer, so that a refractive index value thereof is substantially of the same order as that of said active layer, that a refractive index value in predetermined regions of said second buried layers covering both side faces of said active layer and in contact with at least one of said light reflecting side faces of said active layer, becomes higher than that of said active layer due to carrier concentration difference and electro-optic effect so that laser oscillation stops at a first predetermined voltage, when a second predetermined voltage higher than a voltage impressed across said anode and said cathode electrodes for lasing operation and lower than said first predetermined voltage, is impressed across said at least one gate electrode and said cathode electrode.
Claim 22
Dependent Claim
423 words
A field effect semiconductor laser comprising: a semiconductor substrate, a stripe-shaped mesa part of a double heterostructure including a first clad layer, an active layer, a second clad layer and a cap layer on the top face of said semiconductor substrate in this order, both of said first and said second clad layers having lower refractive indexes than that of said active layer, buried layers buried in both side parts of said stripe-shaped mesa part on said semiconductor substrate, each of said buried layers comprising a first buried layer formed on said semiconductor substrate and a second buried layer thereon where said first and said second buried layers have conductivity types different from each other so that these buried layers are reverse-biased when a voltage of the same direction as the forward direction of a voltage to be impressed across said stripe-shaped mesa part, is impressed across said second buried layer and said semiconductor substrate, an anode electrode, a cathode electrode and at least one gate electrode provided respectively on said cap layer, the bottom surface of said semiconductor substrate and said second buried layers, characterized in that said active layer has the same conductivity type as that of said first clad layer, light reflecting faces at both ends thereof being cleavage planes of (011), that each of said second buried layers disposed on both sides of said active layer completely covers both light reflecting side faces of said active layer in a manner that junction interfaces between said first and said second buried layers are disposed nearer to said semiconductor substrate by a predetermined level difference than the junction interface between said first clad layer and said active layer, that a carrier concentration in said second buried layers is same as or higher than that of said active layer, so that a refractive index value thereof is substantially of the same order as that of said active layer, that a refractive index value in predetermined regions of said second buried layers covering both side faces of said active layer and in contact with at least one of said light reflecting side faces of said active layer, becomes higher than that of said active layer due to carrier concentration difference and electro-optic effect so that laser oscillation stops at a first predetermined voltage, when a second predetermined voltage higher than a voltage impressed across said anode and said cathode electrodes for lasing operation and lower than said first predetermined voltage, is impressed across said at least one gate electrode and said cathode electrode.
Claim 23
Dependent Claim
36 words
A field effect semiconductor laser in accordance with claim 19, wherein said active layer is GaAs, and said first and said second buried layers are Ga 1-x Al x As (x=0 to 0.5) and GaAs, respectively.
Claim 24
Dependent Claim
42 words
A field effect semiconductor laser in accordance with claim 19, wherein said semiconductor substrate, said first clad layer, said active layer and said second buried layers are of n-type, and said second clad layer and said first buried layers are of p-type.
Claim 25
Dependent Claim
35 words
A field effect semiconductor laser in accordance with claim 19, wherein a carrier concentration of said first buried layers is selected to be within a range of 1×10 17 to 5×10 18 cm -3 .
Claim 26
Dependent Claim
46 words
A field effect semiconductor laser in accordance with clim 19, wherein a carrier concentration of said second buried layers is selected to be within a range of 1×10 16 to 5×10 17 cm-3, and is the same as or higher than that of said active layer.
Claim 27
Dependent Claim
46 words
A field effect semiconductor laser in accordance with clim 19, wherein a carrier concentration of said second buried layers is selected to be within a range of 1×10 16 to 5×10 17 cm-3, and is the same as or higher than that of said active layer.
Claim 28
Dependent Claim
28 words
A field effect semiconductor laser in accordance with claim 21, wherein a carrier concentration of said second buried layer is lower than that of said first buried layers.
Claim 29
Dependent Claim
60 words
A field effect semiconductor laser in accordance with claim 19, wherein proton-bombarded layers are provided in said first and said second buried layers in manner to be separated from said stripe-shaped mesa part with a predetermined gap therebetween, the depth of said proton-bombarded layers being deeper than that of the junction plane between said first and said second buried layers.
Claim 30
Dependent Claim
424 words
A field effect semiconductor laser comprising: a semiconductor substrate, a stripe-shaped mesa part of a double heterostructure including a first clad layer, an active layer, a second clad layer and a cap layer on the top face of said semiconductor substrate in this order, both of said first and said second clad layers having lower refractive indexes than that of said active layer, buried layers buried in both side parts of said stripe-shaped mesa part on said semiconductor substrate, each of said buried layers comprising a first buried layer formed on said semiconductor substrate and a second buried layer thereon where said first and said second buried layers have conductivity types different from each other so that these buried layers are reverse-biased when a voltage of the same direction as the forward direction of a voltage to be impressed across said stripe-shaped mesa part, is impressed across said second buried layer and said semiconductor substrate, an anode electrode, a cathode electrode and at least one gate electrode provided respectively on said cap layer, the bottom surface of said semiconductor substrate and said second buried layers, characterized in that said active layer has the different conductivity type from that of said first clad layer, light reflecting faces at both ends thereof being cleavage planes of (011), that each of said first buried layers disposed on both sides of said active layer completely covers both light reflecting side faces of said active layer in a manner that junction interfaces between said first and said second buried layers are disposed nearer to said cap layer by a predetermined level difference than the junction interface between said second clad layer and said active layer, that a carrier concentration in said first buried layers is the same as or lower than that of said active layer, so that a refractive index value thereof is substantially of the same order as that of said active layer, that a refractive index value in predetermined regions of said first buried layers covering both side faces of said active layer and in contact with at least one of said light reflecting side faces of said active layer, becomes higher than that of said active layer due to carrier concentration difference and electro-optic effect so that laser oscillation stops at a first predetermined voltage, when a second predetermined voltage higher than a voltage impressed across said anode and said cathode electrodes for lasing operation and lower than said first predetermined voltage, is impressed across said at least one gate electrode and said cathode electrode.
Claim 31
Dependent Claim
424 words
A field effect semiconductor laser comprising: a semiconductor substrate, a stripe-shaped mesa part of a double heterostructure including a first clad layer, an active layer, a second clad layer and a cap layer on the top face of said semiconductor substrate in this order, both of said first and said second clad layers having lower refractive indexes than that of said active layer, buried layers buried in both side parts of said stripe-shaped mesa part on said semiconductor substrate, each of said buried layers comprising a first buried layer formed on said semiconductor substrate and a second buried layer thereon where said first and said second buried layers have conductivity types different from each other so that these buried layers are reverse-biased when a voltage of the same direction as the forward direction of a voltage to be impressed across said stripe-shaped mesa part, is impressed across said second buried layer and said semiconductor substrate, an anode electrode, a cathode electrode and at least one gate electrode provided respectively on said cap layer, the bottom surface of said semiconductor substrate and said second buried layers, characterized in that said active layer has the different conductivity type from that of said first clad layer, light reflecting faces at both ends thereof being cleavage planes of (011), that each of said first buried layers disposed on both sides of said active layer completely covers both light reflecting side faces of said active layer in a manner that junction interfaces between said first and said second buried layers are disposed nearer to said cap layer by a predetermined level difference than the junction interface between said second clad layer and said active layer, that a carrier concentration in said first buried layers is the same as or lower than that of said active layer, so that a refractive index value thereof is substantially of the same order as that of said active layer, that a refractive index value in predetermined regions of said first buried layers covering both side faces of said active layer and in contact with at least one of said light reflecting side faces of said active layer, becomes higher than that of said active layer due to carrier concentration difference and electro-optic effect so that laser oscillation stops at a first predetermined voltage, when a second predetermined voltage higher than a voltage impressed across said anode and said cathode electrodes for lasing operation and lower than said first predetermined voltage, is impressed across said at least one gate electrode and said cathode electrode.
Claim 32
Independent Claim
399 words
A method of modulating refractive indexes in a field effect semiconductor laser of the type which includes a stripe-shaped mesa part of a double heterostructure on a semiconductor substrate at the center thereof, the stripe-shaped mesa part comprising an active layer doped with impurity atoms of a conductivity type the same as that of impurity atoms doped in the first clad layer, with light reflection faces on both sides thereof of (011) cleavage face direction, and with a refractive index n 1 , sandwiched by a first lower and a second higher clad layers both with another refractive index n 2 smaller than n 1 , and a cap layer on said second clad layer, a pair of a first lower and a second higher buried layers disposed on both sides of the stripe-shaped mesa part and on the semiconductor substrate, an anode on the cap layer, at least one gate on at least one layer among the two second buried layers, and a cathode on the rear surface of the semiconductor substrate, these electrodes being separated from one another, the junction of the first lower and said second higher buried layers completely covering the light reflection faces, and having a height h 1 slightly lower to the side of the semiconductor substrate than a height h 2 of the junction position of the first lower clad layer and the active layer, the first lower and the second higher buried layers being doped with impurity atoms of conductivity types different from each other and reverse-biased when a voltage with a polarity the same as that of a voltage impressed across the stripe-shaped mesa part is impressed across the second higher buried layer and the semiconductor substrate, and a carrier concentration in the second higher buried layer being equal to or higher than a counterpart in the active layer so that a refractive index in the second higher buried layer is substantially on the same order as a counterpart in the said active layer, the method of modulating a refractive index in a predetermined region facing to at least one face of the light reflection faces and in the second higher buried layer due to carrier concentration difference and electro-optic effect by the steps of modulating a reverse bias voltage across the gate and cathode while impressing a predetermined voltage specified for laser operation across the anode and the cathode.
Claim 33
Independent Claim
399 words
A method of modulating refractive indexes in a field effect semiconductor laser of the type which includes a stripe-shaped mesa part of a double heterostructure on a semiconductor substrate at the center thereof, the stripe-shaped mesa part comprising an active layer doped with impurity atoms of a conductivity type the same as that of impurity atoms doped in the first clad layer, with light reflection faces on both sides thereof of (011) cleavage face direction, and with a refractive index n 1 , sandwiched by a first lower and a second higher clad layers both with another refractive index n 2 smaller than n 1 , and a cap layer on said second clad layer, a pair of a first lower and a second higher buried layers disposed on both sides of the stripe-shaped mesa part and on the semiconductor substrate, an anode on the cap layer, at least one gate on at least one layer among the two second buried layers, and a cathode on the rear surface of the semiconductor substrate, these electrodes being separated from one another, the junction of the first lower and said second higher buried layers completely covering the light reflection faces, and having a height h 1 slightly lower to the side of the semiconductor substrate than a height h 2 of the junction position of the first lower clad layer and the active layer, the first lower and the second higher buried layers being doped with impurity atoms of conductivity types different from each other and reverse-biased when a voltage with a polarity the same as that of a voltage impressed across the stripe-shaped mesa part is impressed across the second higher buried layer and the semiconductor substrate, and a carrier concentration in the second higher buried layer being equal to or higher than a counterpart in the active layer so that a refractive index in the second higher buried layer is substantially on the same order as a counterpart in the said active layer, the method of modulating a refractive index in a predetermined region facing to at least one face of the light reflection faces and in the second higher buried layer due to carrier concentration difference and electro-optic effect by the steps of modulating a reverse bias voltage across the gate and cathode while impressing a predetermined voltage specified for laser operation across the anode and the cathode.
Claim 34
Independent Claim
402 words
A method of modulating refractive indexes in a field effect semiconductor laser of the type which includes a stripe-shaped mesa part of a double heterostructure on a semiconductor substrate at the center thereof, the stripe-shaped mesa part comprising an active layer doped with impurity atoms of a conductivity type opposite to that of impurity atoms doped in the first clad layer, with light reflection faces on both sides thereof of (011) cleavage face direction, and with a refractive index n 3 , sandwiched by a first lower and a second higher clad layers both with another refractive index n 4 smaller than n 3 , and a cap layer on the second clad layer, a pair of first lower and a second higher buried layers disposed on both sides of the stripe-shaped mesa part and on the semiconductor substrate, an anode on the cap layer, at least one gate on at least one layer among the two second buried layers, and a cathode on the rear surface of the semiconductor substrate, these electrodes being separated from one another, the junction of the first lower and said second higher buried layers completely covering said light reflection faces, and having a height h 3 slightly higher to the side of the cap layer than a height h 4 of junction position of the first lower clad layer and the active layer, the first lower and the second higher buried layers being doped with impurity atoms of conductivity types different from each other and reverse-biased when a voltage with a polarity the same as that of a voltage impressed across the stripe-shaped mesa part is impressed across the stripe-shaped mesa part is impressed across the second higher buried layer and the semiconductor substrate, and a carrier concentration in the first lower buried layer being equal to or lower than a counterpart in the active layer so that a refractive index in the first lower buried layer is substantially on the same order as a counterpart in the active layer, the method of modulating a refractive index in a predetermined region facing to at least one face of the light reflection faces and in the first lower buried layer due to carrier concentration difference and electro-optic effect comprising the steps of modulating a reverse bias voltage across the gate and cathode while impressing a predetermined voltage specified for laser operation across the anode and the cathode.
Claim 35
Independent Claim
402 words
A method of modulating refractive indexes in a field effect semiconductor laser of the type which includes a stripe-shaped mesa part of a double heterostructure on a semiconductor substrate at the center thereof, the stripe-shaped mesa part comprising an active layer doped with impurity atoms of a conductivity type opposite to that of impurity atoms doped in the first clad layer, with light reflection faces on both sides thereof of (011) cleavage face direction, and with a refractive index n 3 , sandwiched by a first lower and a second higher clad layers both with another refractive index n 4 smaller than n 3 , and a cap layer on the second clad layer, a pair of first lower and a second higher buried layers disposed on both sides of the stripe-shaped mesa part and on the semiconductor substrate, an anode on the cap layer, at least one gate on at least one layer among the two second buried layers, and a cathode on the rear surface of the semiconductor substrate, these electrodes being separated from one another, the junction of the first lower and said second higher buried layers completely covering said light reflection faces, and having a height h 3 slightly higher to the side of the cap layer than a height h 4 of junction position of the first lower clad layer and the active layer, the first lower and the second higher buried layers being doped with impurity atoms of conductivity types different from each other and reverse-biased when a voltage with a polarity the same as that of a voltage impressed across the stripe-shaped mesa part is impressed across the stripe-shaped mesa part is impressed across the second higher buried layer and the semiconductor substrate, and a carrier concentration in the first lower buried layer being equal to or lower than a counterpart in the active layer so that a refractive index in the first lower buried layer is substantially on the same order as a counterpart in the active layer, the method of modulating a refractive index in a predetermined region facing to at least one face of the light reflection faces and in the first lower buried layer due to carrier concentration difference and electro-optic effect comprising the steps of modulating a reverse bias voltage across the gate and cathode while impressing a predetermined voltage specified for laser operation across the anode and the cathode.
References Cited (Backward Citations)
US4212020A
Cited
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