Oscillation polarization mode selective semiconductor laser, light transmitter and optical communication system using the laser

Claim 2

An oscillation polarization mode selective semiconductor laser for selectively performing one of plural oscillations in different polarization modes, said laser comprising: a subtrate (1; 41; 71; 101; 141; 181; 241; 271; 301); a first laser region (111 a; 149a; 191a; 249a; 272a; 302a) having a semiconductor laser structure in which a gain spectrum of one of the different polarization modes is dominant; a second laser region (111 b; 149b; 191 b; 249b; 272b; 302b) having a semiconductor laser structure in which a gain spectrum of another of the different polarization modes is dominant; coupling means (112; 150; 192; 250; 273; 303) for coupling said first laser region and said second laser region; and injecting means (7, 8, 9; 47, 48, 49; 77, 78, 79; 107a, 107b, 109; 148a, 148b, 151; 187a, 187b, 189; 248a, 248b, 251; 287, 289; 317a, 317b, 319) for independently injecting currents into said first laser region and said second laser region to cause a mode competitive state between the oscillations in the different polarization modes.

Claim 3

An oscillation polarization mode selective semiconductor laser according to claim 1, further comprising selecting means (274; 304) for selecting one of the plural oscillations in the different polarization modes to emit light in a selected polarization mode, one of a minute modulated current and a minute modulated voltage being imparted to said selecting means.

Claim 4

An oscillation polarization mode selective semiconductor laser according to claim 1, wherein at least a portion of said injecting means (7, 8, 9; 47, 48, 49; 77, 78, 79; 107a, 107b, 109; 148a, 148b, 151; 187a, 187b, 189; 248a, 248b, 251) also serves as said selecting means.

Claim 5

An oscillation polarization mode selective semiconductor laser according to claim 1, wherein said first laser region (111 a; 149a; 191 a; 249a; 272a; 302a) has a gain for light in a transverse electric mode which is larger than a gain for light in a transverse magnetic mode and said second laser region (111b; 149b; 191 b; 249b; 272b; 302b) has a gain for light in the transverse magnetic mode which is larger than a gain for light in the transverse electric mode.

Claim 6

An oscillation polarization mode selective semiconductor laser according to claim 1, wherein said first laser region (111 a; 149a; 191a; 249a) and said second laser regions (111 b; 149b; 191 b; 249b) are serially arranged along a resonance direction of said semiconductor laser with said coupling means (112; 150; 192; 250) therebetween.

Claim 7

An oscillation polarization mode selective semiconductor laser according to claim 1, wherein said first laser region (272a) and said second laser region (272b) are arranged parallel to each other along a direction perpendicular to a resonance direction of said semiconductor laser.

Claim 8

An oscillation polarization mode selective semiconductor laser according to claim 1, wherein said injecting means (8, 9; 48, 49; 78, 79; 107a, 107b; 148a, 148b; 187a, 187b; 248a, 248b; 287; 317a, 317b) comprises electrodes separately formed on said first and second laser regions, respectively.

Claim 9

An oscillation polarization mode selective semiconductor laser according to claim 1, wherein said first laser region comprises an active layer of a strained quantum well structure into which a compressive strain is introduced.

Claim 10

An oscillation polarization mode selective semiconductor laser according to claim 1, wherein said second laser region comprises an active layer (32; 62; 92; 143b; 243b) of a strained quantum well structure into which a tensile strain is introduced.

Claim 11

An oscillation polarization mode selective semiconductor laser according to claim 1, wherein each of said first laser region and said second laser region respectively comprises a different active layer (31, 32; 61, 62; 91, 92; 143a, 143b; 243a, 243b).

Claim 12

An oscillation polarization mode selective semiconductor laser according to claim 1, wherein at least one of said first laser region and said second laser region comprises an active layer (31, 32; 61, 62; 91, 92; 143b; 184; 243a, 243b; 260a, 260b) of one of a strained quantum well structure and non-strained quantum well structure.

Claim 13

An oscillation polarization mode selective semiconductor laser according to claim 1, wherein said semiconductor laser is constructed as a distributed Bragg reflector laser.

Claim 14

An oscillation polarization mode selective semiconductor laser according to claim 1, wherein said semiconductor laser is constructed as a Fabry-Perot laser.

Claim 15

An oscillation polarization mode selective semiconductor laser according to claim 1, wherein said semiconductor laser is constructed as a distributed feedback laser.

Claim 16

An oscillation polarization mode selective semiconductor laser according to claim 14, wherein said first laser region (111 a; 149a; 191a; 249a; 272a; 302a) comprises a grating (102a; 144a; 182a; 244a; 282; 302a) with a phase shift section (110a; 153a; 190a; 252a; 290; 318a) whose pitch is set such that a Bragg wavelength for light in a transverse electric mode is coincident with a peak of a gain spectrum of light in the transverse electric mode, and said second laser region (111b; 149b; 191 b; 249b; 272b; 302b) comprises a grating (102b; 144b; 182b; 244b; 282; 302b) with a phase shift section (110b; 153b; 190b; 252b; 290; 318b) whose pitch is set such that a Bragg wavelength for light in a transverse magnetic mode is coincident with a peak of a gain spectrum of light in the transverse magnetic mode.

Claim 17

An oscillation polarization mode selective semiconductor laser according to claim 15, wherein a coupling coefficient of said grating (102a; 182a; 244a; 282; 302a) in said first laser region is different from a coupling coefficient of said grating (102b; 182b; 244b; 282; 302b) in said second laser region.

Claim 18

An oscillation polarization mode selective semiconductor laser according to claim 15, wherein a depth of said grating (102a; 182a; 244a; 282; 302a) in said first laser region is different from a depth of said grating (102b; 182b; 244b; 282; 302b) in said second laser region.

Claim 19

An oscillation polarization mode selective semiconductor laser according to claim 15, wherein a location of said grating (102a; 144a; 182a; 244a; 282; 302a) in said first laser region is different from a location of said grating (102b; 144b; 182b; 244b; 282; 302b) in said second laser region to create a difference in confinement coefficients in said first and second laser regions.

Claim 20

An oscillation polarization mode selective semiconductor laser according to claim 15, wherein said first laser region and said second laser region have a common active layer (104; 184; 284; 314).

Claim 21

An oscillation polarization mode selective semiconductor laser according to claim 15, wherein said first laser region and said second laser region respectively comprise different active layers (31, 32; 61, 62; 91, 92; 143a, 143b; 243a, 243b).

Claim 22

An oscillation polarization mode selective semiconductor laser according to claim 15, wherein at least one of said first laser region and said second laser region comprises an active layer (32; 62; 92; 143b; 243b) of a strained quantum well structure.

Claim 23

An oscillation polarization mode selective semiconductor laser according to claim 21, wherein the pitch of the grating in said laser region having said active layer (32; 62; 92; 143b; 243b) of the strained quantum well structure is set such that the Bragg wavelength for light in the transverse magnetic or the transverse electric mode is coincident with one of different peaks of a gain spectrum of said active layer (32; 62; 92; 143b; 243b) of the strained quantum well structure.

Claim 24

An oscillation polarization mode selective semiconductor laser according to claim 22, wherein the different peaks of the gain spectrum of said active layer (32; 62; 92; 143b; 243b) of the strained quantum well structure correspond to different quantum levels, respectively.

Claim 25

An oscillation polarization mode selective semiconductor laser according to claim 23, wherein the different quantum levels correspond to transitions of heavy holes and light holes.

Claim 26

An oscillation polarization mode selective semiconductor laser according to claim 23, wherein the different quantum levels correspond to transitions of different orders.

Claim 27

An oscillation polarization mode selective semiconductor laser according to claim 2, wherein said selecting means (274; 304) comprises an output waveguide portion, said first and second laser regions are arranged parallel to each other and a light wave coupled by said coupling means (273; 303) is emitted through said output waveguide portion.

Claim 28

An oscillation polarization mode selective semiconductor laser according to claim 26, wherein an electrode is formed on said output waveguide portion for one of current injection and voltage application.

Claim 29

An oscillation polarization mode selective semiconductor laser according to claim 26, wherein each of said first laser region (272a; 302a), said second laser region (272b; 302b) and said output waveguide portion respectively has a different active layer.

Claim 30

An oscillation polarization mode selective semiconductor laser according to claim 28, wherein at least one of said different active layers comprises a strained quantum well structure.

Claim 31

An oscillation polarization mode selective semiconductor laser according to claim 6, wherein said coupling means comprises a Y-type coupler (273).

Claim 32

An oscillation polarization mode selective semiconductor laser according to claim 6, wherein said coupling means comprises a T-type coupler (303).

Claim 33

A driving method for driving an oscillation polarization mode selective semiconductor laser for selectively performing one of plural oscillations in different polarization modes, said laser comprising a subtrate (1; 41; 71; 101; 141; 181; 241; 271; 301), a first laser region (111 a; 149a; 191a; 249a; 272a; 302a) on said substrate having a semiconductor laser structure in which a gain spectrum of one of different polarization modes is dominant, a second laser region (111 b; 149b; 191 b; 249b; 272b; 302b) on said substrate having a semiconductor laser structure in which a gain spectrum of another of the different polarization modes is dominant, coupling means (112; 150; 192; 250; 273; 303) for coupling the first laser region and the second laser region, and injecting means (7, 8, 9; 47, 48, 49; 77, 78, 79; 107a, 107b, 109; 148a, 148b, 151; 187a, 187b, 189; 248a, 248b, 251; 287, 289; 317a, 317b, 319) for independently injecting currents into the first laser region and the second laser region to cause a mode competitive state between the oscillations in the different polarization modes, said driving method comprising: a step of injecting a modulated current, which has a modulation frequency, into one of the first laser region (111 a; 149a; 191a; 249a; 272a; 302a) and the second laser region (111 b; 149b; 191 b; 249b; 272b; 302b); and a step of injecting a direct current, which has a constant intensity, into the other of the first laser region (111 a; 149a; 191a; 249a; 272a; 302a) and the second laser region (111 b; 149b;191b;249b;272b;302b).

Claim 34

A driving method for driving an oscillation polarization mode selective semiconductor laser for selectively performing one of plural oscillations in different polarization modes, said laser comprising a subtrate (1; 41; 71; 101; 141; 181; 241; 271; 301), a first laser region (111 a; 149a; 191a; 249a; 272a; 302a) on said substrate having a semiconductor laser structure in which a gain spectrum of one of different polarization modes is dominant, a second laser region (111 b; 149b; 191 b; 249b; 272b; 302b) on said substrate having a semiconductor laser structure in which a gain spectrum of another of the different polarization modes is dominant, coupling means (112; 150; 192; 250; 273; 303) for coupling the first laser region and the second laser region, and injecting means (7, 8, 9; 47, 48, 49; 77, 78, 79; 107a, 107b, 109; 148a, 148b, 151; 187a, 187b, 189; 248a, 248b, 251; 287, 289; 317a, 317b, 319) for independently injecting currents into the first laser region and the second laser region to cause a mode competitive state between the oscillations in the different polarization modes, said driving method comprising: a step of injecting a modulated current, which has a modulation frequency, into one of the first laser region (111 a; 149a; 191a; 249a; 272a; 302a) and the second laser region (111 b; 149b; 191 b; 249b; 272b; 302b); and a step of injecting a direct current, which has a constant intensity, into the other of the first laser region (111 a; 149a; 191a; 249a; 272a; 302a) and the second laser region (111 b; 149b;191b;249b;272b;302b).

Claim 35

A driving method for driving an oscillation polarization mode selective semiconductor laser for selectively performing one of plural oscillations in different polarization modes, said laser comprising a subtrate (1; 41; 71; 101; 141; 181; 241; 271; 301), a first laser region (111 a; 149a; 191a; 249a; 272a; 302a) on said substrate having a semiconductor laser structure in which a gain spectrum of one of the different polarization modes is dominant, a second laser region (111b; 149b; 191 b; 249b; 272b; 302b) on said substrate having a semiconductor laser structure in which a gain spectrum of another of the different polarization modes is dominant, coupling means (112; 150; 192; 250; 273; 303) for coupling the first laser region and the second laser region, and injecting means (7, 8, 9; 47, 48, 49; 77, 78, 79; 107a, 107b, 109; 148a, 148b, 151; 187a, 187b, 189; 248a, 248b, 251; 287, 289; 317a, 317b, 319) for independently injecting currents into the first laser region and the second laser region to cause a mode competitive state between the oscillations in the different polarization modes, said driving method comprising: a step of injecting a first modulated current, which has a modulation frequency, into one of the first laser region (111 a; 149a; 191 a; 249a; 272a; 302a) and the second laser region (111b; 149b; 191b; 249b; 272b; 302b); and a step of injecting a second modulated current, which has a modulation frequency in anti-phase with the modulation frequency of the first modulated current, into the other of the first laser region (111 a; 149a; 191a; 249a; 272a; 302a) and the second laser region (111 b; 149b;191b;249b;272b;302b).

Claim 36

A driving method for driving an oscillation polarization mode selective semiconductor laser for selectively performing one of plural oscillations in different polarization modes, said laser comprising a subtrate (1; 41; 71; 101; 141; 181; 241; 271; 301), a first laser region (111 a; 149a; 191a; 249a; 272a; 302a) on said substrate having a semiconductor laser structure in which a gain spectrum of one of the different polarization modes is dominant, a second laser region (111b; 149b; 191 b; 249b; 272b; 302b) on said substrate having a semiconductor laser structure in which a gain spectrum of another of the different polarization modes is dominant, coupling means (112; 150; 192; 250; 273; 303) for coupling the first laser region and the second laser region, and injecting means (7, 8, 9; 47, 48, 49; 77, 78, 79; 107a, 107b, 109; 148a, 148b, 151; 187a, 187b, 189; 248a, 248b, 251; 287, 289; 317a, 317b, 319) for independently injecting currents into the first laser region and the second laser region to cause a mode competitive state between the oscillations in the different polarization modes, said driving method comprising: a step of injecting a first modulated current, which has a modulation frequency, into one of the first laser region (111 a; 149a; 191 a; 249a; 272a; 302a) and the second laser region (111b; 149b; 191b; 249b; 272b; 302b); and a step of injecting a second modulated current, which has a modulation frequency in anti-phase with the modulation frequency of the first modulated current, into the other of the first laser region (111 a; 149a; 191a; 249a; 272a; 302a) and the second laser region (111 b; 149b;191b;249b;272b;302b).

Claim 37

A driving method for driving an oscillation polarization mode selective semiconductor laser for selectively performing one of plural oscillations in different polarization modes, said laser comprising a subtrate (1; 41; 71; 101; 141; 181; 241; 271; 301), a first laser region (111 a; 149a; 191a; 249a; 272a; 302a) on said substrate having a semiconductor laser structure in which a gain spectrum of one of the different polarization modes is dominant, a second laser region (111b; 149b; 191 b; 249b; 272b; 302b) on said substrate having a semiconductor laser structure in which a gain spectrum of another of the different polarization modes is dominant, coupling means (112; 150; 192; 250; 273; 303) for coupling the first laser region and the second laser region, injecting means (7, 8, 9; 47, 48, 49; 77, 78, 79; 107a, 107b, 109; 148a, 148b, 151; 187a, 187b, 189; 248a, 248b, 251; 287, 289; 317a, 317b, 319) for independently injecting currents into the first laser region and the second laser region to cause a mode competitive state between the oscillations in the different polarization modes, and selecting means (274; 304) for selecting one of the oscillations in the different polarization modes to emit light in a selected polarization mode, said driving method comprising: a step of injecting a first constant current, which is below a threshold current, into one of the first laser region (111 a; 149a; 191a; 249a; 272a; 302a) and the second laser region (111 b; 149b; 191b; 249b; 272b; 302b); a step of injecting a second constant current, which is below a threshold current, into the other of the first laser region (111 a; 149a; 191 a; 249a; 272a; 302a) and the second laser region (111 b; 149b; 191 b; 249b; 272b; 302b); and a step of imparting one of a minute modulated current and a minute modulated voltage to the selecting means (274; 304).

Claim 38

A driving method for driving an oscillation polarization mode selective semiconductor laser for selectively performing one of plural oscillations in different polarization modes, said laser comprising a subtrate (1; 41; 71; 101; 141; 181; 241; 271; 301), a first laser region (111 a; 149a; 191a; 249a; 272a; 302a) on said substrate having a semiconductor laser structure in which a gain spectrum of one of the different polarization modes is dominant, a second laser region (111b; 149b; 191 b; 249b; 272b; 302b) on said substrate having a semiconductor laser structure in which a gain spectrum of another of the different polarization modes is dominant, coupling means (112; 150; 192; 250; 273; 303) for coupling the first laser region and the second laser region, injecting means (7, 8, 9; 47, 48, 49; 77, 78, 79; 107a, 107b, 109; 148a, 148b, 151; 187a, 187b, 189; 248a, 248b, 251; 287, 289; 317a, 317b, 319) for independently injecting currents into the first laser region and the second laser region to cause a mode competitive state between the oscillations in the different polarization modes, and selecting means (274; 304) for selecting one of the oscillations in the different polarization modes to emit light in a selected polarization mode, said driving method comprising: a step of injecting a first constant current, which is below a threshold current, into one of the first laser region (111 a; 149a; 191a; 249a; 272a; 302a) and the second laser region (111 b; 149b; 191b; 249b; 272b; 302b); a step of injecting a second constant current, which is below a threshold current, into the other of the first laser region (111 a; 149a; 191 a; 249a; 272a; 302a) and the second laser region (111 b; 149b; 191 b; 249b; 272b; 302b); and a step of imparting one of a minute modulated current and a minute modulated voltage to the selecting means (274; 304).

Claim 39

A light transmitter comprising: an oscillation polarization mode selective semiconductor laser (402) for selectively performing one of plural oscillations in different polarization modes, said laser including a subtrate (1; 41; 71; 101; 141; 181; 241; 271; 301), a first laser region (111 a; 149a; 191a; 249a; 272a; 302a) on said substrate having a semiconductor laser structure in which a gain spectrum of one of the different polarization modes is dominant, a second laser region (111b; 149b; 191 b; 249b; 272b; 302b) on said substrate having a semiconductor laser structure in which a gain spectrum of another of the different polarization modes is dominant, coupling means (112; 150; 192; 250; 273; 303) for coupling the first laser region and the second laser region, and injecting means (7, 8, 9; 47, 48, 49; 77, 78, 79; 107a, 107b, 109; 148a, 148b, 151; 187a, 187b, 189; 248a, 248b, 251; 287, 289; 317a, 317b, 319) for independently injecting currents into the first laser region and the second laser region to cause a mode competitive state between the oscillations in the different polarization modes; control means (401) for modulating output light (408) of said semiconductor laser in its polarization mode in accordance with an input signal (406) supplied to said control means; and polarization mode selective means (403) for transmitting therethrough only light (409) in one of the different polarization modes from said semiconductor laser (402).

Claim 40

A light transmitter comprising: an oscillation polarization mode selective semiconductor laser (402) for selectively performing one of plural oscillations in different polarization modes, said laser including a subtrate (1; 41; 71; 101; 141; 181; 241; 271; 301), a first laser region (111 a; 149a; 191a; 249a; 272a; 302a) on said substrate having a semiconductor laser structure in which a gain spectrum of one of the different polarization modes is dominant, a second laser region (111b; 149b; 191 b; 249b; 272b; 302b) on said substrate having a semiconductor laser structure in which a gain spectrum of another of the different polarization modes is dominant, coupling means (112; 150; 192; 250; 273; 303) for coupling the first laser region and the second laser region, and injecting means (7, 8, 9; 47, 48, 49; 77, 78, 79; 107a, 107b, 109; 148a, 148b, 151; 187a, 187b, 189; 248a, 248b, 251; 287, 289; 317a, 317b, 319) for independently injecting currents into the first laser region and the second laser region to cause a mode competitive state between the oscillations in the different polarization modes; control means (401) for modulating output light (408) of said semiconductor laser in its polarization mode in accordance with an input signal (406) supplied to said control means; and polarization mode selective means (403) for transmitting therethrough only light (409) in one of the different polarization modes from said semiconductor laser (402).

Claim 41

An optical communication system comprising: (a) a light transmitter (411; 461-1, •••, 461-n), said light transmitter including: an oscillation polarization mode selective semiconductor laser (402) for selectively performing one of plural oscillations in different polarization modes, said laser including a subtrate (1; 41; 71; 101; 141; 181; 241; 271; 301), a first laser region (111 a; 149a; 191 a; 249a; 272a; 302a) on said substrate having a semiconductor laser structure in which a gain spectrum of one of the different polarization modes is dominant, a second laser region (111b; 149b; 191 b; 249b; 272b; 302b) on said substrate having a semiconductor laser structure in which a gain spectrum of another of the different polarization modes is dominant, coupling means (112; 150; 192; 250; 273; 303) for coupling the first laser region and the second laser region, and injecting means (7, 8, 9; 47, 48, 49; 77, 78, 79; 107a, 107b, 109; 148a, 148b, 151; 187a, 187b, 189; 248a, 248b, 251; 287, 289; 317a, 317b, 319) for independently injecting currents into the first laser region and the second laser region to cause a mode competitive state between the oscillations in the different polarization modes; control means (401) for modulating output light (408) of said semiconductor laser in its polarization mode in accordance with an input signal (406) supplied to said control means; and polarization mode selective means (403) for transmitting therethrough only light (409) in one of the different polarization modes from said semiconductor laser; (b) transmission means (405) for transmitting the light selected by said polarization mode selective means; and (c) a receiver (471-1, •••, 471-n) for receiving the light transmitted by said transmission means.

Claim 42

An optical communication system comprising: (a) a light transmitter (411; 461-1, •••, 461-n), said light transmitter including: an oscillation polarization mode selective semiconductor laser (402) for selectively performing one of plural oscillations in different polarization modes, said laser including a subtrate (1; 41; 71; 101; 141; 181; 241; 271; 301), a first laser region (111 a; 149a; 191 a; 249a; 272a; 302a) on said substrate having a semiconductor laser structure in which a gain spectrum of one of the different polarization modes is dominant, a second laser region (111b; 149b; 191 b; 249b; 272b; 302b) on said substrate having a semiconductor laser structure in which a gain spectrum of another of the different polarization modes is dominant, coupling means (112; 150; 192; 250; 273; 303) for coupling the first laser region and the second laser region, and injecting means (7, 8, 9; 47, 48, 49; 77, 78, 79; 107a, 107b, 109; 148a, 148b, 151; 187a, 187b, 189; 248a, 248b, 251; 287, 289; 317a, 317b, 319) for independently injecting currents into the first laser region and the second laser region to cause a mode competitive state between the oscillations in the different polarization modes; control means (401) for modulating output light (408) of said semiconductor laser in its polarization mode in accordance with an input signal (406) supplied to said control means; and polarization mode selective means (403) for transmitting therethrough only light (409) in one of the different polarization modes from said semiconductor laser; (b) transmission means (405) for transmitting the light selected by said polarization mode selective means; and (c) a receiver (471-1, •••, 471-n) for receiving the light transmitted by said transmission means.

Claim 43

An optical communication system according to claim 36, wherein said system is constructed as a wavelength division multiplexing communication system.