Optical modulator and optical communication system utilizing the same

Claim 2

An optical modulator comprising; two cladding layers respectively doped into different conductive types; a light absorption layer formed between said cladding layers for propagating incident light and for absorbing the light in response to a voltage applied between said cladding layers; an optical waveguide layer formed between the cladding layers and optically and operatively connected to the light absorption layer for propagating the light; and a layer transparent to the light in which the optical modulator is buried.

Claim 3

An optical modulator comprising: light absorbing means for propagating incident light and for absorbing the light in response to an applied voltage; light guiding means formed in at least a portion of a periphery of said light absorbing means and approximate to said light absorbing means for propagating the light, wherein said light guiding means is a light waveguide layer of a channel type which has a width corresponding to a width of said light absorbing means; confining means formed around said light absorbing means and said light guiding means for substantially confining the light in said light absorbing means and said light guiding means; and means for applying a voltage to said light absorbing means through said confining means, in response to an input signal.

Claim 4

An optical modulator comprising: light absorbing means for propagating incident light and for absorbing the light in response to an applied voltage; light guiding means formed in at least a portion of a periphery of said light absorbing means and approximate to said light absorbing means for propagating the light, wherein said light guiding means is a light waveguide layer of a channel type which has a width corresponding to a width of said light absorbing means; confining means formed around said light absorbing means and said light guiding means for substantially confining the light in said light absorbing means and said light guiding means; and means for applying a voltage to said light absorbing means through said confining means, in response to an input signal.

Claim 5

An optical modulator according to claim 2, wherein said light absorbing means is made of material having an absorption edge at a wavelength shorter than a wavelength of the light, and has a refractive index higher than that of said confining means.

Claim 6

An optical modulator according to claim 2, wherein said light guiding means is made of material having an absorption edge at a wavelength shorter than a wavelength of the light, and has a refractive index higher than that of said confining means.

Claim 7

An optical transmitter comprising: light emitting means for generating light which has a substantially constant wavelength; multiplexing means for multiplexing inputted electric signals; and optical modulation means for carrying out intensity modulation for the light from said light emitting means in accordance with a multiplexed signal from said multiplexing means, said optical modulation means comprising. light absorbing means for propagating the light and for absorbing the light in response to an applied voltage, light guiding means formed in at least a portion of a periphery of said light absorbing means and optically connected to said light absorbing means, for propagating the light, confining means formed around said light absorbing means and said light guiding means, for confining the light in said light absorbing means and said light guiding means, and means for applying the voltage to said light absorbing means through said confining means in response to the multiplexed signal.

Claim 8

An optical transmitter comprising: light emitting means for generating light which has a substantially constant wavelength; multiplexing means for multiplexing inputted electric signals; and optical modulation means for carrying out intensity modulation for the light from said light emitting means in accordance with a multiplexed signal from said multiplexing means, said optical modulation means comprising. light absorbing means for propagating the light and for absorbing the light in response to an applied voltage, light guiding means formed in at least a portion of a periphery of said light absorbing means and optically connected to said light absorbing means, for propagating the light, confining means formed around said light absorbing means and said light guiding means, for confining the light in said light absorbing means and said light guiding means, and means for applying the voltage to said light absorbing means through said confining means in response to the multiplexed signal.

Claim 9

An optical transmitter according to claim 5, wherein each of said light absorbing means and said light guiding means is made of material having an absorption edge at a wavelength shorter than a wavelength of the light, and has a refractive index higher than that of said confining means.

Claim 10

An optical transmitter according to claim 5, wherein material and thickness of each of said light absorbing means and said light guiding means are selected so that total change in refractive index is negative or zero, the total change being defined by a sum of products of light confinement factors and corresponding change in refractive index due to the applied voltage for each of said light absorbing means and said light guiding mean.

Claim 11

An optical transmitter according to claim 5, wherein each of said light absorbing means and said light guiding means is formed of a multiple quantum well structure, and thickness and material of each of their well and barrier layers are selected so that each of said light absorbing means and said light guiding means has a predetermined refractive index and an absorption edge at a predetermined wavelength.

Claim 12

An optical transmitter according to claim 6, wherein a portion of said light absorbing means, or a portion of said light guiding means and all portion of said light absorbing means is undoped to form a p-i-n structure from said confining means, said light absorbing means and said light guiding means.

Claim 13

An optical transmitter according to claim 5, wherein said light emitting means and said optical modulation means are integrated on a single substrate.

Claim 14

An optical communication system comprising: light transmitting means comprising: light emitting means for generating light which has a substantially constant wavelength, multiplexing means for multiplexing inputted electric signals, and optical modulation means for carrying out intensity modulation for the light from said light emitting means in accordance with a multiplexed signal from said multiplexing means, wherein said optical modulation means comprises light absorbing means for propagating the light and for absorbing the light in response to an applied voltage, light guiding means formed in at least a portion of a periphery of said light absorption means, for propagating the light, confinement means formed around said light absorption means and said light guiding means for confining the light in said light absorption means and said light guiding means and means for applying the voltage to said light absorption means through said confinement means in response to an input signal; transmission means connected to said light transmitting means for propagating an intensity-modulated light signal; and reception means connected to the transmission means and receiving the intensity-modulated light signal for converting the intensity-modulated light signal into a received electric signal and for decomposing the received electric signal into a plurality of output signals to be delivered.

Claim 15

An optical communication system comprising: light transmitting means comprising: light emitting means for generating light which has a substantially constant wavelength, multiplexing means for multiplexing inputted electric signals, and optical modulation means for carrying out intensity modulation for the light from said light emitting means in accordance with a multiplexed signal from said multiplexing means, wherein said optical modulation means comprises light absorbing means for propagating the light and for absorbing the light in response to an applied voltage, light guiding means formed in at least a portion of a periphery of said light absorption means, for propagating the light, confinement means formed around said light absorption means and said light guiding means for confining the light in said light absorption means and said light guiding means and means for applying the voltage to said light absorption means through said confinement means in response to an input signal; transmission means connected to said light transmitting means for propagating an intensity-modulated light signal; and reception means connected to the transmission means and receiving the intensity-modulated light signal for converting the intensity-modulated light signal into a received electric signal and for decomposing the received electric signal into a plurality of output signals to be delivered.

Claim 16

An optical communication system according to claim 11, wherein said light emitting means and said optical modulation means are integrated on a single substrate.

Claim 17

An optical device integrated circuit comprising: a waveguide layer formed on a substrate; a laser diode formed on said waveguide layer; an optical modulator formed on said waveguide layer at a position proximate to said laser diode; and an insulating layer formed on that portion of said waveguide layer where said laser diode and said optical modulator does not exist, and on said substrate, for electrically insulating said optical modulator from said laser diode.

Claim 18

An optical device integrated circuit comprising: a waveguide layer formed on a substrate; a laser diode formed on said waveguide layer; an optical modulator formed on said waveguide layer at a position proximate to said laser diode; and an insulating layer formed on that portion of said waveguide layer where said laser diode and said optical modulator does not exist, and on said substrate, for electrically insulating said optical modulator from said laser diode.

Claim 19

An optical device integrated circuit according to claim 13, wherein said optical modulator comprises: a cladding layer of different conductive type from said substrate, and a light absorption layer formed between said cladding layer and said waveguide layer, for propagating light from said laser diode and for absorbing the light in response to a voltage applied between said cladding layer and said substrate.

Claim 20

An optical device integrated circuit according to claim 14, wherein said light absorption layer is extended along said waveguide layer to said laser diode in place of said insulating layer between said laser diode and said optical modulator.

Claim 21

An optical device integrated circuit according to claim 13, wherein said laser diode comprises: an active layer formed on said waveguide layer; an electrode layer of a different conductive type from said substrate; and grating formed between said waveguide layer and said substrate under said laser diode.

Claim 22

An optical modulator comprising: two cladding layers respectively doped into different conductive types; a light absorption layer formed between said cladding layers for propagating incident light and for absorbing the light in response to a voltage applied between said cladding layers; an optical waveguide layer formed between the cladding layers and optically and operatively connected to the light absorption layer for propagating the light; and a layer in which the optical modulator is buried and which has a refractive index smaller than a refractive index of said optical waveguide layer.

Claim 23

An optical modulator comprising: two cladding layers respectively doped into different conductive types; a light absorption layer formed between said cladding layers for propagating incident light and for absorbing the light in response to a voltage applied between said cladding layers; an optical waveguide layer formed between the cladding layers and optically and operatively connected to the light absorption layer for propagating the light; and a layer in which the optical modulator is buried and which has a refractive index smaller than a refractive index of said optical waveguide layer.

Claim 24

An optical modulator comprising: light absorbing means for propagating incident light and for absorbing the light in response to an applied voltage; light guiding means formed in at least a portion of a periphery of said light absorbing means and approximate to said light absorbing means for propagating the light; confining means formed around said light absorption means and said light guiding means for substantially confining the light in said light absorbing means and said light guiding means for substantially confining the light in said light absorbing means and said light guiding means; and means for applying a voltage to said light absorbing means through said confining means, in response to an input signal; wherein a crystal for forming said light guiding means is arranged so that change in its refractive index for the light due to its electrooptic effect is negative.

Claim 25

An optical modulator comprising: light absorbing means for propagating incident light and for absorbing the light in response to an applied voltage; light guiding means formed in at least a portion of a periphery of said light absorbing means and approximate to said light absorbing means for propagating the light; confining means formed around said light absorption means and said light guiding means for substantially confining the light in said light absorbing means and said light guiding means for substantially confining the light in said light absorbing means and said light guiding means; and means for applying a voltage to said light absorbing means through said confining means, in response to an input signal; wherein a crystal for forming said light guiding means is arranged so that change in its refractive index for the light due to its electrooptic effect is negative.

Claim 26

An optical modulator comprising: light absorbing means for propagating incident light and for absorbing the light in response to an applied voltage; light guiding means formed in at least a portion of a periphery of said light absorbing means and approximate to said light absorbing means for propagating the light; confining means formed around said light absorbing means and said light guiding means for substantially confining the light in said light absorbing means and said light guiding means for substantially confining the light in said light absorbing means and said light guiding means; and means for applying a voltage to said light absorbing means through said confining means, in response to an input signal; wherein when the voltage is applied, said light absorbing means has a positive change in refractive index and said light guiding means has a negative change in refractive index.

Claim 27

An optical modulator comprising: light absorbing means for propagating incident light and for absorbing the light in response to an applied voltage; light guiding means formed in at least a portion of a periphery of said light absorbing means and approximate to said light absorbing means for propagating the light; confining means formed around said light absorbing means and said light guiding means for substantially confining the light in said light absorbing means and said light guiding means for substantially confining the light in said light absorbing means and said light guiding means; and means for applying a voltage to said light absorbing means through said confining means, in response to an input signal; wherein when the voltage is applied, said light absorbing means has a positive change in refractive index and said light guiding means has a negative change in refractive index.

Claim 28

An optical modulator comprising: light absorbing means for propagating incident light and for absorbing the light in response to an applied voltage; light guiding means formed in at least a portion of a periphery of said light absorbing means and approximate to said light absorbing means for propagating the light; confining means formed around said light absorbing means and said light guiding means for substantially confining the light in said light absorbing means and said light guiding means; and means for applying a voltage to said light absorbing means through said confining means, in response to an input signal; wherein thickness and material of each of said light absorbing means and said light guiding means are selected so that total change in refractive index is negative or zero, the total change being defined by a sum of products of light confinement factors and corresponding changes in refractive indexes due to the applied voltage for each of said light absorbing means and said light guiding means.

Claim 29

An optical modulator comprising: light absorbing means for propagating incident light and for absorbing the light in response to an applied voltage; light guiding means formed in at least a portion of a periphery of said light absorbing means and approximate to said light absorbing means for propagating the light; confining means formed around said light absorbing means and said light guiding means for substantially confining the light in said light absorbing means and said light guiding means; and means for applying a voltage to said light absorbing means through said confining means, in response to an input signal; wherein thickness and material of each of said light absorbing means and said light guiding means are selected so that total change in refractive index is negative or zero, the total change being defined by a sum of products of light confinement factors and corresponding changes in refractive indexes due to the applied voltage for each of said light absorbing means and said light guiding means.

Claim 30

An optical modulator comprising: light absorbing means for propagating incident light and for absorbing the light in response to an applied voltage; light guiding means formed in at least a portion of a periphery of said light absorbing means and approximate to said light absorbing means for propagating the light; confining means formed around said light absorbing means and said light guiding means for substantially confining the light in said light absorbing means and said light guiding means; and means for applying a voltage to said light absorbing means through said confining means, in response to an input signal; wherein said light absorbing means and said light guiding means are formed of multiple quantum well structure, and thickness and material of each of their well and barrier layers are selected so that each of said light absorbing means and said light guiding means has a predetermined refractive index and an absorption edge at a predetermined wavelength.

Claim 31

An optical modulator comprising: light absorbing means for propagating incident light and for absorbing the light in response to an applied voltage; light guiding means formed in at least a portion of a periphery of said light absorbing means and approximate to said light absorbing means for propagating the light; confining means formed around said light absorbing means and said light guiding means for substantially confining the light in said light absorbing means and said light guiding means; and means for applying a voltage to said light absorbing means through said confining means, in response to an input signal; wherein said light absorbing means and said light guiding means are formed of multiple quantum well structure, and thickness and material of each of their well and barrier layers are selected so that each of said light absorbing means and said light guiding means has a predetermined refractive index and an absorption edge at a predetermined wavelength.

Claim 32

An optical modulator comprising: two cladding layers respectively doped into different conductive types; a light absorption layer formed between said cladding layers for propagating incident light and for absorbing the light in response to a voltage applied between said cladding layers; and an optical waveguide layer formed between the cladding layers and optically and operatively connected to the light absorption layer for propagating the light; wherein one of said cladding layers is a substrate; and wherein in a case where the crystal plane orientation of the substrate and a direction in which the voltage is applied are, a direction of crystal growth of said optical waveguide is, and wherein in a case where the crystal plane orientation of the substrate and a direction in which the voltage is applied are, the crystal growth direction of said optical waveguide is.

Claim 33

An optical modulator comprising: two cladding layers respectively doped into different conductive types; a light absorption layer formed between said cladding layers for propagating incident light and for absorbing the light in response to a voltage applied between said cladding layers; and an optical waveguide layer formed between the cladding layers and optically and operatively connected to the light absorption layer for propagating the light; wherein one of said cladding layers is a substrate; and wherein in a case where the crystal plane orientation of the substrate and a direction in which the voltage is applied are, a direction of crystal growth of said optical waveguide is, and wherein in a case where the crystal plane orientation of the substrate and a direction in which the voltage is applied are, the crystal growth direction of said optical waveguide is.

Claim 34

An optical modulator according to claim 22, wherein each of said light absorption layer and said optical waveguide layer is formed in a multiple quantum well structure, and thickness and material of each of well and barrier layers of the multiple quantum well structure are selected so that each of said light absorption layer and said optical waveguide layer has a predetermined refractive index and an absorption edge at a predetermined wavelength.

Claim 35

An optical modulator according to claim 22, further comprising a layer transparent to the light for burying the optical modulator therein.

Claim 36

An optical modulator according to claim 22, further comprising a layer in which the optical modulator is buried and which has a refractive index smaller than a refractive index of said optical waveguide layer.