Optical device with an asymmetric dual quantum well structure

A terminal for use in an optical communication system, comprising:

• an optical receiver;
• and
• an optical transmitter having an optical modulator;
• said optical modulator comprising:
• a first quantum well layer;
• a second quantum well layer having a smaller band gap and a smaller width than the band gap and width of said first quantum well layer;
• a first barrier layer disposed between said first and second quantum well layers and having a greater band gap than the band gaps of said first and second quantum well layers, electron waves in said first and second quantum well layers interfering with each other across said first barrier layer;
• second and third barrier layers including therebetween said first barrier layer and said first and second quantum well layers, said second and third barrier layers having band gaps greater than the band gap of said first barrier layer;
• and
• application means for applying an electric field to said first and second quantum well layers to change refractive indices of said first and second quantum well layers for light of predetermined wavelengths while suppressing change of absorption factors of said first and second quantum well layers for the light of predetermined wavelengths, thereby modulating the light of predetermined wavelengths for emission by said first and second quantum well layers,
• wherein a shift of an exciton peak wavelength due to quantum confined Stark effect by application of an electric field is small within a predetermined range of wavelengths.

A terminal for use in an optical communication system, comprising:

• an optical transmitter;
• and
• an optical receiver having an optical filter;
• said optical filter comprising:
• a first quantum well layer;
• a second quantum well layer having a smaller band gap and a smaller width than the band gap and width of said first quantum well layer;
• a first barrier layer disposed between said first and second quantum well layers and having a greater band gap than the band gaps of said first and second quantum well layers, electron waves in said first and second quantum well layers interfering with each other across said first barrier layer;
• second and third barrier layers including therebetween said first barrier layer and said first and second quantum well layers, said second and third barrier layers having band gaps greater than the band gap of said first barrier layer;
• and
• application means for applying an electric field to said first and second quantum well layers to change refractive indices of said first and second quantum well layers for light of predetermined wavelengths while suppressing change of absorption factors of said first and second quantum well layers for the light of predetermined wavelengths, thereby filtering the light of predetermined wavelengths,
• wherein a shift of an exciton peak wavelength due to quantum confined Stark effect by application of an electric field is small within a predetermined range of wavelengths.

An optical communication system, comprising:

• a plurality of terminals each including an optical transmitter and an optical receiver;
• and
• a plurality of terminals each including an optical transmitter and an optical receiver;
• and
• optical paths which interconnect said terminals;
• wherein said optical transmitter has an optical modulator which comprises:
• a first quantum well layer;
• a second quantum well layer having a smaller band gap and a smaller width than the band gap and width of said first quantum well layer;
• a first barrier layer disposed between said first and second quantum well layers and having a greater band gap than the band gaps of said first and second quantum well layers, electron waves in said first and second quantum well layers interfering with each other across said first barrier layer;
• second and third barrier layers including therebetween said first barrier layer and said first and second quantum well layers, said second and third barrier layers having band gaps greater than the band gap of said first barrier layer;
• and
• application means for applying an electric field to said first and second quantum well layers to change refractive indices of said first and second quantum well layers for light of predetermined wavelengths while suppressing change of absorption factors of said first and second quantum well layers for the light of predetermined wavelengths, thereby modulating the light of predetermined wavelengths for emission by said first and second quantum well layers,
• wherein a shift of an exciton peak wavelength due to quantum confined Stark effect by application of an electric field is small within a predetermined range of wavelengths.

An optical communication system comprising:

• a plurality of terminals each including an optical transmitter and an optical receiver;
• and
• optical paths which interconnect said terminals;
• wherein said optical receiver has an optical filter which comprises:
• a first quantum well layer;
• a second quantum well layer having a smaller band gap and a smaller width than the band gap and width of said first quantum well layer;
• a first barrier layer disposed between said first and second quantum well layers and having a greater band gap than the band gaps of said first and second quantum well layers, electron waves in said first and second quantum well layers interfering with each other across said first barrier layer;
• second and third barrier layers including therebetween said first barrier layer and said first and second quantum well layers, said second and third barrier layers having band gaps greater than the band gap of said first barrier layer;
• and
• application means for applying an electric field to said first and second quantum well layers to change refractive indices of said first and second quantum well layers for light of predetermined wavelengths while suppressing change of absorption factors of said first and second quantum well layers for the light of predetermined wavelengths, thereby filtering the light of predetermined wavelengths,
• wherein a shift of an exciton peak wavelength due to quantum confined Stark effect by application of an electric field is small within a predetermined range of wavelengths.

An optical device comprising:

• a first quantum well layer;
• a second quantum well layer having a smaller band gap and a smaller width than the band gap and width of said first quantum well layer;
• a first barrier layer disposed between said first and second quantum well layers and having a greater band gap than the band gaps of said first and second quantum well layers, electron waves in said first and second quantum well layers interfering with each other across said first barrier layer;
• second and third barrier layers including therebetween said first barrier layer and said first and second quantum well layers, said second and third barrier layers having band gaps greater than the band gap of said first barrier layer;
• first application means for applying an electric field to said first and second quantum well layers to change refractive indices of said first and second quantum well layers for light of predetermined wavelengths while suppressing change of absorption factors of said first and second quantum well layers for the light of predetermined wavelengths;
• and
• a grating formed near said first and second quantum well layers,
• wherein a shift of an exciton peak wavelength due to quantum confined Stark effect by application of an electric field is small within a predetermined range of wavelengths.

A terminal for use in an optical communication system, comprising:

• an optical receiver;
• and
• an optical transmitter having an optical modulator;
• said optical modulator comprising:
• a first quantum well layer;
• a second quantum well layer having a smaller band gap and a smaller width than the band gap and width of said first quantum well layer;
• a first barrier layer disposed between said first and second quantum well layers and having a greater band gap than the band gaps of said first and second quantum well layers, electron waves in said first and second quantum well layers interfering with each other across said first barrier layer;
• second and third barrier layers including therebetween said first barrier layer and said first and second quantum well layers, said second and third barrier layers having band gaps greater than the band gap of said first barrier layer;
• application means for applying an electric field to said first and second quantum well layers to change refractive indices of said first and second quantum well layers for light of predetermined wavelengths while suppressing change of absorption factors of said first and second quantum well layers for the light of predetermined wavelengths, thereby modulating the light of predetermined wavelengths for emission by said first and second quantum well layers;
• and
• a grating formed near said first and second quantum well layers,
• wherein a shift of an exciton peak wavelength due to quantum confined Stark effect by application of an electric field is small within a predetermined range of wavelengths.

A terminal for use in an optical communication system, comprising:

• an optical transmitter;
• and
• an optical receiver having an optical filter;
• said optical filter comprising:
• a first quantum well layer;
• a second quantum well layer having a smaller band gap and a smaller width than the band gap and width of said first quantum well layer;
• a first barrier layer disposed between said first and second quantum well layers and having a greater band gap than the band gaps of said first and second quantum well layers, electron waves in said first and second quantum well layers interfering with each other across said first barrier layer;
• second and third barrier layers including therebetween said first barrier layer and said first and second quantum well layers, said second and third barrier layers having band gaps greater than the band gap of said first barrier layer;
• application means for applying an electric field to said first and second quantum well layers to change refractive indices of said first and second quantum well layers for light of predetermined wavelengths while suppressing change of absorption factors of said first and second quantum well layers for the light of predetermined wavelengths, thereby filtering the light of predetermined wavelengths;
• and
• a grating formed near said first and second quantum well layers,
• wherein a shift of an exciton peak wavelength due to quantum confined Stark effect by application of an electric field is small within a predetermined range of wavelengths.

An optical communication system comprising:

• a plurality of terminals each including an optical transmitter and an optical receiver;
• and
• optical paths which interconnect said terminals;
• wherein said optical transmitter has an optical modulator which comprises:
• a first quantum well layer;
• a second quantum well layer having a smaller band gap and a smaller width than the band gap and width of said first quantum well layer;
• a first barrier layer disposed between said first and second quantum well layers and having a greater band gap than the band gaps of said first and second quantum well layers, electron waves in said first and second quantum well layers interfering with each other across said first barrier layer;
• second and third barrier layers including therebetween said first barrier layer and said first and second quantum well layers, said second and third barrier layers having band gaps greater than the band gap of said first barrier layer;
• application means for applying an electric field to said first and second quantum well layers to change refractive indices of said first and second quantum well layers for light of predetermined wavelengths while suppressing change of absorption factors of said first and second quantum well layers for the light of predetermined wavelengths, thereby modulating the light of predetermined wavelengths for emission by said first and second quantum well layers;
• and
• a grating formed near said first and second quantum well layers,
• wherein a shift of an exciton peak wavelength due to quantum confined Stark effect by application of an electric field is small within a predetermined range of wavelengths.

An optical communication system comprising:

• a plurality of terminals each including an optical transmitter and an optical receiver;
• and
• optical paths which interconnect said terminals;
• wherein said optical receiver has an optical filter which comprises:
• a first quantum well layer;
• a second quantum well layer having a smaller band gap and a smaller width than the band gap and width of said first quantum well layer;
• a first barrier layer disposed between said first and second quantum well layers and having a greater band gap than the band gaps of said first and second quantum well layers, electron waves in said first and second quantum well layers interfering with each other across said first barrier layer;
• second and third barrier layers including therebetween said first barrier layer and said first and second quantum well layers, said second and third barrier layers having band gaps greater than the band gap of said first barrier layer;
• application means for applying an electric field to said first and second quantum well layers to change refractive indices of said first and second quantum well layers for light of predetermined wavelengths while suppressing change of absorption factors of said first and second quantum well layers for the light of predetermined wavelengths, thereby filtering the light of predetermined wavelengths;
• and
• a grating formed near said first and second quantum well layers,
• wherein a shift of an exciton peak wavelength due to quantum confined Stark effect by application of an electric field is small within a predetermined range of wavelengths.

A method for modulating a light of predetermined wavelength in an optical modulator comprising a first quantum well layer, a second quantum well layer having a smaller band gap and a smaller width than the band gap and width of said first quantum well layer, a first barrier layer disposed between said first and second quantum well layers and having a greater band gap than the band gaps of said first and second quantum well layers, electron waves in said first and second quantum well layers interfering with each other across said first barrier layer, second and third barrier layers including therebetween said first barrier layer and said first and second quantum well layers, said second and third barrier layers having band gaps greater than the band gap of said first barrier layer and application means for applying an electric field to said first and second quantum well layers;

• said method comprising the steps of:
• coupling the light of predetermined wavelength to said first and second quantum well layers;
• changing refractive indices of said first and second quantum well layers for the light of predetermined wavelength while suppressing change of absorption factors of said first and second quantum well layers for the light of predetermined wavelength by applying the electric field to said first and second quantum well layers, thereby modulating the light of predetermined wavelength;
• and
• emitting the modulated light from said first and second quantum well layers,
• wherein a shift of an exciton peak wavelength due to quantum confined Stark effect by application of an electric field is small within a predetermined range of wavelengths.

An optical receiver comprising:

• an optical filter comprising:
• a first quantum well layer;
• a second quantum well layer having a smaller band gap and a smaller width than the band gap and width of said first quantum well layer;
• a first barrier layer disposed between said first and second quantum well layers and having a greater band gap than the band gaps of said first and second quantum well layers, electron waves in said first and second quantum well layers interfering with each other across said first barrier layer;
• second and third barrier layers including therebetween said first barrier layer and said first and second quantum well layers, said second and third barrier layers having band gaps greater than the band gap of said first barrier layer;
• first application means for applying an electric field to said first and second quantum well layers to change refractive indices of said first and second quantum well layers for light of predetermined wavelengths while suppressing change of absorption factors of said first and second quantum well layers for the light of predetermined wavelengths, thereby filtering the light of predetermined wavelengths;
• and
• a grating formed near said first and second quantum well layers,
• wherein a shift of an exciton peak wavelength due to quantum confined Stark effect by application of an electric field is small within a predetermined range of wavelengths.

A method for filtering a light of predetermined wavelength in an optical filter comprising a first quantum well layer, a second quantum well layer having a smaller band gap and a smaller width than the band gap and width of said first quantum well layer, a first barrier layer disposed between said first and second quantum well layers and having a greater band gap than the band gaps of said first and second quantum well layers, electron waves in said first and second quantum well layers interfering with each other across said first barrier layer, second and third barrier layers including therebetween said first barrier layer and said first and second quantum well layers, said second and third barrier layers having band gaps greater than the band gap of said first barrier layer and application means for applying an electric field to said first and second quantum well layers;

• said method comprising the steps of:
• coupling the light of predetermined wavelength to said first and second quantum well layers;
• changing refractive indices of said first and second quantum well layers for the light of predetermined wavelength while suppressing change of absorption factors of said first and second quantum well layers for the light of predetermined wavelength by applying the electric field to said first and second quantum well layers, thereby filtering the light of predetermined wavelength;
• and
• emitting the filtered light from said first and second quantum well layers,
• wherein a shift of an exciton peak wavelength due to quantum confined Stark effect by application of an electric field is small within a predetermined range of wavelengths.

An optical modulator comprising:

• a first quantum well layer;
• a second quantum well layer having a smaller band gap and a smaller width than the band gap and width of said first quantum well layer;
• a first barrier layer disposed between said first and second quantum well layers and having a greater band gap than the band gap of said first and second quantum well layers, electron waves in said first and second quantum well layers interfering with each other across said first barrier layer;
• second and third barrier layers including therebetween said first barrier layer and said first and second quantum well layers, said second and third barrier layers having band gaps greater than the band gap of said first barrier layer;
• and
• application means for applying an electric field to said first and second quantum well layers to change refractive indices of said first and second quantum well layers for light of predetermined wavelengths while suppressing change of absorption factors of said first and second quantum well layers for the light of predetermined wavelengths, thereby modulating the light of predetermined wavelengths for emission by said first and second quantum well layers;
• wherein a shift of an exciton peak wavelength due to quantum confined Stark effect by application of an electric field is small within a predetermined range of wavelengths.

An optical filter comprising:

• a first quantum well layer;
• a second quantum well layer having a smaller band gap and a smaller width than the band gap and width of said first quantum well layer;
• a first barrier layer disposed between said first and second quantum well layers and having a greater band gap than the band gap of said first and second quantum well layers, electron waves in said first and second quantum well layers interfering with each other across said first barrier layer;
• second and third barrier layers including therebetween said first barrier layer and said first and second quantum well layers, said second and third barrier layers having band gaps greater than the band gap of said first barrier layer;
• and
• application means for applying an electric field to said first and second quantum well layers to change refractive indices of said first and second quantum well layers for light of predetermined wavelengths while suppressing change of absorption factors of said first and second quantum well layers for the light of predetermined wavelengths, thereby filtering the light of predetermined wavelengths;
• wherein a shift of an exciton peak wavelength due to quantum confined Stark effect by application of an electric field is small within a predetermined range of wavelengths.

An optical transmitter comprising:

• an optical modulator comprising:
• a first quantum well layer;
• a second quantum well layer having a smaller band gap and a smaller width than the band gap and width of said first quantum well layer;
• a first barrier layer disposed between said first and second quantum well layers and having a greater band gap than the band gap of said first and second quantum well layers, electron waves in said first and second quantum well layers interfering with each other across said first barrier layer;
• second and third barrier layers including therebetween said first barrier layer and said first and second quantum well layers, said second and third barrier layers having band gaps greater than the band gap of said first barrier layer;
• and
• application means for applying an electric field to said first and second quantum well layers to change refractive indices of said first and second quantum well layers for light of predetermined wavelengths while suppressing change of absorption factors of said first and second quantum well layers for the light of predetermined wavelengths, thereby modulating the light of predetermined wavelengths for emission by said first and second quantum well layers,
• wherein a shift of an exciton peak wavelength due to quantum confined Stark effect by application of an electric field is small within a predetermined range of wavelengths.

An optical receiver comprising:

• an optical filter comprising:
• a first quantum well layer;
• a second quantum well layer having a smaller band gap and a smaller width than the band gap and width of said first quantum well layer;
• a first barrier layer disposed between said first and second quantum well layers and having a greater band gap than the band gap of said first and second quantum well layers, electron waves in said first and second quantum well layers interfering with each other across said first barrier layer;
• second and third barrier layers including therebetween said first barrier layer and said first and second quantum well layers, said second and third barrier layers having band gaps greater than the band gap of said first barrier layer;
• and
• application means for applying an electric field to said first and second quantum well layers to change refractive indices of said first and second quantum well layers for light of predetermined wavelengths while suppressing change of absorption factors of said first and second quantum well layers for the light of predetermined wavelengths, thereby filtering the light of predetermined wavelengths,
• wherein a shift of an exciton peak wavelength due to quantum confined Stark effect by application of an electric field is small within a predetermined range of wavelengths.

An optical modulator comprising:

• a first quantum well layer;
• a second quantum well layer having a smaller band gap and a smaller width than the band gap and width of said first quantum well layer;
• a first barrier layer disposed between said first and second quantum well layers and having a greater band gap than the band gaps of said first and second quantum well layers, electron waves in said first and second quantum well layers interfering with each other across said first barrier layer;
• second and third barrier layers including therebetween said first barrier layer and said first and second quantum well layers, said second and third barrier layers having band gaps greater than the band gap of said first barrier layer;
• first application means for applying an electric field to said first and second quantum well layers to change refractive indices of said first and second quantum well layers for light of predetermined wavelengths while suppressing change of absorption factors of said first and second quantum well layers for the light of predetermined wavelengths, thereby modulating the light of predetermined wavelengths for emission by said first and second quantum well layers;
• and
• a grating formed near said first and second quantum well layers,
• wherein a shift of an exciton peak wavelength due to quantum confined Stark effect by application of an electric field is small within a predetermined range of wavelengths.

An optical filter comprising:

• a first quantum well layer;
• a second quantum well layer having a smaller band gap and a smaller width than the band gap and width of said first quantum well layer;
• a first barrier layer disposed between said first and second quantum well layers and having a greater band gap than the band gaps of said first and second quantum well layers, electron waves in said first and second quantum well layers interfering with each other across said first barrier layer;
• second and third barrier layers including therebetween said first barrier layer and said first and second quantum well layers, said second and third barrier layers having band gaps greater than the band gap of said first barrier layer;
• first application means for applying an electric field to said first and second quantum well layers to change refractive indices of said first and second quantum well layers for light of predetermined wavelengths while suppressing change of absorption factors of said first and second quantum well layers for the light of predetermined wavelengths, thereby filtering the light of predetermined wavelengths;
• and
• a grating formed near said first and second quantum well layers,
• wherein a shift of an exciton peak wavelength due to quantum confined Stark effect by application of an electric field is small within a predetermined range of wavelengths.

An optical transmitter comprising:

• an optical modulator comprising:
• a first quantum well layer;
• a second quantum well layer having a smaller band gap and a smaller width than the band gap and width of said first quantum well layer;
• a first barrier layer disposed between said first and second quantum well layers and having a greater band gap than the band gaps of said first and second quantum well layers, electron waves in said first and second quantum well layers interfering with each other across said first barrier layer;
• second and third barrier layers including therebetween said first barrier layer and said first and second quantum well layers, said second and third barrier layers having band gaps greater than the band gap of said first barrier layer;
• first application means for applying an electric field to said first and second quantum well layers to change refractive indices of said first and second quantum well layers for light of predetermined wavelengths while suppressing change of absorption factors of said first and second quantum well layers for the light of predetermined wavelengths, thereby modulating the light of predetermined wavelengths for emission by said first and second quantum well layers;
• and
• a grating formed near said first and second quantum well layers,
• wherein a shift of an exciton peak wavelength due to quantum confined Stark effect by application of an electric field is small within a predetermined range of wavelengths.