Canon Kabushiki Kaisha

Kazuhito Fujii

Akira Shimizu

Masahiro Okuda

Takeo Ono

An optical device includes an asymmetric dual quantum well (ADQW) structure which is comprised of a plurality (at least two) of different semiconductor quantum well layers coupled to each other. In the ADQW structure, the width of a deeper quantum well layer having a narrower band gap is made narrower than that of a less deeper quantum well layer having a wider band gap such that the shift of an exciton wavelength is scarcely caused due to the quantum confined Stark effect by the application of an electric field in a predetermined range. As a result, only a refractive index of the ADQW structure is changed, but an absorption factor is scarcely changed for a given range of wavelength by the application of the electric field. Further, there is provided a member for applying an electric field to the asymmetric dual quantum well structure.

Optical device with an asymmetric dual quantum well structure

Novel electron wave combining and/or branching devices and Aharonov-Bohm type quantum interference devices are proposed, which have no curved electron waveguide structures to form an electron branching or decoupling part or ring geometry. But instead the electron branching part or ring geometry is effectively constructed in a straight double quantum well structures, by the control of the shapes of the wave functions or of the subband energy levels relative to the Fermi level by electric fields.

Electron wave combining/branching devices and quantum interference

Disclosed is a photodetector adapted to detect light having a predetermined level of photon energy, comprising: a first semiconductor layer, a second semiconductor layer having a quantum well or a quantum wire structure, a barrier layer provided between the first and second semiconductor layers, a device for applying voltage to the barrier layer and the first and second semiconductor layers in order to generate a tunnel current flowing through the barrier layer, and a device for detecting the tunnel current. The second semiconductor layer exhibits a plurality of quantized electron energy levels, the energy difference between which is slightly smaller or slightly larger than the photon energy of the detected light. Further, incidence of the detected light upon the second semiconductor layer causes the quantized electron energy levels to shift by the photo Stark effect, resulting in variation of the tunnel current.

Photodetector and photodetection method

An electron wave is propagated through a plurality of quantum-structure paths of a quantum interference device and is branched into into plural electron waves that are confined in the quantum-structure paths. The electron waves from the quantum-structure paths are combined into a plurality of kinds of different energy level electron waves with varying magnitudes dependent on phase differences between the branched electron waves. The currents of the plurality of kinds of electron waves are detected and a non-fluctuating current is produced from the detected currents. The fluctuation of the electron wave current does not influence the non-fluctuating current and the phase differences among branched electron waves may be modulated by light, an electric field or a magnetic field applied to the branching portion of the device.

Quantum interference devices and methods for processing interference

A photo-detector for detecting a light having a predetermined photon energy, comprises: a semiconductor member having a source region, a gate region and a drain region; a first path for propagating an electron wave from the source region to the drain region through the gate region; a second path for propagating an electron wave from the source region to the drain region through the gate region; the second path being of quantum well structure or a quantum line structure and having a plurality of electron levels having an energy difference therebetween slightly smaller or slightly larger than the photon energy of the light to be detected; a wave function of the electron wave propagating through the second path being coupled with a wave function of the electron wave propagating through the first path in the source region and the drain region and separated from the wave function of the electron wave propagating through the first path in the gate region; means for applying a voltage across the source region and the drain region; means for detecting a current flowing across the source region and the drain region. When the light to be detected is applied to the second path, the electron levels are shifted by an optical Stark effect and phase difference is created between the electron wave propagating through the first path and the electron wave propagating through the second path so that the current changes.

Photo-detector and photo-detection method using the same

A quantum interference device includes a source, a drain and waveguides with quantum structures between the source and the drain. An electron wave from the source that is confined in the waveguides is split into plural electron waves. The phase difference between the split electron waves is controlled and the split electron waves are combined into a single electron wave. The combined electron wave is directed to the drain or out of the waveguides according to an energy state of the combined electron wave by a real space transfer such as a tunneling effect. The phase difference control may be achieved by varying an electric field, a magnetic field, or light.

Growing community of inventors

Atsugi, Japan

Kazuhito Fujii