Coupled quantum well strained superlattice structure and optically bistable semiconductor laser incorporating the same

A strained superlattice structure comprising:

• a plurality of coupled quantum well layers;
• and
• a barrier layer formed between each two adjacent quantum well layers respectively;
• the quantum well layers having a bandgap energy which is lower than the bandgap energy of the barrier layer;
• the quantum well layers having a lattice parameter which is selected to be different from the lattice parameter of the barrier layer such that a permanent strain is created in the quantum well layers and the barrier layer;
• wherein the lattice parameter of the quantum well layers is higher than the lattice parameter of the barrier layer.

A superlattice structure comprising:

• a plurality of quantum well structures and a buffer layer formed between each two adjacent quantum well structures;
• each quantum well structure comprising two quantum well layers and a barrier layer formed between the quantum well layers;
• the quantum well layers having a bandgap energy which is lower than the bandgap energy of the barrier layer and the buffer layer;
• the quantum well layers having a lattice parameter which is selected to be different from the lattice parameters of the barrier layer and the buffer layer such that a permanent strain is created in the superlattice structure;
• the quantum well layers, barrier layer and buffer layer having thicknesses selected such that the quantum well layers, barrier layer and buffer layer remain in an unrelaxed state, thereby precluding formation of misfit dislocations therein, and tunneling will occur between adjacent quantum well layers.

An optically bistable semiconductor laser including an active region, confinement means for creating an optical waveguide effect in the active region, electrode means for applying a bias voltage to the active region, and a substrate for supporting the active region, confinement means and electrode means, the active region comprising:

• a plurality of coupled quantum well layers;
• and
• a barrier layer formed between each two adjacent quantum well layers respectively;
• the quantum well layers having a bandgap energy which is lower than the bandgap energy of the barrier layer;
• the quantum well layers having a lattice parameter which is selected to be different from the lattice parameter of the barrier layer such that a permanent strain is created in the quantum well layers and the barrier layer which causes optical bistability.

An optically bistable semiconductor laser, comprising:

• an active area which includes:
• a plurality of coupled quantum well layers;
• and
• a barrier layer formed between each two adjacent quantum well layers respectively;
• the quantum well layers having a bandgap energy which is lower than the bandgap energy of the barrier layer;
• the quantum well layers having a lattice parameter which is selected to be different from the lattice parameter of the barrier layer such that a permanent strain is created in the quantum well layers and the barrier layer which causes optical bistability;
• first and second optical and charge confinement layers which sandwich the active region therebetween;
• first and second electrode layers formed over the first and second confinement layers respectively;
• and
• a substrate for supporting the active area, first and second confinement layers, and first and second electrode layers.

An optically bistable a semiconductor laser including an active region, confinement means for creating an optical waveguide effect in the active region, electrode means for applying a bias voltage to the active region, and a substrate for supporting the active region, confinement means and electrode means, the active region comprising:

• a plurality of coupled quantum well layers;
• and
• a barrier layer formed between each two adjacent quantum well layers respectively;
• the quantum well layers having a bandgap energy which is lower than the bandgap energy of the barrier layer;
• the quantum well layers having a lattice parameter which is selected to be different from the lattice parameter of the barrier layer such that a permanent strain is created in the quantum well layers and the barrier layer which causes optical bistability;
• the lattice parameter of the quantum well layers being higher than the lattice parameter of the barrier layer.

An optically bistable semiconductor laser including an active region, confinement means for creating an optical waveguide effect in the active region, electrode means for applying a bias voltage to the active region, and a substrate for supporting the active region, confinement means and electrode means, the active region comprising:

• a plurality of quantum well structures and a buffer layer formed between each two adjacent quantum well structures respectively;
• each quantum well structure comprising two quantum well layers and a barrier layer formed between the quantum well layers;
• the quantum well layers having a bandgap energy which is lower than the bandgap energy of the barrier layer and the buffer layer;
• the quantum well layers having a lattice parameter which is selected to be different from the lattice parameters of the barrier layer and the buffer layer such that a permanent strain is created in the active region which causes optical bistability;
• the quantum well layers, barrier layer and buffer layer having thicknesses selected such that the quantum well layers, barrier layer and buffer layer remain in an unrelaxed state, thereby precluding formation of misfit dislocations therein, and tunneling will occur between adjacent quantum well layers.

An optically bistable semiconductor laser including an active region, confinement means for creating an optical waveguide effect in the active region, electrode means for applying a bias voltage to the active region, and a substrate for supporting the active region, confinement means and electrode means, the active region comprising:

• a plurality of coupled quantum well layers;
• and
• a barrier layer formed between each two adjacent quantum well layers respectively;
• the quantum well layers having a bandgap energy which is lower than the bandgap energy of the barrier layer;
• the quantum well layers and the barrier layer having thicknesses selected such that the quantum well layers are interactively coupled, and tunneling will occur between adjacent quantum well layers.