EP0358229A2 — Semiconductor optical device having a non-linear …

Claim 1

Independent Claim 175 words

A semiconductor optical device having a refractive index changed responsive to irradiation of an incident optical beam, comprising a first material layer (M1) having a first band gap (Eg1) and a first thickness (l₁) set so as to allow existence of a two-dimensional exciton (LE) interacting with the incident optical beam, a second material layer (M2) having a second band gap (Eg2) substantially larger than said first band gap and disposed at both sides of said first material layer, characterized in that said second material layer has a second thickness (l₂) for allowing a tunneling of electron therethrough, and said device further comprises a third material layer (M3) having a third band gap (Eg3) substantially smaller than said second band gap and provided at least on one side of the second material layer, said third material layer having a third thickness (l₃) set such that there are formed one or more quantum levels (L3) of electron all of which being energetically different from at least one of those (L1) formed in the first material layer.

Claim 2

Dependent Claim 175 words

A semiconductor optical device having a refractive index changed responsive to irradiation of an incident optical beam, comprising a first material layer (M1) having a first band gap (Eg1) and a first thickness (l₁) set so as to allow existence of a two-dimensional exciton (LE) interacting with the incident optical beam, a second material layer (M2) having a second band gap (Eg2) substantially larger than said first band gap and disposed at both sides of said first material layer, characterized in that said second material layer has a second thickness (l₂) for allowing a tunneling of electron therethrough, and said device further comprises a third material layer (M3) having a third band gap (Eg3) substantially smaller than said second band gap and provided at least on one side of the second material layer, said third material layer having a third thickness (l₃) set such that there are formed one or more quantum levels (L3) of electron all of which being energetically different from at least one of those (L1) formed in the first material layer.

Claim 3

Dependent Claim 45 words

A semiconductor optical device as claimed in claim 1 characterized in that said first through third material layers (M1 - M3) form a structural unit, and said optical device has a superlattice structure comprising a repetition of said structural unit for a plurality of times.

Claim 4

Dependent Claim 83 words

A semiconductor optical device as claimed in claim 1 or 2 characterized in that said first material layer (M1) comprises a material selected from a group comprising gallium arsenide, indium gallium arsenide and indium gallium arsenide phosphide, said second material layer (M2) comprises a material selected from a group comprising aluminium gallium arsenide, indium aluminium arsenide, indium aluminium arsenide antimonide and indium phosphide, and said third material layer (M3) comprises gallium arsenide, aluminium gallium arsenide, indium gallium arsenide and indium gallium arsenide phosphide.

Claim 5

Dependent Claim 143 words

A semiconductor optical device as claimed in any one of claims 1 to 3 characterized in that said first thickness (l₁) is chosen such that there is formed a quantum well structure wherein electrons and holes assume discrete quantum levels (L1, L1′) respectively at a conduction band and a valence band in the first material layer (M1), said third thickness (l₃) is chosen such that there is formed a quantum well structure wherein electrons and holes assume another discrete quantum levels (L3, L3′) respectively at the conduction band and the valence band in the third material layer (M3) and such that there exists at least one quantum level (L3) of electron in the third material layer of which energy is substantially lower than the that of one quantum level (L1) of electron interacting with the incident optical beam in the first material layer.

Claim 6

Dependent Claim 92 words

A semiconductor optical device as claimed in claim 4 characterized in that said first and third material layers (M1, M3) have respective composition and thickness chosen such that there exists an energy difference (ΔE₃) between the quantum level (L3) of electron and the quantum level (L3′) of hole in the third material layer which is substantially larger than that (ΔE₁) between the quantum level (L1) of electron interacting with the incident optical beam in the first material layer (M1) and the quantum level (L1′) of hole in the first material layer (M1).

Claim 7

Dependent Claim 132 words

A semiconductor optical device as claimed in claim 4 or 5 characterized in that said first and second material layers (M1, M2) have respective thickness and composition chosen such that there exists an energy difference (E H ) between the quantum level of hole (L1′) in the first material layer (M1) and a top edge of the valence band (Ev) of the second material layer (M2) which is substantially reduced as compared to that (E E ) between a bottom edge of the conduction band (Ec) in the second material layer (M2) and said quantum level of electron (L1) interacting with the incident optical beam in the first material layer, so that tunneling of electron from the first material layer to the third material layer through the second material layer is facilitated.

Claim 8

Dependent Claim 62 words

A semiconductor optical device as claimed in claim 6 characterized in that said energy difference (E H ) between the quantum level of hole and the top edge of the valence band is set equal to or smaller than about one-fifth of the energy difference (E E ) between the quantum level of electron and the bottom edge of the conduction band.

Claim 9

Dependent Claim 62 words

A semiconductor optical device as claimed in any one of claims 1 to 7 characterized in that said device is defined by a pair of side surfaces extending perpendicularly to the first, second and third layers (M1 - M3), and a material having a composition identical to that of the second material layer (M2) is provided on said pair of side surfaces.

Claim 10

Dependent Claim 62 words

A semiconductor optical device as claimed in claim 8 characterized in that said device is further defined by another pair of side surfaces extending perpendicularly to the first, second and third layers (M1 - M3) and further perpendicularly to said first side surfaces, and a material identical to that provided on the first side surfaces is provided on said second side surfaces.

Claim 11

Dependent Claim 60 words

A semiconductor optical device as claimed in any one of claims 1 to 7 characterized in that the device is defined by a front side and a rear side extending parallel to said first, second and third material layers (M1 - M3) and said device further comprises a pair of reflecting means (E1, E2) at said front and rear sides.

Claim 12

Dependent Claim 200 words

An optical device having a variable reflectivity comprising a stacked body of an alternate repetition of a first optical layer (50) having a first refractive index and a second optical layer (51) having a second refractive index, characterized in that either one of the first and second optical layers comprises a first material layer (M1) having a first band gap (Eg1) and a first thickness (l₁) set so as to allow existence of a two-dimensional exciton (LE) interacting with the incident optical beam, a second material layer (M2) having a second band gap (Eg2) substantially larger than said first band gap and disposed at both sides of said first material layer, said second material layer having a second thickness (l₂) for allowing a tunneling of electron therethrough, and a third material layer (M3) having a third band gap (Eg3) substantially smaller than said second band gap and provided at least on one side of the second material layer, said third material layer having a third thickness (l₃) set such that there are formed one or more quantum levels (L3) of electron all of which being energetically different from at least one of those (L1) formed in the first material layer.

Claim 13

Dependent Claim 200 words

An optical device having a variable reflectivity comprising a stacked body of an alternate repetition of a first optical layer (50) having a first refractive index and a second optical layer (51) having a second refractive index, characterized in that either one of the first and second optical layers comprises a first material layer (M1) having a first band gap (Eg1) and a first thickness (l₁) set so as to allow existence of a two-dimensional exciton (LE) interacting with the incident optical beam, a second material layer (M2) having a second band gap (Eg2) substantially larger than said first band gap and disposed at both sides of said first material layer, said second material layer having a second thickness (l₂) for allowing a tunneling of electron therethrough, and a third material layer (M3) having a third band gap (Eg3) substantially smaller than said second band gap and provided at least on one side of the second material layer, said third material layer having a third thickness (l₃) set such that there are formed one or more quantum levels (L3) of electron all of which being energetically different from at least one of those (L1) formed in the first material layer.

Semiconductor optical device having a non-linear operational characteristic

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