Picosecond bistable optical switch using two-photon transitions
First Claim
1. A bistable optical device with switching times in the picosecond range comprising:
- an optical resonator with an optical resonant cavity therein and including means for extracting a light output beam from said optical resonant cavity,a nonlinear material which is essentially optically transparent disposed in said optical resonant cavity, said nonlinear material having a conduction band and at least an upper and a lower valence bands with an energy spacing therebetween such that a two-hw photon transition can occur from a non-minimum energy location in said upper valence band to said conduction band, and a one-hw photon virtual transition at a non-minimum energy can occur between said upper and lower valence bands, said nonlinear material having an optical length which depends on the intensity of light in said optical resonant cavity; and
means for pumping photon energy hw in the range 1/2Δ
g <
hw<
Δ
g into said optical resonant cavity in order to stimulate said virtual transition via the two-photon transition, where Δ
g is the bandgap between the upper valence band and the conduction band of said nonlinear material.
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Abstract
A bistable optical switch comprising a Fabry-Perot resonator containing a nonlinear semiconductor medium with a desired band structure and whose susceptibility (refractive index) varies with optical energy density. The Fabry-Perot resonator is biased to a point where two stable transmission states are possible. Switching is accomplished by pumping the nonlinear material with an energy hw in the range 1/2Δg <hw<Δg, where Δg is the bandgap between the upper valence band and the conduction band of the nonlinear material, in order to stimulate a two-photon valence-to-conduction band absorption transition at a non-minimum energy and thereby make possible a one-hw photon virtual transition between the heavy hole and split-off valence bands of the nonlinear material. This virtual transition alters the susceptibility thereby switching the resonator to a different stable transmission state. Switching times on the order of picoseconds are obtained because switching-time is not dependent on the carrier recombination time.
17 Citations
17 Claims
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1. A bistable optical device with switching times in the picosecond range comprising:
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an optical resonator with an optical resonant cavity therein and including means for extracting a light output beam from said optical resonant cavity, a nonlinear material which is essentially optically transparent disposed in said optical resonant cavity, said nonlinear material having a conduction band and at least an upper and a lower valence bands with an energy spacing therebetween such that a two-hw photon transition can occur from a non-minimum energy location in said upper valence band to said conduction band, and a one-hw photon virtual transition at a non-minimum energy can occur between said upper and lower valence bands, said nonlinear material having an optical length which depends on the intensity of light in said optical resonant cavity; and means for pumping photon energy hw in the range 1/2Δ
g <
hw<
Δ
g into said optical resonant cavity in order to stimulate said virtual transition via the two-photon transition, where Δ
g is the bandgap between the upper valence band and the conduction band of said nonlinear material. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A bistable optical switch with switching times in the picosecond range comprising:
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a Fabry-Perot resonator including an optical resonant cavity; a nonlinear semiconductor material disposed in said optical resonant cavity of said Fabry-Perot resonator, said semiconductor material having a conduction band, a heavy hole valence band, and at least one other valence band, and having a refractive index which depends on the intensity of light in said optical resonant cavity; and means for optically biasing said Fabry-Perot resonator with an optical input power such that the Fabry-Perot resonator has at least two stable transmission states, and for pumping photon energy hw in the range 1/2Δ
g <
hw<
Δ
g into said optical resonant cavity in order to stimulate a two-photon absorption transition between said heavy hole valence band and said conduction band and thus switch between said two stable transmission states in said Fabry-Perot resonator, where Δ
g is the bandgap between the heavy hole valence band and the conduction band of said semiconductor material,wherein said semiconductor material has a band structure with a one-hw photon potential virtual transition between two valence bands thereof at a non-minimum energy. - View Dependent Claims (10, 11, 12, 13, 14)
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15. A method for switching an optical Fabry-Perot resonator with switching times in the picosecond range, said Fabry-Perot resonator having an optical resonant cavity with a nonlinear semiconductor material disposed therein, said semiconductor material having a conduction band, a heavy hole valence band and at least one other valence band with a band structure such that a two-hw photon transition can occur from a non-minimum energy location in said heavy hole band to said conduction band, and a one-hw photon virtual transition can occur at a non-minimum energy between two of the valence bands, said semiconductor material also having a refractive index which depends on the intensity of light in said optical resonant cavity, said method comprising the steps of:
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biasing said optical resonant cavity of said Fabry-Perot resonantor with an optical input power such that said Fabry-Perot resonator has at least two stable transmission states at the bias input power; and pumping photon energy hw in the range 1/2Δ
g <
hw<
Δ
g into said optical resonant cavity in order to stimulate a virtual transition between valence bands via a two-photon absorption transition and thus switch between said at least two stable transmission states in said Fabry-Perot resonator, where Δ
g is the bandgap between the heavy hole valence band and the conduction band of the semiconductor material.
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16. A bistable optical switch with switching times in the picosecond range comprising:
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a Fabry-Perot resonator including an optical resonant cavity; a nonlinear semiconductor material disposed in said optical resonant cavity of said Fabry-Perot resonator, said semiconductor material having a conduction band, a heavy hole valence band, and at least one other valence band and having a band structure with a direct bandgap between said heavy hole valence and conduction bands, and capable of having a 2-hw photon transition occur from a non-minimum energy location in said heavy hole band to said conduction band, and a 1-hw photon virtual transition occur at a non-minimum energy location between two of the valence bands, said semiconductor material also having a refractive index which depends on the intensity of light in said optical resonant cavity; means for optically biasing said Fabry-Perot resonator with an optical input power such that the Fabry-Perot resonator has at least two stable transmission states at this optical bias; and means for perturbing the populations of energy states with energies near the valence band energy states with virtual transitions that can give a contribution to the susceptibility to thereby switch between said two stable transmission states in said Fabry-Perot resonator, wherein said energy state perturbing means comprises means for pumping photon energy hw in the range 1/2Δ
g <
hw<
Δ
g into said optical resonant cavity in order to stimulate a two-photon absorption transition at said perturbed energy states, where Δ
g is the bandgap between the heavy hole valence band and the conduction band of said semiconductor material. - View Dependent Claims (17)
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Specification