US 6,608,774 B1 · Two-photon four-dimensional optical memory

Abstract

Selected domains, normally 2×103×2×103 such domains arrayed in a plane, within a three-dimensional (3-D) volume of radiation-sensitive medium, typically 1 cm3 of spirobenzopyran containing 2×103 such planes, are temporally and spatially simultaneously illuminated by two radiation pulses, normally laser light pulses in various combinations of wavelengths 532 nm and 1024 nm, in order, dependent upon the particular combination of illuminating light, to either write binary data to, or read binary data from, the selected domains by process of two-photon (2-P) interaction/absorption. One laser light pulse is preferably directed to illuminate all domains during its propagation along one directional axis of the volume. The other laser light pulse is first spatially encoded with binary information by 2-D spatial light modulator, and is then (i) directed and (ii) time sequenced to intersection with the other light pulse in a locus of intersection domains. During writing the selected, simultaneously illuminated, intersection domains change their index of refraction, attendant upon a change in isomeric molecular form, by process of 2-P absorption. During reading selected intersection domains selectively refract each of two read light pulses identically—as well as fluoresce—dependent upon their individually pre-established, written, states. The selective refraction of each read pulse in its passage straight through the volume is sensed in a detector array. I/O bandwidth to each cm3 of radiation-sensitive medium is on the order of 1 Gbit/sec to 1 Tbit/sec.

Claims21

Dependent claims

A radiation memory comprising:

a three-dimensional volume of a medium
that is sensitive to radiation in its absorption band so as to undergo an anomalous, stable, change in a physical property of the medium, which physical property affects the passage of radiation through the medium, from a first level to a second level,
that, regardless of a prevailing level of the physical property of the medium, has and exhibits a relatively greater impediment to a transmission of radiation of a relatively shorter wavelength, a relatively higher frequency and a relatively higher energy in a straight path through the medium, and
that, regardless of a prevailing level of the physical property of the medium, has and exhibits a relatively lesser impediment to a transmission radiation of a relatively longer wavelength, a relatively lower frequency and a relatively lower energy in a straight path through the medium;
and
radiation-directing means for directing two radiation pulses,
each of which has an individual wavelength sufficiently long, a frequency sufficiently low and an energy sufficiently low so as to be non-interactive with the medium to cause (i) any change in the physical property of the medium, or (ii) any change in a straight-line propagation, which straight-line propagation through the medium is unaffected regardless of what level of its physical property the medium exhibits along the path or portions thereof,
to temporal and spatial intersection within the volume of the medium so that, by satisfaction of the quantum mechanical equations of two-photon interaction, (i) a portion of the volume of the medium at a locus of intersection interacts with each and with both of the radiation pulses by process of two-photon interaction, while (ii) portions of the volume of medium outside this locus are non-reactive with either radiation pulse;
and
radiation-timing means for controlling the temporal phase of one of the two directed radiation pulses relative to the other of the two directed radiation pulses in order to select the volume portion of their intersection whereat occurs the two-photon interaction.

7 more elements

A method of reacting radiation at and only at, with an only with, a selected portion of a three-dimensional volume of radiation-sensitive medium while unselected volume portions are un-reacted with the radiation to change either (i) these volume portions or (ii) the radiation, the method comprising:

illuminating a three-dimensional volume of a medium
that is sensitive to radiation in its absorption band so as to undergo an anomalous, stable, change in a physical property of the medium, which physical property affects the passage of radiation through the medium, between a first and a second level,
that, regardless of whether the physical property is at the first or the second level, has and exhibits a relatively greater impediment to a transmission of radiation of a relatively shorter wavelength, a relatively higher frequency and a relatively higher energy in a straight path through the medium, and
that, regardless of whether the physical property is at the first or the second level, has and exhibits a relatively lesser impediment to a transmission radiation of a relatively longer wavelength, a relatively lower frequency and a relatively lower energy in a straight path through the medium,
with two radiation pulses,
each of which is of a selectively predetermined time duration, and phase relative to the other, while
each of which has an individual wavelength, frequency and energy that is both (i) non-interactive with the medium to cause the anomalous, stable, change in the level of its physical property, and (ii) that is unaffected in passage along a path through the medium regardless of what level of its physical property the medium exhibits along the path or portions thereof,
so that a temporal and spatial intersection within the volume of the medium satisfies the quantum mechanical equations of two-photon interaction to cause a portion of the volume of the medium as is defined by the time durations and the relative phase of the two radiation pulses at a locus of intersection to interact with each and with both of the radiation pulses by process of two-photon interaction, while portions of the volume of medium outside this locus are non-reactive with either and with both radiation pulses, and
so that each radiation pulse is itself un-reacted with all portions of the volume of the medium, passing straight through these portions regardless of the level of the physical property of these portions of the volume of the medium, save only that each and both radiation pulses are reacted with the portion of the volume of the medium at the locus of intersection, and at this portion each and both of the radiation pulses interacts with the physical property of the volume of the medium at this portion by process of two-photon interaction so as to be selectively relatively more greatly, or relatively less greatly, impeded in further transmission dependent upon whether the physical property of the medium is at its first, or at its second, level.

6 more elements

A radiation memory comprising:

a source of at least two time-resolved wave fronts of radiation, an energy of either of which radiation wave fronts is below a threshold energy level but the sum energy of both which radiation wave fronts equals the threshold energy level;
a three-dimensional volume of a radiation-sensitive medium having at least two stable states each of which stable states has an associated index of diffraction different from the index of diffraction of the other state, and one of which states is responsive to radiation of the threshold energy level to change to the other state while being (i) transparent, and (ii) insensitive to change state, to radiation of energy below this threshold energy level;
a radiation wave front data modulating means, receiving a one radiation wave front from the source, for two-dimensionally spatially manipulating the received radiation wave front so that it becomes two-dimensionally regionally encoded with information;
a radiation wave front variable time delay means, receiving a one radiation wave front from the source, for variably delaying the received radiation wave front in time;
and
a radiation directing means for directing at least two radiation wave fronts from the source, at least one of which radiation wave fronts is two-dimensionally regionally-encoded by the modulating means and at least one of which radiation wave fronts is variably time-delayed by the delay means, into a spatial and temporal intersection within the three-dimensional volume of radiation-sensitive medium so that
a set of domains that are within the three-dimensional volume of radiation-sensitive medium are defined by the spatial and temporal coincidence of the at least two intersecting radiation wave fronts,
the defined set of domains is unique, and non-inclusive, of any corresponding set of domains that are likewise defined in the three-dimensional volume upon any alternative time delay of a radiation wave front by the delay means, and
each of the domains that is within the defined unique set receives sufficient and sufficiently long radiation from the at least two intersecting radiation wave fronts so as to interact therewith to selectively change states, and state-associated index of refraction, by process of two-photon absorption, while
each and all the domains that are not within the defined unique set do not interact with either of the wave fronts of radiation.

7 more elements

A method of radiatively selectively manipulating a selectively unique, two-dimensional, plurality of domains within a three-dimensional volume of radiation-sensitive medium containing a three-dimensionally arrayed multiplicity of such domains, the method of radiatively manipulating selected plural domains within a volume comprising:

radiatively illuminating a volume of radiation-sensitive medium, the medium sensitive to radiation of a threshold energy to undergo change, with a first spatially-two-dimensionally-extended first radiation wave front having a first energy less than the threshold energy;
radiatively illuminating the volume with a second spatially-two-dimensionally-extended second radiation wave front having a second energy, also less than the threshold energy, so that the first and the second radiation wave fronts spatially and temporally intersect within the volume;
wherein each of the first and the second radiation wave fronts has a corresponding plurality of arrayed regions in its two-dimensional spatial extension;
wherein the combined first energy of the first radiation wave front and the second energy of the second radiation wave front is equal of greater than the threshold energy;
wherein the first and the second wave fronts are jointly sufficiently short so that their region of intersection is, by the quantum mechanical equations of two-photon absorption in the radiation-sensitive medium of the three-dimensional volume, compact to cause the change in only a an intersection region containing (i) less than the totality of the volume, and (ii) a plurality of three-dimensional sub-regions, called domains, defined and located where the plurality of regions that are two-dimensionally spatially arrayed upon the first wave front spatially and temporally intersect a corresponding plurality of regions that are two-dimensionally spatially arrayed upon the second wave front so as to satisfy thereat the quantum mechanical equations of two-photon absorption in the radiation-sensitive medium;
wherein plural domains have been radiatively manipulated within a homogeneous volume of radiation-sensitive medium as a function of the distance over which two intersecting two-dimensionally-spatially-extended wave fronts of radiation interact by process of two-photon absorption within the volume.

3 more elements

A method of producing a localized inhomogeneity pattern in a volume of radiation-sensitive medium in response to directed radiation, the method comprising:

time-resolving two spatially-two-dimensionally-extended radiation beams into a corresponding two pulse wave fronts jointly sufficiently short so that any spatial and temporal region of intersection of the two wavefronts will, by the quantum mechanical equations of two-photon absorption, be compact in at least one spatial dimension to a distance of less than x;
directing the two pulse wave fronts into spatial and temporal intersection within a volume of radiation-sensitive medium
that has at least one spatial dimension greater than x,
that has at least two states each of which has an associated index of diffraction different from the index of diffraction of the other state, and
that is responsive to radiation to change from one of its states to the other,
in order to change a selected portion of the volume of radiation-sensitive medium, less than the entirety thereof, from a one state having an associated index of refraction to a different state having a different associated index of refraction by process of plural-photon absorption.

3 more elements

Dependencies are inferred from the claim text.

Two-photon four-dimensional optical memory

Life of this patent

Two-photon four-dimensional optical memory

Life of this patent

Abstract

Claims21