Holographic Storage

Abstract

The holographic data storage system includes an emitter system, a holographic recording medium, and an input waveguide network formed from one or more multimode optical waveguides. The holographic recording medium has a plurality of recording regions each optically coupled to a corresponding one of the plurality of outcoupling regions of the input waveguide network, and the holographic data storage system is configured to persistently write data of an input beam received at any one of the outcoupling regions to the corresponding recording region. A controller is coupled to at least one of the emitter system and the at least one controllable steering element of the input waveguide network and controls at least one optical property of the input beam or the at least one steering element to steer the input beam from the incoupling region to any selected one of the plurality of outcoupling regions. Similar waveguide networks are provided to carry the reference and output beams.

Description

[Technical field]

[0001] Technical Field This disclosure relates generally to holographic storage. [Background technology]

[0002] background

[0002] Holographic storage is a form of computer storage in which information is recorded in a photosensitive holographic recording medium by exposing the medium to a light pattern. For example, a region (subvolume) of the medium can be exposed to a light interference pattern resulting from the interference of an input beam embedded with a set of data and a reference beam. The beam can be, for example, a laser beam generated using a single laser and a beam splitter. To embed the set of data in the input beam, spatial light modulation (SLM) can be used (for example, an image encoding the set of data can be spatially modulated and embedded in the input beam). For the avoidance of doubt, in this specification, the terms "light", "optical" and similar are not limited to visible light. Holographic storage can be implemented using, for example, infrared or ultraviolet beams in the non-visible part of the electromagnetic spectrum.

[0003]

[0003] With sufficient beam power and exposure time, the optical interference pattern produces a persistent state change within the sub-volume (at which point the interference pattern is said to be persistently recorded or written to the sub-volume herein). The state change of the sub-volume is such that, at a subsequent point in time, an output beam is produced that is essentially consistent with the original input beam, in the sense that upon exposure of the sub-volume to a substantially consistent reference beam, the interaction between the consistent reference beam and the sub-volume allows recovery from the output beam of the set of data originally embedded in the input beam (this may be referred to herein as reading the recorded pattern).

[0004]

[0004] Rather than storing individual bits as discrete units, a single interference pattern can encode many (e.g., millions) of bits. For example, the set of data can be a megapixel image embedded in the input beam. Moreover, by exploiting the sensitivity of certain forms of holographic recording media to small changes in the angle of the reference beam, it is possible to record many (e.g., hundreds or thousands) of such patterns in the same subvolume. For such media, once an interference pattern has been generated with a reference beam at a given angle, the recorded pattern can only be read by using a reference beam that closely matches the reference beam originally used to generate it. This effect can be exploited to record multiple patterns (encoding different sets of data) in the same subvolume at different reference beam angles. In theory, the data storage capacity is limited only by the wavelength of the beam, potentially hundreds of megabytes per cubic millimeter for red light and tens of gigabytes for ultraviolet light. In practice, there may be other limiting factors, but nevertheless there is great potential for high density data storage. Summary of the Invention [Means for solving the problem]

[0005] overview

[0005] This Summary is provided to introduce selected concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter. Nor is the claimed subject matter limited to implementations that solve any or all of the disadvantages described herein.

[0006]

[0006] Holographic data storage / retrieval systems that provide spatial multiplexing across a holographic recording medium, in the sense of being able to write / read from different physical sub-volumes of the medium, typically require some form of mechanical actuator to cause controllable mechanical movement of the holographic medium, for example to move the medium relative to the system's read / write head (from which the input and reference beams are emitted and where the output beam is detected) or to move the read / write head relative to the medium. This imposes limitations on the speed at which data can be written / read, as well as the scalability and reliability of such systems. Aspects of the technology disclosed herein reduce or eliminate the need for such mechanical movement.

[0007]

[0007] A first aspect of the present specification provides a holographic data storage system, the holographic data storage system including an emitter system, at least one holographic recording medium, and an input waveguide network formed of one or more multimode optical waveguides for simultaneously carrying multiple propagation modes. The emitter system is configured to emit an input beam in the form of a multimode optical signal encoding multiple image pixels as multiple propagation modes of the input beam propagating in different directions. The input waveguide network has an in-coupling region for receiving the input beam from the emitter system and multiple out-coupling regions. The at least one holographic recording medium has multiple recording regions optically coupled to corresponding ones of the multiple out-coupling regions of the input waveguide network, and the holographic data storage system is arranged to persistently and simultaneously write the multiple image pixels encoded in the input beam received at any one of the out-coupling regions to the corresponding recording regions. A controller is coupled to at least one of the emitter system and the at least one controllable directing element of the input waveguide network, the controller being configured to control at least one optical property of the input beam or the at least one directing element to direct the input beam from the in-coupling region to any selected one of the plurality of out-coupling regions. With this arrangement, different ones of the plurality of recording regions can be written from the same in-coupling region by varying the at least one optical property or controlling the at least one directing element to direct the input beam to different ones of the plurality of out-coupling regions while the plurality of out-coupling regions of the multi-mode optical waveguide network remain in fixed locations relative to corresponding recording regions of the holographic recording medium.

[0008]

[0008] Accordingly, in a first aspect, spatial multiplexing across the holographic recording medium is achieved for the writing option without requiring any mechanical movement of the emitter system, the holographic recording medium or the input waveguide network. In the case where the guiding elements are controllable, the guiding elements can be controlled to steer the input beam along different routes through the input waveguide network to different regions of the medium, and in the case where the optical properties of the beam are changed, the input waveguide network may be active or not (i.e., passive or active), but in any case, the input waveguide network responds to the change in the optical properties of the input beam, such that the input beam is similarly steered along different routes.

[0009]

[0009] A second aspect of the present specification provides a holographic data recovery system, comprising an emitter system, at least one detector array for detecting an image, at least one holographic recording medium, and a reference waveguide network formed from one or more multimode optical waveguides. The reference waveguide network has an in-coupling region for receiving a reference beam from the emitter system, and a plurality of out-coupling regions optically coupled to corresponding recording regions of the at least one holographic recording medium, respectively. A controller is coupled to at least one of the emitter system and at least one controllable guiding element of the reference network, and the controller is configured to control at least one optical property of the reference beam or at least one guiding element to steer the reference beam to any selected one of the recording regions to be read, thereby generating an output beam to be received by the detector array and to recover data of the stored pattern from the output beam through the reference beam interacting with the pattern stored therein. With this arrangement, different ones of a plurality of recording regions can be read using the same emitter system by modifying the at least one optical property of the reference beam or controlling the at least one directing element of the reference network while a plurality of outcoupling regions of the multi-mode optical waveguide network remain in fixed locations relative to corresponding recording regions of the holographic recording medium. The controller is configured to vary the angle of the reference beam to read different patterns stored in the same selected recording region, and the multi-mode optical waveguide of the reference waveguide network is for carrying the reference beam at any one of a plurality of possible angles.

[0010]

[0010] A third aspect of the present specification provides a holographic data recovery system, comprising at least one detector array, at least one holographic recording medium, and an output waveguide network formed from one or more multimode optical waveguides. The output waveguide network has an outcoupling region for providing an output beam to the detector array, and a plurality of incoupling regions each optically coupled to a corresponding recording region of the at least one holographic recording medium. The controller is configured to direct the output beam from any selected one of the recording regions through the output waveguide network to the outcoupling region via the incoupling region optically coupled thereto for reception at the detector array by controlling at least one controllable directing element of the output waveguide network or at least one optical property of the reference beam used to generate the output beam. With this arrangement, different ones of the multiple recording regions can be read using the same detector array, without moving the detector array or the holographic recording medium, by modifying the at least one optical property or controlling the at least one inductive element while the multiple in-coupling regions of the output waveguide network remain in fixed locations relative to the corresponding recording regions of the holographic recording medium. The holographic data recovery system is configured to generate an output beam by interacting a reference beam with a pattern stored in selected recording regions, the stored pattern encoding a plurality of image pixels, the plurality of image pixels being encoded in the output beam as a plurality of propagation modes propagating simultaneously in different directions through the output waveguide network.

[0011]

[0011] In the second and third aspects, spatial multiplexing across the holographic recording medium is achieved without requiring any mechanical movement of the emitter system / detector array, the holographic recording medium or the reference / output waveguide network. In the case where the guiding element is controllable, the guiding element can be controlled to steer the reference / output beam along different routes through the reference / output waveguide network to / from different regions of the medium, and in the case where the optical properties of the beam are changed, the reference / output waveguide network may be active or not (i.e., passive or active), but in any case, the reference / output waveguide network responds to the change in the optical properties of the reference / output beam, and such a change causes the reference / output beam to be steered along different routes in a similar manner.

[0012] Brief explanation of the figure

[0012] For a better understanding of the present disclosure and to show how embodiments of the disclosure may be put into effect, reference is made by way of example only to the following figures: [Brief description of the drawings]

[0013] [Figure 1A]

[0013] A schematic perspective view of a holographic recording medium is shown. [Figure 1B]

[0013] A schematic perspective view of a holographic recording medium is shown. [Figure 2A]

[0014] FIG. 1 shows a schematic perspective view of a holographic storage system including a set of waveguides that can be used to direct beams to / from different sub-volumes of a holographic recording medium to provide spatial multiplexing across the medium. [Figure 2B]

[0015] A top view of the system during writing is shown. [Figure 2C]

[0015] A side view of one side of the system during a write period is shown. [Figure 2D]

[0015] A side view of one side of the system during a write period is shown. [Figure 2E]

[0016] 1 shows a top view during a reading period. [Figure 2F]

[0016] A side view of one side during a reading period is shown. [Figure 2G]

[0016] A side view of one side during a reading period is shown. [Figure 3A]

[0017] 1 shows a schematic side view of an active light pipe in one configuration. [Figure 3B] 1 shows a schematic side view of an active light pipe in one configuration. [Figure 3C] 1 shows a schematic side view of an active light pipe in one configuration. [Figure 3D] 1 shows a schematic side view of an active light pipe in one configuration. [Figure 3E]

[0017] A plan (cross-sectional) view of an active light pipe is shown. [Figure 3F]

[0017] A plan (cross-sectional) view of an active light pipe is shown. [Figure 4A]

[0018] 1 shows a side view of one side of a portion of an optical waveguide network. [Figure 4B]

[0018] A side view of one side of an optical waveguide network (part thereof) is shown. [Diagram 5]

[0019] FIG. 1 shows a schematic diagram of an example of a multiplexed waveguide network used for multiplexing across multiple pieces of holographic storage media. [Figure 6A]

[0020] 1 illustrates an example of an emitter system for providing input and reference beams in a holographic storage system. [Figure 6B]

[0020] A variant of the emitter system with simplified optics is shown. [Figure 7]

[0021] An example data recovery system is presented that uses spatially coherent detection to measure the optical field of the output beam and uses signal processing to mitigate waveguide distortions in the measured optical field. [Figure 8]

[0022] FIG. 1 shows a functional block diagram illustrating the functions performed within a holographic storage system. [Figure 9]

[0023] An alternative holographic storage system is presented that uses at least one waveguide network to spatially multiplex in two dimensions across a slab of holographic recording medium. [Figure 10A]

[0024] It is shown how spatial multiplexing can be achieved using passive inductive elements, where spatial multiplexing is achieved by modulating the beam characteristics. [Figure 10B]

[0024] We show how spatial multiplexing can be achieved using passive inductive elements, where spatial multiplexing is achieved by modulating the beam characteristics. [Figure 11A]

[0025] 1 shows a light pipe with passive optical filters having different frequency responses. [Figure 11B]

[0025] A light pipe with passive optical filters having different frequency responses is shown. [Figure 12]

[0026] 1 shows an example of a waveguide network having three hierarchical levels. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

[0027] To achieve spatial multiplexing across one or more holographic storage media in a manner that reduces or eliminates the need for mechanical movement, "active" light pipes, "passive" light pipes, or a combination of active and passive light pipes can be used. Note that the terms "waveguide" and "light pipe" are used interchangeably herein.

[0015]

[0028] An "active light pipe" refers to a waveguide having one or more active switching or other guiding elements attached to the surface of the waveguide or within the bulk of the waveguide, and thus is configurable (i.e. has changeable optical properties) to cause "one to many" light transfer (i.e. light is directed from a first surface region to one of multiple possible second surface regions (where the first surface region becomes an in-coupling region and the second region becomes an out-coupling region)) or "many to one" light transfer (i.e. light is directed from any one of the second surface regions (now becoming an in-coupling region) to the same first surface region (now becoming an out-coupling region). The term "passive light pipe" refers to a light pipe with guiding elements having different light sensitivities (e.g. different wavelength and / or polarization sensitivities), where a similar effect can be achieved by instead changing the optical properties or beam (e.g. using a tunable laser to change its wavelength, polarization, etc. so that it is directed along different routes by guiding elements with different wavelength / polarization responses, etc.). The term "passive light induction" is merely a convenient label to coincide with the fact that in this case the inductive elements need not be active, but in this context active or passive inductive elements having different light sensitivities (e.g., different wavelength and / or polarization sensitivities, etc.) can be used (i.e. the inductive elements can be active and have different light sensitivities).

[0016]

[0029] A digital image (or data encoded as a digital image) can be propagated as a beam along an active or passive light pipe, whose inductive elements can be individually controlled to transmit or reflect an incident light beam.

[0017]

[0030] Many such light pipes (active, passive or a combination of both types) can be combined in various geometries to create a switching network that can be used to steer beams and images to one of many addressable locations in one or more spatial dimensions. The input to the light pipes can be generated using a spatial light modulator (SLM) and the output is read, for example, on a CCD (charge-coupled device). Phase interference and noise can be corrected using a combination of optical and computational techniques, including machine learning techniques, which would involve learning one or more signal processing parameters from training data. Some embodiments use coherent detection in combination with such techniques to provide more effective waveguide distortion mitigation.

[0018]

[0031] In contrast to the types of optical switches and fibers conventionally used in optical data communication, the described embodiments use light pipes that can transmit an entire image at once. This takes advantage of currently available high-resolution optical devices such as SLMs and digital cameras. These devices have millions of pixels, allowing the encoding and decoding of many megabytes of data. This allows high-bandwidth transmission even with modest switching rates of the SLM, camera and active light pipe elements (in the case of active light pipes) or beam optical properties (in the case of passive light pipes). In addition, applications such as holographic storage require interference between multiple beams, at least one of which is modulated with an image. In holographic storage, active light pipes can be used to efficiently steer beams and images to interfere at any desired location of the holographic storage medium. As described, similar advantages can be achieved with passive light pipes, where switching is applied instead at the emitter stage.

[0019]

[0032] The light pipes described below are "multimode" waveguides in the sense that they have sufficient physical dimensions to support a wide range of "modes" (i.e., spatial paths through the waveguide for a given channel, e.g., corresponding to different propagation directions). This is in contrast to simple single-mode optical waveguides, such as thin optical fibers used in fiber optic systems, whose purpose is to essentially confine the light entering the fiber to a single propagation mode. While single-mode optical waveguides can only carry data using amplitude, phase, or frequency modulation, multimode optical waveguides can carry much more data (e.g., potentially an entire image of millions of pixels) through angular variations within the waveguide. Stated differently, multimode waveguides provide greater bandwidth through increased angular and / or spatial diversity by providing multiple optical paths through the waveguide from emitter to detector for any given channel, with different paths corresponding to different propagation modes.

[0020]

[0033] Another aspect disclosed herein is a holographic data storage system that uses one or more waveguide networks to spatially multiplex (i.e., read from / write to different sub-volumes of the medium) across a holographic recording medium without requiring any relative mechanical motion between the medium and the waveguide network. Examples of such systems are described below, which utilize active and / or passive light pipes. In the described examples, a multimode waveguide can be used to simultaneously carry an entire digital image to / from the holographic recording medium or to carry a reference beam at one of multiple possible angles.

[0021] Active Light Pipes:

[0034] 3A-D show schematic side views of example configurations of active light pipes 300 having particular physical structures. As will be appreciated, this is merely one example of a suitable physical structure that can provide the desired optical configurability. Further examples are considered below.

[0022]

[0035] The active light pipe 300 is shown to have at least a first surface area 300-0 and a number of active switches in the form of switchable Bragg gratings (SBGs), which may be on the surface or volume embedded. In this example, two such SBGs 300-1, 300-2 are shown on the first surface 300-S1 of the waveguide 300, but it will be understood that more SBGs can be placed at suitable locations on the surface 300-S1 of the waveguide 300 and / or embedded within the bulk of the waveguide 300. Each SBG 300-1, 300-2 can be individually controlled to change its reflection / transmission properties to transmit or reflect an incident beam. The SBGs 300-1, 300-2 form respective surface areas of the active light pipe 300 where light can enter (in-coupling) or exit (out-coupling) the waveguide 300 depending on how the waveguide 300 is used.

[0023]

[0036] The first surface region 300-0 is the end region of the waveguide 300 from which a first side surface 300-S1 of the waveguide extends along the axis 301 of the waveguide 300.

[0024]

[0037] 3E and 3F each show a cross-sectional view of a waveguide 300, which in this example has a rectangular shaped cross-section, as can be seen with four sides 300-S1, 300-S2, 300-S3, 300-S4 extending along an axis 301 of the waveguide 300. In this example, as depicted in the figures, the SBGs 300-1, 300-2 are all located along the first side 300-S1, although in general such SBGs can be attached to multiple surfaces of the waveguide 300 depending on the application.

[0025]

[0038] The SBGs 300-1, 300-2 are positioned at increasing distances from the first region 300-0 along the first side 300-S1 of the waveguide, with the first SBG 300-1 being positioned closest to the first region 300-0.

[0026]

[0039] 3A, 3B, and 3E depict a "one to many" use case, where the first surface region 300-0 serves as an in-coupling region and the second surface regions 300-1, 300-2 of the SBG serve as out-coupling regions. As an example, FIG. 3 shows a first light ray 304 being coupled into the waveguide 300 via the in-coupling region 300-0. In this example, the first surface region 300-0 is angled with respect to the sides 300-S1, ..., 300-S4, such that the first light ray 304 passes through the first surface region 300-0 into the bulk of the waveguide 300 at an angle sufficient to achieve total internal reflection at each of the sides 300-S1, ..., 300-S4 within the waveguide 300.

[0027]

[0040] Each of the SBGs 300-1, 300-2 can be configured to change between a reflective state and a transmissive state. Figure 3A shows a configuration in which the first SBG 300-1 is in a reflective state, where an incident light ray 304 is reflected back into the waveguide 300 by the first SBG 300-1 and guided along the waveguide 300 until it reaches the second SBG 300-2. The SBG 300-2 is shown in a transmissive state, where the light ray 304 is diffracted out of the waveguide 300 via the second SBG 300-2, and thereby extracted from the waveguide 300 via the surface region of the second SBG 300-2. This configuration of the SBGs 300-1, 300-2 creates a "channel" through the waveguide 300 between the first surface region 300-0 and the surface region of the second SBG 300-2.

[0028]

[0041] In contrast, Figure 3B shows the first SBG 300-1 in a transmissive state. Thus, upon reaching the first SBG 300-1, the first light ray 304 is instead diffracted out of the waveguide 300 via the first SBG 300-1, and is thereby instead extracted from the waveguide 300 via the surface region of the first SBG 300-1. This configuration creates a channel through the waveguide 300 between the first surface region 300-0 and the surface region of the first SBG 300-1.

[0029]

[0042] In this manner, a first light ray 304 can be guided through the waveguide 300 from a first region 300-0 until it exits the waveguide 300 at a surface region of SBG 300-1 or 300-2. For simplicity, only two SBGs 300-1, 300-2 are described in relation to each other, but it will be appreciated that the same principles can be applied to many more SBGs.

[0030]

[0043] FIG. 3E shows, when viewed in cross section, how first light ray 304 may propagate through TIR from some or all of sides 300-S1, ..., 300-S4 depending on the angle of first light ray 304.

[0031]

[0044] It is equally feasible to use the depicted active light pipe 300 for many-to-one light transfer, as depicted in Figures 3C, 3D and 3F.

[0032]

[0045] Figure 3C shows the same SBG configuration as in Figure 3A. The only difference is the use of the waveguide 300, where a second light ray 308 is shown entering the second SBG 300-2 from an external source (not shown). With the second SBG in a transmitting state, the second light ray 308 is diffracted into the waveguide 300 via the second SBG (now providing in-coupling at its surface region) and from there is guided through the waveguide 300 to the first surface region 300-0 (now the out-coupling region). This includes a reflection from the first SBG 300-1, which is now in a reflecting state. The reflecting state of the first SBG 300-1 prevents the light ray 308 from exiting the waveguide via the first SBG 300-1. Moreover, external light rays 309 that by chance may enter the first SBG 300-1 are essentially reflected away from the first SBG 300-1 and therefore do not enter the waveguide 300.

[0033]

[0046] Figure 3D shows the same configuration as Figure 3B, but here a second light ray 308 is incident on the first SBG 300-1 from an external source. With the first SBG 300-1 in a transmissive state, the second light ray 308 enters the waveguide 300 at that location by diffraction and is guided to the first surface region 300-0.

[0034]

[0047] FIG. 3F illustrates in cross section how a second light ray 308 may propagate within the waveguide 300, with the same explanation as in FIG. 3E being applicable, but with the light ray direction reversed.

[0035]

[0048] The above description assumes perfect reflectivity / transmittance of the SBGs in the transmission / reflection state. As will be appreciated, this is not an absolute requirement in practice and more typically the system will have some tolerance to imperfections in the SBGs 300-1, 300-2 and the waveguide 300. Suitable signal processing techniques for compensating for distortions introduced in the waveguide 300 are described below.

[0036]

[0049] Although SBGs 300-1, 300-2 are depicted as separate elements, in reality separate, independently controllable regions of a single larger SBG may extend across all or most of first side 300-S1.

[0037]

[0050] SBG is just one possible form of active switching element. For example, with polarized light beams, the same effect can be achieved using a controllable polarizing filter attached to the surface of the waveguide 300 or embedded within the bulk of the waveguide. SBG and controllable polarizing filters are examples of non-mechanical active switches that can change the optical properties of the waveguide 300 through non-mechanical effects. Other examples of inductive elements include controllable mirrors such as micromirror devices or other microelectromechanical systems (MEMs), which are examples of mechanical inductive elements.

[0038]

[0051] When using polarizing filters as the steering elements, SBGs 300-1, 300-2 can be replaced with passive diffractive elements, with the polarizing filters operating to steer the beams towards or away from the passive diffractive elements in a controllable manner as needed, without the need to reconfigure the diffractive elements.

[0039]

[0052] Note that even though the inductive elements themselves are mechanical, they still avoid the need for mechanical movement of the waveguide 300 as a whole.

[0040] Active Light Pipe Network

[0053] As used herein, a "waveguide network" can take the form of a single waveguide or multiple interconnected waveguide networks. Waveguide networks comprising multiple active light pipes have particular advantages in terms of flexible optical data transmission.

[0041]

[0054] 4A and 4B show a side view of one side of a waveguide network (portion thereof) including first and second active light pipes 400, 420. The second light pipe 420 has a first surface area 420-0 positioned to be aligned adjacent to a corresponding surface area of ​​the first light pipe 400 to receive a beam from or direct a beam to the second waveguide 420 via the first surface area 400-0. Purely by way of example, a light ray 404 is shown propagating through the first waveguide 400 to a corresponding surface area of ​​the first waveguide 400, which is adjacent to the first surface area 420-0 of the second waveguide 420. The light beam 404 is extracted from the first waveguide 400 via SBG 400-1 attached to an adjacent surface region of the first waveguide 400 and is coupled into the second waveguide 420 via the first surface region 400-0. From there, the light beam 404 can be guided to any one of multiple SBGs 420-1, 420-2 of the second waveguide 420 in a one-to-many manner. The same arrangement can also be used to reverse the direction of the light beam and direct the beam in the other direction from the second waveguide 420 to the first waveguide 400 in a many-to-one manner.

[0042]

[0055] Although this example considers two interconnected waveguides 400, 420, the principles can be applied to many more interconnected waveguides to enable flexible data routing through a waveguide network.

[0043]

[0056] More generally, a surface region of the medium may be optically coupled to a corresponding surface region of the waveguide in another manner, such as via an air interface or one or more other optical components (which may themselves be waveguides, and which may or may not provide active or passive switching functionality).

[0044] Holographic Storage

[0057] Here we describe the application of active light pipes to holographic storage.

[0045]

[0058] 1A and 1B show schematic perspective views of a holographic recording medium 102, which is a volume of relatively thick photosensitive material capable of persistently storing a light pattern as a "hologram" embodied within the holographic recording medium 102 (which for simplicity may simply be referred to as medium 102). A hologram is generated by exposing a sub-volume 110 (region) of the medium 102 to a light pattern such that a persistent state change occurs within that sub-volume 110. The hologram generated in the sub-volume 110 by that state change records the light pattern into the medium 102 from which it may be reproduced at a later time. The hologram is persistent in that, once generated, the medium 102 does not require power to maintain it. The composition and structure of the medium 102 may be such that the hologram cannot be erased once generated (thus providing a form of "write once read many" (WORM) storage) or such that the hologram can be erased and replaced (but persists unless and until erased).

[0046]

[0059] A single hologram can record a light pattern that encodes a very large number (e.g., millions) of bits, allowing very large amounts of data to be written in parallel (simultaneously) to / read from the holographic recording medium 102. Another advantage of holographic storage is that many holograms can be written to the same sub-volume 110 of the holographic recording medium 102, thereby greatly increasing the data storage capacity per unit volume of the holographic recording medium 102.

[0047]

[0060] More specifically, FIG. 1A shows how an input beam 104 and a reference beam 106 are directed to a subvolume 110 via a first and second side 102-4, 102-6 of the medium 102, respectively, to write a set of data in the medium 102. This generates a light pattern in the form of an interference pattern caused by interference between the input beam 104 and the reference beam 106. If the beams 104, 106 have sufficient power and the subvolume 110 is exposed for a sufficient duration, the interference pattern generated by the interfering beams 104, 106 will be persistently recorded in the subvolume 110 as a hologram. As will be explained below, the set of data is embedded in the input beam 104 and can be recovered from the resulting hologram. In this way, an encoded set of data is written to the subvolume 110. In the following example, the set of data is encoded as a digital image and then embedded in the input beam 104 via spatial modulation.

[0048]

[0061] 1B, to read data from subvolume 110, a matched reference beam 116 is directed into subvolume 110 via a second side 102-6 of medium 102, where it interacts with the hologram to generate an output beam 108 that is essentially matched to the input beam 104 used to write the hologram to the extent that the embedded data is recoverable from the output beam 108. The output beam 108 propagates out of subvolume 110 via a third side 102-8 of medium 102.

[0049]

[0062] The reference beam 116 used to read the data is substantially aligned with the reference beam 106 originally used to write the data, and in particular is oriented at an angle (or, more generally, a direction) that closely matches the angle of the original reference beam 106. This is because the ability to read the hologram (i.e., generate an output beam 108 from which the data can be recovered) is sensitive to angular deviations between the reference beam 106 used to write the hologram and the reference beam 116 used to read the hologram. This sensitivity can be exploited to record multiple holograms in the same subvolume 110, each hologram generated using a different reference beam angle, such that two entirely different holograms can be generated with only slight differences in the reference beam angle. In this way, many (e.g., hundreds or thousands) of holograms can be written to the same subvolume 110, each encoding many (e.g., millions) of bits.

[0050]

[0063] 2A shows a schematic perspective view of an example of a holographic storage system 200 incorporating certain principles of the present disclosure. In this particular example, three separate waveguides 204, 206, 208 are used to carry the input beam 104, the reference beams 106, 116, and the output beam 108, and the three separate waveguides 204, 206, 208 can be referred to as the input waveguide 204, the reference waveguide 206, and the output waveguide 208, respectively. As described, the terms "optical waveguide" and "light pipe" are used interchangeably herein. Each of the waveguides 204, 206, 208 provides spatial multiplexing in the sense that it can direct signals to any one of a number of subvolumes in the holographic recording medium 102 (in the case of the input and reference waveguides 204, 206) or from any one of a number of subvolumes in the holographic recording medium 102 (in the case of the output waveguide 208). This provides spatial multiplexing over the volume of the holographic recording medium 102 without the need for any mechanical movement of the waveguides 204, 206, 208 relative to the holographic recording medium 102. To avoid the need for such mechanical movement, inductive elements are located on or within each waveguide 204, 206, 208, and can be configured to change the optical properties of the waveguides 204, 206, 208 in order to direct signals to or from different sub-volumes of the medium 102, i.e. to create different channels within the waveguides 204, 206, 208 as required. In this particular example, the inductive elements take the form of active optical switching elements (switches). There are various forms that the switches can take. In this example, the switches take the form of SBGs located at different surface regions of the waveguides 204, 206, 208 in the same general arrangement as in Figures 3A-F. That is, each waveguide 204, 206, 208 takes the form of an active light pipe, and each waveguide 204, 206, 208 has the same general physical structure as active light pipe 300 of Figures 3A-F.

[0051]

[0064] Each waveguide 204, 206, 208 is disposed such that its first surface (i.e., the surface on which its SBG is located) is adjacent to a different side of the medium 102, such that its SBG extends along that side of the medium 102. The first and second SBGs of each waveguide 204, 206, 208 are indicated by reference numbers 204-1, 204-2, 206-1, 206-2, 208-1, 208-2, respectively, and they are all configurable in the manner described above. Additional SBGs are depicted without reference numbers, and the number of SBGs can be selected to accommodate any size of holographic recording medium 102. The following description refers to the first and second SBGs of each waveguide 204, 206, 208 for simplicity, but it will be understood that the description applies to more SBGs.

[0052]

[0065] 2B-2D show how input and reference waveguides 204, 206 are used to write data to the medium 102 in a one-to-many fashion. FIG. 2B shows a schematic top view of the system 200, while FIGS. 2C and 2D show side views of one side showing the input and reference waveguides 204, 206, respectively. The input waveguide 204 is used to direct the input beam 104 to any one of a number of sub-volumes of the medium 102 via any one of the SBGs 204-1, 204-2 of the input waveguide 204 in the manner described above. The reference waveguide 206 is configured to simultaneously direct the reference beam 106 to the same sub-volume to generate the desired interference pattern to be written in that sub-volume. In the depicted example, both the input waveguide 204 and the reference waveguide 206 are configured to direct the input and reference beams 104, 106, respectively, to a subvolume indicated by reference numeral 110, here via the second SBGs 204-2, 206-2 of each waveguide 204, 206, respectively.

[0053]

[0066] Figures 2E-2G show how the reference and output waveguides 206, 208 can be used to read data from the medium 102. Figure 2E is a plan view, and Figures 2F and 2G show side views of one side where the reference and output waveguides 206, 208 are visible. The reference waveguide 206 is used in exactly the same way as depicted in Figures 2B-2D, but now the reference beam 116 is directed to the subvolume where the hologram is to be read (subvolume 110 in this case). The output waveguide 208 is used in a one-to-many fashion to direct the resulting output beam 108 from the subvolume 110 through the waveguide 208 for subsequent detection.

[0054]

[0067] Each sub-volume 110 may have, for example, a height and width of a few millimeters as measured along any side, which would typically be sufficient to store a few million pixels per data "page" (e.g., multiplexed angle). In this case, the volume of the sub-volumes is sufficient to store (millions of pixels)*(#number of multiplexed angles).

[0055]

[0068] The inductive elements of the input waveguide 204 and the reference waveguide 206 (SBG in this example) are configured to provide channels for the input beam 104 and the reference beam 106, 116 from the beam source (emitter system) to the sub-volume 110 being read, as required. The SBG is set in a transmissive or reflective state as required to create the channels. Similarly, the inductive elements of the output waveguide 208 (also SBG in this example) are similarly set to provide channels from the sub-volume 110 being read to the detector. To provide additional context, this will be described in more detail below with reference to the multiple waveguide network depicted in FIG. 5. However, the principles described in relation to the specific example of FIG. 5 apply more generally to other waveguide network topologies, both simpler networks (e.g., single waveguide) and more complex waveguide networks.

[0056]

[0069] As discussed above, this allows spatial multiplexing across the medium 102 without mechanical motion of the medium 102 relative to the waveguides 204, 206, 208. This is true whatever form the inductive elements take (which, as discussed above, can themselves be mechanical or non-mechanical).

[0057] Holographic storage using multiplexed waveguide networks.

[0070] FIG. 5 shows an example of a holographic storage system incorporating a multiplexed waveguide network of the type shown in FIG.

[0058]

[0071] The input waveguide network is shown to include a first input light pipe 203 (the "parent" waveguide) to which a number of second input light pipes 204A, 204B (the "child" waveguides) are coupled. An input beam 104 from an emitter system 504 is coupled into the first input waveguide 203 through its in-coupling region, from where it can be directed to a second input waveguide 204A or 204B.

[0059]

[0072] The reference waveguide network is shown to include a first reference waveguide 205 to which multiple second reference waveguides 206A, 206B are coupled. Reference beams 106, 116 from an emitter system 504 can similarly be coupled into the first reference waveguide 205 and directed to the second reference waveguides 206A or 206B.

[0060]

[0073] The output waveguide network is shown to include a first output waveguide 207 to which a plurality of second output waveguides 208A, 208B are coupled.

[0061]

[0074] The depicted arrangement allows beams to be directed to / from different sub-volumes of multiple pieces 102A, 102B of holographic storage medium.

[0062]

[0075] FIG. 5 shows input beam 104, reference beams 106, 116 and output beam 108, but it will be understood that the sub-volumes would typically be written and read at different times in the manner described above with reference to FIGS. 2A-G.

[0063]

[0076] A first group of second waveguides 204A, 206A, 208A (one each of input, reference and output) are positioned around a first piece 102A (first medium) of holographic storage media, and a second group of second waveguides 204B, 206B, 208B are positioned around a second piece 102B (second medium), each in the same general arrangement as in Figures 2A-G. Thus, the input and reference beams 104, 106, 116 can be directed to any sub-volume of any media piece 102A, 102B by first steering those beams into the desired second waveguides of the input and reference networks, respectively, and then steering them into the desired sub-volume of the media piece adjacent to the desired waveguide.

[0064]

[0077] The output waveguide network can be used to direct the output beam 108 from any sub-volume of any media piece 102A, 102B from the applicable second output waveguide 208A, 208B to the first output waveguide 207 and then from the first output waveguide 207 to the detector 508 via the outcoupling region of the first output waveguide 207. To read from a particular sub-volume, the SBGs are configured to provide a channel from that sub-volume to the detector, so in this case SBGs 204A-2 and 207-1 are set to a transmissive state and other SBGs of the output waveguide network are set to a reflective state as necessary to provide a channel for the output beam 108 to the detector 508 (e.g., in this case SBG 207-2 of the first output waveguide 207 is set to a reflective state to prevent the propagation of the output beam 108 to waveguide 208B). Other SBGs in the output waveguide network can be set to be reflective to the extent necessary to prevent unwanted light transmission (i.e., "leakage") from other areas of the same media piece 102A or from different media pieces 102B (e.g., in this example, SBG 204A-1, which is close to the sub-volume being read, is shown to be set to be reflective to prevent unwanted leakage).

[0065]

[0078] Although in the above example three separate waveguide networks are used for the input, reference and output beams 104, 106, 116, 108, this is not necessary. For example, the same waveguide network could be used to carry both the input beam 104 and the reference beam 106, 116, and / or the same waveguide network could be used to carry the input beam 104 and the output beam 108, and / or the same waveguide network could be used to carry the output beam 108 and the input beam 104. In general, having three separate networks is expected to provide optimal performance, although there are nevertheless perfectly viable implementations using only one or two waveguide networks.

[0066]

[0079] Although not depicted in any of the figures, a fourth waveguide network can be used to deliver beams to the remaining sides of the media pieces 102A, 102B. For example, a fourth network can be used to deliver an erase beam to a desired sub-volume that is at least suitable for erasing a hologram therefrom (in the case of erasable holographic storage).

[0067]

[0080] 9 illustrates an alternative physical structure, where a single "slab" of holographic medium 102 is used instead of the individual pieces 102A, 102B of FIG. 5. An input waveguide network is depicted, having essentially the same physical configuration, but here second input waveguides 204A, 204B are configured to direct input beams 104 to different sub-volumes of the same slab 102. Whereas in FIG. 5, each of the second input waveguides 204A, 204B provides multiplexing in one dimension along the length of a different single media piece 102A, 102B, in FIG. 9, the second waveguides 204A, 204B provide spatial multiplexing in two dimensions across the slab of holographic medium 102 (each waveguide individually provides one-dimensional multiplexing, but there is two-dimensional multiplexing across the slab 102 as a whole).

[0068]

[0081] The system of Figure 9 is limited to a maximum of two waveguide networks (one on each side of the slab 102). As noted above, this is still a viable arrangement since the same network can be used to carry multiple beams.

[0069]

[0082] FIG. 9 illustrates another advantage of the use of waveguides. Some existing holographic storage systems use beams propagating in free space, with optical components (reflectors, beam splitters, etc.) placed separately to guide the beam. Such systems are not easily scalable and are practically only suitable for laboratory-type settings. This is because each component is required to be placed and calibrated separately. In contrast, the use of waveguides makes the manufacture and subsequent deployment of a "self-contained" system much easier. The system of FIG. 9 is similar in some ways to "off-the-shelf" solid-state storage devices, which not only have no moving parts but can also be built and provided as a complete unit, thereby significantly reducing the time and effort required for its deployment (e.g., in a data center). The use of multimode waveguides allows for simultaneous reading / writing of the entire image and allows for angular multiplexing across multiple reference beam angles, thus greatly improving the scalability of holographic storage devices without compromising bandwidth or storage capacity. FIG. 9 is simply one arrangement illustrating these advantages, which apply more generally to other waveguide systems within the scope of this disclosure.

[0070] Data Encoding

[0083] 6A shows an example of an emitter system 504 that provides both the input beam 104 and the reference beam 106. The input beam is an expanded spatially modulated laser beam. A laser 600 emits a coherent narrow laser beam, which is split using a beam splitter 602.

[0071]

[0084] A portion of the beam from the beam splitter 602 is used as the reference beam 106. In this example, the reference beam 106 is steered to enter the reference waveguide 206 at a desired angle using a controllable reference beam steering element 612. By varying the angle of the reference beam 106 before it is introduced into the reference waveguide 206, different holograms can be written / read from the same sub-volume of the medium in the manner described above.

[0072]

[0085] As an alternative or in addition to beam angle multiplexing, multiple patterns can be stored in and read from the same sub-volume with different phases of the reference beams 106, 116 (phase multiplexing). Thus, a logical address may correspond to a particular reference beam angle and / or phase characteristic. All statements regarding modulation of the reference beam angle apply equally to phase modulation.

[0073]

[0086] The other portion of the beam from the beam splitter 602 is expanded using a beam expander 604, and the expanded beam passes through a spatial light modulator (SLM) 606. An encoder 610 receives the set of data to be encoded and encodes the set of data as a digital image, which is then modulated through the SLM 606 and embedded in the expanded beam. An in-coupling optic (in this case, a Fourier lens 608) positioned such that the plane of the SLM 606 is substantially in the focal plane of a Fourier lens 608 is used to separate the expanded beam into distinct propagation modes, in this example, where the modes correspond to unique propagation directions, where each mode corresponds to a particular point in the plane of the SLM 606. The different propagation modes are captured in the input waveguide 204 and guided therefrom in the manner described above. With the in-coupling optic 608, the data is "angle encoded" in the input beam in the sense that points in the digital image essentially correspond to unique propagation directions (i.e., unique propagation modes of the input beam 104). This is analogous to a light beam from a distant object taken to be at infinity. The angle-encoded input beam 104 of Figure 6A is an example of multiple propagation modes (i.e., components propagating in different directions) of a "multimode" optical signal, and this arrangement provides a form of angular diversity.

[0074]

[0087] It should be noted that the term "multimode" does not necessarily imply the use of such incoupling optics 608, nor does it necessarily require that all image points correspond uniquely to a given propagation direction. That is, multimode does not necessarily imply a one-to-one correspondence between propagation modes and image / data points. For example, FIG. 6B shows an alternative possible emitter system in which the spatially modulated beam is directly coupled into the input waveguide 204. In this case, there are still multiple modes (i.e., multiple spatial paths through the waveguide for any given channel), but there is no one-to-one correspondence between propagation directions and image points, and possibly no one-to-one correspondence between image / data points and modes. This provides a form of spatial diversity based on a form of MIMO (multiple-input multiple-output) transfer through multiple pixels of the SLM 606 and the detector array of the spatially coherent detector 508.

[0075] Data Decryption

[0088] 7 shows a spatially coherent detector 508 used to measure the optical field of the output beam 108. In contrast to conventional "direct detection", the spatially coherent detector 508 includes an array of pixels (or more generally detector elements), each of which is configured to measure both the amplitude and phase (not just the intensity) of the optical field at the location of that pixel. These can be measured, for example, using a local oscillator 712 of the spatially coherent detector 508. The array of pixels can thus measure the variations in phase and amplitude of the optical field in both time and space, and thus provide an analog or digital representation of the measured optical field. In this case, the optical field being measured is the optical field of the output beam 108 directed to the spatially coherent detector 508 via the output waveguide 208.

[0076]

[0089] Although only a single array is depicted, there may in fact be multiple physical arrays acting together as a single "logical array." For example, this logical array may be split across two physical cameras.

[0077]

[0090] A physical detector array can take the form of a single camera (each detector element is a pixel or set of pixels in the camera) or multiple cameras. In the extreme case, each detector element can be a separate camera, in which case the logical detector array can potentially be split across a large number of physical detectors.

[0078]

[0091] As described, the route from a particular in-coupling region where a beam enters a waveguide network to a particular out-coupling region where the beam exits the waveguide network (these regions may be in the same or different waveguides) may be referred to herein as a "channel." As described, in a multimode waveguide network, a single channel encompasses multiple spatial paths. The output beam 108 will be directed through a particular channel of the output waveguide network (i.e., from that particular in-coupling region to the out-coupling region of the output waveguide 208). Moreover, the output beam 108 will be generated from a hologram generated using an input beam directed from the in-coupling region of the input waveguide network to that particular out-coupling region. The hologram will be generated and read using a reference beam similarly directed through a particular channel through the reference waveguide network. The input beam 104, the reference beams 106, 116, and the output beam 108 are all subject to distortions within the associated waveguide network specific to the channel through which they are directed. To compensate for such distortions, the signal processing component 700 applies analog and / or digital signal processing to the representation of the measured field. It does so using a channel model associated with the subvolume currently being read (i.e., from which the output beam 108 was generated). The channel model associated with a particular subvolume models not only the channel through which the output beam 108 is directed to the detector 508, but also the channel through which the input beam 104 used to write the hologram is directed to that subvolume and the channel through which the reference beams 106, 116 used to write / read the hologram are directed to that subvolume.

[0079]

[0092] Each channel model can take the form of, for example, a transfer function (which models the channel directly) or an inverse transfer function (which models the channel with its approximate inverse). Note that the transfer function is applied to a representation of the measured light field (i.e., both its measured phase and amplitude at different spatial points), and not just the light intensity. Spatially coherent detection offers a greater scope for removing or reducing such channel distortions, with the goal of recovering the original digital image accurately enough to easily decode the encoded data from the recovered image by the decoder 704.

[0080]

[0093] The signal processing 700 can, for example, use a combination of optical and computational techniques (which may include, for example, machine learning techniques) to correct for phase interference and noise.

[0081]

[0094] Although described in the context of holographic storage, the use of such signal processing 700 in combination with spatially coherent detection is not limited in this respect and may be applied in other contexts such as optical communications or optical computing, or any other context in which a received output beam is susceptible to distortions introduced in one or more waveguide networks.

[0082]

[0095] Figure 7 shows outcoupling optics 715 arranged to essentially reverse the effect of incoupling optics 608 of Figure 6B (i.e., to essentially resolve each propagation mode to a single point in the plane of the spatially coherent detector 508). Again, this is not required and outcoupling optics 715 can be omitted by using the alternative emitter system of Figure 6B.

[0083]

[0096] Although not depicted in Figures 6A or 6B, some level of pre-processing can be applied to the digital image before it is modulated and embedded into the input beam 104. This can reduce the level of compensation required at the detector side. Even with such pre-processing, some degree of detector side processing can be applied to account for different distortion effects between different channels.

[0084] Dynamic Scheduling

[0097] 8 shows a controller in the form of a scheduler 800 capable of scheduling read and write operations in a holographic storage system of the type described above. To facilitate effective scheduling, sub-volumes within the medium 102, or within each media piece 102A, 102B, are assigned unique addresses. This provides a form of addressable holographic storage that is similar to more conventional forms of addressable electronic storage. However, there are a number of features that go beyond conventional addressing.

[0085]

[0098] First, as described above, a single subvolume can store multiple holograms at different reference beam angles. To accommodate this, each address uniquely corresponds to a specific subvolume in combination with a specific reference beam direction (i.e., each available tuple is assigned a unique address), indicates a specific subvolume in the medium 102 or in one of the media pieces 102A, 102B, and indicates a specific reference beam direction (e.g., an angle or set of angles that defines a beam direction; the term "angle" can be used as a shorthand for referring to the direction of the reference beam, but it will be understood that the direction can in fact be defined by multiple angles depending on the configuration of the system). Thus, a subvolume can be associated with potentially many addresses that correspond to different reference beam angles. The tuple defines a logical storage location, and the same subvolume at different reference beam angles provides multiple logical storage locations at the physical level. Each of the logical storage locations has a unique address (ADDR). This notation is used as a shorthand for meaning an address corresponding to a subvolume and a reference beam angle, but it will be understood that this does not imply a representation of a specific address. Any address space and addressing mechanism that uniquely identifies logical locations of this nature may be used.

[0086]

[0099] Second, in contrast to conventional storage devices, each logical memory location can store an entire image, and thus a single logical memory location can potentially store a very large number (e.g., thousands or millions) of bits.

[0087]

[0100] Scheduler 800 operates at the logical storage level and schedules incoming read and write operations on different addresses within appropriate time intervals.

[0088]

[0101] Reference numbers 804, 806, and 808 are used to denote input, reference, and output optical waveguide networks, respectively. As described above, each can be a single waveguide network or a multiple waveguide network (e.g., similar to FIG. 5), with one or more configurable inductive elements (e.g., SBG or other active switching elements) that can be used to create channels to different sub-volumes of a piece (or pieces) of holographic storage media.

[0089]

[0102] During the period when a write operation for a particular address is scheduled (the write period), the inductive elements in the input and reference waveguide networks 804, 806 are configured to create a channel for the input beam 104 and the reference beam 106 from the emitter system 504 through the input and reference networks 804, 806, respectively, to the corresponding sub-volume. In addition, the reference beam steering element 612 is configured to steer the reference beam 106 in a corresponding direction to the reference network 806. This creates a desired interference pattern at the reference beam angle in the sub-volume, which can then be persistently stored as a hologram if the sub-volume is exposed to the interference pattern for a sufficiently long duration.

[0090]

[0103] During the period when a read operation for a particular address is scheduled (the read period), the steering elements in the reference and output networks 806, 808 are similarly configured to create a channel for the reference beam 116 through the reference network 806 to the subvolume, and a channel for the output beam 108 from the subvolume through the output network 808 to the detector 508. The reference beam steering element 612 is similarly configured to steer the reference beam 116 to the reference network 806 in a corresponding direction to read the intended hologram at the reference beam angle in the subvolume.

[0091] Alternative Waveguide Networks:

[0104] 10A and 10B show an alternative system in which spatial multiplexing is achieved instead by modulating one or more optical properties of the input and reference beams 104, 106, 116. In such a system, passive (non-switchable) inductive elements may be used in place of the active (switchable) inductive elements of the previous figures.

[0092]

[0105] The example of Figure 10A considers frequency (or equivalently wavelength) modulation: in this case, the light pipes themselves are passive and have static wavelength-dependent outcoupling (such as continuous long-pass dichroic interference filters or variable center wavelength bandpass filters).

[0093]

[0106] FIG. 11A shows a light pipe 1100 having an outer surface 1100-S along which are multiple passive filters 1100-1, 1100-2. The configuration of the light pipe 1100 is the same as in FIGS. 3A-D, apart from the fact that the filters 1100-1, 1100-2 replace the SBGs 300-1, 300-2. The filters 1100-1, 1100-2 have different frequency responses (i.e., they act as frequency filters). More specifically, each filter 1100-1, 1100-2 essentially transmits a relatively narrow range of optical frequencies and is essentially reflective for frequencies outside that range. FIG. 11A shows an in-coupling beam 1104, whose frequency is within the range of the second filter 1100-2 but outside the range of the first filter 1100-1. Thus, beam 1104 is reflected by the first filter 1100-1 but is transmitted through the second filter 1100-2 (and thus exits the light pipe 1100 at that location). Figure 11B shows a different frequency beam 1104', where the frequency is within the range of the first filter 1100-1 and thus is transmitted through the first filter 1100-1.

[0094]

[0107] Such a light pipe 1100 can be used in place of the active light pipe described above, and the above description applies equally to the following system variations.

[0095]

[0108] 10A shows a scheduler 800 communicatively coupled to the laser 600 of the emitter system for varying the frequency (or even wavelength) of the input and reference beams 104, 106, 116. In this case, either beam can be directed to a desired holographic storage area by setting the frequency accordingly. Here, different beam frequencies correspond to different routes (defined by different frequency characteristics of the passive filters) through the waveguide network, and the frequency can be set to correspond to any desired route.

[0096]

[0109] In this case, wavelength is used as the switching dimension.Laser 600 is a high speed tunable laser that functions as the active element.

[0097]

[0110] In such a realization, the switching can be in only one spatial dimension (i.e., along a single pipe). However, with a laser having sufficient range and narrow linewidth, the first light pipe can filter coarsely (i.e., over a relatively wide wavelength range) and subsequent light pipes sample more finely (i.e., over a narrower wavelength range). Another factor limiting the linewidth is the requirement for a relatively long coherence length, so that in any event the linewidth can be sufficiently narrow. In the context of holographic storage, this implementation can be combined with a second implementation using, for example, a different switchable parameter (e.g., polarization) to achieve replication of the input field to addressable locations across a two-dimensional output space.

[0098]

[0111] In connection with the read operation, the frequency of the output beam 108 is matched to the frequency of the reference beam 116 used to read a particular sub-volume, and the same principles can be applied to return it to the detector using appropriate filters in the output waveguide network 808.

[0099]

[0112] FIG. 10B shows an example of such an implementation with a controllable polarizing element 601 that can be used to vary the polarization of the input and reference beams 104, 106, 116. This can be combined with a passive polarizing filter on or in the light pipe. This can be implemented as an alternative or in addition to the passive frequency filter of the example of FIG. 10A. Such polarization modulation provides two independent routes and can be useful in combination with, for example, passive wavelength filtering and / or active light pipes. Polarization modulation of the beam can also be combined with active polarizing filters.

[0100]

[0113] It should be noted that the various "passive" and "active" implementations described above can all be implemented separately or in combination (e.g., a combination of active and passive inductive elements can be used), i.e., it is possible for a waveguide to have both passive and active elements and / or to combine active and passive waveguides in the same network.

[0101] Additional hierarchical levels:

[0114] The above examples consider a waveguide network having two hierarchical "levels", a parent waveguide and a child waveguide. However, a multiplexed waveguide network may have three (parent, child, grandchild) or more levels. Note that the terms "child", "parent" and "grandchild" do not necessarily imply a direct hierarchical relationship. That is, the term child or grandchild may refer to any waveguide at any hierarchical level below the parent or child waveguide, respectively. That is, a child / grandchild waveguide may be optically coupled to a parent / child waveguide, for example, not only via an air interface (direct descendants) but also via one or more other child / grandchild waveguides thereof (indirect descendants).

[0102]

[0115] 12 shows an example of a waveguide network with three hierarchical levels: a parent waveguide 1200 has two direct child waveguide networks 1202A, 1202B optically coupled to the parent waveguide 1200 in the manner described above, and each of those child waveguides 1202A / 1202B has two grandchild networks 1204A-A, 1204A-B / 1204B-A, 1204B-B optically coupled to the child waveguides 1202A / 1202B in the same manner.

[0103]

[0116] An extreme example is a "binary tree" architecture where every waveguide has exactly two direct children, potentially with more than three levels of waveguides, although in practice there may be situations where it is preferable to increase the number of direct children in order to reduce the number of hierarchical levels required.

[0104]

[0117] The scheduler 800 shown in Figures 8, 10A and 10B is a functional component of the system. Similarly, the encoder 610, the decoder 704 and the signal processing component 700 are also functional components. Such components can be implemented in software (i.e., as program code running on one or more programmable hardware processors such as a CPU, accelerator, e.g., GPU) or using other forms of processor hardware such as field programmable gate arrays and / or application specific integrated circuits. The signal processing performed by the signal processing component 700 can be analog or digital signal processing or any combination thereof. Such program code and other data (e.g., the channel model 702) can be encoded in a computer readable storage device. Examples of computer readable storage devices include optical, magnetic and / or solid state storage devices, capable of storing code, data and the like in a non-transitory form. This is in contrast to a transitory medium such as a transitory signal carrier wave.

[0105]

[0118] A first aspect of the present specification is a holographic data storage system comprising: an emitter system; an input waveguide network formed from one or more multimode optical waveguides, the input waveguide network having an in-coupling region for receiving an input beam from the emitter system and a plurality of out-coupling regions; and at least one holographic recording medium having a plurality of recording regions each optically coupled to a corresponding one of the plurality of out-coupling regions of the input waveguide network, the holographic data storage system being arranged to persistently write data of the input beam received at any one of the out-coupling regions to the corresponding recording region; and and a controller coupled to at least one of the at least one controllable directing element and configured to control at least one optical property of the input beam or the at least one directing element to direct the input beam from the in-coupling region to any selected one of a plurality of out-coupling regions, wherein by modifying the at least one optical property to direct the input beam to a different one of the plurality of out-coupling regions or controlling the at least one directing element, different ones of a plurality of recording regions may be written from the same in-coupling region while a plurality of out-coupling regions of the multi-mode optical waveguide network remain in fixed locations relative to corresponding recording regions of the holographic recording medium.

[0106]

[0119] In an embodiment, the emitter system may be configured to provide a reference beam, the holographic data storage system may be configurable to direct the reference beam to any one of the recording regions, and the controller may be configured to direct the reference beam and the input beam to the same recording region during a writing period to store data of the input beam as a pattern caused by interference between the input beam and the reference beam.

[0107]

[0120] For example, the holographic data storage system may include a reference waveguide network formed from one or more further multi-mode optical waveguides, the reference waveguide network having an in-coupling region for receiving a reference beam from an emitter system and a plurality of out-coupling regions, each of the plurality of recording regions of the holographic recording medium also optically coupled to a corresponding one of the plurality of out-coupling regions of the reference waveguide network, the controller may be configured to control at least one optical property of the reference beam or at least one controllable directing element of the reference waveguide network to direct the reference beam from the in-coupling region of the reference waveguide network to any selected one of the plurality of out-coupling regions of the reference waveguide network, and the controller is configured to direct the reference beam to an out-coupling region optically coupled to the same recording region during the writing period.

[0108]

[0121] Alternatively, the input waveguide network may be arranged to receive both the input beam and the reference beam, and the controller may be configured to control at least one optical property of the input beam and at least one optical property or steering element of the reference beam to direct both beams to the same recording region during the writing period.

[0109]

[0122] A controller may be coupled to the emitter system to control the phase characteristics of the reference beam and / or the angle at which the reference beam is coupled into the input waveguide network or the reference waveguide network such that multiple patterns generated with different phase characteristics and / or different angles of the reference beam are stored in a single one of the recording regions.

[0110]

[0123] The holographic data storage system may include at least one detector array, and the controller may be configured to, during a readout period, direct a reference beam from the emitter system to one of the recording regions to be read out, thereby causing an output beam generated by the reference beam interacting with the pattern stored therein to be received by the detector array for recovering data of the stored pattern from the output beam.

[0111]

[0124] An input waveguide network or a reference waveguide network may be arranged to receive the output beam, and the controller may be configured to control optical properties of the reference beam or at least one directing element of the input waveguide network or the reference waveguide network to direct the output beam to a detector array, such that the same detector array may be used for reading from different ones of the recording regions.

[0112]

[0125] Alternatively, the holographic data storage system may include an output waveguide network formed from one or more further multi-mode waveguides, the output waveguide network having a plurality of in-coupling regions, each of the plurality of recording regions of the holographic recording medium also optically coupled to a corresponding one of the plurality of in-coupling regions of the output waveguide network for receiving the output beam therefrom, and an out-coupling region for providing the output beam to a detector array. The controller may be coupled to at least one of the emitter system for controlling at least one optical property of the reference beam and thus at least one corresponding optical property of the output beam, and at least one controllable directing element of the output waveguide network, the controller may be configured to control at least one optical property of the reference beam or at least one directing element of the output waveguide network during said readout period to direct the output beam to the detector array, such that different ones of the recording regions may be read out using the same detector array while the in-coupling region of the output waveguide network remains at a fixed location relative to the recording regions of the holographic recording medium.

[0113]

[0126] The multimode waveguide of the input waveguide network may have a side extending along an axis of the waveguide, the side aligned with a first side of the holographic recording medium, and an outcoupling region of the input waveguide network at a different location on the side of the waveguide.

[0114]

[0127] A plurality of second multimode optical waveguides of the input waveguide network may be optically coupled to a first multimode optical waveguide of the input waveguide network at different locations along a side of the first waveguide, said multimode optical waveguide of the input waveguide network being one of the second waveguides, each of the other second waveguides may also have a plurality of out-coupling regions optically coupled to respective further recording regions of the holographic recording medium or respective recording regions of the at least one further holographic recording medium, and the controller may be configured to control at least one optical property of the input beam or at least one directing element of the input waveguide network to direct the input beam from the in-coupling region, via the first waveguide, to any one of the second waveguides and any one of the out-coupling regions of that second waveguide.

[0115]

[0128] The multimode optical waveguide of the reference waveguide network may have a side extending along an axis of the waveguide, the side being aligned with a second side of the holographic recording medium, and the outcoupling region of the reference waveguide network being at a different location on the side of the waveguide.

[0116]

[0129] A plurality of second multimode optical waveguides of the reference waveguide network may be optically coupled to a first multimode optical waveguide of the reference waveguide network at different locations along a side of the first waveguide, said multimode optical waveguide of the reference waveguide network being one of the second waveguides of the reference waveguide network, and each of the other second waveguides of the reference waveguide network may also have a plurality of outcoupling regions optically coupled to respective further recording regions of the holographic recording medium or respective recording regions of the at least one further holographic recording medium.

[0117]

[0130] The controller may also be configured to control at least one optical property of the reference beam or at least one directing element of the reference waveguide network to direct the reference beam from the in-coupling region, through a first waveguide of the reference waveguide network, to any one of the second waveguides of the reference waveguide network and to any one of the out-coupling regions of that second waveguide.

[0118]

[0131] A second aspect of the present specification is a holographic data storage or retrieval system, comprising: an emitter system; at least one detector array; at least one holographic recording medium; a reference waveguide network formed from one or more multimode optical waveguides, the reference waveguide network having an in-coupling region for receiving a reference beam from the emitter system and a plurality of out-coupling regions each optically coupled to a corresponding recording region of the at least one holographic recording medium; and a controller coupled to at least one of the emitter system and at least one controllable inductive element of the reference network, for controlling at least one optical property of the reference beam or the at least one inductive element to obtain a readout. and a controller configured to direct a reference beam to any selected one of the recording regions to be taken, thereby generating an output beam for receiving at a detector array to recover data of the stored pattern from the output beam through interaction of the reference beam with a pattern stored therein, wherein by modifying said at least one optical property of the reference beam or controlling said at least one directing element of the reference network, different ones of the multiple recording regions may be read using the same emitter system while a plurality of outcoupling regions of the multi-mode optical waveguide network remain in fixed locations relative to corresponding recording regions of the holographic recording medium.

[0119]

[0132] In an embodiment, the holographic data recovery system may include an output waveguide network in the form of one or more further multimode optical waveguides, the output waveguide network having an outcoupling region and a plurality of incoupling regions optically coupled respectively to the recording regions of the at least one holographic recording medium, the controller may be coupled to at least one of the emitter system and the at least one controllable guiding element of the output waveguide network and configured to control the at least one guiding element of the output waveguide network as well as at least one optical property of the reference beam and thus the corresponding optical property of the output beam to steer the output beam from a selected recording region, via the incoupling region optically coupled thereto, to the outcoupling region of the output waveguide network for reception at the detector array, such that different ones of the recording regions may be read using the same detector array while the incoupling region of the output waveguide network remains in a fixed location relative to the recording regions of the holographic recording medium.

[0120]

[0133] The multimode waveguide of the output waveguide network may have a side extending along an axis of the waveguide that is aligned with a side (e.g., a third side) of the holographic recording medium, and an incoupling region of the output waveguide network is at a different location on that side of the waveguide.

[0121]

[0134] A plurality of second multimode optical waveguides of the output waveguide network may be optically coupled to a first multimode optical waveguide of the output waveguide network at different locations along a side of the first waveguide, said multimode optical waveguide of the output waveguide network being one of the second waveguides, each of the other second waveguides may also have a plurality of in-coupling regions optically coupled to respective further recording regions of the holographic recording medium or respective recording regions of the at least one further holographic recording medium, and the controller may be configured to control at least one optical property of the reference beam or at least one directing element of the output waveguide network to direct the output beam from the in-coupling region optically coupled to the recording region being read, through that second waveguide, to the first waveguide and to an out-coupling region of the output waveguide network for reception at the detector array.

[0122]

[0135] A third aspect of the present specification provides a holographic data recovery system including at least one detector array, at least one holographic recording medium, an output waveguide network formed from one or more multimode optical waveguides, the output waveguide network having an outcoupling region for providing an output beam to the detector array and a plurality of incoupling regions each optically coupled to a corresponding recording region of the at least one holographic recording medium, and a controller configured to direct the output beam from any selected one of the recording regions through the output waveguide network to the outcoupling region optically coupled thereto for receipt at the detector array by controlling at least one controllable directing element of the output waveguide network or at least one optical property of a reference beam used to generate the output beam, wherein by changing the at least one optical property or controlling the at least one directing element, different ones of a plurality of recording regions may be read using the same detector array while the multiple incoupling regions of the output waveguide network remain in fixed locations relative to the corresponding recording regions of the holographic recording medium.

[0123]

[0136] In an embodiment, a multimode waveguide of an output waveguide network may have a side extending along an axis of the waveguide that is aligned with a side (e.g., a third side) of the holographic recording medium, and an incoupling region of the output waveguide network is at a different location on that side of the waveguide.

[0124]

[0137] A plurality of second multimode optical waveguides of the output waveguide network may be optically coupled to a first multimode optical waveguide of the output waveguide network at different locations along a side of the first waveguide, said multimode optical waveguide of the output waveguide network being one of the second waveguides, each of the other second waveguides may also have a plurality of in-coupling regions optically coupled to a respective further recording region of the holographic recording medium or a respective recording region of the at least one further holographic recording medium, and the controller is configured to control at least one optical property of the reference beam or at least one directing element of the output waveguide network to direct the output beam from the in-coupling region optically coupled to the recording region being read, through that second waveguide, to the first waveguide and to an out-coupling region of the output waveguide network for reception at the detector array.

[0125]

[0138] In certain embodiments described above, a waveguide network as described below may be used.

[0126]

[0139] The multimode optical waveguide network may include a parent waveguide and a plurality of child waveguides, each of the parent and child waveguides being a multimode optical waveguide having a first surface region, a plurality of second surface regions, and at least one guiding element attached to a surface of the waveguide or embedded within the waveguide, each of the second surface regions of the parent waveguide being optically coupled to a first surface region of a corresponding one of the child waveguides, the at least one guiding element of the parent waveguide being arranged to guide a beam from or to its first surface region to or from a selected second surface region of the plurality of second surface regions, the beam propagating through the second surface region of the parent waveguide. and a first surface region of the corresponding child waveguide is coupled to or received from the corresponding child waveguide, the first surface region being coupled to the second surface region of the parent waveguide, and the at least one guiding element of each child waveguide is arranged to guiding a beam from or to its first surface region to or from a selected second surface region of the plurality of second surface regions, the at least one guiding element of each waveguide being configurable to select the second surface region of that waveguide and / or in response to the at least one beam characteristic to select the second surface region of that waveguide via modulation of the at least one beam characteristic.

[0127]

[0140] The multimode optical waveguide network may include a plurality of grandchild waveguides, each of which is a multimode optical waveguide having a first surface region, a plurality of second surface regions, and at least one inductive element attached to a surface of the grandchild waveguide or embedded within the grandchild waveguide, each of the second surface regions of each grandchild waveguide being optically coupled to a first surface region of a corresponding one of the grandchild waveguides, and the at least one inductive element of each grandchild waveguide being coupled to or from its first surface region by a selected second surface region of the plurality of second surface regions. The at least one guiding element of each grandchild waveguide may be configured to select the second surface region of that grandchild waveguide and / or may be responsive to at least one beam characteristic to select the second surface region of that grandchild waveguide via modulation of the at least one beam characteristic.

[0128]

[0141] Each of the waveguides may have at least one active inductive element that is configurable to select a second surface region of that waveguide.

[0129]

[0142] Each of the waveguides can have at least one inductive element responsive to the at least one beam characteristic to select a second surface region of that waveguide via modulation of the at least one beam characteristic.

[0130]

[0143] At least one of the waveguides may have at least one active inductive element configurable to select the second surface region of that waveguide, and at least another of the waveguides may have at least one inductive element responsive to at least one beam characteristic to select the second surface region of the other waveguide via modulation of the at least one beam characteristic.

[0131]

[0144] One of the parent waveguides and one of the child waveguides may have at least one wavelength-responsive inducing element, whereby a beam in a first wavelength range is guided from or to its first surface region to a first of the child or grandchild waveguides and a beam in a second wavelength range is guided from or to its first surface region to a second of the child or grandchild waveguides and the first child or grandchild waveguide may have at least one wavelength-responsive inducing element, whereby a beam in a first sub-range of the first wavelength range is guided from or to its first surface region to one of its second surface regions. The second waveguide may have at least one wavelength-responsive directing element whereby a beam within a first sub-range of the second wavelength range is directed from or to the first surface region to one of the second surface regions and a beam within a second sub-range of the second wavelength range is directed from or to the first surface region to one of the second surface regions and a beam within a second sub-range of the second wavelength range is directed from or to the first surface region to one of the second surface regions and a beam within a second sub-range of the second wavelength range is directed from or to the first surface region to one of the second surface regions.

[0132]

[0145] The or each active inductive element may have at least one of a configurable transmittance and reflectance and a configurable refractive index.

[0133]

[0146] The or each active inductive element may be a switchable grid or grid region.

[0134]

[0147] At least one of the inductive elements may be a wavelength and / or polarization filter having a fixed or configurable wavelength response and / or a fixed or configurable polarization axis.

[0135]

[0148] At least one of the waveguides may have two or more inductive elements and three or more second surface regions, any of which may be selected by configuring one or both of the two or more inductive elements and / or modulating at least one beam characteristic.

[0136]

[0149] An optical system incorporating such a waveguide network may include a first optical system component, a plurality of second optical system components, at least one multimode optical waveguide network according to any of the aspects or embodiments described above, the multimode optical waveguide network being arranged to steer a beam from or to the first optical system component to or from a selected second optical system component of the plurality of second optical system components, and a controller configured to select one second optical system component of the plurality of second optical system components and to steer a beam from or to the first optical system component to or from the selected second optical system component by configuring at least one of the steer elements of the multimode optical waveguide network and / or modulating at least one beam characteristic of the multimode optical waveguide network.

[0137]

[0150] The first system component may include an emitter system for emitting and directing the beam to a selected second system component or a detector array from which the beam is directed from the selected second system component.

[0138]

[0151] The optical system may include one or more holographic recording media, and at least some of the second system optical components may be respective sub-volumes of the one or more holographic recording media.

[0139]

[0152] The optical system may include a second multimode optical waveguide network according to any of the aspects or embodiments described above, and the controller may be configured to direct a second beam from or to the first optical system component to or from the same selected second optical system component by configuring at least one of the directing elements of the second multimode optical waveguide network and / or modulating at least one beam characteristic.

[0140]

[0153] The optical system may include a third multimode optical waveguide network according to any of the aspects or embodiments described above, and the controller may be configured to direct a third beam from or to the first optical system component to or from the same selected second optical system component by configuring at least one of the directing elements of the third multimode optical waveguide network and / or modulating at least one beam characteristic.

[0141]

[0154] It will be understood that the above-described embodiments are described by way of example only. Other variations or uses of the disclosed techniques will be apparent to those skilled in the art given the disclosure herein. The scope of the present disclosure is not limited by the described embodiments, but only by the appended claims.

Claims

1. 1. A holographic data storage system comprising: an emitter system configured to emit an input beam in the form of a multimode optical signal that encodes a plurality of image pixels as a plurality of propagation modes of the input beam propagating in different directions; an input waveguide network formed from one or more multimode optical waveguides for simultaneously carrying a plurality of propagation modes, the input waveguide network having an in-coupling region for receiving an input beam from the emitter system and a plurality of out-coupling regions; a reference waveguide network formed from one or more further multimode optical waveguides, the reference waveguide network having an in-coupling region for receiving a reference beam from the emitter system and a number of out-coupling regions; at least one holographic recording medium having a plurality of recording areas respectively optically coupled to corresponding ones of the plurality of outcoupling areas of the input waveguide network, the holographic data storage system being arranged to persistently and simultaneously write a plurality of image pixels encoded in an input beam received at any one of the outcoupling areas to a recording area corresponding to any one of the outcoupling areas; a controller coupled to at least one of the emitter system and at least one controllable directing element of the input waveguide network, configured to control at least one optical property of the input beam or the at least one directing element to direct the input beam from the in-coupling region to any selected one of the plurality of out-coupling regions, wherein different ones of the plurality of recording regions may be written from the same in-coupling region by changing the at least one optical property or controlling the at least one directing element to direct the input beam to different ones of the plurality of out-coupling regions while the plurality of out-coupling regions of the input waveguide network remain in a fixed location relative to the corresponding recording region of the holographic recording medium; Including, the emitter system is configured to provide a reference beam, the holographic data storage system is configurable to direct the reference beam to any one of the recording regions, and the controller is configured to direct the reference beam and the input beam to the same recording region during a writing period to store data of the input beam as a pattern caused by interference between the input beam and the reference beam; Each of the plurality of recording regions of the holographic recording medium is also optically coupled to a corresponding one of the plurality of outcoupling regions of the reference waveguide network, and the controller is configured to control at least one optical property of the reference beam or at least one controllable steering element of the reference waveguide network to steer the reference beam from the incoupling region of the reference waveguide network to any selected one of the plurality of outcoupling regions of the reference waveguide network, and the controller is configured to steer the reference beam to the outcoupling region optically coupled to the same recording region during the writing period; The reference waveguide network may be a common waveguide network with the input waveguide network or may be a different waveguide network.

2. the input waveguide network is arranged to receive both the input beam and the reference beam, and the controller controls the input waveguide network to direct both the input beam and the reference beam to the same recording region during the writing period; the at least one optical property of the input beam and at least one optical property of the reference beam; or The inductive element The holographic data storage system of claim 1 , configured to control:

3. 2. The holographic data storage system of claim 1, wherein the controller is coupled to the emitter system to control the phase characteristics of the reference beam and / or the angle at which the reference beam is coupled to the input waveguide network or the reference waveguide network such that multiple patterns generated with different phase characteristics and / or different angles of the reference beam are stored in a single one of the recording regions.

4. 2. The holographic data storage system of claim 1, further comprising at least one detector array, wherein the controller is configured to, during a readout period, direct the reference beam from the emitter system to one of the recording areas to be read out, thereby causing an output beam generated by the interaction of the reference beam with a pattern stored therein to be received by the detector array in order to recover data of the stored pattern from the output beam.

5. 5. The holographic data storage system of claim 4, wherein the input waveguide network is positioned to receive the output beam, and the controller is configured to control the optical properties of the reference beam or the at least one directing element of the input waveguide network to direct the output beam to the detector array, whereby the same detector array can be used to read from different ones of the recording regions.

6. an output waveguide network formed from one or more further multi-mode optical waveguides, the output waveguide network having a plurality of in-coupling regions, each of the plurality of recording regions of the holographic recording medium also optically coupled to a corresponding one of the plurality of in-coupling regions of the output waveguide network for receiving an output beam therefrom, and an out-coupling region for providing the output beam to the detector array, the controller further comprising: the emitter system for controlling the at least one optical property of the reference beam and therefore at least one corresponding optical property of the output beam; and At least one controllable inductive element of the output waveguide network.

5. The holographic data storage system of claim 4, wherein the controller is configured to control, during the readout period, the at least one optical property of the reference beam or the at least one directing element of the output waveguide network to direct the output beam to the detector array, and wherein different ones of the recording regions can be read out using the same detector array while the in-coupling region of the output waveguide network remains at a fixed location relative to the recording regions of the holographic recording medium.

7. 2. The holographic data storage system of claim 1, wherein the multimode optical waveguide of the input waveguide network has a side extending along an axis of the multimode optical waveguide, the side being aligned with a first side of the holographic recording medium, and the outcoupling region of the input waveguide network is at a different location on the side of the multimode optical waveguide.

8. a plurality of second multimode optical waveguides of the input waveguide network are optically coupled to a first multimode optical waveguide of the input waveguide network at different locations along a side of the first multimode optical waveguide, the multimode optical waveguide of the input waveguide network being one of the second multimode optical waveguides, and each of the other second multimode optical waveguides is also a respective further recording area of ​​said holographic recording medium, or A respective recording area of ​​the at least one further holographic recording medium.

8. The holographic data storage system of claim 7, further comprising a plurality of outcoupling regions optically coupled to at least one of the first and second multimode optical waveguides, and wherein the controller is configured to control the at least one optical property of the input beam or the at least one directing element of the input waveguide network to direct the input beam from the incoupling region, through the first multimode optical waveguide, to any one of the second multimode optical waveguides and to any one of the outcoupling regions of the second multimode optical waveguide.

9. 9. The holographic data storage system of claim 8, wherein the multimode optical waveguide of the reference waveguide network has a side extending along an axis of the multimode optical waveguide, the side being aligned with a second side of the holographic recording medium, and the outcoupling region of the reference waveguide network is at a different location on the side of the multimode optical waveguide.

10. a plurality of second multimode optical waveguides of the reference waveguide network are optically coupled to a first multimode optical waveguide of the reference waveguide network at different locations along a side of the first multimode optical waveguide, the multimode optical waveguide of the reference waveguide network being one of the second multimode optical waveguides of the reference waveguide network, and each of the other second waveguides of the reference waveguide network also being the respective further recording area of ​​the holographic recording medium, or 10. The holographic data storage system of claim 9, further comprising a plurality of outcoupling regions optically coupled to the respective recording regions of at least one further holographic recording medium, and wherein the controller is configured to control the at least one optical property of the reference beam or the at least one directing element of the reference waveguide network to direct the reference beam from the incoupling region, via the first multimode optical waveguide of the reference waveguide network, to any one of the second waveguides of the reference waveguide network and to any one of the outcoupling regions of the second multimode optical waveguide.

11. 1. A holographic data recovery system comprising: Emitter system, at least one detector array for detecting an image; At least one holographic recording medium; a reference waveguide network formed from one or more multimode optical waveguides, the reference waveguide network having an in-coupling region for receiving a reference beam from the emitter system and a plurality of out-coupling regions each optically coupled to a corresponding recording region of the at least one holographic recording medium; an output waveguide network in the form of one or more further multimode optical waveguides, said output waveguide network having an outcoupling region and a plurality of incoupling regions each optically coupled to the recording region of said at least one holographic recording medium; a controller coupled to at least one of the emitter system and at least one controllable guiding element of the reference waveguide network, configured to control at least one optical property of the reference beam or the at least one guiding element to steer the reference beam to any selected one of the recording areas to be read, thereby generating an output beam for reception at the detector array to recover data of the stored pattern from the output beam via the reference beam interacting with a pattern stored therein; different ones of a plurality of the recording areas may be read using the same emitter system by changing the at least one optical property of the reference beam or controlling the at least one guiding element of the reference waveguide network while the multiple out-coupling regions of the reference waveguide network remain in fixed locations relative to the corresponding recording areas of the holographic recording medium; the controller configured to vary an angle of the reference beam to read different patterns stored in the same selected recording area; the multi-mode optical waveguide of the reference waveguide network is for carrying the reference beam at any one of a plurality of possible angles. Including, the controller is coupled to at least one of the emitter system and at least one controllable inductive element of the output waveguide network; and the at least one inductive element of the output waveguide network; and the at least one optical characteristic of the reference beam, and therefore the corresponding optical characteristic of the output beam; to direct the output beam from the selected recording region through the in-coupling region optically coupled thereto to the out-coupling region of the output waveguide network for receipt at the detector array, such that different ones of the recording regions may be read using the same detector array while the in-coupling region of the output waveguide network remains in a fixed location relative to the recording regions of the holographic recording medium; The holographic data recovery system, wherein the output waveguide network may be a common waveguide network with the reference waveguide network or may be a different waveguide network.

12. 1. A holographic data recovery system comprising: An emitter system; at least one detector array; At least one holographic recording medium; a reference waveguide network formed from one or more multimode optical waveguides, the reference waveguide network having an in-coupling region for receiving a reference beam from the emitter system and a plurality of out-coupling regions each optically coupled to a corresponding recording region of the at least one holographic recording medium; an output waveguide network formed from one or more multimode optical waveguides, the output waveguide network having an outcoupling region for providing an output beam to the detector array and a plurality of incoupling regions each optically coupled to a corresponding recording region of the at least one holographic recording medium; a controller coupled to at least one of the emitter system and at least one controllable guiding element of the reference waveguide network, configured to control at least one optical property of the reference beam or the at least one guiding element to steer the reference beam to any selected one of the recording areas to be read, thereby generating an output beam for reception at the detector array to recover data of the stored pattern from the output beam through the reference beam interacting with a pattern stored therein; different ones of a plurality of the recording areas may be read using the same emitter system by changing the at least one optical property of the reference beam or controlling the at least one guiding element of the reference waveguide network while the multiple out-coupling areas of the reference waveguide network remain in fixed locations relative to the corresponding recording areas of the holographic recording medium; the controller configured to vary an angle of the reference beam to read different patterns stored in the same selected recording area; the multi-mode optical waveguide of the reference waveguide network is for conveying the reference beam at any one of a plurality of possible angles; the controller is configured to direct the output beam through the output waveguide network from any selected one of the recording regions to the outcoupling region via the incoupling region optically coupled thereto for receipt at the detector array by controlling at least one controllable directing element of the output waveguide network or at least one optical property of a reference beam used to generate an output beam, wherein different ones of a plurality of the recording regions can be read using the same detector array by varying the at least one optical property or controlling the at least one directing element while the plurality of incoupling regions of the output waveguide network remain in fixed locations relative to the corresponding recording regions of the holographic recording medium; and configured to generate the output beam by interacting a reference beam with a pattern stored in the selected recording region, the stored pattern encoding a plurality of image pixels, the plurality of image pixels being encoded in the output beam as a plurality of propagation modes propagating simultaneously in different directions through the output waveguide network. The reference waveguide network may be a common waveguide network with the output waveguide network or may be a different waveguide network.

Images