JP4626993B2 - Method for recording information on light-guided linear medium and optical memory element - Google Patents

Description

  The present invention relates to a method for recording information on a light-guided linear medium and an optical memory element, and more particularly, to a method for recording information on a light-guided linear medium in which information is recorded using light, and The present invention relates to an optical memory device using the same.

  In recent years, the amount of information handled due to the development of information equipment and communication means has increased dramatically, and along with this, the recording capacity has increased even for information recording media for recording and storing information. There is a growing demand for higher information recording density.

  Here, as an information recording medium having a low bit unit price and a large recording capacity, a magnetic tape or an optical disk has been conventionally used. In recent years, optical disks, particularly write-once optical disks such as CD-R and DVD-R, have been actively used due to random accessibility and ease of media exchange.

  However, in most of these optical discs, information can be recorded on only one layer with respect to one disc having a diameter of about 12 cm, and the area of the disc directly determines the total recording capacity. In addition, there is a problem that an optical disk whose area of the disk determines the total recording capacity as it is, the limit is visible even when the recording capacity is increased.

  In view of such problems, for example, development of a technique for recording information in a three-dimensional space by increasing one dimension is proposed instead of recording information only in a two-dimensional plane. As one of technologies for recording information in such a three-dimensional space, a three-dimensional multilayer optical memory that records information in multiple layers on one disk has been developed.

  However, in the above-described three-dimensional multilayer optical memory, in order to record information in a three-dimensional space with high accuracy, there is a problem that processing of the disk itself must be managed with extremely high accuracy, Disturbances such as mechanical shape changes such as disk deflection and vibration during recording and playback, and material property changes such as refractive index changes due to thermal expansion and humidity changes must also be corrected with high accuracy. There was a problem.

Note that the prior art that the applicant of the present application knows at the time of filing a patent application is not an invention related to a known literature invention, so there is no prior art document information to be described.

  The present invention has been made in view of the above-described various problems of the prior art, and its object is to increase the recording capacity by an approach different from that of the prior art. An object of the present invention is to provide a method for recording information on a light-guided linear medium and an optical memory element.

  In order to achieve the above object, the information recording method on the light guide linear medium according to the present invention records information serially inside the light guide linear medium such as an optical fiber.

  Also, the optical memory device according to the present invention is configured so that the light guide linear medium on which information is recorded by the information recording method on the light guide linear medium according to the present invention is packed in a three-dimensional space in an arbitrary shape. It is a thing.

  That is, in the present invention, information is recorded as a one-dimensional line inside an optical fiber, for example, as a light-guided linear medium, and the present invention appropriately stores it in a three-dimensional space. In this arrangement, the information itself is uniformly distributed in the three-dimensional space, but the recording form itself can be recorded in a one-dimensional space that is easy to access. As the light guide linear medium, for example, information recorded in a one-dimensional line shape inside the optical fiber is read out by irradiating light from the end face of the optical fiber and observing fluorescence.

  The present inventor proposes to refer to an entirely new type of optical memory device, which is completely different from the prior art according to the present invention, as a “three-dimensional optical fiber memory”.

Note that recording information in a one-dimensional line is not a novel technique, and information is recorded on a spiral (or concentric) line called a track even in the current optical disc. However, in the current optical disk, in order to record information in a specific area on the disk or to reproduce information from the area, light (usually laser light) is obtained by some mechanical means. It is necessary to guide the irradiation to a desired place. On the other hand, according to the present invention, a light guide linear medium such as an optical fiber is used, and information is recorded on the light guide linear medium, so that light is emitted from the end face of the light guide linear medium. The light differs from the current optical disc in that light is guided without leaking from the light-guiding linear medium only by being incident, and the light reaches the point where the information is recorded and the information is read out.

That is, the invention described in claim 1 of the present invention is one of the light-guided linear media configured to contain a material that absorbs only light of a predetermined frequency that causes two-wavelength two-photon absorption. The pulse laser beam having one frequency divided from the predetermined frequency is incident from the end, and the pulse laser beam having the other frequency divided from the other end of the light guide linear medium is input. The light is absorbed only at a position where the pulse of the one frequency pulse laser beam and the pulse laser beam of the other frequency meet in the light guide linear medium. .

  In the invention according to claim 2 of the present invention, in the invention according to claim 1 of the present invention, the one frequency obtained by dividing the predetermined frequency is not matched with the other frequency. It is a thing.

  The invention described in claim 3 of the present invention is the invention described in any one of claims 1 or 2 of the present invention, wherein the light-guiding linear medium is an optical fiber. Is.

  According to a fourth aspect of the present invention, in the invention according to the third aspect of the present invention, the optical fiber is an optical fiber obtained by doping a spiropyran-based or azo-based photochromic dye into glass or a polymer. It is what I did.

  Further, the invention according to claim 5 of the present invention is a light-guided linear medium in which information is recorded according to any one of claims 1, 2, 3 or 4 of the present invention, Arranged in an arbitrary three-dimensional shape.

  According to a sixth aspect of the present invention, in the fifth aspect of the present invention, the light-guiding linear medium is composed of a plurality.

  Since the present invention is configured as described above, it is possible to provide a method for recording information on a light-guided linear medium and an optical memory element, which have an increased recording capacity by an approach different from the conventional one. There is an excellent effect of being able to.

  Hereinafter, an example of an embodiment of an information memory recording method and an optical memory device according to the present invention will be described in detail with reference to the accompanying drawings.

First, an information recording method for a light guide linear medium according to the present invention will be described. In the information recording method for a light guide linear medium according to the present invention, as shown in FIG. Light can be incident from the first end 10a as one end and the second end 10b as the other end, and the light incident from the first end 10a is not leaked to the outside. The light is guided to the two end portions 10b and the light incident from the second end portion 10b is guided to the first end portion 10a without leaking to the outside. Medium 10 is used.

  The light guide linear medium 10 is configured to contain at least a material that absorbs only light of a predetermined frequency that causes two-wavelength two-photon absorption.

  In addition, such a light guide linear medium 10 can be comprised using the optical fiber etc. which were formed using the fine ceramic, for example.

  When light is incident from the first end 10a of the light guide linear medium 10, the light is guided through the light guide linear medium 10 and then emitted from the second end 10b. When light is incident from the second end 10b of the linear medium 10, the light is guided through the light guide linear medium 10 and then emitted from the first end 10a.

  Here, if the light guide linear medium 10 is formed of a photosensitive material that is sensitive to light incident on the light guide linear medium 10, the light guide linear medium in which light is guided. Photosensitivity occurs over the entire area 10 and light and the photosensitive material cannot interact with each other only at a specific location of the light guide linear medium 10.

By the way, the phenomenon of two-wavelength two-photon absorption has been known so far, but this two-wavelength two-photon absorption absorbs two photons having two frequencies of f ₁ and f ₂ at the same time. This is a phenomenon in which light absorption corresponding to light absorption of f ₁ + f ₂ (referred to as “f ₁ + f ₂ = f ₀ ”) corresponding to the sum of the two frequencies occurs.

As described above, the light-guiding linear medium 10 contains a material that absorbs only light of a specific frequency (f ₀ in the above example) that causes two-wavelength two-photon absorption. Therefore, due to the phenomenon of two-wavelength two-photon absorption described above, the material does not absorb light other than light of the specific frequency (for example, f ₁ and f ₂ in the above example), but these two frequencies Light absorption occurs only at the moment when the light is simultaneously present.

Therefore, as shown in FIG. 1, a pulse laser beam having a frequency f ₁ is incident from the end portion 10 a of the light guide linear medium 10, and a pulse laser having a frequency f ₂ is input from the end portion 10 b of the light guide linear medium 10. When light is incident, light absorption occurs only at the position A where each pulse in the light guide linear medium 10 meets.

  For this reason, by appropriately shifting the timing of the pulse of the pulsed laser light incident on the end portion 10a and the end portion 10b of the light guide linear medium 10, respectively, for example, as shown in FIG. It is possible to control (scan) so that the positions B, C, and D where light absorption occurs in the optical linear medium 10 are arbitrarily changed.

  In addition, after the pulse laser light incident on the end portion 10a and the end portion 10b of the light guide linear medium 10 is emitted from the end opposite to the end portion on the incident side, the light guide linear medium is again formed. By repeating the above-described processing of being incident on the end portion 10a and the end portion 10b, for example, as shown in FIG. 2, a position where a plurality of light absorption occurs on the same light guide linear medium 10 is performed. B, C, and D can be formed.

  As described above, light absorption is caused at an arbitrary position of the light-guiding linear medium 10, and a modified local region such as a change in refractive index (hereinafter referred to as “bit”) is appropriately set at the arbitrary position. Is formed). Information is recorded by forming bits on the light guide linear medium 10, and therefore the information can be recorded in a one-dimensional line on the light guide linear medium 10.

  For example, a pulse laser having a pulse width of 10 femtoseconds is used as a light source of pulse laser light incident on the light guide linear medium 10, and the end 10 a and the end 10 b of the light guide linear medium 10 Consider the case where a pulse laser beam generated by a pulse laser is incident.

  Here, if the refractive index of the light-guiding linear medium 10 is ignored for simplification of description, the light travels 3 μm in 10 femtoseconds. When 10b to 10 femtosecond pulses propagate and collide with each other, an interference region of about 6 μm width is formed, and two-photon absorption occurs only within this region.

  That is, information is recorded by locally forming a bit having a width of about 6 μm inside the light guide linear medium 10.

Hereinafter, specific examples of the material of the light guide linear medium 10 and the wavelength and pulse width of the pulsed laser light incident on the light guide linear medium 10 will be described.

  First, as a material for the light-guiding linear medium 10, an optical fiber doped with glass or polymer with a spiropyran-based or azo-based photochromic dye can be used.

The wavelength of light incident on the light-guiding linear medium 10 is, for example, a wavelength corresponding to two-photon absorption of 800 nm, which is a typical oscillation wavelength of a titanium sapphire laser, of 400 nm, and a frequency of this wavelength of 400 nm. Is divided into a frequency f ₁ incident on the end portion 10 a of the light guide linear medium 10 and a frequency f ₂ incident on the end portion 10 b of the light guide linear medium 10. The calculation formula for dividing the wavelength is as follows.

The wavelength of 400 nm (the frequency of the wavelength of 400 nm is f ₀ ) is f = c / λ (f: frequency, c: speed of light, λ: wavelength),
f ₀ = (3.0 × 10 ⁸ ) / (400 × 10 ⁻⁹ ) = 750 THz
Since it suffices to divide so that f ₀ = f ₁ + f ₂ , for example,
f ₁ = 500 THz
f ₂ = 250 THz
And it is sufficient. When these are converted back to wavelength, if the wavelength of f ₁ is λ ₁ and the wavelength of f ₂ is λ ₂ ,
λ ₁ = c / f ₁ = 600 nm
λ ₂ = c / f ₂ = 1200 nm
It becomes.

Note that the above is merely an example, and in essence, the frequency f _{0 of the} fundamental wave, which is a specific frequency that causes the two-wavelength two-photon absorption in the light-guiding linear medium 10, is determined, and f ₀ = f ₁ + F ₂
Any combination may be used as long as the combination becomes.

  The pulse width of the light incident on the light guide linear medium 10 is, for example, about 10 fsec.

Next, recording is determined by the length of the light guide linear medium 10, the pulse width of the pulse laser light incident on the light guide linear medium 10, and the repetition frequency of the pulse laser light incident on the light guide linear medium 10. An example of calculation regarding density and transfer rate is as follows.

That is, the speed of light in vacuum is 3 × 10 ⁸ m / s. Here, if the refractive index of the light-guiding linear medium 10 is ignored and this is set to 1.0, a time of 10 fsec from the speed of light corresponds to a light propagation length of 3 μm.

  For example, when pulse laser light having a pulse width of 10 fsec is incident from both ends 10 a and 10 b of the light guide linear medium 10, the time during which the light pulses overlap each other is 20 fsec, The distance is 6 μm. This is the relationship between the pulse width and the recording density.

Next, assuming that the length of the light guide linear medium 10 is L (m), the time required for the light pulse to pass through the light guide linear medium 10 is as follows.
L / (3.0 × 10 ⁸ ) sec
It becomes. For example, if L = 3 m, it will take 10 ⁻⁸ seconds.

Here, until the incident light pulse passes through the light guide linear medium 10, the next pulse laser beam cannot enter the light guide linear medium 10, which increases the information transfer rate. For example, in the case of L = 3 m, the reciprocal of 10 ⁻⁸ seconds, and eventually 10 ⁸ Hz = 100 MHz. In general, it is (3.0 × 10 ⁸ ) / L Hz.

  Therefore, since the transfer rate decreases as the length of the light-guiding linear medium 10 becomes longer, the light-guiding linear medium is shorter than using one long light-guiding linear medium 10. The transfer rate can be improved by using a plurality of 10.

In the above description, the refractive index of the medium is ignored and is set to 1.0. However, when the refractive index is n in consideration of the refractive index of the medium, the speed of light in this medium is set to 1 / n. That is,
3.0 × 10 ⁸ / n (m / s)
Calculate as follows.

For example, the length of the medium recorded with a laser pulse of 10 fsec (overlap region of two pulses) is 6 / n μm, and the transfer rate when using a fiber of length L is
(3.0 × 10 ⁸ ) / (n × L) (Hz)
It becomes.

In addition, the information recorded on the light guide linear medium 10 as described above is read by applying a pulse laser beam from both or one of the end 10a and the end 10b of the light guide linear medium 10. The detection may be performed by detecting a bit in the light-guiding linear medium 10, that is, fluorescence due to an interaction with an area where information is recorded.

  The region where two-photon absorption occurs in the light-guiding linear medium 10, that is, the scanning of the recording position is performed by controlling laser oscillation using the Q switch method, thinning out pulse laser light using a pulse picker, or optical. The position where both pulses meet within the fiber may be changed by shifting the timing of both pulses using a technique such as a time delay using a delay.

Next, the optical memory element according to the present invention will be described. The optical memory element according to the present invention is a method for recording information on the light-guided linear medium according to the present invention (hereinafter referred to as “method of the present invention” as appropriate). The light guide linear medium 10 on which the information is recorded is arranged in an arbitrary three-dimensional shape.

  That is, FIG. 3 shows an example of an embodiment of an optical memory device according to the present invention, and this optical memory device 100 according to the present invention has a light guide linear medium 10 on which information is recorded by the method of the present invention. It is bent into an arbitrary three-dimensional shape. In addition, the light guide linear medium 10 shall be comprised with the flexible material. When the light guide linear medium 10 is bent into a three-dimensional shape, the light guide linear medium 10 may be bent with an appropriate law or may be bent randomly as shown in FIG.

  The optical memory element 100 is configured by bending one light guide linear medium 10 into an arbitrary three-dimensional shape. However, a plurality of light guide linear media 10 are bent into an arbitrary three-dimensional shape. Of course, they may be configured.

  FIG. 4 shows another example of the embodiment of the optical memory device according to the present invention. The optical memory device 200 according to the present invention is obtained by housing the above-described optical memory device 100 in a case 202. .

  Further, FIG. 5 shows another example of the embodiment of the optical memory device according to the present invention. The optical memory device 300 according to the present invention extends a plurality of light-guiding linear media 10 linearly. Then, a desired number of layers arranged in parallel on the same plane are stacked and stored in the case 302.

  Furthermore, FIG. 6 shows another example of the embodiment of the optical memory device according to the present invention. The optical memory device 400 according to the present invention bundles a plurality of light-guiding linear media 10 and ribbons. A shape is produced, and it is spirally wound.

  FIG. 7 shows another example of the embodiment of the optical memory device according to the present invention. The optical memory device 500 according to the present invention spirals one light-guiding linear medium 10 spirally. It is a thing. Although the arrangement of the optical memory device 500 according to the present embodiment is two-dimensional, it goes without saying that the optical memory device 500 is included as an example of the embodiment of the optical memory device according to the present invention.

In the case where a plurality of light guide linear media 10 are used as the optical memory device according to the present invention, such as the optical memory devices 300 and 400, in order to introduce light into a desired light guide linear medium 10, Optical switches and optical waveguide elements (for example, “APPLIED OPTICS / Vol. 17, No. 8/15 April 1978”, “Japan Journal of Applied Physics”) used for coupling light to a plurality of optical fibers in communication. , Vol. 43, No. 8B, 2004, pp. 5824-5827, etc.).

Here, as a method for generating an optical pulse obtained by dividing a predetermined frequency, that is, a pulsed light having a frequency f ₁ and a frequency f _{2 obtained} by dividing the predetermined frequency f ₀ , for example, there are the following methods.

That is, the generation of the pulsed light, for example, optical parametric amplifier (OPA: Optical Parametric Amplifier) using, from one laser having a frequency of _{f 0} creates both of the pulsed light of _{f 1} and _{f 2} Alternatively, two lasers having different frequencies may be used to generate pulsed light of frequencies f ₁ and f ₂ , respectively.

In addition, when generating pulsed light with frequencies of f ₁ and f ₂ using two lasers having different frequencies, respectively, f ₀ = f ₁ + f ₂ is accurate.
Since it is difficult to match the frequencies so that the phase of two pulses emitted from separate laser resonators is essentially uniform, it is practically possible to use f ₁ and f using an optical parametric amplifier. It is more effective to obtain pulsed light having a frequency of ₂ .

The embodiment described above can be modified as shown in the following (1) to (5).

  (1) In the above-described embodiment, the light guide linear medium 10 is configured to contain a material that absorbs only light of a specific frequency that causes two-wavelength two-photon absorption. In the present specification, the meaning of “the light guide linear medium 10 includes a material that absorbs only light of a specific frequency that causes two-wavelength two-photon absorption” means “light guide. The light guide linear medium 10 includes a material that absorbs only light of a specific frequency that causes two-wavelength two-photon absorption as a part of the total material constituting the conductive linear medium 10. In addition, it also means that “the light-guiding linear medium 10 is composed only of a material that absorbs only light of a specific frequency that causes two-wavelength two-photon absorption”.

  (2) In the above-described embodiment, the description of the cover that covers the light-guiding linear medium 10 is omitted, but the light-guiding linear medium 10 is disposed on the outer periphery of the light-guiding linear medium 10. Of course, a cover for shielding from the external environment may be provided.

(3) In the above-described embodiment, when the light guide linear medium 10 divides a specific frequency that causes two-wavelength two-photon absorption, the divided frequencies do not match (f ₁ ≠ f ₂ ). However, the present invention is not limited to this, and the divided frequencies may match.

  However, if the divided frequencies are matched, light absorption may occur over the entire area of the light guide linear medium 10 on which light is guided. Therefore, the control is strictly performed when light is incident. Since it is necessary to do so, it is preferable that the divided frequencies do not match.

  (4) In the above-described embodiment, the pulse widths of the light incident on the end portion 10a and the end portion 10b of the light guide linear medium 10 are the same. However, the present invention is not limited to this. Of course, the pulse widths of the light incident on the end portion 10a and the end portion 10b of the light guide linear medium 10 may not be the same.

  (5) You may make it combine suitably the embodiment shown above and the modification shown in said (1) thru | or (4).

  The present invention is used as a recording medium for various information such as a computer program, music, or video.

FIG. 1 is an explanatory diagram of a conceptual configuration of a light guide linear medium used in a method for recording information on a light guide linear medium according to the present invention. FIG. 2 is an explanatory diagram showing a position where light absorption occurs in the light guide linear medium. FIG. 3 is a conceptual structural explanatory diagram showing an example of an embodiment of an optical memory device according to the present invention. FIG. 4 is a conceptual structural explanatory view showing another example of the embodiment of the optical memory device according to the present invention. FIG. 5 is a conceptual structural explanatory view showing another example of the embodiment of the optical memory device according to the present invention. FIG. 6 is a conceptual structural explanatory view showing another example of the embodiment of the optical memory device according to the present invention. FIG. 7 is a conceptual structural explanatory view showing another example of the embodiment of the optical memory device according to the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Light guide linear medium 10a 1st edge part 10b 2nd edge part 100, 200, 300, 400, 500 Optical memory element 202, 302 Case

Claims (6)

From one end of a light-guided linear medium configured to contain a material that absorbs only light of a predetermined frequency that causes two-wavelength two-photon absorption, the frequency of one frequency divided from the predetermined frequency A pulse laser beam is incident, and a pulse laser beam having the other frequency obtained by dividing the predetermined frequency is incident from the other end of the light guide linear medium, and the one of the light guide linear media is A method of recording information on a light-guided linear medium, wherein light absorption occurs only at a position where a pulse of a pulse laser beam having a frequency meets a pulse of a pulse laser beam having the other frequency. In the recording method of the information to the light guide linear medium according to claim 1,
The method of recording information on a light-guided linear medium, wherein the one frequency obtained by dividing the predetermined frequency does not match the other frequency. In the recording method of the information to the light guide linear medium of any one of Claim 1 or 2,
The light guide linear medium is an optical fiber. A method of recording information on the light guide linear medium. In the recording method of the information to the light guide linear medium according to claim 3,
The optical fiber is an optical fiber obtained by doping glass or polymer with a spiropyran-based or azo-based photochromic dye. A method for recording information on a light-guided linear medium. The light guide linear medium on which information is recorded by the method of recording information on the light guide linear medium according to any one of claims 1, 2, 3, or 4 is arranged in an arbitrary three-dimensional shape. An optical memory device characterized by the above. The optical memory device according to claim 5,
An optical memory element comprising a plurality of the light guide linear media.

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