JPH02210627A - Optical recording and reproducing device - Google Patents

Abstract

PURPOSE:To reproduce a presence/absence signal as to the reflection of light from a pulse laser oscillation device by arraying fine refractive index discontinuous parts where reflected waveguide light is generated in an optical waveguide according to information to the recorded and guiding the light from a pulse laser oscillation device. CONSTITUTION:Laser light pulses are converted by a microlens 41 on the end surface of the waveguide and guided to one channel optical waveguide. The width and intervals of respective channel type optical waveguides are set typically to about 1mum. When a response of 0.5 picosecond is considered on the whole system, refractive index discontinuous parts are at intervals of 50mum and recording of 1Mbit/cm<2> is enabled; when the length of the optical waveguide is 5cm, one light pulse is inputted to read information of 1,000 bit in an extremely short time of 0.7ns. The information recorded in one optical waveguide is read out and then a substrate where many optical waveguides are arrayed or the laser oscillator and an optical detector are moved to read recording information of a next channel out.

Description

Detailed Description of the Invention [Technical Field] The present invention uses an optical waveguide that records information depending on the presence or absence of a refractive index discontinuity that produces reflected guided wave light, guides a light pulse, and extracts information from the reflected light pulse. It is used in an optical recording and reproducing device for reproducing.

[Prior Art] A conventional optical recording/reproducing apparatus is configured as shown in FIG. Here, 11 is a semiconductor laser, 12 to 15 are lenses, 16 is a condenser lens installed on the focus actuator, 17 and 18 are half mirrors, 19 is an I/2 wavelength plate, 20 is a shaping prism, and 21 to 23 are photodetectors. vessel, 2
4 is a laser beam recording medium, such as a disk, and 25 is a beam splitter using a prism.

The light from the semiconductor laser 11 is incident on the recording medium 24 through the lens 12) shaping prism, the half mirror 17, and the condensing lens 16, and recording is performed.

As for the recording format, information is written by changing the reflectance of the recording medium by light irradiation by making holes with the energy of laser light or by utilizing phase transformation between crystalline and non-crystalline states. In some cases, information is written by applying a magnetic bias to a magnetic medium and reversing the magnetization by turning on and off a laser beam.

A conventional optical recording medium is constructed as shown in FIG. Here, the optical recording medium lOO uses a recording medium as a substrate,
Concave portions 101 with low light reflectance and flat portions +02 with high light reflectance recorded on the substrate surface are arranged on a line, and recording and reproduction is performed while moving the recording medium in the direction of arrow 103. . The ratio of the light reflectance between the flat portion 102 and the concave portion 81sIO+ is at most about 1:0.3 to 0.5, and the signal-to-noise ratio of light intensity is by no means good and is difficult to improve. In addition, in such a recording medium +00, during reproduction, a semiconductor laser is focused on each concave portion 101 or flat portion 102, reflected light is detected, and the time-series signal is reproduced only by movement of the recording medium 100, and the recording is performed. medium 100
The access time for playback and recording is limited by the moving speed of the player, making high-speed access difficult.

Here, if the laser beam recording medium 24 is a medium that records information as a change in reflectance, such as a perforated recording medium or a phase change l-shaped medium, the reflected light from the disk 24 is detected by the photodetector 21. Detected.

On the other hand, in a medium where the laser beam recording medium 24 records information as magnetization reversal, such as a magneto-optical disk, the rotation of the polarization plane of the reflected light by the recording section is separated by the prism beam splitter 25, which is an analyzer, and the separated Light is detected by differential outputs of photodetectors 22 and 23.

During such recording and reproduction, in order to cause the above-mentioned device to follow the surface deflection of the laser beam recording medium 24, the condenser lens 16 and the like are moved in the optical axis direction in accordance with the focus error signal to focus.

In such a conventional method, (1) since a light reflection method using bits is used, it is necessary to focus on each recorded portion of a recording medium, and the signal-to-noise ratio of the optical signal is poor, resulting in poor reliability.

(ii) Since the optical signal is reproduced for each recorded portion of the recording medium, the time-series signal is reproduced only by the movement of the recording medium, and the cycle time is limited by the moving speed of the recording medium.

(l1i) Since individual optical components and mechanical components are interwoven, it takes time to adjust the optical axis, and the reliability is poor.

(iv) Since the device is large and heavy, there are problems such as high-speed access and multi-head configuration are difficult.

[Purpose] The present invention solves these drawbacks and provides an optical recording/reproducing device that can read a large amount of information all at once at ultra-high speed. A plurality of them are arranged in an optical waveguide according to the information to be obtained, guide the light from the pulse laser excavation device, and reproduce the presence/absence signal of the reflection.The drawings will be described in detail below.

[Structure of the invention] Eleventh! I is a principle diagram explaining the present invention, 30 is a core part of an optical waveguide, 31 is a substrate that becomes a cladding layer of the optical waveguide, 32 is air or a film that becomes a cladding layer, and 33 is information to be recorded. As shown in Figure 0, a pulsed laser beam with a pulse width T is optically guided from the optical coupling part of the optical waveguide. It couples to the wave path and propagates. When there is a discontinuity in the refractive index, the incident guided light is scattered and some of it is reflected as guided light.As shown in the figure, this refractive index discontinuity has the information to be recorded (in the figure, it is a digital signal of 0.1). If the distance between the refractive index discontinuities is 1, the effective refractive index of the optical waveguide is n, and the speed of light is C, it will be recorded. The optical pulses encoded with the information obtained at time intervals of t=2nl/c will be returned. therefore,
If the length of one refractive index discontinuity is shorter than cT/n and the pulse width T is shorter than t, there is no overlap between the reflected lights,
The recorded information can be read by detecting the returned light pulses. Of course, optical signals reflected back and forth at a plurality of points are also mixed in, but their amplitude is extremely small and can be easily removed by providing a threshold of a certain level or higher for light reception. In addition, by providing a light absorption part or a light leakage part at the final end of the optical waveguide, it is possible to ignore the reflected light from the final end.
ce on La5ers and Ele
As disclosed in ctrooptics MDI (1987), light pulses from dye laser devices are as short as 6 femto (6X 10-'') seconds, and such light pulses can be used to reduce the effective refractive index to n= 0.5 as 2
Reading can be performed even if refractive index discontinuities are provided at intervals of μ1. Currently, light pulses of about 1 pico (IX 1G-12) seconds can be generated using semiconductor lasers, which are small and have simple equipment; Subsecond light pulses will become easier to form in the future.

Next, we will explain the material of the optical waveguide, which is the recording medium, and the method of manufacturing the refractive index discontinuity.In the present invention, it is necessary to create an optical waveguide, so for example, it is necessary to create an optical waveguide on a glass substrate, which has a higher refractive index than the substrate. Polymer materials such as PMMA that are transparent to laser light, glass with a high refractive index, chalcogenide materials such as AS2S3, and semiconductor materials such as TeOx are used at approximately 1 μII.
Those with FJ added are used. It goes without saying that a polymer material with a refractive index smaller than that of the waveguide can be used as the substrate.Methods for forming the refractive index discontinuity include forming minute bits,
A change in refractive index due to a phase change in TeO or TeO can be used.

In this configuration example, a case has been shown in which the refractive index discontinuity portion serving as the optical recording portion is provided in the core portion of the optical waveguide, but the same effect as the present principle can be achieved even if the refractive index discontinuity portion is provided in the cladding layer.

[Embodiment] FIG. 2 shows an embodiment of the present invention, in which 40 the optical waveguide is made into a channel type and a large number of them are arranged side by side on an optical disk or optical card substrate, 41 is a microlens for coupling to the optical waveguide, and 42 is a high-speed optical receiver, and 43 is a beam splitter. The laser light pulse is focused on the end face of the waveguide by the microlens 41 and guided into one channel optical waveguide. The width and spacing of each channel-type optical waveguide is typically about 1
Selected by uw. In addition, as a high-speed optical receiver, for example, the USA 1988 Annual Meeting
An optical semiconductor photodetector with a response speed of 0.5 picoseconds as disclosed in TaF5 can be used. Considering a 0.5 picosecond response for the entire system, the interval between the refractive index discontinuities will be 50 μm, making it possible to record lNb1t/c2, and assuming the length of the optical waveguide to be 5c2, one By inputting a light pulse, 1000 bits of information can be read out within an extremely short time of O, Tns. After reading out the information recorded in one optical waveguide, the recorded information in the next channel can be sequentially read out by moving the substrate on which many guiding waveguides are arranged side by side, or the laser oscillator and the photodetector.

In this explanation, a case has been described in which light is directly focused on the end face of an optical waveguide as an optical coupling part, but of course a taper, a diffraction grating, etc. fabricated on the waveguide can also be used.

31st! I is another embodiment of the present invention, 50 is a laminated drum type optical recording medium, 51 is a lens, 52 is a light receiver, 53
54 is a beam splitter, and 54 is a reproduction laser oscillator. The laminated drum type optical recording medium 50 constitutes a three-dimensional memory in which tapes having optical waveguides on which information is recorded due to discontinuity of refractive index are superimposed. If the thickness of one tape is 1 μm and the optical waveguide is 1 μm thick in the same way as in the lateral direction, a 3D memory of 5 Gb + t/cm' will be realized. drum has approximately 2000 Gbit. At the time of reproduction, a laser beam is focused on each optical waveguide end face optical coupling portion to retrieve the recorded information, and the drum 50 is rotated to sequentially reproduce the signal.

FIG. 4 shows still another embodiment of the present invention, showing the configuration of a laminated plate type optical recording and reproducing device, in which 60 is a recording laser transmitter,
61 and 61' are lenses, 62 is a laminate type three-dimensional optical recording medium, 63 is an optical recording section, 64 is a double laser beam oscillator,
65 is a beam splitter, and 66 is a composite photodetector.

The laminate type three-dimensional optical recording medium 62 is formed by multilayering optical disks or optical cards in which the channel optical waveguide GA type recording medium 40 shown in FIG. The three-dimensional dimension of the recording medium 62 is 5xlO
x1cm, its recording capacity is 250Gb it
It is.

During recording, as shown in the figure, a recording laser beam is focused on the recording part of the waveguide of the layer to be recorded, and as it moves along the optical waveguide, it causes a phase change in the recording member, thereby changing the refractive index. Record the continuous portion according to the information to be recorded. When recording on a different layer, the recording laser oscillation device 60 and lens 62 or the laminated three-dimensional optical recording medium 62 are moved up and down to change the focusing position, and the areas that are not in focus are It takes advantage of the fact that it is difficult to record because the optical energy density is low.

During reproduction, in this example, a double laser beam oscillator 464 is used to simultaneously guide the wave to two optical waveguides to extract the reproduced light, and a composite optical detector @66 is used to perform parallel high-speed reproduction for each of the two waveguides. This can be achieved while accessing. Access is performed while moving the dual laser beam oscillator 64 and the composite photodetector 66 or the laminate-type three-dimensional optical recording medium 62.Currently, two to five laser beam semiconductor oscillators are commercially available. By using , parallel high-speed playback with three or more consecutive beams can be realized.

Since a phase change material or the like can be used as the optical waveguide material as described above, an additional laser oscillation device for recording is provided as shown in FIG. 4, and its laser output is modulated according to the information to be recorded. A write-once type is possible by recording the presence or absence of refractive index discontinuities on the medium, and a rewritable type is also possible by further introducing an erasing beam.

[Effects] As explained above, the optical recording/reproducing device of the present invention has the advantage of being able to read out a large amount of information at an ultra-high speed by only inputting a single pulse of light, and can also realize a three-dimensional high-density memory. Because of these advantages, it is possible to provide an extremely useful device as a high-capacity, high-speed recording and reproducing device compatible with computers, a high-capacity, high-speed video reproducing device compatible with high-definition, and furthermore, as a large-capacity optical card recording and reproducing device.

[Brief explanation of the drawing]

FIG. 1 is a detailed explanation of the present invention, FIG. 2 is an embodiment of the present invention, FIG. 3 is another embodiment of the present invention, FIG. 4 is a further embodiment of the present invention, Figure 5 shows an example of the configuration of a conventional optical recording/reproducing device, and Figure 6 shows an example of a conventional optical recording medium. Cladding part of optical waveguide, ・Refractive index discontinuity, 40・41 conflict 43・・Channel optical waveguide type・Coupling lens, ・Photodetector, ・Beam splitter, Recording medium, 50・; 51・52・54φ・Lamination Drum-type optical recording medium, ・Lens, ・Photoreceiver, ・Beam splitter, ・Laser oscillator, 60Φ 61.61' - 620, 64, 65φ 66mm ・Recording laser transmitter, ・Lens, ・Laminated plate type three-dimensional Optical recording medium, ・Optical recording section, ・Double laser beam oscillator, ・Beam splitter, ・Combined photodetector, Drawing engraving 11 ・ 12 - 15 ・ 16 @ 17, 18 Meeting 19 ・ 20 ・ 21 - 23 ・24. ・Semiconductor laser, ・Lens, ・Condensing lens, ・Half mirror, ・l/2 wavelength plate, ・Shaping prism, ・Photodetector, ・Recording medium, ・Beam splitter 100・101 Φ 102 ・ 103Φ ・Light Recording medium, ・Concave portion with low light reflectance, ・Flat portion with high light reflectance, ・Movement direction arrow.

Claims (1)

[Claims] 1) An optical waveguide having a plurality of recording sections arranged in the optical waveguide to determine the presence or absence of minute refractive index discontinuities that generate reflected guided light within the optical waveguide, depending on the information to be recorded. A recording medium, a pulse laser oscillation device and a photodetector arranged opposite to an optical coupling part provided in a part of the optical waveguide that is the recording medium, and a member that supports each of the optical waveguides. The light from the pulsed laser excavation device is guided into the optical waveguide by the optical coupling part, and the refractive index discontinuity of the optical waveguide reflects a part of the incident guided light, and the reflected guided light has a propagation distance. An optical recording/reproducing apparatus characterized in that after a time corresponding to , the light returns to the optical coupling part, the light is received by a photodetector disposed in the optical coupling part, and the recorded information is reproduced. 2) In the optical recording/reproducing device according to claim 1, the recording portion of the optical waveguide serving as the recording medium has a predetermined length, and a plurality of the optical waveguides are arranged on a tape, card, or disk substrate, Guide the light from the pulsed laser oscillation device through the optical coupling part of one of the optical waveguides,
By increasing or decreasing the amount of guided light reflected by the refractive index discontinuity of the optical waveguide, the information recorded on the optical waveguide recording medium is reproduced, and then the information recorded on the optical waveguide recording medium is reproduced. An optical recording and reproducing apparatus characterized in that a photodetector is moved and reproduction is performed sequentially in the same manner from different optical waveguides. 3) An optical recording and reproducing apparatus according to claim 1, characterized in that two or more tapes, disks, or cards on which optical waveguide recording media are arranged are stacked. 4) In the optical recording and reproducing apparatus according to claim 1, during recording, the recording-only additional laser oscillation device is provided, or the laser oscillation device is used together, and the laser beam is modulated according to the information to be recorded. Then, when the recording medium is laminated, the light is focused on the recording medium of the target layer to be recorded, and the presence or absence of the refractive index discontinuity is recorded, and at the time of reproduction, the patent An optical recording and reproducing apparatus characterized in that the recorded information is reproduced by the reproducing method according to claim 1.