JPH0366098A - Optical storage device - Google Patents

Abstract

PURPOSE:To attain ultrahigh speed access by providing a tap guide path corresponding to information to be stored in the guide path to write the information, introducing an ultra-short optical pulse to the guide path and reading the information with an optical signal extracted through the tap guide path. CONSTITUTION:Taps T1, T2,...Tn are provided or not provided corresponding to information to be written in address positions P1, P2,...Pn of a waveguide 2, and when installed, '1' is detected by a detector 5 in the case of readout operation and when not provided, '0' is detected. A trigger pulse is supplied in the readout timing to an optical pulse generator 1, from which an ultrashort optical pulse is generated, the optical pulse is introduced to the guide path 2 and propagated in the guide path 2 and the information is read out in response to the propagation speed of the optical path in the guide path 2. Through the constitution above, since the information is accessed in response to the propagation speed of the optical pulse in the waveguide path 2, very high speed access is attained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] This invention relates to an optical storage device that allows extremely high-speed access.

[Conventional technology]

Conventionally, various methods have been proposed for optical storage devices, such as methods for directly recording information such as microfiche technology based on photographic technology, and methods for storing diffraction images, which are Fourier transformed images, in the form of holograms. ing. Among these, an optical disk device that is attracting particular attention for use in communications and information processing is an optical disk device that uses a laser beam for writing (storage), reading, and reproduction. There are a variety of optical disk devices of this type, from those that are widely used as consumer devices such as compact disks and video disks, to those that are in the development stage as large-capacity storage media for large computers. . The basic operating principle is: ■ By irradiating a specific spot on the disk with laser light, a spot with a different reflectance from the surrounding area is generated due to optical damage, optical structure changes, magnetic transition, etc., and the presence or absence of this spot is determined by Information is accumulated based on spot density, etc.

(2) A laser beam is irradiated onto a spot or a position where a spot should exist, and information is read out by changing the intensity of the reflected light.

(2) Scanning of the space where the information corresponding to the address exists is performed by mechanical scanning by rotating the disk and moving the head in the radial direction.

■In the case of a storage method that involves irreversible structural changes, the storage device becomes a read-only storage device, but if magnetic transition is used, it becomes a rewritable storage device.

[Problem to be solved by the invention]

By the way, the above-mentioned conventional optical storage device has superior features, such as large capacity, simplified peripheral circuitry, and long life due to non-contact, as compared to magnetic storage devices.

However, as described above, since accessing information involves mechanical scanning, only extremely slow access can be expected. That is, although conventional optical storage devices are effective as secondary storage media, they cannot be used as storage devices that require high-speed access, such as semiconductor cache memories.

The object of the present invention is to realize an optical storage device that does not require any mechanical scanning as in the past and is capable of ultra-high-speed access.

[Means to solve the problem]

This invention provides a waveguide for guiding an optical signal, a tap waveguide for extracting a part of the optical signal propagating within the waveguide from each position of the waveguide corresponding to information to be stored, and a tap waveguide for guiding the optical signal. The device is characterized by comprising an optical pulse generating means for introducing an optical pulse with an extremely short pulse width into the tap waveguide, and a detecting means for detecting the optical signal taken out by the tap waveguide as stored information.

Further, the waveguide and the tap waveguide are constructed of a material having a large electro-optic effect, and an electrode is installed at a portion where the waveguide and the tap waveguide are coupled, and a voltage is applied to the electrode. Accordingly, the coupling efficiency between the waveguide and the tap waveguide is changed.

[Effect]

According to the above configuration, information is written by installing a tap waveguide corresponding to the information to be stored in the waveguide, which is an information storage area, and this information is read by sending an extremely short optical pulse to the waveguide. This is done by introducing the optical signal, propagating it in the waveguide, and detecting the optical signal taken out in each tap waveguide.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of a read-only optical storage device according to a first embodiment of the present invention.

In this figure, l is an optical pulse generator that generates optical pulses with an extremely short pulse width, such as a mode-locked laser, a semiconductor laser with a gain switch, or a device using an optical gate. Any device that can generate light or ultrashort optical pulses may be used. Reference numeral 2 denotes a waveguide constructed of, for example, an optical fiber or a planar waveguide, into which the optical pulse is introduced from the optical pulse generator l, and taps T r , T * to be described later.
. . . Any type of device may be used as long as it is possible to propagate the optical pulse signal without distortion and with low loss in a portion other than the location where Tn is installed. 3.3. . . . are tap waveguides disposed at positions corresponding to information to be stored in the waveguide 2 and extracting a portion of the optical signal propagating within the waveguide 2; 5.5. ... is a waveguide for each tap 3.3
These are detectors that detect the optical signals extracted by ゜.... Then, the waveguide 2 and the tap waveguides 3 and 3 are placed at a position corresponding to the information to be stored among the address positions P , , P , . . . +Pn set at regular intervals along the waveguide 2. ．． The tap 'r,,T, that ... is connected to is
,...Tn are installed. That is, tap T
,,T t+...4n is the waveguide 2 and this waveguide 2
For example, in the case of an optical fiber, light leaking from a portion where stress is applied due to local bending is coupled to the tap waveguide 3. It is possible to realize this by In addition, in the case of dielectric waveguides or semiconductor guides obtained by diffusing titanium into lithium niobate, tap waveguide 3 is placed adjacent to waveguide 2, and the coupling mode of these two waveguides is utilized. Just do it and make it happen. Furthermore, the coupling coefficients at each tap T1Tx, .

Next, the operation of the first embodiment described above will be explained.

“Writing Operation” Information is written by writing the waveguide 2 to a position corresponding to the information to be stored among the address positions P , , P , . . . +Pn set at regular intervals along the waveguide 2. Waveguide for Totsubu 3.3. ... is connected to the tap T11Ttl
...This is done by installing Tn. In this embodiment, each address position Pt, Pt, ..., P of the waveguide 2 is
n, the tap T1.n corresponds to "l" or "0" of the information to be written. If T,...,Tn are installed or not, and if taps T,,T,,...+Tn are installed, the detector 5 will read "" during the subsequent readout operation.
l” is detected and taps 'rl,'rt,...,Tn
If it is not installed, the detector 5 detects "0". The address is each tap T + , T t ,...
, Tn are installed at the address position P1. Pa...
Determined by Pn, for each address! Bits of information are stored.

"Reading Operation" To read information, a trigger pulse is supplied to the optical pulse generator 1 according to the read timing.

The optical pulse generator l supplied with this trigger pulse generates an extremely short optical pulse, which is introduced into the waveguide 2, propagates within the waveguide 2, and is transmitted to each tap T11Ttl...
Reach the part where T n is installed. These tap'r
l,'I'! , ..., in the part where Tn is installed, most of the energy of the optical pulse signal propagates as is because the transmission coefficient is small, but a part of it is transmitted through the tap waveguide 3.
It will spread to At this time, tap T +, T
* , ..., depending on the structure of Tn and the shape of the propagating optical pulse, the waveform may be slightly disturbed, but the incident optical pulse is divided into two parts while maintaining most of its shape, and one part remains in the waveguide 2. and the other tap waveguide 3
propagate to. The optical pulses propagating in the waveguide 2 tap T ,,T ! one after another. , . . . , Tn to generate an output signal at each tap T + , T * , . In this case, address positions P ,,P ,,...
Since Pn corresponds to the taps Tr, Tx, . . . +Tn, the light pulses are sequentially applied to the taps T, T
n, the detector 5 detects "1" at the part where the taps T,, Tt,...,Tn are installed,
"O" is detected in the portions where the taps T, , T, . . . , Tn are not installed, and thereby information is read out. That is, the time τ after the optical pulse generator l generates the optical pulse in response to the supply of the trigger pulse.

Each detector At step 5, the presence or absence of a light pulse is detected. Since the presence or absence of the optical pulse corresponds to the presence or absence of each tap Tt, 'r t, ..., Tn, that is, the information "summer" or "0", the information is This means that reading has been performed.

22:1 The time required for the above readout operation is the tap T that is farthest from the time when the optical pulse is introduced into the input end of the waveguide 2;
approximately equal to the time it takes to propagate up to In other words, the address on the input end side is read immediately, but the other end is read last, so the time until this address is read becomes the entire read time. For example, if a short optical pulse of about femtoseconds is used as the input optical pulse signal, and the address position interval is about 10μ steel, then τ = to-' = ±x 10-I3
Since it is 3xlO@3, it becomes τ-0, about 1 ps. storage capacity l
If Kb is the address position P,,P,,...
Since the number of Pn is 1000, the access time is 10
The speed is about 00xO,I=100ρ8.

Next, FIG. 2 is a block diagram showing the configuration of a read-only optical storage device according to a second embodiment of the present invention.

In the first embodiment described above, the reading of information was all processed in parallel, but in the second embodiment, some or all of the information was detected in series. That is, all taps 'r,,T,,...
, Tn are coupled to a single tap waveguide 10,
In other words, the waveguide 2 and the tap waveguide 3 are coupled to each other at multiple locations. In this case, unlike the first embodiment, only one detector 15 is required.

In such a structure, for example, the optical pulse reaching the tap T is transmitted to each tap T r of the waveguide 2 and the tap waveguide 3.
, T t , . . . , the next tap T is reached when the time difference ΔL/C required to propagate the distance difference ΔL between Tn has elapsed. That is, the detector 15 detects each tap T
+, T x , . . . , pulse trains from Tn are detected. “l” is detected from the taps T , , T , . . . In the detector 15, the optical pulse signals from each address position P+, Pt, . However, in reality, a reference synchronization signal is required. The readout time in this second embodiment is approximately determined by the time required to propagate through the waveguide 2, and therefore:
As in the first embodiment, extremely high-speed access is possible.

Next, FIG. 3 is a diagram showing the configuration of a main part of a rewritable optical storage device according to a third embodiment of the present invention.

The above mentioned number! And in the second embodiment, the information “l”
Tap T t , T *, ... corresponding to "0"
, Tn was configured to write information depending on whether or not it was installed, so it was read-only, but a directional coupler was used that could vary the coupling efficiency of each tap T, Tt, ..., Tn. This makes it possible to realize a rewritable optical storage device. That is, in FIG. 3, the waveguide 2 and the tap waveguide 3 are made of LiNbO.
5 doped with Ti, a tap waveguide 3 is provided adjacent to the waveguide 2, and an electrode E and a ground electrode GND are provided at the portion where the waveguide 2 and the tap waveguide 3 are coupled. It has a similar structure. Then, by applying a voltage to these electrodes E and the ground electrode GND and applying an electric field to the waveguides 2 and 3, a refractive index change is caused by the electro-optic effect, and the propagation constant of one of the waveguides is changed. .

In this case, the coupling coefficient of adjacent waveguides (the rate at which an optical signal propagating in one waveguide transfers to the other coupled waveguide) changes depending on the difference in coupling length or propagation constant. . Therefore, by appropriately setting the wavelength of the optical signal, the dimensions of the element, and the electric field strength, the coupling coefficient becomes O when no electric field is applied, and a small coupling efficiency when an electric field is applied, or vice versa. It is easy to realize that the coupling coefficient becomes 0 when this happens.

In this third embodiment, information can be written depending on whether an electric field is applied or not depending on whether the information is "1" or "0".The refractive index changes when an electric field is applied, but the electric field When the multiplication is stopped, it returns to the original state.Therefore, in this third embodiment, a removable optical storage device can be realized.Information can be written in all bits in parallel, so it is possible to write at high speed. The read operation is exactly the same as in the first embodiment, and high-speed access is possible.

Note that since the configuration and basic operation of the device are substantially the same, the details will be omitted, but even if a semiconductor waveguide is used, a similar device can be realized with the same structure as each of the above-described embodiments. Furthermore, when a semiconductor guide is used, peripheral circuits such as a drive circuit can be configured monolithically.

〔Effect of the invention〕

As explained above, according to the present invention, it is possible to realize an optical storage device that does not require any conventional mechanical scanning and is capable of extremely high-speed access determined by the propagation speed of light within the waveguide. You can get the effect that you can.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of a first embodiment of this invention, FIG. 2 is a block diagram showing the configuration of a second embodiment of this invention, and FIG. 3 is a main part of a third embodiment of this invention. FIG. 1... Optical pulse generator, 2... Waveguide, 3... Tap waveguide, TIT! ,..., Tn...Tap, P ,,
P! ,...,Pn...address position, 5.
15...Detector, E...Electrode, GND...--Grounding electrode.

Claims (2)

[Claims] (1) A waveguide that guides an optical signal, a tap waveguide that extracts a part of the optical signal propagating within the waveguide from each position of the waveguide corresponding to information to be stored, and An optical storage device comprising: an optical pulse generating means for introducing an optical pulse with an extremely short pulse width; and a detecting means for detecting an optical signal taken out by the tap waveguide as stored information. (2) The waveguide and the tap waveguide are constructed of a material with a large electro-optic effect, and an electrode is installed at a portion where the waveguide and the tap waveguide are coupled, and a voltage is applied to this electrode. 2. The optical storage device according to claim 1, wherein the coupling efficiency between the waveguide and the tap waveguide is changed by changing the coupling efficiency between the waveguide and the tap waveguide.